Mallee Salinity Workshop May 30, 2012

Mallee Catchment

Management Authority

www.malleecma.vic.gov.au

PO Box 5017 Mildura 3502

Telephone 03 5051 4377

Facsimile 03 5051 4379

Copyright

© Mallee Catchment Management

Authority 2013

Disclaimer

Publications produced by the Mallee

Catchment Management Authority may

be of assistance to you but the Mallee

Catchment Management Authority and

its employees do not guarantee that the

publication is without flaw of any kind or

is wholly appropriate for your particular

purpose and therefore disclaims all

liability for any error, loss or other

consequence which may arise from you

relying on any information in any Mallee

Catchment Management Authority

publication.

Publication details

Mallee Salinity Workshop May 30, 2012

Executive Summary.

Project Number: 1525-2-103

April 2013

Authors: Deidre Jaensch1 & John Cooke2

1 Mallee Catchment Management Authority 2 Victorian Department of Sustainability and Environment

Acknowledgements

The authors would like to acknowledge the

strong relationship developed over the past

20 or more years between community,

government and scientists in working

together to better understand and manage

land practices in a saline landscape.

Cover images

Middle: Psyche Bend Lagoon, Mildura.

Top Right: Salt crystals.

All photos: Mallee CMA

Executive Summary

Authors: Deidre Jaensch 1and John Cooke

2

Introduction

A workshop was held in Mildura on 30 May 2012, at which technical experts were invited to outline the key

scientific investigations that have contributed to developing our present level of understanding of salinity in

the Mallee and its management over the past 20 years. This summary paper has been prepared following the

compilation of nine technical reports presented at the workshop relevant to salinity and its management in

Victoria’s Mallee.

Our present state of knowledge is derived from state and federal Government investment into projects that

have explored the causes and effects of salinity mobilisation and expression in the landscape. Land

management practices have been developed to control salinity processes based on this sound technical

understanding. The knowledge derived from some of these projects has modified our thinking about salinity

processes and has refined our focus for future investment to effectively manage this issue.

The purpose of the workshop was to provide a forum for experts, selected on their knowledge of salinity

processes and management in the Mallee, to present their views and provide opportunity to discuss these

views in a public forum. Importantly, these discussions recognised and documented the policy reform,

community involvement and other driving forces during this period.

The choice of timing of the workshop was appropriate for three reasons: the impending fifteen year review of

the achievements and understandings gained under the Murray-Darling Basin Salinity Management Strategy

(2001-2015); the implementation of new federal legislation under the Basin Plan that changes the priority of

river management from agriculture to environment; and to document the collective knowledge from those

who were involved in ensuring political, scientific and community imperatives.

The summary statements below are based on the science as presented and discussed during the workshop in

May 2012. It is a summary of our current status of knowledge and understanding of salt behaviour and

management in the Victorian Mallee. It provides a sound foundation for a new generation of policy makers to

examine past scientific investigations as well as provide a fresh basis of agreed knowledge from which salinity

management and policy development can be formulated into the future.

Geological and hydrogeological drivers of salinity in the Mallee

1. Understanding the geology, hydrogeology and groundwater processes is an essential step in

determining what drives the salinity processes in the Mallee and developing appropriate

management strategies. The influence of the geomorphology on regional groundwater recharge and

discharge processes and their interaction with land use activities has been well understood for some

time and documented prior to the commencement of the main salinity management plans developed

in the 1990s.

2. The highly saline Parilla Sand aquifer dominates the salinity processes and spans across a significant

area in the Mallee landscape. It is highly conductive (i.e. its high permeability absorbs water readily)

but has a low rate of water movement through the aquifer due to the low hydraulic gradient (i.e. the

slope of the groundwater is flat across a broad area ~ 2 cm/km). The flat expanse of saline water

underlying the soil surface means that even small recharge events can cause rapid changes in

groundwater levels that dissipate across vast areas. The aquifer outcrops at the numerous salinas and

boinkas across the Mallee which reduces the pressure built up in the aquifer and lead to an overall

1 Mallee Catchment Management Authority

2 Department of Sustainability and Environment

flattening of the groundwater level. In turn this reduces the pressure exerted on areas bounded by

the river trench which transmits saline groundwater directly into the river. This in-land discharge

(‘pressure release’) mechanism is distinct to the Victorian Mallee and means land-based activities

such as irrigation has less impact on the river compared to irrigation areas observed downstream.

Concentrations of groundwater under Lake Tyrell tells us that there is potential to contain and

accumulate high concentrations of salt in the Mallee groundwater without issue.

3. The annual balance of salt moving into and out of the Mallee is very small in comparison with the

total salt store. The system appears to be ‘in balance’ and highly responsive to rainfall. The Parilla

Sand aquifer is the principle conduit for the distribution of recharge through groundwater movement

and salt mobilisation processes to the river and inland discharge sites. Semi-arid conditions and high

potential evaporation rates of the Mallee mean that less than one per cent of rainfall ends up as

recharge. However, during periods of high rainfall or extended rainfall periods the Parilla Sand aquifer

may respond rapidly with corresponding groundwater level rise. Land and water management

strategies prepare for such high rainfall events by lowering water tables and providing space in the

aquifer (unsaturated zone) that can absorb additional water before waterlogging and salinization

occur.

4. Characteristic of the Mallee region is the presence of sedimentary layers e.g. Blanchetown Clay. This

layer has low permeability and can delay localised rainfall from reaching the groundwater by 12 years

and in some areas of great thickness up to 200 years. This means that a lot of the impacts associated

with early European settlement and dryland clearing, may not be realised in the Murray River for

some time and likely to be well beyond our lifespan.

5. The Murray River is the only means by which salt can leave the Victorian Mallee region. It is the

Mallee’s largest saline discharge feature and eventually receives most of the salt moving down-basin

via the regional groundwater systems. The direction of groundwater flow is in a westerly direction

towards the lowest point of the Murray-Darling Basin and largely follows the direction of flow of the

Murray River.

6. The Murray River is also a source of salt that flows into the region and recharge through irrigation

activities. As with high rainfall events, continuous application of water via irrigation can reset the

balance of recharge and increase pressures on the regional aquifers resulting in irrigation mounds and

greater discharge of saline groundwater to the river.

7. Construction of locks and weirs along the length of the River Murray has enabled the extraction of

water to supply irrigation districts since the 1920s. The heightened elevation of the river has in turn

increased groundwater levels adjacent to weir pools and created flush zones at the interface of saline

groundwater and fresh river water. These flush zones have supported the establishment of vegetation

communities that may not have established in an un-locked river system. Downstream of the Weirs,

the flow patterns are reversed.

Policy background

8. Before European settlement the rate of saline groundwater discharge to the river would have been

controlled by the natural recharge rate (driven by rainfall events), transmissivity of regional aquifers,

groundwater gradients and seasonal river flows. With removal of approximately two thirds of the

Mallee’s native vegetation local recharge rates increased 100 fold. Local recharge rates have been

further exacerbated with the application of irrigation water and drainage disposal systems. This

increase in recharge is the primary predisposing cause of secondary salinity of land and water in the

Mallee landscape.

9. Groundwater levels are still increasing due to clearing of native vegetation over the last 100 years,

hence the term ‘legacy of history’. Concern about the cumulative impact of land management

activities causing high salt levels for downstream water users led to the development of a co-

ordinated effort by the Basin States. The purpose was to efficiently, equitably and sustainably manage

the water resource in the Murray-Darling Basin which resulted in the agreed Basin Salinity

Management Strategy (BSMS 2001-2015). The BSMS is implemented through the Schedule B (Murray

Darling Basin Agreement) of Schedule 1 of the Commonwealth Water Act (2007). The primary

objective of the BSMS is to: maintain water quality; control the rise in salt loads; control land

degradation and maximise net benefits of salinity control across the Basin.

10. The BSMS provides the framework for Basin States to account for and monitor land management

activities that dispose of salt into the river (salinity debit) or those that have a salinity benefit by

preventing salt from entering the river (salinity credit). All land use activities that have the potential

to change the salt influx must be investigated by each State using an approved modelling approach

and expressed in common terms of EC impact at Morgan. The Murray Darling Basin Authority (MDBA)

quantifies the size of each accountable action using a computer model of the river system known as

MSM BigMod. The MDBA maintains the official record in the Salinity Register equivalent to a financial

ledger requiring each Basin State to maintain a positive balance of salinity credits against debits.

11. The BSMS framework recognises the difficulty in measuring many of the parameters important to

quantifying physical processes active in the aquifer/river system being modelled. Accordingly, an

adaptive management approach is implemented whereby the original estimates of salinity impact are

reviewed every five years, known as ‘rolling reviews’. These reviews incorporate new knowledge,

monitoring data and re-test the assumptions that underpin the model to reduce the uncertainty and

refine the salinity impact estimates. It is recognised in the BSMS that modelling linked to monitoring is

the only practical way to measure progress of actions directed towards salinity management.

12. The Mallee Catchment Management Authority (CMA), as agents of the state of Victoria, maintains a

Mallee regional salinity register of credits and debits. An annual program of groundwater and surface

water monitoring is undertaken to collect data that inform the annual reporting and scheduled five

year reviews for each of the seven accountable actions pertaining to the region.

Modelling tools used to estimate salinity impact

13. Modelling is used within the BSMS to better understand the complex interactions of salinity processes

and provide a predictive tool for determining appropriate solutions to landscape and water

management. A ground-water model provides the scientific means to draw together the available

data into a numerical characterisation of a groundwater system. Salt loads in the river, salinity in the

water and salt in the regolith is not easily quantified. Water flows in the river have a major influence

on salt load, salinity concentration and salt movement into and out of the river.

14. Without doubt the greatest advancement in our hydrogeological knowledge over the past 20 years

and improved understanding of the patterns of variation and replication within and between

landforms has been realised through improved data and modelling capacity, specifically:

- Improved technologies in field measure of geophysical parameters (e.g. electromagnetic

surveys);

- Data collection through an annual program of monitoring of bore networks, stream gauging,

irrigation footprint and climate data;

- Improved computing capacity and imagery from global information systems (GIS);

- Improved conceptualisation and representation of complex natural systems captured within

surface water and groundwater models.

15. While many of the parameters important to hydrogeological process are not able to be directly

measured with an acceptable level of accuracy3, these advances in technology have provided an

insight into their degree of complexity and enabled estimations to be calculated with a known degree

3 For example it is not possible to measure recharge for the simple reason that the errors associated with the

overall water balance are greater than the magnitude of the recharge. Rootzone drainage can only be

reasonably inferred with knowledge of soil water content changes. Recharge can only be reasonably estimated

from information gained from observation wells.

of confidence or at least with a better understanding of the error bands associated with these

estimates. As such multiple lines of evidence are relied on to characterise salinity processes.

16. The BSMS provides a framework for the development, accreditation and use of models from which

salinity impacts are estimated and the key hydrogeological flow processes are represented such as

transmissivity. Improvements in modelling and calibration against field data sets under the BSMS

framework have enabled the Mallee region to:

- Develop a suit of models deemed fit for the purpose of demonstrating salinity benefits

associated with reduced groundwater infiltration achieved through improved water use and

irrigation efficiencies;

- Fine-tune the legacy of history 100 year prediction from 100 EC down to approximately 5.9

EC for the dryland actions;

- Attribute the salinity benefit of salt interception schemes in the Mallee region;

- Better understand the scale of complexity and variability in the floodplain areas;

- Consider the complexity of each model and importance of potential errors introduced

through having complex models.

17. While modelling provides an agreed technical platform and promotes consistency, transparency and

best practice, it also provides a formula for those involved in management to agree on how costs and

benefits should be distributed. The modelled output is accepted as an independent assessment by

those who benefit or pay costs associated with the action.

Salt interception schemes that prevent saline groun dwater entering the river

18. The most immediate salinity threats to the Murray River from dryland and irrigation actions have

largely been dealt with by salt interception schemes (SIS). Progressive investment in salinity

management through SIS, from 1979 to present, has had considerable benefit as evidenced by very

few instances when salinity exceeded the Basin Salinity Target of average daily salinity of less than

800 EC for at least 95% of the time at Morgan South Australia. The 2010-11 BSMS Annual

Implementation Report (MDBA 2012)4 reports that the “Morgan target” has been achieved.

19. Salt interception schemes are constructed as a key component of the BSMS under a joint works and

measures program encompassing a total of 19 salt interception schemes within the Murray-Darling

Basin. These schemes a constructed at ‘high risk’ river reaches where saline groundwater discharges

from the alluvial sediments of the floodplain into the river. The primary purpose of these schemes is

to reduce groundwater pressures immediately adjacent to the river by extracting and redirecting

saline groundwater to disposal lakes inland. By reducing the groundwater pressure the hydraulic

gradient of saline groundwater increases away from the river. In 2010-11 approximately 324,162

tonnes of salt was diverted away from the River Murray through the operation of salt interception

schemes in the Murray-Darling Basin4.

20. Utilisation of technologies such as Run of River (RoR - measuring saline concentration from which

infiltration is derived), NanoTEM (and river bed resistivity), in-stream fixed salinity monitoring stations

and MSMBigmod, have greatly improved our ability to identify where the salt enters the river and the

occurrence of ‘high risk’ river reaches or ‘hot spots’. This has enabled construction and refurbishment

of SIS in Sunraysia in reaches targeting high saline groundwater discharge so as to maximise the

interception of salt while minimising capital and operational costs.

4 http://www.mdba.gov.au/files/BSMS-Annual-Implementation-Report-2010-11.pdf accessed 22nd March

2013

21. There is a core cluster of Murray-Darling Basin SIS around Mildura and in South Australia. The data

shows significant salt load inflows or ‘hot spots’ occur in two localised areas: from Mallee Cliffs to

Psyche Bend; and from Lock 11 to Merbein Common. This correlates with the location of the three

main SISs within the NSW/Victorian Mallee reach of the Murray River being Mallee Cliffs, Buronga and

Mildura-Merbein.

22. There may be future opportunity to consider using SIS (pumps, pipeline and disposal) to remove

floodplain salt and modify or enhance the benefits to the river and/or the floodplain environment. For

example, targeted building of freshwater lenses at critical locations and timely operations may in-turn

reduce peak salt loads and enhance environmental benefits. SISs have the potential to manipulate

freshwater sources to provide positive environmental outcomes for the floodplain environment.

Irrigation management in a saline landscape

23. The construction of weirs and locks along the length of the Murray River historically provided a path

for navigation in, and out of, the Mallee. While originally constructed for navigational purposes the

weirs and locks are now predominantly used to support irrigation industries. The locking of the river

to enable water extraction has elevated water levels above natural levels especially during periods of

low flow. Prior to locking and irrigation it is thought that the river would have recharged the

groundwater system under most flow regimes. Under a ‘locked river’ a new balance has been

realised. Associated with the weirs and locks that support irrigation districts are heightened

groundwater levels and freshwater zones extending into the adjacent groundwater aquifer on the

upstream side; these are referred to as ‘gaining’ streams. Conversely, saline groundwaters gravitate

towards the downstream side creating a ‘losing’ stream.

24. The early irrigators in the Sunraysia region quickly learned that irrigation is not sustainable in the

Mallee landscape without adequate drainage. The location of the early irrigation footprint biased

towards the loamier soils within close proximity to the river to achieve pumping efficiencies. These

soils were known to have good vertical movement of water down through the soil profile and very

little surface run off. However after only a short period of watering, severe waterlogging and

salinisation started to form on top of underlying clay layers and threatened future prospects for

irrigation in the Victorian Mallee. An extensive subsurface drainage network was installed under

much of the irrigation areas in the 1930s5 to remove excess water from the soil profile and dispose of

drainage water either to inland evaporative basins or to the river. However tile drains do not

intercept all the water percolating through the rootzone. A small component continues to recharge

the regional water table below.

25. More than one hundred years of irrigation and heightened groundwater recharge rates, compared

with those under native vegetation, has resulted in groundwater mounds forming in the underlying

regional groundwater aquifer. While irrigation water is relatively fresh, the mounding increases the

hydraulic pressure on the highly saline groundwater aquifer and exacerbates discharge of saline

groundwater towards the floodplain and into the river, as well as low-lying inland discharge sites.

26. More recently one could be forgiven for thinking the salinity problem had gone away, with the

observed reduction in river salinity concentrations and reduced irrigation drain flows. The ‘extended

dry period’ and reduced water allocations applied to irrigation areas in the early 2000s meant that the

amount of water that drained through the soil profile and past the root zone was not enough to build

up the water table and reactivate the subsurface drains. Most of the time drainage from irrigation is

only a small volume. This drainage volume continues to seeps through to the regional groundwater

aquifer below even when the drains aren’t flowing. The impact on the regional water table from

irrigation remains even though the flow in lateral drains has declined.

5 Subsurface tile drainage schemes were installed in many parts of Red Cliffs, Mildura and Merbein in the

1930s however not all properties in these areas have access to the drainage system. Drains were not

installed in Nangiloc-Colignan.

Irrigation planning to reduce recharge

27. Irrigation recharge to the underlying aquifers is a major driver of salt discharging to the Murray River.

Cautionary estimates of groundwater recharge in irrigation areas has reduced from 42-108 mm per

year in the 1980s to be between 15 and 23 mm per year in 2000, depending on irrigation district and

the presence or absence of underlying Blanchetown Clay.

28. While it is recognised that groundwater recharge is an unavoidable consequence of irrigation in the

Mallee environment, the risk has been pro-actively managed through the adoption of salinity impact

zoning and water use efficiency strategies built into the local salinity management plans developed 20

years ago. Better matching of the water application and required leaching fraction6 with crop water

requirements and soil water holding capacity reduces the amount of excess water that drains past the

rootzone into the ground water.

29. The salinity impact zoning and water trading mechanism implemented under the Nyah to the SA

Border SMP has been successful in supporting the expansion of area that is able to be irrigated in the

private diversion areas to over 54,880 hectares (total irrigation area in the Mallee is 72,450 ha,

Sunrise 21 2012). Despite this expansion environmental damage has been avoided and river salinity

minimised through:

• guiding greenfield irrigation development into those parts of the Mallee landscape where they

would have the least impact on Murray River salinity;

• maximising the long term economic benefits for the region through sustainable irrigation

development;

• providing greatest level of opportunity for the highest number of irrigators by encouraging

development to occur in areas of lowest impact, slowing the consumption of salinity credits;

• protecting the environment and biodiversity from irrigation impacts.

30. Private diversion expansion demonstrates a strong preference for irrigation development in the

lowest salinity impact zone L1 (approximately 80 per cent of total private diversion area, or 44,625 ha,

is situated in L1). Without suitable control mechanisms in place it is not unlikely that expansion would

have been focussed in the high salinity impact zones (closer to the river) and would have prematurely

exhausted the salinity credits available and the associated financial benefit realised by few individuals.

31. Under the Salt Action: Joint Action initiative the Mallee communities developed salinity management

plans to address local salinity issues. Four salinity management plan (SMP)s were developed:

- Nangiloc-Colignan SMP – addressed issues of waterlogging and salinization for private diverters

outside of the pumped irrigation districts through constructing a co-ordinated community

drainage diversion scheme;

- Nyah to South Australian Border SMP - adopted a zoning approach based on hydrogeological

characteristics coupled with trading rules and market mechanisms directing new irrigation

development to areas of least impact on the river in response to water trade into the Mallee;

- Sunraysia SMP – to reduce irrigation drainage from historic plantings by offering incentives to

adopt pressurised irrigation systems, scheduling equipment and irrigation training. These efforts

have culminated in a salinity credit claim (2010) for reducing the groundwater mounding under

irrigation areas dubbed the reduced irrigation salinity impact (RISI);

- Dryland SMP – to deal with the high level of uncertainty associated with developing cost effective

salinity management approaches for an issue that is largely un-retractable.

6The leaching fraction is the amount of drainage required to remove the salt that concentrates in the soil

around the plant roots from evapotranspiration. If not removed fast enough the soil will increase in

concentration and reduce crop production.

32. Victorian Mallee Irrigation Region Land and Water Management Plan (LWMP, Mallee CMA 2011)

replaces the SMP however few changes have been made to the salinity management approach. The

LWMP largely carries-on the focus of the earlier salinity plans through water management. We can be

confident that the potential rise in salinity predicted in the Salinity Audit 1999 is delayed and may

never reach the worst case scenario originally identified in the Salinity Audit.

Land use and management of secondary salinity and l and use management in dryland areas

33. Secondary salinity or induced salinity is generally associated with the expansion of primary saline

discharge zones, known as salinas and boinkas7, which are a ‘natural feature’ of the Mallee landscape

and characteristic of its geomorphology. These areas of secondary salinity expand and contract in

direct response to rainfall recharge events. Groundwater levels increase and a steepening of the

groundwater gradient, or mounding within the aquifer, expands the extent of saline groundwater

discharge and salinization at the soil surface. Widespread clearing of deep rooted native vegetation

and replacement with shallow rooted agricultural crops across approximately two thirds of the Mallee

has exacerbated recharge in the dryland areas. As a result the estimate for groundwater recharge

rates under dryland systems is approximately 100 times higher (approximately 10 mm per year) than

recharge rates under native vegetation (approximately 0.1 mm per year).

34. Clearing of native vegetation in dryland areas has also increased regional groundwater flows towards

the Murray River in a westerly direction. Depending on the presence and thickness of underlying

sedimentary layers such as Blanchetown Clay, it may take some time before the effects of this action

is observed in the river. In the 1990s there was great concern that the delayed salinity impacts

attributable to ‘legacy of history’ actions (i.e. before January 1988 as determined under the Basin

Salinity Management Strategy) would have severe impacts on downstream river users with 100 year

predictions of salinity effect at Morgan in the order of 100 EC. With the development of more

sophisticated models of recent times, this estimate has been dramatically refined to approximately

5.9 EC (BSMS Register B, 2011). However the ‘confidence rating’ against this entry remains ‘low’

reflecting the +/- 25 per cent uncertainty within the model due to dryland recharge rates, timelags

and floodplain process complexity.

35. In the dryland, recharge of groundwater is dominated by rainfall events. The extended dry period

observed in the 2000s lowered groundwater levels and retracted inland saline lakes. However the

aquifer responded rapidly to high rainfall events where spikes of groundwater level occurred in

response to the high rainfall seasons in the 1970s and 2010/11 and a number of historic boinkas were

again reactivated.

36. Modern dryland farming and agronomic practices focus on minimising the expansion of secondary

areas by improving crop use of natural rainfall and reducing groundwater recharge through:

- Increasing the depth and effectiveness of the plant root system;

- Expanding the proportion of the landscape covered in vegetation and replacing fallow crops with

alternative strategies;

- Developing new cultivars and perennial crops that allow more water to be extracted from the

sandy dune soils, which were identified as preferential recharge areas.

37. The modern era of dryland salinity management acknowledges that mitigation activities such as

revegetation are likely to have only a minimal effect on lowering water tables across the broad Mallee

7 Salinas (saline lakes) or boinkas (shallow depression with a distinct suite of landforms) are natural

discharge sites in the Mallee where the Parilla Sand aquifer intercepts the land surface and the

groundwater evaporates. The groundwater salinity concentrates and the groundwater gradient flattens,

and in some cases reverses, at these sites as described by Macumber (1991).

landscape. Increased focus has been towards managing discharge sites and revegetation of water

logged areas with salt tolerant species to mitigate the spread of secondary salinity.

38. The proportion of the landscape that is impacted by rising water levels is a function of the local

topography. Flatter landscape such as the plains in the eastern Mallee around Manangatang are at

greater risk of secondary salinity than are the landscapes dominated by rolling dunes and swales.

The floodplain – a new focus for salinity

39. Floodplain studies undertaken in 2008-2010, using airborne electro-magnetic surveys of the Murray

River floodplain and immediate hinterland, have illustrated floodplain complexities and identified that

the differentiation of land features occur on a much finer scale in terms of ‘tens-of-meters’ as

opposed to earlier thinking of ‘kilometres’ by Thorne et al. in the 1970s. This understanding has

redefined the scale of floodplain investigation required to better understand the impact of

intervention actions.

40. Recent work undertaken by Cartwright has shown that the near river hydrogeology dominates the

magnitude of the salt that reaches the river. Near river sand lenses, or ‘flush zones’, contain

groundwater with a salinity concentration close to that of river water. In contrast, adjacent and

interwoven clay sediments have salinity levels approaching, and at times exceeding, the salinity of

seawater.

41. Interaction of fresh water flush zones with the saline water at the floodplain extremities is still unclear

and highlights the need to better understand the dynamics of specific parts of the floodplain for

environmental watering intervention activities and refinement of landscape models.

42. The floodplain acts as a groundwater buffer between the higher ground of the Mallee aeolian

landform and the river. It can be both a source of groundwater recharge as well as a sink for discharge

but little is known about how salt is removed from the floodplain. Concentration of groundwater

salinity in the floodplain extremities is thought to be due to transpiration of native vegetation and

evaporation via capillary rise into upper soil profile. Changed river flows of both the modern Murray

through river regulation and from ancient river pathways has created areas of the floodplain more

saline than that of adjacent Mallee soils.

43. The floodplain vegetation follows with the River Red Gums occupying the sand based fresh lenses.

Black Box dominate the saltier clay soils and at highest salinity salt bush is the dominant vegetation.

The symptoms of water stress and salinity stress are very similar. The rate of salt accumulation in the

floodplain is very slow (less than 1 % per year). Unlike the recently observed high rate of decline of

floodplain health. It is now thought that this decline of floodplain health is more likely a cause of

reduced availability of fresh water rather than the commonly held perception that salt accumulation

causes floodplain health decline.

44. Despite being only a very small proportion of the total landscape it is accepted that floodplain

hydrogeological processes dominate land and water management influences on river salinity.

This summary represents the present level of understanding as documented in nine technical papers that

encapsulate the key points of more than 350 scientific papers and related documents in the area of salinity in

the Victorian Mallee.

These nine papers were developed by technical experts following a salinity workshop hosted by the Mallee

CMA in May 2012. The technical papers represent the great volume of work that has been undertaken in this

area over the past 15-20 years. They also acknowledge the wealth of scientific knowledge gained from past

investment in better understanding Mallee salinity processes. These papers will serve as a valuable tool for

those involved and interested in salinity management and policy development in the Mallee region. Copies of

the full technical reports and references are available via the Mallee CMA website

(http://www.malleecma.vic.gov.au).

Mallee Salinty Workshop

May 30, 2012

Executive Summary

Chapter 1: Geology and hydrogeology – Ray Evans (SKM)

2 Influence of tectonic movements

3 Groundwater flow

4 Groundwater recharge and discharge processes

5 Groundwater level trends

6 Estimating River Murray salinity – pre-development

7 Landscape processes in the Victorian Mallee that influence salt mobilisation & contemporary salinity management

Reference

Chapter 2: Floodplain processes – Ray Evans, Greg Hoxley and Keith Collett (SKM)

1 Key features of the floodplain

2 Salt accumulation and salt distribution in the floodplain

3 Consequences for floodplain vegetation

4 Export of salt to the river and consequences for river salinity

5 Conclusions

References

Chapter 3: Salt Interception Schemes and in-stream processes - Andrew Telfer, Rob Burnell and Alison Charles (AWE)

1 Regional salinity context

2 Salt risk

3 Salt interception schemes

4 Disposal

5 Variability of salt inputs

6 SIS design tools – in-stream salinity and salt loads

7 Features of modern SIS design

8 Possible future SIS

9 Future trends under the Basin Plan

References

Chapter 4: Dryland salinity drivers and processes - Jon Fawcett (SKM) 1 Introduction

2 Why is the Mallee susceptible to land salinisation?

3 Key drivers and processes of dryland salinity

4 Mapping the salinity threat in the Dryland Mallee

5 Dryland salinity statement (Victorian State Government perspective)

6 Summary

References

Chapter 5: The irrigation footprint Sunraysia – Tim Cummins (Tim Cummins and Associates) and Charles Thompson (RM Consulting Group)

1 Summary

2 Footprint – A careless metaphor?

3 Pattern-making

4 Nike or Psyche?

5 Evidence at the scene of the incident

6 Into the distance

7 Appendix A. Pattern-making with works licences

8 Appendix B. Pattern-making with water-use licences

References

Chapter 6: Drainage – Charles Thompson with inputs from Keith Collett (SKM) and Tim Cummins (Tim Cummins and Associates) Summary – Key lessons and future challenges

1 The need for drainage

2 Drainage Practices

3 The salinity impacts of drainage disposal

4 How drainage has changed according to key drivers

5 Salinity Credits/debits from drainage disposal

6 Issues

References

Chapter 7: Key tools (strengths and weaknesses) – Hugh Middlemis (RPS Aquaterra)

Summary

1 Background on tools

2 Review of strengths and weaknesses of tools

3 Wide range of tools and data for various purposes

4 Convergence towards multi-purpose tools?

References

Chapter 8: Policy and regulatory environment – Charles Thompson (RM Consulting Group) and Tim Cummins (Tim Cummins and Associates) Key messages

1 Precursors

2 Foundations

3 Community-driven plans address real salinity problems

5 Broadening the scope - some interesting asides

6 Contemporary settings

7 Where to now?Error! Bookmark not defined.

References

Chapter 9: Community involvement – Tim Cummins (Tim Cummins and Associates) with input from Charles Thompson (RM Consulting Group)

Summary

1 Introduction

2 Building the support system

3 Empowering the community

4 The legacy of community involvement in salinity management plans

References

1. Geology and Hydrogeology Author: Ray Evans1

Mallee Catchment






Copyright


Authority 2013

Disclaimer













publication.

Publication details

Mallee Salinity Workshop May 30, 2012:

Chapter 1 - Geology and hydrogeology.


April 2013

Author: Ray Evans1

1 Sinclair Knight Merz

Cover images




Project partners

[Place partner or funding party logos here, evenly sized in neat rows. Only the Mallee CMA logo should appear on the cover.]

Table of Contents 1 History of deposition and erosion ............................................................................................................ 1

2 Influence of tectonic movements ........................................................................................................... 13

3 Groundwater flow .................................................................................................................................. 14

4 Groundwater recharge and discharge processes ................................................................................... 16

5 Groundwater level trends ...................................................................................................................... 19

6 Estimating River Murray salinity – pre-development ............................................................................. 20

7 Landscape processes in the Victorian Mallee that influence salt mobilisation & contemporary salinity management .......................................................................................................................................... 23

References ...................................................................................................................................................... 25

List of Figures Figure 1: Maximum extent of sea incursion into Murray Basin around 5 million years ago. .......................... 2

Figure 2: Diagram of cross-section stratigraphy of the Murray Basin. ............................................................. 3

Figure 3: Relationship between past Climate Cycles and Dune Formation History. ........................................ 4

Figure 4: Near-maximum extent of Lake Bungunnia in Murray Basin ............................................................. 6

Figure 5: Aerial topographic imaging of the palaeo-lake shore of Lake Bungunnia (dashed line) near Swan Hill, Victoria. ..................................................................................................................................... 7

Figure 6: Conceptualised hydrogeological cross-section of the Murray River floodplain at Lindsay Island, Victoria.............................................................................................................................................. 8

Figure 7: Landforms interpreted from DEM data for River Murray near Lake Victoria showing Multiple Terraces and Complexity of Erosion and Deposition. ...................................................................... 9

Figure 8: Cross-section of the Murray Trench typical of the Nangiloc-Colignan Reach. Terracing and erosion of the Coonambidgal Formation. ................................................................................................... 10

Figure 9: Water level oscillations from the Willandra Lakes over the last 50 000 years showing Dune-Building and Freshwater Phases.. ................................................................................................... 11

Figure 10: A satellite image of parabolic siliceous dune fields of Lowan Sands............................................. 12

Figure 11: Flow Directions in the Parilla sand Aquifer. .................................................................................. 14

Figure 12: Mildura airport (Station no. 076031) daily rainfall and evaporation data for 2011-12 ................ 16

Figure 13: Time of Recharge Pulse to reach the Watertable.. ....................................................................... 18

Figure 14: Groundwater bore hydrographs – ground water responses to high summer rainfall event in 2011 under irrigated areas, Red Cliffs. ........................................................................................... 19

Figure 15: Groundwater bore hydrographs - responses to groundwater levels in the Parilla sand aquifer. 20

Figure 16: Pre-development Murray River levels versus regional groundwater at different flow rates. . ... 22

Figure 17: Post-development Murray River level versus regional groundwater in the Parilla Sand.. ........... 22

Figure 18: Conceptual Diagram of Landscape Processes in the Victorian Mallee. ........................................ 24

Introduction

This chapter has been prepared for the Mallee Catchment Management Authority as a contribution to a definitive statement on Salinity in the Mallee. The intent of this chapter is to describe the fundamental geological and hydrogeological concepts and processes in the Mallee that are critical for an understanding of salinity that provide the foundation of salinity management in the Mallee. This paper provides an overview of the key geological and hydrogeological elements and sources of further information.

Fundamentally, the geology and hydrogeology of the Mallee is well known at regional and sub-regional scales. For the purposes of managing the regional groundwater system sufficient detail is currently available to underpin sound salinity management. To the extent that knowledge gaps exist they are for detailed analysis and management on a finer scale, typically at the paddock scale. For instance, while the processes of groundwater movement under the Murray floodplain are known, specific detail at any particular site is still uncertain.

1

1 History of deposition and erosion

The geology and hydrogeology of the Murray Basin have been extensively studied over the last 50 or more years. In large part this research has been driven by the need to understand salinity processes and how groundwater interacts with the Murray River. There are many excellent and comprehensive references for the geology and hydrogeology of Mallee. Key references are listed at the end of this chapter, but of particular note and stature is the synthesis published by Brown and Stephenson (1991). This summary paper highlights the key geological components of specific relevance to the Mallee region, a small component of the large body of work that is available on the topic. Also of particular importance is the work of Phil Macumber (see various references) and its role in setting the foundation for the important hydrogeological processes operating. Our understanding of the large scale stratigraphic sequence has not altered significantly in the last 20 years and the description that follows presents a well established picture of the main geological units. This paper will discuss the relevance and importance of these units to salinity management in the Mallee.

The Mallee region is part of the larger Murray Basin, a shallow geological basin that covers about 300 000 km2, across the States of Victoria, South Australia and New South Wales. The depositional and erosional patterns of the western Murray Basin have been dominated, from 65 million years ago to the present, by a combination of changing sea levels, cyclically driving sea inundation of the continent and incision of river valleys (Figure 1) and minor tectonic movements. The breakup of the Gondwana supercontinent, which had seen the uplift of the Great Dividing Range around 95 million years ago, continued, with the landmass of Australia starting to separate from Antarctica at about 150 million years ago, and the Southern Ocean developing at about 65 million years ago. During the Paleocene period, a cycle of deposition began to create what is now the Murray Basin when rivers in what is now Victoria flowed north from the Dividing Range and deposited their sediment on the lower lands. On top of the basement rock (mostly comprising Precambrian to Silurian-aged metamorphosed sediments, volcanics and granites) the region’s first major geological units were deposited comprising the sand, silt and carbonaceous layers of the Renmark Group (Figure 2).

2

Figure 1: Maximum extent of sea incursion into Murray Basin around 5 million years ago.

The Parilla Sand strand line dunes can be seen as the parallel features running northwest-southeast. Numbering in circles represents estimated shoreline positions at 1 to 6 million years ago (Source: Modified after Kotsonis 1995, and Kotsonis 1999, in Bowler et al. 2006).

The fluvial (river-borne) and lacustrine (lake-bed) sediments of the Renmark Group formed between around 65 and 15 million years ago (Figure 2) on top of the basement rock. In the central Mallee region, the Renmark group terminates with the onset of deposition of the Murray Group at about 56 million years ago, whereas in the east, deposition continued on the landward side of the marine incursion until about 15 million years ago. The Renmark Group in the Mallee region is split into two major formations – the Warina Sand and the Olney Formation. Elsewhere, the Group is often partitioned into Upper, Middle and Lower Renmark Group aquifers, but this partitioning is not necessarily applicable to the Mallee. The Renmark Group consists of sands silts and carbonaceous (as peat and lignite) materials with some major lignitic layers at the top of the sequence around Kerang, Torrumbarry and Echuca. The Group lies between 60m thick in the Loddon valley and 300m thick around Mildura; the thickness governed by the palaeo-topography of the basement (VEAC 2008). The Renmark Group does not outcrop within the Mallee; rather, it generally underlies the Murray Group marine sediments.

3

The sediments of the Murray Group were deposited in the Murray Basin between about 56 and 15 million years ago (Figure 2). Generally, the Group encompasses the marine mud, clay and limestone sediments between the Renmark and Wunghnu Groups. The Murray Group outcrops at the surface in limited locations, mostly along the Murray River in South Australia. Important units within the Murray Group are the Duddo Limestone, Geera Clay and Ettrick Formation. The Ettrick Formation forms an aquitard between the aquifers of the Murray Group (the Duddo Limestone in Victoria) and the Renmark Group below, limiting vertical groundwater flow (VEAC 2008). The Geera Clay forms a lateral/horizontal boundary to flow between the aquifer systems of the Riverine Plain (to the east of the Mallee), and the aquifers within the Mallee itself.

Figure 2: Diagram of cross-section stratigraphy of the Murray Basin, with the left side representing a generalised western side of the basin. The chart shows temporal and spatial relationships of the key geological units (Source: Lewis et al. 2008, after Brown & Stephenson 1991).

The Duddo Limestone unit, which can be up to 130 metres thick, is a major aquifer of western Victoria (and the south east of South Australia) and forms the basis for the Murrayville Water Supply Protection Area (WSPA). The unit is an important aquifer containing low salinity groundwater and is the key groundwater resource in the Mallee. Within the Victorian Mallee the groundwater within this unit is considered as fossil water, i.e. it is a non-renewable resource under the current climate. Water quality is possibly threatened by the potential for leakage from the more saline Parilla Sand aquifer that overlies it. A program of decommissioning failed bores between 1993 and 2003 attempted to remove the major risk of saline intrusion into the Murray Group limestones. In 2003, local groundwater users reported that the salinity of water was increasing (i.e. deteriorating). In response to these concerns, the Mallee Catchment Management Authority undertook a water quality monitoring program in 2004 which showed no deterioration in water quality - however the risk of infiltration from the Parilla Sand remains (SKM 2004). Ongoing monitoring of groundwater levels and salinity are conducted by Grampians Wimmera Mallee Water under the Murrayville Water Supply Protection Area and reported annually.

4

Following the deposition of the Duddo Limestone sea levels retreated across the Murray Basin. After a short period of erosion and weathering, sea levels rose once again, leading to the third major package of sediments in the region. The marine incursion dominated the landscape (Figure 1) and at its peak around 6 million years ago, sea water covered this area up to 70 metres deep in places with the coast lying near Kerang. The sea was formed, not only at a time of higher sea levels, but also at a time when the climate was very different from today being a much wetter environment with high summer rainfall and rainforest dominating the landscape (illustrated with yellow shading above the line in Figure 3).

The marine incursion was responsible for the deposition of two important units in the region; the Bookpurnong Formation and the Parilla Sand. The clay of the Bookpurnong Formation was deposited in a low energy marine environment in the deepest areas of the Murravian Gulf sea bed, creating a layer that acts as an upper confining layer (aquitard) to the underlying Murray Group across the region (SKM & AWE 2003).

Time scale- MILLIONS OF YEARS AGO

War

me

r &

mo

re h

um

id t

han

no

wC

old

er

& m

ore

ari

d t

han

no

w

2012 5-60.7 0.4 2.5

Graph showing Climate versus Time

Below this line conditions are so dry dune building occurs

Figure 3: Relationship between past Climate Cycles and Dune Formation History. The cycle of changes between cold, arid and windy conditions (i.e. period of glaciations in the Northern hemisphere) with warm, wet and humid climatic conditions have influenced the development of lake formation, river flows and the movement of salt across the Basin for many millions of years (re-drawn after Bowler& Magee 1978).

The Parilla Sand, more broadly called the ‘Loxton-Parilla Sands’, was deposited on top of the Bookpurnong Formation and older units in the form of a sand sheet. The Parilla Sand is comprised of layers of sand, silt and clay that has since been consolidated in places, and is between 20 and 70 metres thick. Retreat of the sea, as sea levels fell, led to a migrating shoreline episodically over the next five million years and left clearly distinguishable strand line dunes (beaches) of Parilla Sand in locations where the sea level halted temporarily. These northwest-southeast trending sandstone ridges vary in height (up to 50 metres), width (from one to one-and-a-half kilometres) and length (from one to 50 kilometres) (Bowler et al. 2006). The sands in the Parilla Sand were reworked by aeolian processes to form the Woorinen Formation and Lowan Sands. An example of the Parilla Sand beach ridge complex is the Millewa Ridge near Mildura. Heavy mineral bands often occur within the formation and are the focus of mining exploration in the region.

5

The Parilla Sand is a regional aquifer (SKM & AWE 2003). The unit shows cementation layers typical in sands of this age, which are considered to be surfaces which were ferruginised (‘rusted’) at the time of deposition. The Karoonda Surface is a weathering surface of fossilised soil or cementation layer on top of the upper-most Parilla Sand layer, which acts as an aquitard in places where it is intact. The surface was formed in a tropical climate after the initial deposition of Parilla Sand, where an elevated watertable led to evaporation of groundwater (SKM & AWE 2003). The Karoonda Surface is present in most of the extent of the Parilla Sand, except where the unit has been eroded. Thorne et al. (1990a and b) showed that the upper surface of the Parilla Sand has been extensively weathered to kaolinite clay across broad areas, also indicating prolonged periods of intense weathering.

Salinity (estimated via electrical conductivity) of groundwater within the Parilla Sand in areas away from the River Murray generally ranges between 20 000 and 100 000 microSiemens per centimetre (µS/cm) (Aquaterra 2009). In recent times, irrigation of the surface has caused ‘freshening’ in the upper section of the Parilla Sand aquifer, reducing concentrations to between 2,000 and 50 000 µS/cm (Aquaterra 2009). Hydraulic conductivities in the unit are thought to be between 1 and 15 metres per day in the horizontal direction, and between 0.1 and 1.5 m and 15 metres per day vertically (Aquaterra 2009). Around Mildura, the hydraulic conductivity ranges between 5 and 10 metres per day (Aquaterra 2006). This high hydraulic conductivity means that the large body of salt, sitting in the aquifer not too far from the river, has the capacity to be readily transmitted to the river if the conditions are right. This ever-present possibility of salt being mobilised fundamentally informs salinity management in the region.

The gradual draining of the sea at this time was not a constant process. Detailed studies and sediment aging show that remnant shore lines gradually regressed to the modern coastline with several periods of return inundation. From a maximum depth of 70 metres in places, the level of water over the area oscillated 20 to 40 metres in depth from around 6 million years ago with a frequency of around 20 000 years (Bowler et al. 2006).

By around 3.2 million years ago, uplift of the Pinnaroo Block from faulting near Swan Reach had created a depression in the region. This area began to fill by the great inland rivers of the time that drained into the basin, creating the shallow mega-Lake Bungunnia (Figure 4).

Lake Bungunnia is one of the largest remnant lakes from this period in existence. The fresh and brackish water of the lake is postulated to have been up to 70 metres deep in places, spanning from Blanchetown in South Australia, over Mildura, to past Lake Mungo in the north, Boundary Bend on the Murray and arms extending southwards including Lake Tyrrell (Figure 5), an expanse of around 200 kilometres in diameter (Bowler et al. 2006).

Estimated sediment deposition rates into Lake Bungunnia from tributary rivers in the region suggest that the catchments of the lake were relatively stable for the bulk of the water body’s life (between 4 and 7 millimetres per thousand years (Bowler et al. 2006)). The rainfall and runoff necessary to maintain a lake of the size of Bungunnia for almost 2 million years suggests the climate must have been considerably wetter or less evaporation than experienced in today’s climate, with a humid climate and vegetated slopes.

6

Figure 4: Near-maximum extent of Lake Bungunnia in Murray Basin (Source: Bowler et al. 2006).

The fluvial and lacustrine environment of the diminishing Lake Bungunnia and surrounding rivers led to the formation of the relatively thin but hydrogeologically important Blanchetown Clay unit; a mottled silty to sandy clay with quartz sand and gravel beds. Sitting above the Parilla Sand, deposition of Blanchetown Clay followed palaeo-topographic depressions which led to varying depositional thicknesses of a few metres to around 50 metres in the centre of the water bodies (Bowler et al. 2006). The Blanchetown Clay unit acts as a regional aquitard to around a topographic level of 65 metres AHD (Australian Height Datum), which is considered the maximum height of the Lake. Blanchetown Clay is extensive in the Mallee region, but can be seen eroded entirely in places along Murray flood plain largely between Lamberts Island/Karadoc and Curlwaa (SKM & AWE 2003).

Hydraulic conductivities in the Blanchetown Clay are thought to be approximately 0.003 metres per day in the horizontal direction, and 0.0003 metres per day vertically (Aquaterra 2009). This is a significantly lower conductivity than the surrounding materials, so the Blanchetown Clay is locally an aquitard, or barrier to widespread flow. This is particularly important for vertical flow, specifically, leakage from irrigation is often slowed down by the presence of Blanchetown Clay delaying the impact of irrigation on the occurrence of river salinity. Small areas where the Blanchetown Clay has been eroded e.g. Red Cliffs and Merbein, provide direct access of surface and irrigation waters to the underlying saline aquifers.

The fossil fish species evident in Blanchetown Clay and the absence of prevailing saline sediments indicates that Lake Bungunnia was predominantly a freshwater environment during deposition of the bulk of the Blanchetown Clay, while the lake probably moved toward becoming saline at end of its life as indicated by the gypsum component of the Clay (VEAC 2008).

7

Figure 5: Aerial topographic imaging of the palaeo-lake shore of Lake Bungunnia (dashed line) near Swan Hill, Victoria. The basin of the modern Lake Tyrrell is visible in light blue (Source: Bowler et al. 2006).

By around 1 million years before the present, the Australian continent had seen the extinction of the Mega-fauna, and the regressing of the Pliocene shore had arrived at Naracoorte in South Australia. The frequency of the still oscillating sea level cycle had lengthened to around 100 000 years (Bowler et al. 2006).

Around 600 000 years ago, the Pinnaroo Block containing Lake Bungunnia was hypothesised to have been breached, causing the lake to drain (Bowler et al. 2006). Ancient rivers draining the palaeo-Murray Basin into the sea incised channels into sediments deposited by the sea and Lake Bungunnia. Cutting through the Blanchetown Clay and Parilla Sand, the river re-worked deposited Parilla Sand sediments to create the Monoman Formation, or Channel Sand Aquifer within the Murray River Trench. The Monoman Formation consists of fine to coarse sand and gravel and is an aquifer confined to the incised channel extent. Thickness of this unit is generally between 2 to 40 metres and assumed to average 10 meters thickness in the Sunraysia region (SKM & AWE 2003). Salinity within the Monoman Formation ranges from less than 1000 µS/cm close to the river to 100 000 µS/cm (Aquaterra 2009). Hydraulic conductivities in the aquifer are thought to be around 15 metres per day in the horizontal direction, and around 1.5 metres per day vertically (Aquaterra 2009). Thus, this aquifer (where present) provides a direct and high degree of connection between the salt store and the River.

In more recent times the Murray River has incised through the river trench leaving a generally lower elevation floodplain environment. Within the Victorian Mallee there is significant interaction between the river and this aquifer, with fresh water flowing out of the river (river as a recharge feature) as well as salt water flowing to the river (river as a discharge feature) at different locations along the river (refer Mallee Salinity Workshop Chapter 3: Salt Interception Schemes and Instream Processes). This is in contrast to further downstream in South Australia where the river is essentially a groundwater discharge feature (Figure 6).

8

Figure 6: Conceptualised hydrogeological cross-section of the Murray River floodplain at Lindsay Island, Victoria.

The Monoman Formation is shown in this diagram as the Channel Sand Aquifer and represents the incision of the river through Blanchetown Clay and Parilla Sand after the draining of Lake Bungunnia (Source: SKM 2000).

As the coast of the previous sea approached the current shoreline location, the modern alluvial unit of the Coonambidgal Formation (Fine Alluvium in Figure 6) was being deposited in river valleys and floodplains of the major waterways in the Mallee and western Murray Basin, overlying the Monoman Formation (Channel Sand Aquifer in Figure 6). The Coonambidgal Formation contains unconsolidated silt, silty clay, sand and gravel units, and is around five metres thick. The Coonambidgal Formation is thought to act as an aquitard on top of lower river terraces (SKM & AWE 2003). The floodplain consists of a sequence of four alluvial terraces which represent periods of changed base levels due to sea level rise and fall (VEAC 2008). The youngest of these terraces was formed through deposition by modern rivers in their channels and floodplains along the Murray and its tributaries (Figure 7).

9

Figure 7: Landforms interpreted from DEM data for River Murray near Lake Victoria showing Multiple Terraces and Complexity of Erosion and Deposition (Source: Clarke et al. 2008).

10

Figure 8: Cross-section of the Murray Trench typical of the Nangiloc-Colignan Reach. Terracing and erosion of the Coonambidgal Formation. The underlying Monoman Formation is largely preserved. Incision of the Murray Trench has eroded the Blanchetown Clay situated on the northern bank of the Murray Trench due to the upward lift of the adjoining Neckarboo Ridge providing direct connectivity with underlying saline Parilla sand (Source: SKM & AWE 2003).

South of Lamberts Island/Karadoc Swamp, widespread land subsidence has occurred and the floodplain sediments of the Murray, the Monoman and Coonambidgal, have spread over a wide area on top of the Blanchetown Clay as illustrated in Figure 8.

The recession of Lake Bungunnia, some 500 000 years ago, marks the end of a relatively wet phase. Drying of the lake was accompanied by aeolian (wind-driven) processes that generated an extensive system of dunes and lunette features in the Mallee. Since then the climate underwent a series of oscillations from wet to dry (dune building) conditions.

The cycle of change, between cold and arid with warm and humid climatic conditions, has influenced the development of sediments (aeolian versus alluvial) and the trapping of salt in the landscape. There have been four dune-forming periods in the last 400 000 years, spaced 100 000 years apart (Figure 3). A closer look at the drying and wetting cycles around the Willandra Lakes (to the north east of the Victorian Mallee) over the last 50 000 in Figure 9, illustrates periods of high salt phases corresponding to dune formation during the dry climatic periods. At various times in geological history, the active salt phase appears dormant where this is little salt expression in the landscape. This appears to correlate with periods of wet climates with high freshwater levels and abundant tree growth (Bowler 1990).

Further to this, excavations of Mallee dunefields produce layers of red calcareous (also called calcium carbonate or limestone) soils demonstrating episodes of rhythmic change from dry to wet conditions, corresponding with active and dormant salt cycles while these dunes were forming over the last 500 000 years (Bowler 1990).

Episodes of salinisation that are now reappearing in the landscape (as illustrated in Figure 9) are thought to be a human initiated re-activation of much older patterns through clearing of vegetation and irrigation. Therefore it is important to understand the recent history of hydrogeological processes locally and their influence on salt mobilisation and expression in the landscape.

11

Figure 9: Water level oscillations from the Willandra Lakes over the last 50 000 years showing Dune-Building and Freshwater Phases. As the climate dries, surface water evaporates, lake levels fall and groundwater levels drain into the lake system and concentrate to produce a highly saline lake floor. These saline conditions create small clay aggregates that are picked up by strong winds to form lunette dune features on the eastern margins of remnant lake systems (Source: Bowler 1990).

During the period of episodic aeolian processes, Parilla Sand and Blanchetown Clay sediments were blown from the surface of the lake floor and re-worked into the Woorinen Formation, a unit of orange-brown sand and silty clay forming linear dunes that still dominate the Mallee lanscape. The Mallee dune fields are a distinct feature in the landscape with east-west orientation and relatively low elevation (2 to 10 metres high) with rounded crests and flanks and regular spacing. The Mallee dunes, which are more common on the south side of the Murray River, vary in thickness, sediment composition and subsequent erosion rate (SKM & AWE 2003; Aquaterra 2009). Since deposition, the Woorinen Formation has been impacted by the watertable and weathering processes producing calcrete, gypsum and carbonaceous material within the formation (SKM & AWE 2003).

Further re-working of the Woorinen Formation and Parilla Sand sediments created the Lowan Sands siliceous dune fields. These dunes are distinctive in their irregular parabolic shape often occurring in nested groups with several ridges and crests overlapping (Figure 10). Their height normally exceeds the east-west dunes of the Woorinen Formation, commonly exceeding 30 meters. These dunes are prone to wind erosion due to the fine grade of yellow quartz sand that is loosely packed with very little clay content. Extensive belts of Lowan Sands dune fields dominate the Big Desert and Sunset Country (Aquaterra 2009). The Woorinen Formation and Lowan Sand units form the dunes around the Hattah Lakes. The modern day Hattah Lakes sit in the basin of what was once a ‘mega’ Lake Hattah, of around 50 square kilometres, formed during a period of wetter climate (VEAC 2008). The size of the lake and estimated river flows in this period suggest it was a freshwater body. There are several phases of dune formation over-printed in this area. Recent crescent dunes over-print source bordering dunes and lineal dunes, indicating a very complex aeolian pattern.

12

Figure 10: A satellite image of parabolic siliceous dune fields of Lowan Sands (Source: Mallee CMA unpublished).

13

2 Influence of tectonic movements

Tectonic movement through faulting in the Mallee region has played a major role in both large and small scale geomorphology through altering erosion and depositional patterns, though these influences are secondary compared to those from the geological time scale sea level changes. Along the River Murray, fault lines created troughs and ridges in the geology that have influenced the surface expression of sediments, the distribution of hydrogeological units and the various changes in course of the River Murray in general. The impact of modern irrigation practices and salt interception schemes (SIS) are also dependent to some degree on the local tectonic movements as the shifts in the landscape create pathways for underlying saline waters to rise to the surface.

In general, the major episodes of faulting that can be seen reflected in surface geomorphology occurred after the deposition of the Parilla Sand, beginning about 3.7 million years ago (Bowler et al. 2006) and continuing through the deposition of Blanchetown Clay but ceasing before the incision of the Murray Trench and deposition of the Monoman Formation (Thorne et al. 1990a; SKM & AWE 2003).

It is possible that this period of tectonic activity coincided with the vulcanicity that created Victoria’s western volcanic district, beginning approximately 4 million years ago.

Three main faults have impacted the Mallee region; the Danyo, Neckarboo and Tyrrell Faults, all running roughly northeast-southwest, the location and extent of which are shown in Figure 4 above.

The predominant movement along the Danyo and Tyrrell faults was downwards (i.e. normal faulting) with the downthrown block on the eastern side. This subsidence along the Danyo Fault created the Koorlong Trough, and along the Tyrell Fault created a large basin of deposition roughly centred on Lake Tyrrell (SKM & AWE 2003). The Neckarboo Ridge (more pronounced in NSW) was uplifted relative to the surrounding landscape with the trough to the east hosting the Willandra Lakes complex. The Leaghur Fault to the east marks the division of the Riverine Plain from the Mallee.

The Danyo Fault, the most westerly of the three major faults, is situated to the east of Merbein Ridge. This regional fault had a down throw of up to 20 metres on the eastern side creating the Koorlong Trough (SKM and AWE 2003). Within the Koorlong Trough the Parilla Sand is markedly thicker and provides a zone of relatively high transmissivity. Lock 11 lies over the approximate centre of the Koorlong trough where the thickness of Parilla Sand reaches 50 metres. Thick regions of Blanchetown Clay are also present on the eastern side of the Danyo Fault, except where it has been completely eroded in the Murray Trench upstream of the fault (SKM & AWE 2003).

The Neckarboo Ridge is an uplift structure of up to 40 metres in the northern end to 65 metres at the southern extent. Within the River Trench it appears that the upward lift of the structure has eroded the Blanchetown Clay on the northern side of the Murray Trench. This has had a major impact on the hydrogeology of the local area by allowing access of the incised river channel to the saline Parilla Sand aquifer directly beneath the River Murray as illustrated in Figure 8. As well, the general uplift has caused the Parilla Sand to thin causing an upward gradient towards the River. The salt discharged to the Murray River at this point from the groundwater upwelling due to the Neckarboo Ridge has been illustrated in River salinity plots around Red Cliffs/ McFarlane’s Reef (Collett 1978). This salt inflow led to the development of the Mallee Cliffs SIS to intercept the groundwater and divert it to inland disposal basins (SKM & AWE 2003), refer Mallee Salinity Workshop Chapter 3: Salt Interception Schemes and Instream Processes.

A barrier to westerly groundwater drainage along the River Murray was created when the Tyrrell Fault tilted/dropped its upstream block, forming the Robinvale Ridge (Thorne et al. 1990a). The effect of this in groundwater flow patterns and river patterns can be seen in the floodplain extent up- and downstream of the Tyrrell Fault line (SKM & AWE 2003; Thorne et al. 1990b), with the upstream floodplain being much wider. It is interesting to note that some of the major early irrigation developments are associated with major fault features. Mildura (Danyo/ Neckarboo fault), Robinvale (Tyrell fault) and Nyah (Leaghur fault) irrigation district are closely associated with fault structures and coincide with groundwater gradient to the river.

14

3 Groundwater flow There are three main regional aquifers in the Mallee, namely the Parilla Sand, Murray Group Limestone, and Renmark Group. The Parilla Sand aquifer, being the upper-most aquifer, is of relevance to land management and is dominant in influencing salinity processes and in dictating suitable management responses. The Parilla Sand Aquifer spans across a significant area starting at the margins of the Mallee region (the presence of Parilla Sand defines the extent of the dunefields that give the Mallee landscape its name). The aquifer is largely unconfined to semi-unconfined (delayed drainage) but may be semi-confined where it is overlain by a thicker development of Blanchetown Clay.

Figure 11: Flow Directions in the Parilla sand Aquifer (Source: MDBC 1999).

At the Basin level the direction of regional groundwater flow is dominated by the saucer-shaped features of the Murray (Geological) Basin (Evans et al. 1990):

1. The Basin is a closed system and groundwater drains to its lowest point in the central west, rather than directly to the sea. Regional groundwater flow in the Parilla Sand is generally from the margins of its extent in the Mallee, towards the west (Figure 11).

2. The River Murray also drains to the lowest point in the central west providing the only natural pathway for removing groundwater and dissolved salts out of the Murray-Darling system.

3. The sedimentary layers within the Basin are largely saturated with water tables occurring near the surface. Hydraulic gradients are very flat, mirroring the topography, and groundwater levels rise rapidly in response to any increase in recharge.

4. Groundwater is contained in the sediment profiles and can only be released through seepage into the river system (river salinity) or evaporation where the water table reaches the ground surface and the salt concentrates (land salinisation). Evaporation at inland discharge basins represents

15

only a small proportion of the water lost. Most of the water loss occurs through groundwater flow to the central west of the Basin.

At a regional scale the Parilla Sand aquifer is very flat with a fall in head of less than 80 metres from Wycheproof to Renmark, a distance of approximately 350 kilometres. This low hydraulic gradient together with its high hydraulic conductivity (or permeability) means that the Parilla Sand aquifer is responsive to recharge events where the effects of rising groundwater levels may be seen across a vast area. The River Murray provides the only natural pathway for removal of saline groundwater out of the Mallee.

Local groundwater flow systems are defined by areas where recharge and discharge occur in close proximity to one another and may occur across individual sand dunes scattered across the Woorinen and Lowan Sands Formation with discharge occurring at the break-of-slope of the dune. Thus groundwater flow paths in these instances are short and the entire flow system generally spans less than 5km. These areas can be important in land management activities and the management of localised salinity occurrences, but are not regionally connected to major groundwater flow systems. Understanding the connection of the Woorinen / Lowan areas with broader salinity impacts is a significant issue for dryland salinity management. This is further addressed in the Mallee Salinity Workshop Chapter 4: Dryland Salinity Drivers and Processes.

The current salinity management programs have been based on a sound understanding of the influence of the geomorphology on the regional groundwater recharge and discharge processes and their interaction with land use activities.

16

4 Groundwater recharge and discharge processes

Recharge to the Parilla Sand aquifer is the principal driver of groundwater movement and salt mobilisation in the Mallee. Recharge of the aquifer is via two means: localised downward leakage by rainfall / irrigation or by lateral movement within the aquifer originating from rainfall in areas associated with the extent of the Parilla Sand. The Murray River may also provide recharge of floodplain areas in reaches where the river is higher than the adjacent groundwater level and is considered to be a ‘losing’ stream. This recharge occurs as flow out of the Monoman Formation.

The semi-arid climatic conditions that prevail in the Mallee mean that only major rainfall events and /or extended high rainfall periods have a significant impact on recharge to the groundwater system. The average annual rainfall decreases in a north-westerly direction ranging from 373 mm per year at Birchip (Station no. 077007) to 292 mm per year at Mildura (Station no. 076031). In Mildura the average evaporation rate is in the order of 2171 mm each year, more than seven times that of the average rainfall. Daily evaporation at Mildura generally exceeds rainfall on a daily basis resulting in the progressive concentration of residual salts (Figure 12).

0

20

40

60

80

100

120

140

Janu

ary 20

11

Janu

ary 20

11

Mar

ch 2

011

April 20

11

May

201

1

May

201

1

June

201

1

July 2

011

Augus

t 201

1

Septe

mbe

r 201

1

Octob

er 2

011

Nov

embe

r 201

1

Dec

embe

r 201

1

Janu

ary 20

12

Febru

ary 20

12

Mar

ch 2

012

April 20

12

Da

ily r

ain

fall

and

eva

po

ratio

n (

mm

) Daily Rainfall (mm) Daily Evaporation (mm)

Figure 12: Mildura airport (Station no. 076031) daily rainfall and evaporation data for 2011-12 shows that only major events exceed evaporation rates (source: Bureau of Meteorology

1).

Recharge increases the hydraulic pressure on the underlying saline Parilla Sand aquifer forcing this salt towards discharge sites either inland or into the River. In some of the inland discharge sites, evaporation of millennium has caused salinity increases to the point where such lakes start to precipitate salt (such as at Lake Tyrrell and others). This results in highly concentrated salt water settling into the aquifer under these lakes. Over long times the amount of water that discharges from the aquifer is closely dependant on the amount of recharge. Within the Parilla aquifer the amount of recharge is relatively constant when measured over long times and the flow system in the aquifer is in equilibrium. Changes in the rate of recharge from rainfall or irrigation activities throw out this equilibrium. The effects of the change are transmitted to the discharge zone until the aquifer flow system can attain a new equilibrium.

1 http://www.bom.gov.au/climate/

17

Prior to European settlement of the area, only small amounts of recharge were able to pass below the roots of the native vegetation, due to its highly evolved and extensive ability to access and utilize available soil moisture. This was altered by the widespread landscape changes brought about by European settlement, during which approximately two thirds of the area was cleared for dryland agriculture and irrigation commenced immediately adjacent to the River. Cleared areas have higher recharge rates, typically 10 to 100 times higher than areas of native vegetation, while under irrigation, recharge rates can increase by a further order of magnitude up to 1000 times greater than recharge under native vegetation (Allison et al. 1990; Cook et al. 2001). For example, irrigation recharge can be up to 300 mm/yr whereas native recharge can be as low as 0.01 mm/yr. This increased recharge through changed landuse and irrigation has resulted in the formation of groundwater mounds associated with irrigation districts. In this way European settlement has changed the balance of the aquifer flow system and thus re-activated natural discharge systems until a new equilibrium is reached. The changes observed over the last 150 years of European occupation are similar to those that would have occurred naturally as a result of climatic changes but have been condensed into a much shorter timescale.

Depending on the geological features of the underlying sedimentary layers, it may take some time for the localised recharge events to reach the watertable especially when the aquifer is deep and there are large depths between the recharge and water table. The depth to the watertable in the regional Parilla Sand aquifer in some parts of the Mallee region may be greater than 10 metres. This means that the increased recharge resulting from land-use change may not yet have reached the watertable, particularly in dryland areas. An estimate of time required for post-settlement impacts to influence the water table in these areas ranges from 12 years to over 200 years (Figure 13; REM 2005).

In the Mallee region, groundwater discharge commonly takes the form of small salinas2 scattered throughout the Mallee landscape or in the large groundwater discharge complexes, the boinkas3. There are many examples of natural discharge basins throughout the Mallee. The size of the salina is reflective of the past groundwater conditions and generally reflect proximity to the watertable and the volume of discharge over time. However the largest discharge feature in the Mallee region is the River Murray and eventually receives most of the salt moving down-basin via the regional groundwater systems (Macumber 1990).

2 Salinas – a saline spring or marsh that intercepts the saline water table; these discharge features are commonly

scattered throughout the Mallee dunefields (MDBC 1990) 3 Boinka – a regional groundwater discharge complex; a broad, shallow depression containing its own distinct suite of

landforms including sand plains, gypsum flats, gypsite hills, salinas and various types of bordering dunes.eg. Raak and Pink Lakes Boinka (Macumber 1991)

18

Figure 13: Time of Recharge Pulse to reach the Watertable. Drainage rate, depth to watertable and clay thickness determines the time it takes for a recharge pulse to transit to the unsaturated zone (Source: REM 2005).

19

5 Groundwater level trends

An annual groundwater monitoring program is undertaken by the Mallee CMA for a network of selected groundwater monitoring bores across the Mallee dryland, irrigation areas and floodplains. This monitoring event collects salinity and groundwater level information and compliments the state-wide monitoring of groundwater levels through the State Observation Bore Network (SOBN).

Recharge from irrigation areas of the Sunraysia pumped districts, are evidenced with high groundwater levels adjacent to local discharge basins such as Cardross Lakes (Figure 14; bore 7743). However with the introduction of the water use efficiency program within the framework of the Sunraysia Salinity Management Plan (1992) there has been a marked improvement in the water use efficiency of irrigation systems and targeted water application to better meet crop requirement and soil water holding capability (This is further addressed in the Mallee Salinity Workshop Chapter 5: The Irrigation Footprint Sunraysia). This can be seen as a gradual decline in groundwater levels in irrigated areas commencing around 1995 for many bores in irrigated areas. The low allocation rates and extended dry period further facilitated wide spread adoption of water saving strategies while some properties were abandoned. The driest period was experienced in 2010 where groundwater levels were at their lowest in many parts of the Mallee (Figure 14).

The salinity impact zoning scheme implemented under the Nyah to South Australian SMP (1994) provided a strategic approach for irrigation development with the premise of minimising the level of groundwater discharge to the River by directing new development to areas away from the River (Thorne et al. 1990a) . This plan was based on the geological structures and groundwater flows discussed earlier and is further addressed in the Mallee Salinity Workshop Chapter 5: The Irrigation Footprint Sunraysia). This has ensured that while there has been a large expansion of irrigation in the Mallee region the regional groundwater trends have remained relatively stable in the private diversion areas (Figure 15). Groundwater levels in the Nyah district show that there is a gradient away from the river with highest levels closest to the river. The effects of irrigation may have slowed the temporal decline in groundwater levels relative to other areas (Figure 15; bore 26158).

35

36

37

38

39

40

1981 1986 1992 1997 2003 2008

Rela

tive g

roundw

ate

r le

vel (m

AH

D)

7743 Cardross Lakes - 30m deep 7695 Calder Hwy - 30m deep 7740 Nursery Ridge Rd - 30.3m deep

Figure 14: Groundwater bore hydrographs – ground water responses to high summer rainfall event in 2011 under irrigated areas, Red Cliffs (Mallee CMA unpublished).

20

In February 2011 some areas in the Mildura district (notably Mildura, Merbein, Irymple and Red Cliffs) experienced an unprecedented single rainfall event receiving up to 300mm within a 30 hour period. Official records include: 187.4mm at Mildura Airport (Station no. 076031); 197.0mm at Irymple (Station no. 076015); and 239.8mm at Red Cliffs (Station no. 076052). With some parts of Sunraysia receiving more rain in two days than the total average annual rainfall (288mm), the irrigation drainage & stormwater drainage systems (including stormwater retention basins) were completely overwhelmed and many areas experienced extensive flooding and prolonged surface water pooling.

Groundwater levels indicate a relatively quick response to this groundwater recharge event in the underlying Parilla aquifer. Subsequent measures indicate that the groundwater levels are returning to their previous trend however the recharge effects may not have been fully realised to date with inland discharge basins e.g. Cardross Lake retaining high groundwater levels (Figure 14; bore 7743).

Increased recharge rates are evidenced by the gradual increase in groundwater levels over the long term like those observed near the natural regional discharge site Lake Tyrell, where groundwater levels show a gradual incline over a long period (Figure 15, bore 26160). This increase in groundwater level is observed for many groundwater bores in the Mallee dryland, though the increase is not large (generally less than 2 metres). Decadal fluctuations in rainfall patterns also affects groundwater levels in dryland areas, with water levels at some bores in the regional Parilla Sand aquifer appearing to be only now finishing a response to the very wet period of the middle 1970s (for instance, Figure 15, bore 26160).

53

54

55

56

57

58

59

60

61

1984 1989 1995 2000 2006 2011

Rle

ative g

roundw

ate

r le

vel (m

AH

D)

26157 irrigation area (MVHwy) - 31m deep 26158 Irrigation area (central) - 25.48m deep

26159 irrigation (inland margin) - 25.3m deep 26160 Dryland - 29m deep

Figure 15: Groundwater bore hydrographs - responses to groundwater levels in the Parilla sand aquifer (Mallee CMA unpublished). Bore distance from the river increases sequentially with 26157 being closest and 26160 being furthest from the river. The slowed rate of decline observed for Bore 26158 may be due to the influence of irrigation on groundwater recharge processes.

6 Estimating River Murray salinity – pre-development

Aquaterra (2009) modelled the pre-development salt load input to the River from Nyah to Lock 7 to be in the order of 285 tonnes per day (t/day) and further estimating that 185 t/day are derived from Victoria and 100 t/day from NSW. The total salt discharge is in the order of 105 000 tonnes per year.

21

Aquaterra (2009) have mapped simulated groundwater elevation contours across the river in an attempt to determine the “Pre-Development” groundwater situation being post-locking, but no dryland clearing, no irrigation and no SIS.

This information has been used to indicate where the groundwater elevations would lie in relation to the River water levels under natural conditions (no locks), to indicate heads of groundwater relative to the River (Figure 16).

Under natural conditions (pre-development) the typical Murray River winter flow was about 50,000 ML/d and in summer about 10 000 – 15 000 ML/d. Figure 16 suggests that for much of its length in the Mallee Zone, the River was either recharging the watertable (groundwater less than river elevation), or was at least in equilibrium with the watertable.

Prior to locking and irrigation, it is thought that the river would have recharged the groundwater system under most flow regimes (SKM & AWE 2003). The Geoscience Australia AEM atlas from Nyah to Karadoc and from Merbein to the Border (Karadoc to Merbein was not surveyed) shows that continuous flush zones (zones of fresh groundwater adjacent to the river channel), containing water of less than 3000 EC exist sporadically over the length of the River except for the Tooleybuc to Wakool Junction sector. This is further supported by stable isotopic and age dating work carried out by Cartwright et al. (2010).

With river regulation and the contemporary reliance on river water for irrigation and potable water use there has been an increased focus on river salinity. Salt inflows are closely monitored and river flows managed to ensure the water quality is maintained to the contemporary acceptable standards (i.e. 800 EC for 95% of the time at Morgan, South Australia). The change in the amount of salt inflows and their timing is likely to be very different to conditions that existed during pre-European times which may affect species composition for native vegetation that has evolved over time especially on the river edge of the floodplain.

Geological features such as the Danyo and Tyrrell Faults, had a major influence on salt load to the river under natural flow regimes pre-development. Zones of more saline groundwater with salinity levels of ~25,000 EC, may have discharged to the river at times of low flow under pre-development conditions resulting in significant additional salt loads and salinity levels.

While there is some uncertainty in the confidence of the pre-development salt load estimate as proposed by Aquaterra (2009) it is the current agreed input to the modelled salinity impact for Mallee Legacy of History including in the Basin Salinity Management Strategy Register B.

With the construction of Locks and Weirs along the length of the Murray River, the water levels in the weir pools were elevated above natural levels at low flows as shown by the steps in water levels in Figure 17. This has enabled large pumps to extract water with a degree of certainty of supply. However these increased weir pool water levels have also imposed a very large head on the groundwater system as is apparent by the increased groundwater elevations near irrigation districts (IDs) around Mildura. The Robinvale ID probably has too small a footprint to register at this scale, and its location partly above a thick sequence of Blanchetown Clay possibly means that its effect on regional groundwater levels is muted.

22

Figure 16: Pre-development Murray River levels versus regional groundwater at different flow rates. NOTE: The rapid change in groundwater level between Robinvale and Wemen is probably associated with the Tyrrell Fault and particularly the change from confined to un-confined aquifer conditions.

Figure 17: Post-development Murray River level versus regional groundwater in the Parilla Sand. At high river flows the weirs are removed and river elevations return to those of their natural level for flows of 50 000ML/day (Source: Lock levels from MDBA River Information Centre (http://www.mdba.gov.au/water/river_info) and non-locked river levels from Stations 409204C, 414200A and 414203C).

http://www.mdba.gov.au/water/river_info

23

7 Landscape processes in the Victorian Mallee that influence salt mobilisation & contemporary salinity management

Identifying and understanding the key salt mobilisation processes and the groundwater recharge and discharge responses is fundamental to determining suitable mechanisms to address the salinity problem. Figure 18 provides a conceptual diagram of the water cycle and key surface and groundwater processes at play within the Mallee region. While the regional groundwater flow process, hydrogeology and aquifer distribution have been well understood for decades, and have greatly influenced salinity management in the Mallee to-date, work continues on the finer details of surface water and groundwater movement and interaction to improve the confidence and accuracy of salinity estimations. An area of intense study is groundwater flow on the floodplain, as further discussed in the Mallee Salinity Workshop Chapter 2: Floodplain processes. Other processes are addressed in further detailed within the Mallee Salinity Workshop chapters.

In some areas, in order to design specific control measures, further detailed data collection may be required to better understand the groundwater responses to localised processes at play.

Key areas of ongoing interest include:

Detailed stratigraphy in the Parilla Sand, especially in the vicinity of the river and salt interceptions schemes

Detail on the rates of vertical leakage between the Parilla Sand and deeper units, in order to understand the capacity for the upper aquifer to drain during periods of drought

The response of shallow watertables to large rainfall events (such as over the summers of 2011 and 2012)

Perched watertables in the Dryland Mallee (see also the dryland chapter) where these are of specific biodiversity or social consequence

Ongoing watertable response to irrigation development.

24

Figure 18: Conceptual Diagram of Landscape Processes in the Victorian Mallee (Source: SKM 2010).

25

References

Allison, GB, Cook, PG, Barnett, SR, Walker, GR, Jolly, ID and Hughes, MW 1990, ‘Land clearance and river salinization in the western Murray Basin, Australia’. Journal of Hydrology, vol. 119, pp. 1-20.

Aquaterra 2006. ‘Hydrogeological Modelling for B Register “Legacy of History” assessments in the Mallee Zone of Victoria and NSW – Eastern Mallee “EM1” Model’. Presentation, September 2006.

Aquaterra 2009. Mallee Zone 5-Year Rolling Salinity Review – B-Register ‘Legacy of History’ Assessments – Eastern Mallee Model Version 1.2 (EM1.2). Murray Darling Basin Authority, July 2009.

Bowler, J 1990, ‘The last 500,000 years’, in Mackay, N & Eastburn, D (eds.) The Murray. Murray Darling Basin Commission. Melbourne Victoria, pp 363.

Bowler, JM & Magee, JW 1978, ‘Geomorphology of the Mallee region in semi-arid northern Victoria and western New South Wales’. Proceedings of the Royal Society of Victoria, vol. 90, pp. 5-25.

Bowler, JM, Kotsonis, A and Laurence, CR 2006, ‘Environmental evolution of the Mallee region, Western Murray Basin.’ Proceedings of the Royal Society of Victoria, vol. 118, no. 2, pp. 161-210.

Brown, CM and Stephenson, AE 1991, ‘Geology of the Murray Basin, Southeastern Australia.’ Bulletin 235. Canberra, Bureau of Mineral Resources, in Lewis, SJ et al. 2008, Assessment of Groundwater Resources in the Broken Hill Region, Geoscience Australia Professional Opinion 2008/05.

Cartwright, I, Weaver, TR, Simmons, CT, Fifield, LK, Lawrence, CR, Chisari, R, Varley, S 2010, ‘Physical hydrogeology and environmental isotopes to constrain the age, origins and stability of a low-salinity groundwater lens formed by periodic river recharge: Murray Basin, Australia’. Journal of Hydrology, vol. 380, pp. 203-221.

Clarke, JDA, Wong, CF, Pain, H, Apps, H, Gibson, D, Luckman and Lawrie, K 2008, Geomorphology and surface materials: Lindsay-Wallpolla and Lake Victoria –Darling Anabranch. Co-operative Research Centre for Landscape Environments and Mineral Exploration Open File report 23, December 2008.

Collett, K ,1978, ‘The present salinity position in the River Murray Basin.’ Royal Society of Victoria Proceedings, vol. 90, Part 1, 30 November 1978, pp. 111-123.

Cook, PG, Leaney, FW and Jolly, ID 2001, ‘Groundwater Recharge in the Mallee Region, and Salinity Implications for the Murray River – a Review’. CSIRO Technical Report 45/01. Prepared for the Murray Mallee Local Action Planning Association.

DPI 2012, ‘5.2 Siliceous dunefields (Sunset, Big and Little Desert).’ Victorian Department of Primary Industries Victorian Resources Online. Available at: http://vro.dpi.vic.gov.au/dpi/vro/vrosite.nsf/pages/landform_geomorphological_framework_5.2 Accessed 9 May 2012.

Evans, R, Brown, C and Kellett, J 1990,’Geology and groundwater’, in, Mackay, N & Eastburn, D (eds.), The Murray. Murray Darling Basin Commission, East Melbourne Victoria, pp363.

Hoxley, G 1990, ‘The Hydrogeological Framework of the Sunraysia Sub-Regional Salinity Management Plan’, Rural Water Commission of Victoria Investigations Branch Report 1990/59, November 1990.

Kotsonis, A 1995, Late Cainozoic climatic and eustatic record from the Loxton-Parilla Sands, Murray Basin, southeastern Australia. MSc thesis, School of Earth Sciences, University of Melbourne.

Kotsonis, A 1999, ‘Tertiary shorelines of the western Murray Basin: weathering, sedimentology and exploration potential’, in Steward, R (ed.) Murray Basin Mineral Sands Conference., Australian Institute of Geoscience Bulletin, no. 79, pp. 517-554,

Lewis, SJ, Roberts, J, Brodie, RS, Gow, L, Kilgour, P, Ransley, T, Coram, JE and Sundaram, B, 2008, ‘Assessment of Groundwater Resources in the Broken Hill Region’, Geoscience Australia Professional Opinion 2008/05.

http://vro.dpi.vic.gov.au/dpi/vro/vrosite.nsf/pages/landform_geomorphological_framework_5.2

26

Macumber, P 1990, ‘The Salinity Problem’, in, Mackay, N & Eastburn, D (eds.), The Murray. Murray Darling

Basin Commission, East Melbourne Victoria, pp363.

Macumber, P 1991, Interaction between ground water and surface systems in Northern Victoria.

Department of Conservation and Environment, Melbourne, Victoria, pp. 345.

MDBC 1999, Murray Darling Basin Groundwater – a Resource for the Future.

Natural Resources and Environment 2002, Shallow groundwater trends in the Mallee dryland region,

Agriculture Victoria Monitoring Report, no. 45. Bendigo, June 2002.

REM 2005, Identification of Key Environmental Assets and Risk Analysis of Groundwater Threats, Mallee

CMA Region. Resource and Environmental Management (REM) Final report for Mallee Catchment

Management Authority, April 2005.

Russ, P 1995, The Salt Traders. A History of Salinity in Victoria. The Department of Premier and Cabinet, Victoria, 1995.

Sinclair Knight Merz 2000, Lindsay River Groundwater Interception, Proposed Groundwater Model Design, Final 1. Victorian Department of Natural Resources and Environment, September 2000.

Sinclair Knight Merz and Australian Water Environments 2003, Integration and Optimisation of Salt Interception in the Sunraysia Region, Final Report, Chapter 3: Hydrogeology. New South Wales Department of Land and Water Conservation, June 2003.

SKM 2010, Murrayville Data Assessment and reporting – review of May 2004 groundwater sampling and analysis round. Sinclair Knight Merz final report for the Mallee CMA, October 2004.

SKM 2010, 10/836 Dryland Salinity Contribution to the Murray - Risk Assessment of Policy and Accounting for Salinity Impacts in the Mallee. Sinclair Knight Merz final report for Mallee CMA, September 2010. SKM Reference VW 05140.

Thorne, R, Hoxley, G, Chaplin, H 1990a, ‘Nyah to the South Australian Border Hydrogeological Project, Volume I, Text’. Investigations Branch Report 1998/5, Rural Water Commission of Victoria, June 1990.

Thorne, R, Hoxley, G, Chaplin, H 1990b, ‘Nyah to the South Australian Border Hydrogeological Project, Volume II, Cross-sections and Plans’. Investigations Branch Report 1998/5, Rural Water Commission of Victoria, June 1990.

VEAC 2008, River Red Gum Forests Investigation, Final Report, Discussion Paper – Part A: Environmental, Social and Economic Setting. Victorian Environmental Assessment Council Victorian Government, July 2008.

2. Floodplain processes Authors: Ray Evans1, Greg Hoxley1 and Keith Collett1

Mallee Catchment






Copyright


Authority 2013

Disclaimer













publication.

Publication details


Chapter 2 - Floodplain processes.


April 2013

Authors: Ray Evans1 Greg Hoxley1 & Keith

Collett1


Cover images




Table of Contents

1 Key features of the floodplain .................................................................................................................. 1

1.1 Flush zones....................................................................................................................................... 7

2 Salt accumulation and salt distribution in the floodplain......................................................................... 9

2.1 Effect of floodplain evaporation and evapotranspiration ............................................................. 11

2.2 Near-surface salt accumulation ..................................................................................................... 12

3 Consequences for floodplain vegetation................................................................................................ 13

4 Export of salt to the river and consequences for river salinity............................................................... 15

4.1 Possible exacerbated salt load returns to the river post-floods.................................................... 15

4.2 Salt wash-off from the surface during floods ................................................................................ 16

4.3 Consequences of salt accumulation in the floodplain during prolonged droughts....................... 18

4.4 Salinity Impact Zoning.................................................................................................................... 20

4.5 Shrinkage of flush zones during prolonged droughts .................................................................... 20

5 Conclusions ............................................................................................................................................. 22

6 References .............................................................................................................................................. 23

List of Figures

Figure 1: Geomorphological Units on the Floodplain in the Vicinity of Lake Victoria and Wallpolla Island

(Source: Clarke et al. 2008). .............................................................................................................................. 2

Figure 2: Profile of the Murray River at regulated flows, showing effect of weirs (locks) (Source: Lock levels

from MDBA River Information Centre (http://www.mdba.gov.au/water/river_info) and unlocked river

levels from Stations 409204C, 414200A and 414203C). ................................................................................... 3

Figure 3: Groundwater contours related to three Reaches of the Murray (Source: AWE 2007)...................... 4

Figure 4: Depth to Groundwater Wallpolla island 2008 (Source: REM & SKM 2008)....................................... 5

Figure 5: Partial Cross Section of the Floodplain at Mulcra West (Source: REM 2008). ................................... 6

Figure 6: Example of Depth of Flooding Across Floodplain (Source: REM 2008).............................................. 7

Figure 7: Example of River Murray Flush Zones. Bright blue is 0-1000 µS/cm water. Lighter blue is 1000-

3000 µS/cm (Source: Geoscience Australia 2009). ........................................................................................... 7

Figure 8: Behaviour of freshwater lenses under HIGH flow conditions (Source: Weaver 2009). ..................... 8

Figure 10: Saturated zone salt storage 0-5m below the regional water table in the floodplain region

downstream of Mildura (Source: Geoscience Australia 2009)........................................................................ 10

Figure 11: Long-Term drawdown of watertables in the Floodplain 1990 - 2009 (Source: REM 2008)........... 11

Figure 12: Soil salinity profile showing Chloride accumulation after 40 years since last leaching (Source: Jolly

2011)................................................................................................................................................................ 12

Figure 13: Effect of Groundwater Salinity on Tree Transpiration (Source: Jolly 2011). .................................. 13

Figure 14: Red Gum Growth near Bullock Swamp/Lake Iraak versus Flush Zones. Lake Iraak is the circular

lake at top left. Bullock Swamp is the elliptical shaped body below it (Source: SKM 2006 and Geoscience

Australia 2009). ............................................................................................................................................... 14

Figure 15: Generic curve of salt load return to the River after flood inundation of Chowilla. The labelled

horizontal lines indicate the flood magnitude that initiates the elevated salt load return (Source: SKM

2005)................................................................................................................................................................ 15

Figure 16: Lindsay River salt export versus Murray flow (Source: SKM 2005)................................................ 17

Figure 17: Diagram of 160 km of modelled floodplain between Lock 5 to Morgan analogous to an

evaporation basin (Based on SKM 2010)......................................................................................................... 18

Figure 18: Simulation of groundwater salinity between Lock 5 and Morgan i.e. ’Normal‘ Conditions (Source:

SKM 2010). ...................................................................................................................................................... 19

Figure 19: Groundwater Salinity in the Floodplain with a 30-year Dry Period b/w Years 70 and 100. During

the Dry Period groundwater seepage to the River is zero (Source: SKM 2010). ............................................ 19

Figure 20: Groundwater level and transpiration at distance from the River Murray (Source: Lamontagne et

al. 2005). .......................................................................................................................................................... 21

List of Tables

Table 1: Salt Loads and Estimated Reductions due to C-Dry Floods (Source: SKM 2010). ............................. 16

Table 2: Modelled flows and salt loads, with extrapolation to estimate the wash-off in the Lindsay area. .. 17

Introduction

The Floodplain in the Mallee Region of Victoria is a geomorphological feature associated with the River

Murray and its tributaries. The precise extent of the floodplain is difficult to describe, but in common usage

in the Mallee it refers to the area of the landscape over which the river has flowed in geological time and in

which there are river-deposited sediments that can be attributed to the Murray River and previous rivers in

the geological past that occupied the same general corridor as the present Murray. A consequence is that

the floodplain does not always carry flood water from the current River Murray.

Over the years there has been a growing awareness that, as far as the river is concerned, the floodplain is a

key area where a number of hydrogeological processes operate that have the potential to influence future

outcomes of salinity management activities and river operations. For a basic description of the geological

setting of the floodplain, refer to the Mallee Salinity Workshop Chapter 1: Geology and Hydrogeology.

Research and investigations into floodplain processes has mostly occurred in the last decade. However, of

note is a major study undertaken by Thorne, Chaplin and Hoxley in the 1970s which underpins much of the

understanding to date. However the understanding is still incomplete due to the highly complex nature of

the floodplain area and additional research is required to develop conceptual models and a refinement in

the understanding of the key floodplain salinity processes.

1

1 Key features of the floodplain

The floodplain area is generally topographically low in the landscape and because of the incised River

Murray, the main recharge processes in the floodplain are from saline regional groundwater flow from the

surrounding higher regions or from fresh water flows from the Murray River.

Landforms on the floodplain are complex due to the depositional environment in which the floodplain was

formed. Periods of high sea levels caused material to be deposited within the Murray Trench, interspersed

with periods of low sea levels that eroded the earlier marine deposits. The result is a gradient of coarse

material at the base being the Monoman Formation (approximately five to six metres deep) becoming

progressively finer towards the top layer which comprises clay or fine sand in the Coonambidgal Formation.

It is estimated that up to four cycles of erosion and deposition resulting in four distinct floodplain terraces.

Figure 1 shows the range of geomorphological units that have been defined on the floodplain.

2

Figure 1: Geomorphological Units on the Floodplain in the Vicinity of Lake Victoria and Wallpolla Island (Source: Clarke et al. 2008).

3

A key determinant of floodplain salinity behaviour is the presence of weirs (often termed ‘locks’) in the River.

Figure 2 shows the profile of the river at regulated flows. As a broad generalisation, downstream of about

1000km from the River Mouth the River can be said to be ‘locked’, and upstream of 1000km, ‘unlocked’. Apart

from the weir at Euston the next weir is at Torrumbarry in the Riverine Plains sector.

Figure 2: Profile of the Murray River at regulated flows, showing effect of weirs (locks) (Source: Lock levels from MDBA

River Information Centre (http://www.mdba.gov.au/water/river_info) and unlocked river levels from Stations 409204C,

414200A and 414203C).

Groundwater flow directions relative to the River are quite variable. Figure 3 gives three images from AWE

(2007) that have groundwater contours showing respectively:

a. Flow away from the River in the Vinifera to Piangil reach;

b. Flow towards the River in the Nangiloc-Colignan irrigation area;

c. Groundwater flow more-or-less parallel to the river in the lower River near Lake Victoria.

However on a finer scale the groundwater flow patterns are variable and highly dependent on topography,

geomorphology, groundwater recharge and river height. For example, Figure 4 used spatial techniques to

map both the watertable surface and the ground surface, and then to present the differences between the

two across the floodplain downstream of Mildura. Generally the watertable is relatively flat-lying. However

groundwater elevation is shown to be affected by lock and weir structures as depicted by light green areas

(shallow groundwater due to weir pool elevations) immediately upstream of Lock 9. Similarly inundated

billabongs (shown in blue) are surrounded by high groundwater levels immediately adjacent to the billabongs

and progressively deepen with distance from these features. Comparing Figure 4 back to Figure 1, it can be

seen that the first terraces closest to the river have groundwater levels close to the surface (pale green areas)

compared with the fourth terraces that have a high thickness of unsaturated zone and therefore large depth

to groundwater level (reddish -brown).

4

a b

c

Figure 3: Groundwater contours related to three Reaches of the Murray (Source: AWE 2007).

5

Figure 4: Depth to Groundwater Wallpolla island 2008 (Source: REM & SKM 2008)

6

A further perspective on groundwater behaviour in the floodplain is given by Figure 5, which is part of a

cross section in REM (2008) investigation of salt accessions between Locks 7 & 10. It shows the seepage

flow out of the River Murray and Potterwalkagee Creek, groundwater discharge by evapotranspiration

(with the potential to salinise) and an un-named lagoon that could either be a source of recharge, or

depending on the conditions, a discharge site. The blue numerals are groundwater salinities in mS/cm, and

clearly show the progression from low salinity groundwater adjacent to the river which becomes more

saline with distance from the river.

Figure 5: Partial Cross Section of the Floodplain at Mulcra West (Source: REM 2008).

Finally, current understanding of the floodplain is based on recent work that has looked in detail at flooding

and salt responses in the lower Mallee floodplain (REM 2008). Numerical modelling and digital elevation

data has mapped the floodplain areas likely to be inundated at different flow rates. Figure 6 shows the

extent of flooding for various flow rates with less than fifty percent of the floodplain inundated with flow

rates of 60 000 ML/day. Even at 122 000 ML/day there are some areas within the floodplain that remain

above water levels. Unsurprisingly, the complex water distribution and soil interactions give rise to

complex salt mobilisation and expression.

7

Figure 6: Example of Depth of Flooding Across Floodplain (Source: REM 2008).

1.1 Flush zones

For at least two decades it has been recognised that there are persistent areas of relatively fresh water

occurring adjacent to the Murray River in large parts of the floodplain in the Mallee. These ‘flushed zones’

have been variously described and mapped from as early as 1982 (Thorne et al. 1990). The ‘River Murray

Corridor AEM Mapping Project’ (Geoscience Australia 2009) has provided information on the spatial

distribution and extent of these zones, including location and lateral extent of 0 to 1000 EC water and 1000

to 3000 EC water, as well as the thickness of the zones. Figure 7 is an example of the mapped extent and

salinity of the zones.

Figure 7: Example of River Murray Flush Zones. Bright blue is 0-1000 µS/cm water. Lighter blue is 1000-3000 µS/cm

(Source: Geoscience Australia 2009).

The significance of the flush zones for the Mallee is explained by Weaver (2009) in ‘Sustainability of

Freshwater Lenses under Major Rivers’. The study focussed on the ’freshwater lens‘ (or ‘flush zone’)

between Nyah and Colignan, that is, this behaviour occurs mainly in the unlocked sections of the River.

Weaver explains the dynamic situation in these zones with reference to high river conditions (Figure 8) and

low river conditions (Figure 9).

8

In Weaver’s words: “At high river stages the lens recharges largely by bank flow, and outward head

gradients cause the lateral margins to move away from the river. Vertical head gradients in the lens are

downward, promoting flow of fresh groundwater into the deeper Parilla Sands. At low river stages

hydraulic gradients are reversed, and the lens margins move towards the river. The groundwater from the

lens forms baseflow to the river and there may also be upward movement from Parilla Sands” (Weaver

2009).

Figure 8: Behaviour of freshwater lenses under HIGH flow conditions (Source: Weaver 2009).

Figure 9: Behaviour of freshwater lenses under LOW flow conditions (Source: Weaver 2009).

9

2 Salt accumulation and salt distribution in the floodplain

A particularly valuable data-set that illustrates the complexity of floodplain processes is from Geoscience

Australia’s ‘River Murray Corridor AEM Mapping Project’ (Geoscience Australia 2009) that mapped the salt

store in the unsaturated zone; the saturated zone 0 to 5 metres below the water table; and the saturated

zone 5 to 30 metres below the watertable. An example of the output is shown in Figure 10.

Figure 10 illustrates the complexity of the salinity distribution or salt store in a wide floodplain

environment. The area shown has no irrigation development, and shows fresher water along the river

channel (in blue, low salt store between 0 and 50 t/ha/m) and a complex distribution of saline and salinising

areas (in red, high salt store from 100 and to over 200 t/ha/m). It is uncertain how these areas of high salt

store in the higher terraces came about, for example salinities at Lake Walla Walla near the edge of the

trench are around 90 000 µS/cm. This water table is deep (5-6 metres) and old and it is not entirely clear

what hydrogeological mechanisms have been at play here to result in this feature.

An issue that has important implications is that of the degree, and mechanism, of long term salt

accumulation in the floodplain, particularly given that in dry periods the salt reaching the River via the

floodplain is generally diminished greatly. The rate of change of the salt store, and what this means for

river salinity and vegetation health, is one of the areas in which further research and investigation is

needed especially in light of the implications of environmental watering.

10

Figure 10: Saturated zone salt storage 0-5m below the regional water table in the floodplain region downstream of Mildura (Source: Geoscience Australia 2009).

2.1 Effect of floodplain evaporation and evapotranspiration

Evaporation from capillary rise and transpiration from native vegetation are key discharge processes that

affect salt storage and salt movement in the floodplain. Because the floodplain is low in the landscape

groundwater is often close to the ground surface and within capillary reach. The presence of native

vegetation allows the discharge zone below the surface to increase as the roots extract water from

underlying aquifers. (The capillary reach refers to the depth above which capillary action can transport

groundwater to the surface. It depends on the combination of soil type and vegetation. Chloride profiles in

Jolly (2011) suggest that it is at least 4 metres).

Figure 11 shows nested bore hydrographs on Lindsay Island close to the Lindsay River, where the long-term

drawdown to ’below-river‘ levels due to groundwater evaporation is apparent. Cases where such behaviour

is not apparent could be the result of:

a. The floodwaters not having access to the aquifer

b. The depth to watertable being such that trees’ ability to transpire from it is limited

c. Lack of tree cover, possibly due to soil salinisation.

Figure 11: Long-Term drawdown of watertables in the Floodplain 1990 - 2009 (Source: REM 2008).

Another factor is that small variations in natural surface elevation relative to the watertable can drive

recharge and discharge processes across the floodplain. As a result, groundwater and salinity distribution

across the floodplain can be complex.

Evans (2011) review of floodplain salinity concludes that:

• Groundwater salinity under the floodplain is more saline than the regional (input) groundwater. This

infers that there is a concentration process operating under the floodplain.

• Isotope data suggests that regional water has at some stage been subject to concentration by

evaporation, even at depth.

• Deeper salinity is always greatest.

12

2.2 Near-surface salt accumulation

Salt accumulation and potential salt discharge mechanisms are slow moving, and it depends on the time

frame of consideration whether they are classifiable as a threat to salinity levels.

Data on salt stored near the surface of the floodplain is available from a number of studies examining pore-

water salinity/depth profiles. For example, Jolly (2011) indicates that it can take almost 20 years for the salt

front to reach the floodplain surface after a major leaching event, and a further 20 years for the ‘high

surface salt’ profile to be established. This is illustrated in Figure 12.

Figure 12: Soil salinity profile showing Chloride accumulation after 40 years since last leaching (Source: Jolly 2011).

Other findings of Jolly’s work include the following:

• Small variations in elevation (which affects depth to groundwater, depth and duration of flooding)

and soil texture leads to greatly varying salt storages.

• During flood inundation the amount of leaching that occurs can be quite variable. It can be minimal if

the soil is sodic and of low permeability.

• If leaching is minimal, river recharge through the Coonambidgal Formation to the Monoman

Formation (Channel Sands aquifer) will be limited. However, where the Coonambidgal Formation is

absent, significant localised recharge can occur.

DE

PT

H (

m)

Chloride (g/L)

13

3 Consequences for floodplain vegetation

Fresh water in the floodplain is a critical resource for vegetation health and in mitigating saline

groundwater movement to the Murray River.

It is clear that the accumulation of salt in the floodplain, and the frequency of flushing by means of

flooding, have a major effect on the health of riparian vegetation. Lamontagne et al. (2012) commented

“The native riparian vegetation on many parts of the floodplains of the Lower River Murray in South

Australia is in severe decline, due to high soil salinity and lack of flooding.” Jolly et al. (1993) also made the

observation that: “Weir pools of the lower River Murray have caused the naturally saline groundwater to

rise nearer the surface in some areas, and irrigated areas nearby also have contributed to shallower

floodplain water tables. In addition, river regulation has reduced the frequency and duration of the floods

that leach salt from the plant root zone. The combined effect is long-term salt accumulation in floodplain

soils, and this, with lack of flooding per se, is a primary cause of vegetation dieback (Jolly et al. 1993).”

Jolly (2011) provides quantitative evidence of the effect of groundwater salinity on tree transpiration

expressed as groundwater discharge rates (Figure 13). Above approximately 10 dS/m (10 000 µS/cm) the

transpiration rate (a surrogate for tree health) appears to be limited to 100 mm/year, whereas under

circumstances where salinity is not a controlling factor (i.e. less than 10 dS/m) the rate of transpiration

(groundwater discharge) could be as high as 1000 mm/year.

If flooding were to occur at a reasonable frequency (e.g. more frequently than decadal timescales) then it

could be expected that groundwater salinity would remain at the lower end of the scale.

Figure 13: Effect of Groundwater Salinity on Tree Transpiration (Source: Jolly 2011).

14

Three potential categories of floodplain hydrogeology, which may have a strong relationship with

vegetation health include:

• Category 1, where the permeability of the Coonambidgal Formation is such that when flooding

occurs there is leaching of the soil profile. For this Category water availability is the key determinant

of tree health.

• Category 2, where the Coonambidgal Formation is such that when flooding occurs, leaching of the

soil profile is limited. For this Category ’accumulated salt in the soil profile‘ has been, and will

probably continue to be, the determinant of tree health unless engineered intervention in the form

of groundwater pumping is employed.

• Category 3, where the floodplain is underlain by a ‘flushed zone’ of low salinity groundwater,

vegetation health is at low risk assuming the flush zone is maintained.

Figure 14 compares the vegetation species in the vicinity of Bullock Swamp and Lake Iraak with the

conductivities as measured in the Geoscience Australia 2009 AEM Survey. Here the coincidence of River

Red Gums with the flush zones (blue and green tones) is clear. The behaviour of flush zones needs further

research to define their role in vegetation health.

Figure 14: Red Gum Growth near Bullock Swamp/Lake Iraak versus Flush Zones. Lake Iraak is the circular lake at top

left. Bullock Swamp is the elliptical shaped body below it (Source: SKM 2006 and Geoscience Australia 2009).

15

4 Export of salt to the river and consequences for river salinity

There are four aspects to be covered in this section:

1. Possible exacerbated salt load returns to the river post-floods;

2. Salt wash-off from the surface during floods;

3. Consequences of Salt accumulation in the floodplain during prolonged droughts;

4. Shrinkage of flush zones during prolonged droughts.

4.1 Possible exacerbated salt load returns to the river post-floods

The response of the Chowilla floodplain to flooding and the salt export in its aftermath has been studied by

a number of researchers. Flood inundation on the extensive Chowilla floodplain recharges the groundwater

system beneath the floodplain, such that after the flood the higher watertable is able to drive salt load into

the watercourses on the floodplain, particularly Chowilla Creek. As a consequence, above-average salt

loads enter the River via Chowilla Creek, possibly causing salinities in excess of 800 EC at Morgan in the

regulated flows that follow the flood. Figure 15 is a ’generic‘ curve of salt load versus time after a flood

event.

0

100

200

300

400

500

600

700

800

900

1000

1100

0 5 10 15 20 25 30

Month after event

Sa

lt R

ele

ase

(t/

d)

90,000 ML/d

80,000 ML/d

70,000 ML/d

60,000 ML/d

50,000 ML/d

40,000 ML/d

100,000 ML/d

Figure 15: Generic curve of salt load return to the River after flood inundation of Chowilla. The labelled horizontal

lines indicate the flood magnitude that initiates the elevated salt load return (Source: SKM 2005).

It appears in the Victorian Mallee Zone (Swan Hill to Lock 7) there is not a major ‘Chowilla-type’

relationship. The support for this statement comes from analyses of post-flood salt loads right through the

Mallee Zone as part of a study by SKM (2010). Error! Reference source not found. 1 shows the reductions

in salt loads predicted for Year 2050 in going from ‘Historic Flows’ to the CSIRO ‘C-Dry’ scenario, where

flows in the Mallee Zone, including floods, are generally 50 – 70% of Historic. Because the C-Dry flood

magnitudes are 50-70% of Historic, any sector that has exacerbated post-flood salt returns should show a

substantial reduction in salt load in C-Dry compared to Historic. It shows that the ‘Chowilla sector’ is a

stand-out in terms of exacerbated salt load returns.

16

Table 1: Salt Loads and Estimated Reductions due to C-Dry Floods (Source: SKM 2010).

Avg. Salt Load Input (t/d).

Year 2050 G/W Conditions River Reach

Historic Flows C-Dry Flows

Reduction Comment

Swan Hill to Euston 118 106 10%

Euston to Mildura 249 216 13%

Mildura to Lock 9 71 64 10%

Lock 9 to Lock 5 235 162 31% Chowilla Creek enters

Lock 5 to Morgan 598 508 15%

Morgan to Murray

Bridge 168 168 0%

There is however a minor case of elevated post-flood salt returns via Lindsay River. Figure 16 (Section 5.2)

shows elevated salt loads following the floods of 1992 and 1993 each of around 800 tonnes per day for

about one month duration immediately post-flood. Apart from the large spikes immediately following a

flood event, the monthly salt loads are not of a great magnitude and average out to 60 tonnes per day over

the total period. This is considered to be only a minor contribution to river salinity levels and 800 EC

exceedances at Morgan.

Groundwater Salt Interception Schemes (SIS) operating at Buronga, Mildura-Merbein and Mallee Cliffs

have been instrumental in ameliorating previous post-flood returns. In particular Mallee Cliffs SIS seems to

be at a site where such returns occurred prior to the Scheme’s implementation (Williams & Woolley 2000).

It appears the most immediate salinity threat to the Murray River has been dealt with by interception

schemes (Mallee Salinity Workshop Chapter 3: Salt Interception Schemes and Instream Processes).

4.2 Salt wash-off from the surface during floods

An issue that has been debated for some time is the quantity of salt that is washed from the floodplain soil

surface during a flood, and how much of this wash-off contributes to establishing a long-term equilibrium in

the store of salt beneath the floodplain? That is, given that salt is accumulating in the floodplain, does

wash-off periodically remove enough salt to prevent the accumulated salt store in the floodplain rising

indefinitely?

There is one known ‘field laboratory’ where the mass of wash-off and the area of contributing floodplain is

known – and that is Lindsay Island.

Figure 16 shows the salt export from Lindsay Island via the Lindsay River from 1991 to 2002 (SKM 2005).

The data shows that during floods the mean monthly salt load exported via the Lindsay River was

approximately as follows:

1992 Flood: 180 t/day 1993 Flood: 150 t/day 1996 Flood: 100 t/day; quite variable.

17

Figure 16: Lindsay River salt export versus Murray flow (Source: SKM 2005).

The data shows that during floods the mean monthly salt load exported via the Lindsay River was

approximately as follows:

1992 Flood: 180 t/day 1993 Flood: 150 t/day 1996 Flood: 100 t/day; quite variable.

Major over-banking occurs on Lindsay Island at flows of 67 000 ML/day in the Murray and higher (Dudding

& Evans 2001). Table 2 shows the duration of flows above 67 000 ML/day according to the MSM-BigMod

model, and the rate of salt wash-off and total load washed off in each of these three flood events. The final

column shows the tonne per hectare wash-off in each of the three events, on the basis that the area of

Lindsay Island is 20 000 ha. Viewed in the context of the existing total salt store in the floodplain, these

amounts of salt are negligible; that is, in this part of the Murray floodplain, the salt store in the unsaturated

zone is about 50 tonnes per hectare per metre depth and so 0.91 t/ha removed in a decade is only a small

fraction of the store.

In conclusion, the amount of salt mobilised during surface wash-off during floods is not a major component

of the total salt inflow-outflow balance in the floodplain.

Table 2: Modelled flows and salt loads, with extrapolation to estimate the wash-off in the Lindsay area.

Flood

Duration

>67 000

ML/day

t/day during

event Total Tonnes Lindsay Area

Tonne per ha

wash-off

1992 42 days 180 7,600 20 000 0.38 t/ha

1993 54 days 150 8,100 20 000 0.41 t/ha

1996 24 days 100 2,400 20 000 0.12 t/ha

Totals in the decade 18,100 0.91 t/ha

18

4.3 Consequences of salt accumulation in the floodplain during prolonged droughts

In a prolonged drought the drop in watertable levels in the floodplain (refer to Section 2.1) might see the

River actually recharge the watertable under the floodplain, and that there might be zero flux of

groundwater out of the floodplain into the River for the duration of the dry period. The potential for

prolonged dry periods in the CSIRO C-Dry Scenario is very substantial.

To investigate this SKM (2010) conceptualised the floodplain as analogous to an evaporation basin filled

with sand, and carried out a simulation of salinity build-up along a 160 km length of floodplain (30 metres

deep) and the River. The 160 km is the distance from Lock 5 to Morgan. Figure 17 shows the layout of the

model.

Figure 17: Diagram of 160 km of modelled floodplain between Lock 5 to Morgan analogous to an evaporation basin

(Based on SKM 2010).

The elements of the processes from left to right in the diagram are:

a. A flux from adjacent irrigation assumed to input 11 000 ML/year of water at a salinity of 30 000

mg/L, amounting to 330 000 tonnes of salt per year.

b. The groundwater beneath the floodplain. This was assumed to have a pre-settlement salinity of

only 500 mg/L, corresponding to the River recharging the groundwater.

c. Evaporation from the floodplain surface (including evapotranspiration) which draws

groundwater but not salt from the watertable to the ground surface. This process concentrates

salt in the groundwater in exactly the way that saline water in an evaporation basin becomes

concentrated. It is assumed that 30% of the input water leaves by this mechanism.

d. Groundwater seepage to the River, at a higher salinity than the input flux from adjacent

irrigation.

The long term simulated behaviour of the salt in the floodplain under ‘normal’ conditions where increases

in the watertable from irrigation, relative to the River level flooding, facilitates movement of groundwater

to the River (Figure 18). A continuation of these conditions will see the modelled aquifer salinity increase

steadily over the first 100 years and then peak and stabilise at 43 000 mg/L, sometime after Year 150.

19

Figure 18: Simulation of groundwater salinity between Lock 5 and Morgan i.e. ’Normal‘ Conditions (Source: SKM

2010).

The simulation was then used to determine what might happen to the floodplain aquifer salinity if there

were 30 years of drought conditions (as defined by the C-Dry climate record (SKM 2010)), starting at the 70

year point, followed by a resumption of a ’normal‘ flood regime. During the 30 years of simulated drought

there was no export of salt to the River and floodplain groundwater salinity increased more than the

‘normal’ scenario (Figure 19).

Figure 19: Groundwater Salinity in the Floodplain with a 30-year Dry Period b/w Years 70 and 100. During the Dry

Period groundwater seepage to the River is zero (Source: SKM 2010).

20

The simulated floodplain salinity response concluded that:

• After 30 years of drought the floodplain groundwater salinity was 13 000 mg/L higher than that

simulated under ‘normal’ conditions.

• The ‘normal conditions’ following 30 drought years did not immediately flush the floodplain

groundwater. The floodplain salinity remained elevated for decades. Depending on the flow paths

operating, this salinity can potentially return to the Murray River giving simulated salt load

accessions proportionally greater than the ‘normal’ scenario.

• Over time the floodplain groundwater salinity begins to revert towards its previous long-term

trajectory for ‘normal’ conditions (dashed grey line).

In conclusion, if prolonged drought conditions do inhibit the ability of the floodplain to pass salt through to

the River, there is potential for subsequent exacerbation of salt accessions to the River, depending on the

available flow paths to the River.

4.4 Salinity Impact Zoning

Figures 18 and 19 are useful to introduce a discussion on the Salinity Impact Zoning approach adopted

within the Nyah to the SA Border Salinity Management Plan (Mallee Salinity Workshop Chapter 5: the

Irrigation footprint Sunraysia). The discussion in Section 5.3 links the rate of salt load to the River to the

volume and salinity of the input from the irrigated higher ground - in the example 11 000 ML/year at 30 000

mg/L or 330 000 tonne per year. Typical MDBA Ready-Reckoner Factors for EC at Morgan suggest that a salt

load of that magnitude would cause a salinity increment of about 130 EC at Morgan. This is well in excess of

the salinity credits assigned to the Mallee, within which it must manage the salinity impacts caused by

irrigation under the Basin Salinity Management Strategy (BSMS). The hazard zoning has directed new

development to areas of much lower salinity impact underpinned by a region-wide hydrogeological

assessment thereby reducing the effect of irrigation development being less than 15 EC on the BSMS

Register. In effect this zoning approach has prevented the salinity threat caused by irrigation to the Murray

River.

4.5 Shrinkage of flush zones during prolonged droughts

Section 2.1 has discussed flush zones and the conclusions of Weaver (2009). Given that the groundwater in

the lens (flush zone) is essentially fresh, the lens provides a buffer between the saline regional groundwater

and the river, thus discharge occurs in the floodplain (~1 km from the river) mitigating the amount of saline

discharge to the river.

Another aspect is the availability of freshwater in these flush zones to support vegetation near river as

explained in Lamontagne et al. (2005). Here the researchers studied transects of piezometers near

Colignan. One transect ran from the river out across a ‘sandbank’ and the other across a ‘claybank’ on the

outside of a river bend. The sandbank transect exhibited much greater connectivity with the river than did

the claybank, highlighting the importance of permeability of the floodplain to the capacity for storage of

fresh water. Figure 20 illustrates this concept showing the trees nearer the River transpiring at 1 to 4

mm/day, or 370 to 1450 mm/year. It appears the trees nearer the river are utilising the flush zone water at

a higher rate of transpiration. The role and importance of these zones especially in dry times is an area of

uncertainty. Transpiration by trees could deplete the flush zone and pose challenges to its integrity. This

could be of relatively more significance in the ‘locked’ sections where River level fluctuations are more

subdued than the unlocked reaches.

21

Figure 20: Groundwater level and transpiration at distance from the River Murray (Source: Lamontagne et al. 2005).

22

5 Conclusions

1. The most immediate salinity threats to the Murray River have already been dealt with by

Interception Schemes and the Salinity Impact Zoning (see Sections 5.1 and 5.4).

2. The ‘discovery’ of the near-ubiquity presence of flush zones is a fairly recent event and warrants a

re-examination of some of the assumptions embedded in existing management arrangements. This

includes the role of flush zones in:

a. buffering the River from the more saline groundwaters inherent in the marine- deposited

strata, i.e. the Parilla Sand.

b. River EC impacts of irrigation development Nyah to the SA Border given their position in the

causal chain, i.e. Irrigation Parilla Sand Floodplain Edge Saline Monoman Formation

Flush Zones River.

c. in maintaining vegetation health, and the implications this might have for environmental

watering plans, e.g. how necessary is watering if River Red Gums are above a flush zone?

3. The accumulation of salt in the floodplain and the potential for increased export in future is still not

sufficiently understood. The modelling described in Section 5.3 suggests that the accumulated salt

load continues to increase, (and the rate might accelerate in future in prolonged droughts) and yet

there is scant knowledge of how salt leaves the floodplain. It is clear that surface wash-off is not a

major means of removal of accumulated salt. It is not known whether the accumulated salt will find

pathways to the river in future decades, or whether it will remain locked within the floodplain.

23

6 References

AWE 2007. In-stream NanoTEM 2006. Wentworth to Torrumbarry. Lindsay-Wallpolla. June 2007. Report to

MDBA and Funding Partners.

Clarke, JDA, Wong, CF, Pain, H, Apps, H, Gibson, D, Luckman and Lawrie, K 2008, Geomorphology and

Surface Materials: Lindsay-Wallpolla and Lake Victoria - Darling Anabranch. Co-operative Research Centre

for Landscape Environments and Mineral Exploration Open File Report 237. December 2008.

Cullen, K, Apps, H, Halas, L, Tan, K, Pain, C, Lawrie, K, Clarke, J, Gibson, D, Brodie, RC and Wong V, 2008,

Lindsay to Wallpolla (East) & Lake Victoria – Darling Anabranch Atlas. River Murray Corridor AEM Salinity

Mapping Project. Prepared by Geoscience Australia for the Bureau of Rural Sciences.

Dudding, M and Evans, R 2001, Soil discharge mechanism into the Murray River Floodplain at Lindsay

Island. Paper 7B4.Proceedings of the 8th Murray Darling Basin Groundwater Workshop, Victor Harbour

South Australia, 4-6 September 2001.

Evans, R 2011, ‘Flood-plain Salt Storage - Conceptualisation of its Movement’, paper presented at the

Murray Darling Basin Authority - Basin Salinity Management Strategy A Targeted Workshop on Flood

Recession Salinity Investigation, Canberra 22 July 2011.

Jolly, ID, Walker, GR and Thorburn, PJ 1993, ‘Salt accumulation in semi-arid floodplain soils with

implications for forest health’, Journal of Hydrology vol. 150, pp. 589-614.

Jolly I, 2011, Floodplain Evapotranspiration and Salinisation’, paper presented at the Murray Darling Basin

Authority - Basin Salinity Management Strategy A Targeted Workshop on Flood Recession Salinity

Investigation, Canberra 22 July 2011.

Lamontagne S, Aldridge KT, Holland KL, Jolly ID, Nicol J, Oliver RL, Paton DC, Walker KF, Wallace TA, Ye Q

2012, Expert panel assessment of the likely ecological consequences in South Australia of the proposed

Murray-Darling Basin Plan. Goyder Institute for Water Research Technical Report Series No. 12/2.

Lamontagne, S, Leaney, FW and Herczeg, A 2005, ‘Groundwater-surface water interactions in a large semi-

arid floodplain: implications for salinity management’. Hydrological Processes, vol. 19, pp. 3063-3080.

REM and SKM 2008, Broad Salt Accessions for the River Reach between Locks 7 & 10. Final Report for

Mallee Catchment Management Authority, Mildura. Project VE 30036.

SKM 2005. Review of drivers for future schemes. 800 EC exceedance at Morgan. Report prepared for the

Murray Darling Basin Commission and the Department of Water, Land and Biodiversity Conservation (South

Australia).

SKM 2006. Regional Floodplain Salt Storage and Mobilisation Processes to the Murray River. Stage 3 Report

- Salt on the Floodplain. December 2006. SKM Reference WC 03727.

SKM 2010. Risk of climate change impacts on salinity dynamics and mobilisation processes in the Murray-

Darling Basin. Report prepared for the MDBA.

Tan KP, Lawrie KC, Halas L, Pain CF, Clarke JD, Gibson D, Apps H, Cullen K, Brodie RC and Wong V 2009,

Methodology for the customised products developed as part of the River Murray Corridor Victorian AEM

Mapping Project. Prepared by Geoscience Australia for the Bureau of Rural Sciences.

Thorne, R, Hoxley, G, Chaplin, H 1990, ‘Nyah to the South Australian Border Hydrogeological Project,

Volume I, Text’. Investigations Branch Report 1988/5, Rural Water Commission of Victoria, June 1990.

Weaver, T 2009, Sustainability of freshwater lenses under major rivers. Final Report to Land & Water

Australia.

Williams, RM and Woolley, DR 2000, ‘Mallee Cliffs Salt Interception Scheme’. Assessment of Efficiency and

Downstream Impact. NSW Department of Conservation and Natural Resources Report No CNR 2000.007.

3. Salt Interception Schemes and instream processes Authors: Andrew Telfer, Rob Burnell, Alison Charles1

Mallee Catchment






Copyright


Authority 2013

Disclaimer













publication.

Publication details


Chapter 3 – Salt interception schemes and

in-stream processes.


April 2013

Authors: Andrew Telfer1, Rob Burnell1 &

Alison Charles1

1 Australian Water Environment

Cover images




Table of Contents

1 Regional salinity context ............................................................................................................... 1

2 Salt risk .......................................................................................................................................... 3

3 Salt interception schemes ............................................................................................................ 7

3.1 Mallee Cliffs SIS ................................................................................................................. 10

3.2 Curlwaa SIS ........................................................................................................................ 10

3.3 Buronga SIS ....................................................................................................................... 11

3.4 Mildura‐Merbein SIS ......................................................................................................... 11

3.5 Scheme reporting .............................................................................................................. 11

3.6 SIS types ............................................................................................................................ 12

4 Disposal ....................................................................................................................................... 15

5 Variability of salt inputs .............................................................................................................. 16

6 SIS design tools – in‐stream salinity and salt loads .................................................................... 24

6.1 Fixed Station EC recording ................................................................................................ 24

6.2 Run of River ....................................................................................................................... 27

6.3 Correlation of Run of River and Fixed Station EC Analysis ................................................ 28

6.4 AEM ................................................................................................................................... 29

6.5 NanoTEM........................................................................................................................... 31

7 Features of modern SIS design ................................................................................................... 35

8 Possible future SIS ...................................................................................................................... 37

9 Future trends under the Basin Plan ............................................................................................ 38

References ............................................................................................................................................ 39

List of figures

Figure 1. Gaining and losing floodplain, groundwater elevation and water table aquifers (AWE 2011). ................................................................................................................................................................ 5

Figure 2. Regional salt risk indicators (AWE 2011). ................................................................................ 6

Figure 3. Salt interception schemes: Murray Darling Basin 2010‐2011 (MDBA 2011). .......................... 8

Figure 4. Salt and flow at Morgan by decade (AWE 2011). .................................................................... 9

Figure 5. Salt and flow at Morgan by decade without the implementation of key SIS (AWE 2011). ..... 9

Figure 6: Mildura‐Merbein and Buronga SIS cross section (AWE 2009d). ............................................ 13

Figure 7: Modelled results of flux to and from river over a series of floods between river kilometres 871 to 875 (AWE 2012). ........................................................................................................................ 16

Figure 8: Correlation of Run of River data 2001 with NanoTEM and river features (AWE 2009d). ..... 19

Figure 9: Correlation of Run of River data 2005 with NanoTEM and river features (AWE 2009d). ..... 20

Figure 10: River bed resistivity and Run of River Mallee Cliffs to SA Border (Telfer et al. 2005b). ...... 21

Figure 11: Differences between In‐Stream salinity data for Chaffey’s Graveyard monitoring station. 23

Figure 12. In‐stream salinity stations. ................................................................................................... 26

Figure 13. Run of River ‐ cumulative salt inflows (AWE 2011). ............................................................. 28

Figure 14. Correlation between RoR and Fixed Station EC – Lock 5 to Loxton (AWE 2011). ............... 29

Figure 15. Holistic conductivity: standing water level minus 5 metres ‐ Murray Floodplain TDS (Munday et al. 2008). ............................................................................................................................ 30

Figure 16: NanoTEM Array Behind Mobile Data Platform (Photo by B Porter in Telfer et al. 2005). .. 31

Figure 17. Formation resistivity and the principles of NanoTEM (Telfer et al. 2005). .......................... 32

Figure 18. Major reaches – saline inflows and fresh water lenses from NanoTEM (AWE 2011). ........ 33

Figure 19. Key reaches ‐ saline inlfows and fresh water lenses inferred from NanoTEM data (AWE 2011). .................................................................................................................................................... 33

Figure 20. Combined AEM (AWE 2011) ................................................................................................ 34

List of tables

Table 1. Salinity Registers A and B (Pers Comm. C Diaconu 2012). ........................................................ 2

Table 2. Floodplain and river classification matrix (AWE 2011). ............................................................ 4

Table 3. Performance of salt interception schemes 2010 – 2011 (adapted from MDBA 2011). ............ 7

Table 4. Interception characteristics of the various aquifer types (Telfer et al. 2008). ....................... 14

Table 5. BIGMOD ‐ unaccounted salt inflow – daily averages (AWE 2011). ......................................... 25

1

1 Regional salinity context

The Murray Basin is a broad, flat and roughly circular basin consisting of up to 600m of Cainozoic sediments which overlie various tectonically active Palaeozoic and Mesozoic basement rocks in the lower reaches of the basin (Brown & Stephenson 1991). Most of the Cainozoic sediments were deposited during a time when the basin was partially inundated by epicontinental seas but other estuarine, fluvial and aeolian sediments are also present. Sediments within the modern river trench comprise of reworked regional aquifer sediments. These Cainozoic sediments form a series of aquifers and aquitards with groundwater salinities ranging from freshwater up to highly saline in the order of 100 000 EC. Groundwater enters aquifers by direct infiltration of rainfall, irrigation waters and from the basin margins. Groundwater salinities generally increase down gradient and to the west especially around evaporative features such as salt lakes (Telfer et al. 2008).

Essentially the Murray Basin is a closed system with little or no opportunity for discharge to the sea, other basins or aquifer systems. The major mechanism for salt discharge is through the River Murray valley including the floodplain and river itself under natural conditions (Telfer et al. 2008). The rate of saline groundwater discharge to the river valley would have been controlled by the natural recharge rate and transmissivity of regional aquifers. Locally much greater rates of recharge to aquifers and consequently a greater rate of groundwater discharge to the river valley have occurred due to the clearance of native vegetation and the proliferation of irrigation and drainage disposal systems. This also corresponds to an increase in the demand for surface water resources. These factors led to projections that salinity of the River Murray would rise above 800EC at Morgan more frequently.

In order to address this trend of increasing salinity, the Murray Darling Basin Commission in partnership with State Government Organisations implemented the Basin Salinity Management Strategy 2001‐2015 (BSMS). This set out a framework to achieve a key benchmark to maintain River Murray salinity at Morgan below 800 EC 95 percent of the time.

Under the Basin Salinity Management Strategy program, salinity credits equivalent to 61 EC will be delivered when all salt interception schemes are commissioned. In 2010–11, the operation of salt interception schemes diverted approximately 324 162 tonnes of salt from the River Murray.

Accountability arrangements outlined in the BSMS allow for four levels of assessment to track progress of achieving and maintaining salinity targets including; assigning all major works salinity credits or debits, annual progress reports regarding works and measures, five year reviews on their impacts on river salinities and review of the Strategy itself (MDBMC 2001).

Each year the Basin states inform MDBA about activities that have significant salinity effects for that year. The MDBA calculates the salinity cost of these activities and updates the salinity registers for independent review by salinity auditors. In November 2010, the auditors confirmed that the contracting governments of New South Wales, Victoria and South Australia remained in net credit on the salinity register, Register A, and in the balance of registers A and B (see Table 1) as required by the strategy. The Australian Capital Territory and Queensland at present do not have any register entries (MDBA 2010).

2

Table 1. Salinity Registers A and B (Pers Comm. C Diaconu 2012).

Ba

sin

Sa

lin

ity

Ma

na

ge

me

nt

Str

ate

gy

(Mu

rra

y-D

arl

ing

Ba

sin

Ag

ree

me

nt

Sc

he

du

le B

)U

pd

ated

Sa

lin

ity

Re

gis

ters

"A

" a

nd

"B

"

I

nte

rpo

lati

on

to

Cu

rre

nt

Ye

ar

De

term

ined

fo

r Y

ea

r =

20

11

Cu

rre

nt

Imp

ac

t o

n

Mo

rga

n

95

%ile

S

alin

ity

(EC

)

Imp

ac

t o

n F

low

a

t M

ou

th

(GL

/y)

20

00

20

15

20

50

21

00

Mo

de

lled

C

urr

en

t C

on

dit

ion

s

(In

terp

ola

tio

n

to C

urr

en

t Y

ea

r)

NS

WV

icS

AQ

ldA

CT

To

tal

JO

INT

WO

RK

S &

ME

AS

UR

ES

Fo

rme

r S

alin

ity

& D

rain

ag

e W

ork

s

Wo

ol p

unda

SIS

SD

SJa

n 1

99

1-8

70

-47

.4-4

7.4

-47

.4-4

7.4

-47

.40

.72

90

.72

93

.89

0Im

pro

ved

Bur

ong

a a

nd M

ildur

a/M

erb

ein

IS

SD

SJa

n 1

99

1-6

0-3

.0-3

.0-3

.0-3

.0-3

.00

.14

00

.14

00

.74

8N

ew

Ope

ratin

g R

ule

s fo

r B

arr

Cre

ek

Pum

psS

DS

Jul 1

99

1-8

0-4

.9-4

.9-4

.9-4

.9-4

.90

.22

50

.22

51

.19

8W

aik

eri

e I

nte

rce

ptio

n S

che

me

SD

SD

ec

19

92

-19

0-1

2.8

-12

.8-1

2.8

-12

.8-1

2.8

0.1

98

0.1

98

1.0

57

Cha

nge

d M

DB

C R

ive

r O

pera

tions

19

88

to

20

00

SD

SA

pr 1

99

3-1

4-1

.6-1

.6-1

.6-1

.6-1

.60

.15

00

.15

00

.79

7M

alle

e C

liffs

Sa

lt In

terc

ept

ion

Sch

em

eS

DS

Jul 1

99

4-2

10

-13

.3-1

3.3

-13

.3-1

3.3

-13

.30

.60

30

.60

33

.21

6C

hang

ed

Ope

ratio

n o

f M

eni

nde

e a

nd L

ow

er

Da

rling

SD

SN

ov

19

97

38

0.9

0.9

0.9

0.9

0.9

-0.1

46

-0.1

46

-0.7

76

Wa

ike

rie

SIS

Pha

se 2

AS

DS

Fe

b 2

00

2-1

40

-8.0

-8.2

-10

.7-8

.9-8

.20

.11

20

.11

20

.59

8C

hang

ed

MD

BC

Riv

er

Ope

ratio

ns 2

00

0 t

o 2

00

2S

DS

Fe

b 2

00

2-2

-1-1

.4-1

.4-1

.7-1

.9-1

.4-0

.14

0-0

.14

0-0

.74

5S

ub

To

tal -

Fo

rme

r S

alin

ity

& D

rain

ag

e W

ork

s-1

54

11

-91

.6-9

1.8

-94

.6-9

3.0

-91

.81

.87

21

.87

20

.00

00

.00

00

.00

09

.98

3B

as

in S

alin

ity

Ma

na

ge

me

nt

Str

ate

gy

Cha

nge

d M

DB

C R

ive

r O

pera

tions

aft

er

20

02

BS

MS

De

c 2

00

31

7-0

.2-0

.2-0

.4-0

.4-0

.20

.02

10

.02

10

.02

10

.12

8P

yra

mid

Ck

GIS

BS

MS

Ma

r 2

00

6-6

0-5

.1-5

.1-5

.2-5

.2-5

.10

.22

70

.22

70

.22

71

.38

5B

oo

kpur

nong

Jo

int

Sa

lt In

terc

ept

ion

Sch

em

eB

SM

SM

ar

20

06

-21

0-1

3.6

-11

.7-1

1.2

-11

.3-1

2.1

0.2

27

0.2

27

0.2

27

1.3

84

Impr

ove

d B

uro

nga

Sch

em

eB

SM

SM

ar

20

06

-10

-0.6

-0.5

-0.5

-0.5

-0.5

0.0

21

0.0

21

0.0

21

0.1

26

Lo

xto

n S

ISB

SM

SJu

n 2

00

8-1

90

-12

.3-1

1.5

-9.7

-9.0

-11

.70

.22

50

.22

50

.22

51

.37

0W

aik

eri

e L

ock

2 S

ISB

SM

SJu

n 2

01

0-1

70

-12

.7-1

0.3

-11

.3-1

1.8

-10

.80

.12

00

.12

00

.12

00

.73

5S

ub

To

tal J

oin

t W

ork

s u

nd

er

BS

MS

-63

6-4

4.4

-39

.3-3

8.4

-38

.2-4

0.5

0.8

40

0.8

40

0.8

40

0.0

00

0.0

00

5.1

28

Jo

int

Wo

rks

Su

b T

ota

l-2

17

17

-13

6.1

-13

1.2

-13

3.0

-13

1.3

-13

2.3

2.7

12

2.7

12

0.8

40

0.0

00

0.0

00

15

.11

1S

TA

TE

WO

RK

S &

ME

AS

UR

ES

Sh

are

d N

ew

So

uth

Wa

les

an

d V

icto

ria

n M

ea

su

res

Pe

rma

nent

Tra

de A

cco

untin

g A

djus

tme

nt -

NS

W t

o V

icto

ria

*5

0N

50

VJu

n 2

00

60

00

.0-0

.1-0

.1-0

.1-0

.10

.00

10

.00

10

.00

3B

arm

ah-

Mill

ew

a F

ore

st O

pera

ting

Rul

es

50

N5

0V

Ma

r 2

00

2-2

33

-1.9

-2.0

-1.9

-2.3

-2.0

0.1

89

0.1

89

0.3

79

Sh

are

d M

ea

su

res

Su

b T

ota

l-2

33

-2.0

-2.1

-2.0

-2.3

-2.1

0.1

91

0.1

91

0.0

00

0.0

00

0.0

00

0.3

81

Ne

w S

ou

th W

ale

sB

ogg

abi

lla W

eir

NS

WD

ec

19

91

00

-0.1

-0.1

-0.1

-0.1

-0.1

0.0

40

0.0

40

Pin

dari

Da

m E

nla

rge

me

ntN

SW

Jul 1

99

40

-17

0.7

0.7

0.7

0.7

0.7

-0.1

21

-0.1

21

Ta

ndo

u pu

mps

fro

m L

ow

er

Da

rling

NS

WS

ep

19

94

2-3

-0.1

-0.1

-0.1

-0.1

-0.1

0.0

34

0.0

34

NS

W M

IL L

WM

P's

NS

WF

eb

19

96

-45

7-4

.0-4

.0-4

.0-4

.0-4

.00

.68

40

.68

4N

SW

Cha

n ge

s to

Edw

ard

-Wa

koo

l and

Esc

ape

sN

SW

Jan

19

90

-24

-2.0

-2.1

-2.0

-2.0

-2.0

0.3

67

0.3

67

Pe

rma

nent

Tra

de A

cco

untin

g A

djus

tme

nt -

NS

W t

o S

A*

NS

WJu

n 2

00

6-2

1-0

.5-0

.4-0

.4-0

.5-0

.40

.10

70

.10

7N

SW

Sun

rays

ia I

rrig

atio

n D

eve

lopm

ent

19

97

to

20

06

NS

WJu

l 20

03

10

0.0

0.9

4.5

6.1

0.7

-0.1

48

-0.1

48

RIS

I N

SW

NS

WJu

n 2

01

0-5

0-2

.7-3

.9-4

.1-4

.1-3

.60

.78

30

.78

3N

SW

S&

DS

Co

mm

itme

nt A

d jus

tme

ntN

SW

No

v 2

00

20

00

.00

.00

.00

.00

.00

.91

00

.91

0N

ew

So

uth

Wa

les

Wo

rks

an

d M

ea

su

res

-11

43

-8.8

-9.1

-5.5

-4.0

-9.0

2.6

56

2.6

56

Vic

tori

aB

arr

Cre

ek

Ca

tchm

ent

Str

ate

gyV

icM

ar

19

91

-12

0-7

.7-7

.7-7

.7-7

.7-7

.71

.96

31

.96

3T

rago

we

l Pla

ins

Dra

ins

at

20

02

leve

lV

icM

ar

19

91

11

0.2

0.2

0.2

0.2

0.2

-0.0

22

-0.0

22

She

ppa

rto

n S

alin

ity M

ana

gem

ent

Pla

nV

icM

ar

19

91

02

41

.41

.41

.51

.51

.4-0

.38

4-0

.38

4N

an g

iloc-

Co

ligna

n S

.M.P

. V

icN

ov

19

91

01

0.5

0.3

0.4

0.3

0.4

-0.1

01

-0.1

01

Nya

h to

SA

Bo

rde

r S

MP

- I

rrig

atio

n D

eve

lopm

ent

Vic

Jul 2

00

31

90

13

.31

3.3

13

.21

3.3

13

.3-3

.14

0-3

.14

0K

era

ng L

ake

s/S

wa

n H

ill S

alin

ity M

ana

gem

ent

Pla

nV

icJa

n 2

00

02

41

.11

.61

.10

.91

.5-0

.34

3-0

.34

3C

am

pasp

e W

est

SM

PV

icA

ug 1

99

31

00

.40

.30

.40

.30

.3-0

.07

6-0

.07

6P

s ych

e B

end

50

V5

0C

Fe

b 1

99

6-4

0-2

.1-2

.1-2

.1-2

.1-2

.10

.23

70

.47

4P

erm

ane

nt T

rade

Acc

oun

ting

Adj

ustm

ent

- V

icto

ria

to

SA

*V

icJu

n 2

00

60

2-0

.7-0

.8-0

.8-1

.0-0

.70

.18

20

.18

2W

oo

rine

n Ir

riga

tion

Dis

tric

t E

xcis

ion

Vic

Se

p 2

00

30

-21

.30

.81

.01

.20

.9-0

.25

1-0

.25

1S

unra

ysia

Dra

ins

Dry

ing

up

Vic

Jun

20

04

-2-4

-2.1

-2.2

-2.1

-2.1

-2.2

0.6

33

0.6

33

La

mbe

rts

Sw

am

pV

icJu

n 2

00

4-5

0-3

.0-3

.0-3

.0-3

.0-3

.00

.62

30

.62

3C

hurc

h's

Cut

de

com

mis

sio

ning

Vic

Ma

r 2

00

61

0-0

.4-0

.3-0

.30

.0-0

.30

.09

80

.09

8M

alle

e D

rain

age

bo

re d

eco

mm

issi

oni

ngV

icJu

n 2

00

80

0-0

.1-0

.3-0

.3-0

.3-0

.20

.05

10

.05

1R

ISI

Vic

V

icJu

n 2

01

0-7

0-2

.0-5

.5-6

.8-7

.1-4

.71

.08

11

.08

1V

icto

ria

n S

&D

S C

om

mitm

ent

Adj

ustm

ent

Vic

No

v 2

00

20

00

.00

.00

.00

.00

.01

.60

01

.60

0V

icto

ria

Wo

rks

an

d M

ea

su

res

-72

60

.1-3

.8-5

.5-5

.7-2

.92

.15

12

.38

8S

ou

th A

us

tra

lia

Irri

gatio

n D

eve

lopm

ent

Due

to

Wa

ter

Tra

de w

ith S

A 1

98

8 t

o 2

00

2/0

3S

AJu

l 20

03

70

-3.2

7.4

36

.05

5.6

4.9

-0.5

85

-0.5

85

Irri

gatio

n D

eve

lopm

ent

Due

to

Wa

ter

Tra

de w

ith S

A 2

00

3/0

4 t

o 2

00

8/0

9S

AJu

n 2

00

60

00

.10

.41

5.1

45

.30

.3-0

.11

7-0

.11

7S

A I

rrig

atio

n D

eve

lopm

ent

Site

Use

d A

ppro

ved

20

09

/10

to

20

10

/11

SA

Jun

20

10

00

-0.1

0.2

8.2

36

.70

.2-0

.02

9-0

.02

9S

A C

om

pone

nt o

f B

oo

kpur

nong

Sch

em

eS

AM

ar

20

06

-40

2.6

-4.5

-11

.6-1

2.3

-2.8

0.3

16

0.3

16

SA

Co

mpo

nent

of

Lo

xto

n S

ISS

AJu

n 2

00

80

00

.1-0

.1-1

.4-2

.50

.00

.00

20

.00

2S

A c

om

pone

nt o

f W

aik

eri

e L

ock

2 S

ISS

AJu

n 2

01

0-1

0-1

.2-0

.7-2

.0-2

.6-0

.80

.05

40

.05

4S

A I

mpr

ove

d Ir

riga

tion

Eff

icie

ncy

Re

g A

SA

Jan

20

00

-32

0-1

6.5

-20

.4-2

1.7

-16

.5-1

9.5

2.4

38

2.4

38

SA

Irr

i ga

tion

Sch

em

e R

eha

bilit

atio

n R

eg

AS

AJa

n 2

00

0-3

00

.0-2

.6-5

.8-5

.6-2

.00

.31

60

.31

6Q

ualc

o S

unla

nds

GW

CS

SA

Se

p 2

00

4-4

0-1

.8-4

.0-6

.5-7

.5-3

.50

.23

60

.23

6S

ou

th A

us

tra

lia S

ub

tota

l-3

70

-20

.0-2

4.2

10

.39

0.4

-23

.22

.63

22

.63

2Q

ue

en

sla

nd

La

nd C

lea

ring

Po

st 2

00

0Q

ldJu

l 20

05

TB

AIr

riga

tion

De

velo

pme

nt P

ost

20

01

Qld

Jul 2

00

5T

BA

Qu

ee

ns

lan

d S

ub

tota

l0

0

Ba

lan

ce -

Re

gis

ter

A-2

75

11

9-1

66

.7-1

70

.3-1

35

.6-5

2.9

-16

9.5

5.5

595

.054

3.4

720

.00

00

.00

023

.168

Sa

linit

y E

ffe

ct

(EC

at

Mo

rga

n)

Pro

vis

ion

al

Sa

linit

y C

red

it

($m

/yr)

Sa

linit

y C

red

its

(In

terp

ola

tio

n t

o C

urr

en

t Y

ea

r B

en

efi

ts $

m/y

ea

r)

AU

TH

OR

ITY

RE

GIS

TE

R A

(Ac

cou

nta

ble

Act

ion

s)

Typ

eD

ate

E

ffe

cti

ve

3

2 Salt risk

Many Salt Interception Schemes have been installed since 1979 to prevent saline groundwater flows entering the River. They have been placed in the high risk areas and reduce the in‐river salinity impact. A key framework controlling river salt risk and hence the location of Salt Interception Schemes (SIS) is the Floodplain and River Classification Matrix (Table 2).

The Floodplain and River Classification Matrix categorises streams as:

Gaining or losing reaches; and

Floodplains as gaining, losing or throughflow systems.

A gaining stream is a reach of river where groundwater is discharging from the alluvial sediments of the floodplain into the river. Conversely losing stream conditions occur where the river is losing water to the floodplain alluvial sediments.

Gaining floodplain conditions occur where the regional groundwater discharges into the floodplain alluvium whereas losing floodplains occur along river reaches where groundwater flow is from the floodplain sediments to the regional groundwater system. Throughflow floodplains are found in reaches where the regional groundwater flow lines show that groundwater flows beneath or through the floodplain. In throughflow reaches, the floodplain alluvium is potentially gaining water from the up‐gradient side, but is losing water to the regional groundwater system on the down‐gradient side (AWE 2011).

The risk of salt inputs to the River from regional groundwater systems increases from the bottom right (i.e. losing stream in a losing floodplain poses virtually no risk) to the top left (gaining stream in a gaining floodplain poses the highest risk of Table 2. SISs are all implemented in floodplains from the top left corner, and the remaining high risk areas along the River also fall within this gaining stream/gaining floodplain category (AWE 2011).

The regional groundwater contours and flow paths are shown on Figure 1, based on data from MDBC (1999). Figure 2 presents regional salt risk indicators. The groundwater contours and flow directions have been used to classify the floodplains into gaining, through‐flow and losing floodplains using the floodplain classification nomenclature in Table 2. The gaining floodplains are classified as high risk.

The regional groundwater heads and flow directions are influenced by an overprint of irrigation induced groundwater mounds. Irrigation has usually resulted in the development of drainage water induced groundwater mounds which in turn displace saline groundwater into the floodplain and River. Impacts can take many decades to become evident. Irrigation practices have improved over the last two decades resulting in reduced drainage volumes. The presence of irrigation can create gaining floodplain conditions where through‐flow conditions existed previously (e.g. in the Sunraysia area), or significantly increase the magnitude of gaining floodplain conditions (e.g. at Loxton and Waikerie) (AWE 2011).

Gaining floodplains occur in two localised areas around Mildura from Mallee Cliffs to Psyche Bend and from Lock 11 to Merbein Common. The groundwater is sourced from natural regional groundwater fluxes at Mallee Cliffs and from irrigation induced groundwater mounds at Mildura (AWE 2011).

The regional hydrogeological maps indicate that the floodplain between the Darling Anabranch and Lock 9 (Wallpolla Island) is a losing floodplain (AWE 2011).

4

Table 2. Floodplain and river classification matrix (AWE 2011).

The remaining floodplains are through‐flow floodplains, i.e. most of the River upstream of Lock 6. The through‐flow floodplains occur between Euston to Mallee Cliffs, Psyche Bend to Lock 11, from Merbein Common to the Darling Anabranch, and from Lock 9 to Lock 6 (AWE 2011).

In the absence of any losses in a floodplain, gaining floodplains would be expected to contain gaining rivers. However, losses do occur.

Floodplain evapotranspiration (ET) causes groundwater losses from the floodplain. The magnitude of these losses will tend to increase with increasing floodplain width, and if ET losses from the floodplain exceed net water gains (e.g. regional groundwater inputs, floodplain rainfall, floodplain irrigation), then the River can become a source of water for the floodplain. The stream classification (i.e. gaining or losing) can vary over time. Floodplain inundations will tend to replenish groundwater levels and increase the length of river where gaining stream conditions occur and extended drought will tend to increase the length of river where losing stream conditions occur. These general trends can be further modified by factors such as depth to water table, seasonality, floodplain inundation, floodplain irrigation and rainfall (AWE 2011).

River management practices also affect the direction of groundwater flow in relation to the River (AWE 2011). The presence of weirs and associated weir pools usually result in losing stream conditions upstream of a weir and gaining stream downstream (Telfer et al. 2004).

Job No. 10156 - 011100519

A u s t r a l i a n

WATEREnvironments

Floodplain Salt Loads

eg Frenchmans Creek eg Lock 7 to Lock 8

eg Loxton eg Chowilla

eg Wallpolla Island

not observed

Gaining Stream Losing Stream

GainingFloodplain

ThroughflowFloodplain

Anabranchor lake

RiverMurray

LosingFloodplain

QR > QE QR < QE

E

R

Groundwater flux directionEvaporation/evapotranspiration

Legend

Q = Regional groundwater flux

Q = Evapotranspiration minus rainfall

5

Figure 1. Gaining and losing floodplain, groundwater elevation and water table aquifers (AWE 2011).

6

Figure 2. Regional salt risk indicators (AWE 2011).

7

3 Salt interception schemes

Salt Interception Schemes (SISs) are key components of the Murray Darling Basin Commission’s Basin Salinity Management Strategy (MDBMC 2001). The location of SISs are illustrated in Figure 2 and Figure 3.

Salt interception is the most viable solution to river salinity problems in the Murray Basin as it can be implemented in a short time frame and can operate for decades. SISs contain three main elements: borefield, pipeline and disposal option.

The aim of SIS is to significantly contribute to the achievement of the salinity benchmark at Morgan as set out by the BSMS. This aim is achieved by constructing borefields that create a zone of pressure in the target aquifer that is equal to or slightly less than the pressure at the river. This creates a gradient where groundwater flow is towards the borefield rather than towards the river and results in a flattening or reversal of the gradient between the borefield and the river.

The objective of the design process is to maximise the interception of salt whilst minimising capital and operational costs. Key performance indicators for schemes include; reduction of in‐river salinity increases to zero and the reduction of groundwater levels at midpoint bores between production bores to density adjusted river level. SISs have a design life of approximately 30 years and disposal basins are typically designed to operate for 100 years (Telfer et al. 2008).

The target of interception is usually the aquifer contributing the majority of salt load to the river as this is often the most practical and cost effective option. SISs have been constructed to address saline groundwater flows to river from the natural groundwater system and from irrigation areas and in future may be required to address any increases in groundwater discharge due to clearance of Mallee vegetation. SISs have been constructed in both alluvial and regional aquifers close to the river valley (Telfer et al. 2008).

Basin wide, SISs were responsible for diverting approximately 324 162 tonnes of salt from the River Murray over the 2010‐2011 reporting period (MDBA 2011). This is less than the estimated 490 000 tonnes diverted over 2009‐2010 reporting period however, it can be noted that high river flows during 2010 and 2011 were responsible for a number of production bores on the floodplain being switched off (MDBA 2011, MDBA 2010). Table 3 below outlines the performance of the key SIS in the Mallee region over the 2010‐2011 reporting period.

Table 3. Performance of salt interception schemes 2010 – 2011 (adapted from MDBA 2011).

SIS Volume Pumped (ML)

Salt Load Diverted (tonnes)

Average Pumped Salinity (EC units)

Target Achieved (% of time)

Mildura‐Merbein 1,276 18,183 49,963 63

Mallee Cliffs 1,650 47,150 52,571 74

Buronga 2,390 60,540 43,830 90

The effect of the SIS and salinity at Morgan is illustrated by comparison of Figure 4 and Figure 5. Figure 4 shows daily flow at Lock 1 and salinity at Morgan. The data is arranged by decade and illustrates the trend in reducing exceedances of the 800 EC target during the few decades. This reduction correlates primarily with implementation of SIS. The effect of implementation of SIS is illustrated in Figure 5, where 240 tonnes of salt per day was added back into the River, equivalent to

8

turning off the Woolpunda and Waikerie SIS’s. This results in exceedances of approximately 40%, compared to the recorded 0.1% exceedance. If all schemes were turned off, the impact would be even more severe.

SIS have been singularly effective in achieving the Morgan benchmark salinity during the last two decades and the Sunraysia SIS have contributed significantly to the outcome.

Figure 3. Salt interception schemes: Murray Darling Basin 2010‐2011 (MDBA 2011).

Note: Noora (icon no. 5) is a drainage basin scheme rather than a salt interception scheme; Pike River (icon no. 19), completed at the end of 2010‐11, is the eighteenth salt interception scheme.

Figure 4.

Figure 5.

Salt and flow

Salt and flow

w at Morgan b

w at Morgan b

by decade (AW

by decade wit

WE 2011).

thout the impplementation of key SIS (AWWE 2011).

9

10

3.1 Mallee Cliffs SIS

The Mallee Cliffs Salt Interception Scheme (MC SIS) is located in south‐western New South Wales on the northern bank of the Murray River and is situated some 20 km south‐east of Mildura near the Mallee Cliffs irrigation area. The scheme is operated by the New South Wales Department of Water on behalf of the Murray Darling Basin Association (MDBA).

The MC SIS has been operational since April 1994 and comprises of seven production bores designed to intercept regional groundwater flow and pump it to a disposal basin located 15km north east of the SIS. Regional groundwater flow is concentrated at Mallee Cliffs due to the influence of the Neckarboo Ridge and the Blanchetown Clay has been eroded at this location providing connection between the Parilla Sand and Monoman Formation (AWE 2009).

The interception strategy of the scheme is to pump saline groundwater from the Parilla Sand Aquifer before it discharges to the Monoman Formation and then to the river. SIS bores are located on both the floodplain and highland and target the Parilla Sand aquifer. The interception site can be considered to behave as a weakly layered unconfined aquifer. Heads in the Parilla Sands Aquifer have been affected regionally by river level fluctuations, rainfall variability, and by operation of the MCSIS within the scheme extent. Each affect is significant in terms of scheme operation and targets (AWE 2009).

The Mallee Cliffs SIS has a maximum pumping capacity of 14 ML/day but is inoperative during river flows of greater than 20 000 ML/day. When the scheme was designed it was envisaged that the scheme would only have to operate continuously for approximately 270 days per year to achieve 100% interception due to the likely frequency of flows greater than 20 000 ML/day. However, the frequency of high flow periods has diminished markedly during 2000’s and the scheme has now operated continuously for nearly 10 years (AWE 2009).

The general pattern of groundwater flow in the study area is from east to west. The groundwater flow patterns are affected by the Neckarboo Ridge, which is a basement ridge trending roughly north‐south just east of Mallee Cliffs. The basement ridge occludes groundwater flow in the Parilla Sand aquifer and redirects the westward flow south towards the river at Mallee Cliffs. The pre‐scheme heads in the Parilla Sand Aquifer at Mallee Cliffs were approximately 0.5 to 1.5m above the river level of 34.5m AHD. By August 2006 a cone of depression had developed around the scheme with the majority of groundwater levels around the scheme are below 34m AHD, well below river level. As a result a study was conducted to optimise the scheme (AWE 2009).

Results from an optimisation study in 2009 concluded that:

The current scheme can control the water levels in “1988 type” conditions (low flow conditions) in all areas except between 1 and 6;

For “mid 1990s” type conditions, when there was a series of high rivers, the current scheme falls just short of the capacity to reduce heads to the target water levels; and

For conditions when there has been no high river for a number of years, the water level in the Parilla Sands aquifer is well below river level.

3.2 Curlwaa SIS

The Curlwaa SIS consists of four wells located on the floodplain within the Curlwaa irrigation district, NSW. The first well became operational in 1971 with an additional three wells constructed in 1974 however, all were replaced in 1983. Groundwater discharges from the Curlwaa groundwater mound to the River Murray and Tuckers Creek. The Curlwaa Scheme was primarily designed to control water table elevations and reduce the risk of salinisation to the irrigation district (SKM 2003).

11

3.3 Buronga SIS

The Buronga SIS began operation in 1979 with a series of five interception bores installed on the northern side of the river around and downstream of Lock 11. Refurbishment of the scheme occurred in 1988 with one additional production bore installed during the scheme upgrade. In 2005, additional refurbishment was conducted on the scheme and an additional 2 production bores installed. The current scheme consists of eight interception bores, spur lines and a delivery main to the disposal basin at Mourquong. The refurbished scheme is designed to pump a total of 100 L/sec. Each bore site consists of a submersible pump, groundwater level transducer, pressure manifold and variable speed drive with electrical equipment housed on stainless steel platforms erected above the 1956 flood level (AWE 2009b).

Installation of the Mildura Lock and groundwater mounding beneath adjacent irrigation districts have increased pressures in the Parilla Sand aquifer and lead to the flux of water from this aquifer to the River Murray. The Buronga SIS has been designed to reduce saline groundwater inflows to the river by reducing the pressure head in the Parilla Sand aquifer and creating a flow gradient from the Monoman Formation to the Parilla Sand aquifer. The production bores are screened in the Parilla Sand aquifer from approximately 5mAHD to 20mAHD (Figure 6) (AWE 2009b).

Performance of the scheme is considered effective when groundwater levels at midpoint observation bores are at or below their target water level, which in this case is assumed to be river level. Complete interception of groundwater fluxes does not occur until midpoint water levels are reduced to this target. The scheme is currently operated and maintained by the NSW Office of Water (AWE 2009b).

3.4 Mildura-Merbein SIS

The Mildura‐Merbein SIS (MM SIS) was implemented in stages between 1979 and 1981 and consists of eighteen production bores located on the southern side of the River Murray (Figure 6).

The target reach of river is between Mildura weir and Merbein pumping station. Pumping sites 4, 4a, 5 and 6a were replaced in 1989 with single down hole submersible pumps whilst the rest of the sites are nested bores connected to a centrifugal pump. The MM SIS is designed to intercept groundwater discharge to the River Murray driven by local groundwater mounds that have developed as a result of irrigation practices and associated drainage water management practices. The volume of groundwater extracted is pumped to Lake Ranfurly East and West basins and Wargan disposal basin (AWE 2009b).

The MM SIS is approaching the end of service life and operation availability and overall effectiveness is low. The borefield in its current configuration cannot intercept 100% of the groundwater flux and as a result the scheme is currently being refurbished. The scheme is currently operated and maintained by Goulburn Murray Water (AWE 2009b).

3.5 Scheme reporting

The credit and debit system is managed through a series of registers held by the MDBA. Where Register A is used to track Salt Disposal Entitlements and Register B for actions to address the “legacy of history”. These registers keep an account of all significant actions undertaken within the Basin. The impact of actions within the Basin is assessed using models that have a defined climate/hydrologic sequence between July 1975 and June 2000 and this is known as the “benchmark period. Actions are defined as significant and are included in the MDBA registers if they are assessed to change the average EC at Morgan by 0.1 EC or more within 30 years (MDBMC 2001).

12

The BSMS also sets out monitoring and reporting requirements to be carried out by the States and includes:

Annual reports that provide a progressive estimate of the salinity impact of works and up to date progress of measures actually implemented; and

Five year reviews provide an audit of register entries to provide an up to date assessment of salinity impacts and an update of the expected change in future flow, salt load and salinity regime due to the “legacy of history”. For example, actions such as new irrigation developments may generate a debit on the register because in some areas they may increase salt loads to the River Murray. By comparison, actions such as investing in infrastructure (e.g. salt interception schemes) or improving irrigation practices may generate a credit.

3.6 SIS types

SIS can be placed into four categories based on aquifer type which include (Table 4):

Unconfined watertable – horizontal flow: This type of SIS targets horizontal groundwater flow within an unconfined aquifer, usually located on the “highland” in Tertiary sediments. Due to partial penetration of the river, borefields can also intercept vertical flow components.

Semiconfined watertable – horizontal flow: These schemes target groundwater interception within the Quaternary aquifer where the water table is located in the confining Coonambidgal Formation and are designed to intercept horizontal flow.

Semiconfined leaky aquifer – horizontal flow: The target of interception is the leaky aquifer within Tertiary sediments where the scheme is designed to intercept horizontal flow to the floodplain.

Semiconfined leaky aquifer – vertical flow: These schemes target interception in the leaky aquifer of Tertiary sediments where the borefield is intercepting vertical flow (upward leakage) to the floodplain.

13

Figure 6: Mildura‐Merbein and Buronga SIS cross section (AWE 2009d).

Other characteristics that can also be considered when categorising SISs include:

14

Interception ratio: This is the ratio of the distance between adjacent production bores and the distance between production bores and the river edge.

Interception response time: The time taken to achieve control of groundwater discharge. Transient salinity events (e.g. salt mobilised by flood recessions) can be controlled by both

Long and short response time schemes however implementation strategies will differ. SISs are currently designed to achieve the Morgan benchmark described above.

Pumping methods: SIS can use three types of pumping methods including bores (wells), wellpoints and horizontal drains. Horizontal drains have been trialled in South Australia at Loxton and are expensive per metre and have some maintenance issues.

Interception Efficiency: In practice the borefield design balances the cost of headworks against the cost of extra pumping to reach the most economically efficient solution.

Table 4. Interception characteristics of the various aquifer types (Telfer et al. 2008).

Interception type/ Characteristics

Unconfined watertable – horizontal flow:

Semiconfined watertable – horizontal flow:

Semiconfined leaky aquifer – horizontal flow:

Semiconfined leaky aquifer – vertical flow:

Interception ratio 2:1 2:1 2:1 Up to 100:1

Interception response time

Years Days to weeks Weeks to months Days

Number of schemes

Woolpunda, Upper Darling, Buronga, Loxton highland, Bookpurnong highland.

Rufus River, Mallee Cliffs, Loxton floodplain, Mildura‐Merbein, Bookpurnong floodplain.

Pyramid Creek, some elements at Qualco.

Wakerie and Wakerie 2A, Lock 2, Qualco sunlands.

Salt load intercepted (t/day)

(MDBC 2008)

190+87+60+200 200+100+65+140+87 100 90+39+19

Pumping method Bores with submersible pumps

Well points or bores with submersible pumps

Bores with submersible pumps

Bores with submersible pumps

15

4 Disposal

Groundwater intercepted by SISs is pumped to nearby disposal basins that use a combination or infiltration and evaporation to accumulate salt at the site. Disposal basins can either be naturally occurring such as saline lagoons and depressions or are artificially constructed. Both types are effective in the Murray Darling Basin due to a low rainfall and high evaporation experienced throughout the area (Telfer et al. 2008). Basins that are currently used for disposal pumped SIS groundwater include Wargan, Mourquong and the Mallee Cliffs Basins.

The Wargan Disposal Basin consists of five natural depressions connected by a series of channels located on the edge of the river trench approximately 17km south‐west of Mildura. The basins overlie a thick sequence of Blanchetown Clay and receive pumped groundwater from the MM SIS via Lake Ranfurly East and West.

The surrounding water table lies within the Blanchetown Clay and is approximately 10m below natural surface (SKM2003). The basins have a total capacity of 8,000ML and can be filled to an elevation of 49.19mAHD.

The Mallee Cliffs Basin is a constructed evaporation basin located approximately 15km north east of the SIS. The disposal basin is split into four bays with a total capacity of 2,200ML and a depth of 3.7m (SKM 2003). The bays were constructed in a wide, shallow depression separated by bunds constructed from Blanchetown Clay. A number of issues were experienced within the first year of pumping from the SIS including inter‐bay leakage and expansion of the perched groundwater mound. This lead to the construction of an enhanced leakage pit that was trialled and subsequently included into the operation of the disposal basin and is designed to deal with the surplus of pumped water over evaporated water. The enhanced leakage pit is approximately 12m deep and has been excavated within a few metres of the Parilla Sand. Previous investigations have indicated the expansion of a saline fringe around the basin and a number of measures have been implemented to reduce lateral seepage from the bays (SKM 2003).

Mourquong Basin is a natural groundwater discharge area located directly north of Lock 11 in NSW. The western part of the basin is used as the disposal point for water pumped from the Buronga SIS. Before the Buronga Scheme was commissioned the basin consisted of a dry lake bed where water tables were close to natural surface and soils were water logged and saline (SKM 2003). Mourquong Basin is also used as a salt harvesting site with exploration beginning in 1997 and a full mining lease granted in 2002 (MDBA 2011).

5 V

Salinity icomplexstream ssalinity nSalinity tsalinity estream s

Groundwmodelleriver anddescribethe groudischargfollowinaverage flows (A

Rechargduring larechargi(i.e. gain

Spatial tlosing/gResults s(AWE 20

Figure 7:875 (AW

Variabilit

is a salt massx processes tsalinity also vnormally occtypically excexceedancessalinities pro

water and sued as part of d groundwated is from kmundwater sysge to the riveg commence recorded flo

AWE 2012).

ge from the rarge floods, wing the aquifning stream c

trends in theaining streamsuggest that012).

Modelled resWE 2012).

ty of salt

s in the Rivethat include svaries with fcurs at low fleeds 800 ECs and this indovide a key p

urface waterinvestigationter interact dm 871 to km stem via losser (red line). ement of puows does not

river (i.e. losiwhen river lefer due to losconditions) d

exchange ofm conditions the river is g

sults of flux to

t inputs

r divided by salt inflow alow in the rivows and lowat flows beldicates the derformance

interactionsns into the reduring and af875 i.e. in frses from the The impact omping in 197t intercept m

ng stream coevel rises absses from theduring flood

f flux betwees indicated frgaining strea

o and from riv

the water vond transfer, ver and is now in‐stream sow 5,000 Milutive role oindicator fo

s during flooefurbishmenfter a series ont of Lake Rriver (blue liof SIS pumpi79. Pumpingmost of the f

onditions) is ove approxime river at therecessions (A

en groundwarom in‐streaam from dow

ver over a ser

olume. In‐ststorage and ormally inversalinity occurL/d, althougof the river (Ar SIS operatio

ds and the rent of the MMof floods (AWRanfurly. Posine). Negativing is evideng from the exlux dischargi

only significmately 33.6e peak of largAWE 2012).

ater and surfm NanoTEMwnstream of

ries of floods

ream salinitystream flowrsely related;rs at high flowh not all lowAWE 2011). ons.

esulting flux M SIS. Figure 7WE 2012). Thsitive fluxes ive fluxes indit by the declxisting SIS bong to the riv

ant (greater mAHD. Mostge floods ret

face water aM survey condLock 11 to M

between rive

y is the resulw (AWE 2011; high in‐strews (Figure 4

w flows result Monitoring

to river hav7 describes hhe reach of rindicate rechicate groundline in flux toores at annuaver, even at l

r than 1 ML/dt of the flux turns to the

are comparedducted in 20Merbein (km

er kilometres

16

lt of ). In‐eam ). t in of in‐

e been how the river harge to dwater o river al ow

day)

river

d with 06. 871).

871 to

17

SIS implementation will continue to mitigate salt inflows and reduce salinity peaks at low flows. While the timing and magnitude of the mobilisation of the additional salt stored in the floodplain during the drought cannot be predicted with certainty, it is considered that the impact on River salinity is more likely to be modest than severe (AWE 2011).

NanoTEM surveys were conducted for the Mallee reach of river in 2004 and 2006 and Run of River (RoR) analysis was conducted for 2001 and 2005.

18

and Figure 9 present correlation between the data. The most conservative groundwater flux estimates tend to be produced by Run of River (RoR) surveys that account for groundwater flux in the river. RoR flux estimates represent the residual groundwater flux that has not been intercepted by the current schemes. The ROR and pumped flux estimates account for groundwater that reaches the river as well as that which is intercepted by the MM SIS.

Resistivity values correlating with losing stream conditions are presented as purple/blue and gaining stream conditions as red/orange. Similarly the rate of salt infiltration calculated from RoR analysis represented by circles with increasing size representing a greater infiltration rate. Factors that affect gaining and losing stream conditions include floodplain losses through evapotranspiration, river stage height controlled by locking and regional groundwater flow gradients and fluxes (AWE 2009b).

The data suggests that gaining stream conditions occur downstream of Mallee Cliffs to Psyche Bend. A very strong NanoTEM signal can be observed adjacent the cliff at Red Cliffs on a bend that cuts into the irrigation groundwater mound and where there is no floodplain between the highland and river. This signal is also supported by the RoR results. Losing stream conditions occur between Psyche Bend and river kilometre 866 just downstream of Lock 11. The river is primarily a gaining stream along most of the reach downstream of Lock 11 adjacent the MM SIS.

19

Figure 8: Correlation of Run of River data 2001 with NanoTEM and river features (AWE 2009d).

20

Figure 9: Correlation of Run of River data 2005 with NanoTEM and river features (AWE 2009d).

21

Figure 10: River bed resistivity and Run of River Mallee Cliffs to SA Border (Telfer et al. 2005b).

22

The graph in Figure 10 illustrates the good correlation between RoR and riverbed NanoTEM results illustrated in Figure 8 and Figure9 is repeated throughout the Victoria and Mallee region. Although not illustrated, the correlation also holds through the South Australia reach. The data shows that low resistivity riverbed sediments are likely to occur where in‐stream salt load inputs exceed around 1 tonne/km/day.

In‐stream salinity data can be used to calculate the salt load, salt inflow or incremental salt inflow. Salt load refers to salinity already in the river and salt inflow refers to salt entering the river.

Salt inflow refers a particular river reach per time, and can be calculated from observations of flow and salinity at the upstream and downstream ends of a reach, taking travel time and channel geometry into account. In a slow‐moving river such as the River Murray, the latter channel geometry is particularly important (AWE 2011). Salt load and input are often expressed as mass, mass per unit length of river, or mass per unit time. Most commonly salt load/inflow is expressed as mass per unit length of river in tonne/km/day.

The MDBA use a model, Bigmod, to account for salt inputs and outputs to the river on a reach by reach basis. Bigmod uses measured river flow and salinity data and ‘accounted’ salt inputs and extractions to calculate ‘unaccounted’ salt loads. Accounted salt inputs are salt inflows to the River Murray from tributaries and drains which are quantified using flow and salinity data. Unaccounted salt inflows refer to inflows from unquantified sources including groundwater flow into the river and surface water inputs from unmonitored tributaries and anabranches (AWE 2011).

Analysis of unaccounted salt loads in AWE 2011 found that:

Persistent negative salt inputs between Euston and Lock 9 suggest a systematic data error(s) that need resolving. An example of this is demonstrated in Figure 11 below which presents the available in‐stream salinity data for Chaffey’s Graveyard monitoring station located adjacent Mildura and shows marked differences between sources.

The Lock 9 to Lock 5 reach showed the greatest variability between the time periods, and has comparatively more salt entering the River during the inter‐flood periods than during the transition and flood periods (compared to the other reaches). This suggests that salt delivery processes differ, or are relatively more active in this reach during the inter‐flood periods compared to the other reaches.

23

Figure 11: Differences between In‐Stream salinity data for Chaffey’s Graveyard monitoring station.

28

29

29

30

30

31

31

32

32

33

33

34

34

35

35

36

0

50

100

150

200

250

300

350

400

450

500

Jan‐2011 Jan‐2011 Mar‐2011 Apr‐2011 May‐2011 Jun‐2011 Jul‐2011 Aug‐2011 Sep‐2011 Oct‐2011 Nov‐2011 Dec‐2011 Jan‐2012 Feb‐2012 Mar‐2012 Apr‐2012 May‐2012

River Level (mAHD)

EC (µS/cm

)

Mildura

In‐Stream Salinity Data2011

Chaffey's (GMW Monitoring)

414216A ‐ Chaffey's MDBA Live Data

41310026 ‐Chaffey's NSW Office of Water

DS River Level

24

6 SIS design tools – in‐stream salinity and salt loads

In‐Stream salinity and the calculation of salt load and salt inflow are the primary data sources when quantifying salt characterisation of particular reaches and the salinity impact of groundwater inflows. They are derived from direct measurements. They are thus the cornerstone of quantifying the need for salt interception and of assessing the salinity impact of SIS operation and other surface water/groundwater management initiatives.

There are two salinity measurement methodologies that are used in the Murray Basin to quantify salt loads and salt inflow that is:

Fixed location recorders that regularly record EC, with frequency varying from daily sampling to continuous EC data loggers.

Run of River Surveys that are conducted along specific reaches, periodically. (e.g. over a week period, usually annually or less).

Fixed station recorders provide temporal data on salt inflow over a whole river reach between the stations. RoR data provide detailed spatial distribution of the salt load along the entire river reach surveyed, during the period of the survey. The two methods are complimentary and discussed and compared in the following sections.

6.1 Fixed Station EC recording

MSM‐BIGMOD

The MSM‐Bigmod model of the Murray Darling Basin Authority (MDBA) accounts for salt inflows and outputs on a reach by reach basis. MSM is a monthly simulation model used for modelling flows, operating rules for storages, irrigation demands, water resource assessment and water accounting (AWE 2011).

BIGMOD is a daily model routing flow and salinity from Hume Dam and Menindee Lakes to the barrages at the Murray Mouth. MSM and BIGMOD are run sequentially to ensure that the simulated flow data from the two models are synchronised.

BIGMOD has an array of input files including: flow, salinity, volumes and travel time for the main River, tributaries and storages. BIGMOD routes flow and salinity to best match the recorded data. Accounted salt loads are the product of flow and salinity from tributaries and drains, and the extraction for consumptive use (irrigation, stock and domestic uses). Where there is a difference between recorded and computed salt concentration in the River, BIGMOD minimises this difference by introducing an ‘unaccounted salt load’ (a negative value indicates a salt outflow).

Unaccounted salt load includes groundwater flow into the river, and surface water inputs from unmonitored anabranches and tributaries (AWE 2011). Since 1970, the unaccounted salt loads comprise about one‐third of total salt inflows (AWE 2011).

AWE considers the BIGMOD model as best suited to track flow and invert the measured data to provide salt inflows for the major river reaches. The Murray Darling Basin Commission (MDBC 2002) concluded that the match between observed and MSM‐BIGMOD simulated salinities at Morgan and at intermediate sites is very good providing assurance that the calculated salt load inflows are reasonable. MDBC (2002) provided statistical comparison between measured and modelled values, which for daily flows at Euston and Lock 1 had coefficient of determination (R2) values of 0.98 and 0.97 respectively. For salinity at Euston and Morgan, R2 values were 0.70 and 0.88 respectively. The results are excellent for flows and reasonable for salinities, given the overall uncertainties regarding salinity processes in the lower River Murray (AWE 2011).

25

BIGMOD uses many, but not all fixed EC recorder stations along the river to trace salinity pathways. The values of unaccounted Salt Inflow from BIGMOD for the two major reaches in Sunraysia are presented in Table 5. The BIGMOD results for the Sunraysia Region are known to have issues with accuracy (AWE 2011) as demonstrated by the consistently negative values for the reach Lock 11 to Lock 9 in table 5.

Table 5. BIGMOD ‐ unaccounted salt inflow – daily averages (AWE 2011).

Period Euston to Lock 11 Lock 11 to Lock 9

Total

Euston to Lock 9

Tonnes/day Tonnes/day Tonnes/day

1970‐1979 382 29 410

1979‐1989 433 ‐12 420

1989‐1999 558 ‐98 459

1999‐2009 66 22 88

Total Period 359 ‐16 343

Simplified Fixed Station Analysis

EC data from selected pairs of stations can be used to estimate salt loads. River flow and channel geometry, and associated travels times between the upstream and downstream stations can be assessed for the intervening river reach.

Using the travel time the EC at each station can be compared to upstream stations for the date when that particular body of water was at the upstream station. The increase in salinity can be attributed to salt load. Salt inflow may be expressed in mass/time (tonnes per day) or for a given river reach, per unit river length (tonnes/km/year).

There as several errors and uncertainties in the methodology, that include:

Measurement errors, including equipment error

Uncertainties related to variations between the in‐stream (point) salinity measurements and the EC distribution across the river cross‐section

In‐stream EC station data are normally obtained at daily intervals therefore intraday variations are not accounted for

Errors in calculating travel times between stations that are related to uncertainties in both flow measurements and channel geometry

Both in‐stream salinity and salt loads are variable, and there may be incomplete mixing in the river.

The errors may become considerable, particularly over short reaches where the increase in salinity due to salt inflow is small compared to the magnitude of the possible errors. Salt inflow calculations may result in a negative value, representing errors and uncertainties.

Moving averages have been used by AWE (2011) to smooth the data, improving visual interpretation. Varying the averaging period (for example 10 or 90 days) may assist different purposes of interpretations.

The simplified fixed Station EC analysis has been demonstrated to match closely with BIGMOD for most reaches most of the time, for reaches analysed in South Australia (AWE 2012b, in preparation).

26

Figure 12. In‐stream salinity stations.

27

There are 15 sites regularly measuring salinity in the Sunraysia region. Seven new stations, continuously measuring both salinity and temperature began monitoring in 2006. These are located at Colignan, Upstream of Mallee Cliffs SIS, Downstream of Mallee Cliffs SIS, Red Cliffs, Chaffey’s Graveyard, Merbein and Curlwaa, as shown in Figure 12. The simplified Salt Inflow analysis of these stations has not been undertaken.

6.2 Run of River

Run of River (RoR) data have been collected since 1985 to provide detailed information of salt accessions to the River Murray. The analysis of results have provided and continue to provide detailed information regarding salt inflows to the River which in turn has been a vital element in the design and performance measurement of Salt Interception Schemes (SIS). Repeated from time to time (normally annually) RoR can provide detailed information both in space and time. The RoR survey measures salinity at each kilometre along a river reach on (nominally) five consecutive days. The Porter (2001) methodology uses river flow to identify how far a body of water has moved from one day to the next. The difference in electric conductivity (EC) of a parcel of water on consecutive days is assumed to be due to saline inflow. The rate of salinity increase (EC per km) due to salt inflow at the downstream location is assumed to be the average that the water body has experienced during the 24 hours between the measurements, divided by the number of kilometres the water body has travelled in that day. This assessment is done at 1 km intervals. For a set of readings over five consecutive days there are four sets of results of rate of EC increase at each location. The average of the four salinity increases (EC/km/day) is converted to salt loads (tonnes/km/day) by converting EC to salinity (mg/L) and multiplying by the river flow to give tonnes per day.

To improve the resolution of RoR data analysis AWE (2009c) developed an alternative method for calculating saline accessions. This method recognises that the river water body has a background salinity variation as the water enters a reach and quantifies this background salinity profile. Deducting the background salinity variation from the EC measured during the survey provides the salinity increase for each kilometre due to salt inflow. The salinity increase is then converted to a salt inflow mass. It has been found that this new methodology more closely assigns the salt inflow to where it actually occurs.

Three Run of River surveys have been conducted in the Sunraysia area since 2001, between Iraak and Lock 10. The daily average cumulative salt increase for each survey is shown in Figure 13. The much higher overall inflow of 140 tonnes per day during the 2001 survey is most likely due to the survey being carried soon after a flood event.

28

Figure 13. Run of River ‐ cumulative salt inflows (AWE 2011).

6.3 Correlation of Run of River and Fixed Station EC Analysis

Salt inflows calculated from EC stations correlate well with those obtained from RoR surveys, especially over the longer river reaches (AWE 2011). The combination of the two data sets (continuous recorders and RoR) is essential to a full understanding of salt accessions.

Whilst the correlation between the methodologies has not been done in Sunraysia an example of the correlation between RoR and Fixed Station EC data is shown for the reach (and sub‐reaches) between Lock 5 and Loxton in Figure 14. In the reach the Bookpurnong, Loxton and Pike SISs have been constructed progressively since 2005 and have cause the decrease in salt inflow.

0

20

40

60

80

100

120

140

160

820840860880900920940960980

Cumulative

Salt Inflows(tonnes/day)

River Location (River kms)

Run of River Iraak to Lock 10 ‐ Cumulative Salt Inflows

Dec‐01 Apr‐05 Aug‐08

29

Figure 14. Correlation between RoR and Fixed Station EC – Lock 5 to Loxton (AWE 2011).

6.4 AEM

Airborne Electromagnetic data (AEM) has been collected along the River corridor. It has proven to be consistent with in‐stream NanoTEM data (Hatch et al. 2007) and correlates well with groundwater salinity data in the Sunraysia region (Munday et al. 2008). The EM data appears to illustrate the groundwater salinity distribution and is valuable in identifying the spatial extent and depth of fresh‐water lenses among other things. Figure 15 presents a comparison between AEM data and measured groundwater salinity.

30

Figure 15. Holistic conductivity: standing water level minus 5 metres ‐ Murray Floodplain TDS (Munday et al. 2008).

31

6.5 NanoTEM

The NanoTEM technique measures the resistivity of saturated geological materials. The resistivity data is collected using a mobile data collection platform towing a concentric square transmitter/receiver away (Figure 16). The principles of operation and the sensitivity of results to pore water salinity and formation porosity are illustrated in Figure 17. Measurements of formational resistivity are affected by: material properties, porosity and saturation of the material and water quality (total dissolved solids).

Figure 16: NanoTEM Array Behind Mobile Data Platform (Photo by B Porter in Telfer et al. 2005).

The riverbed NanoTEM data can be used to infer the location of saline and/or fresh water in the river bed (Telfer et al. 2005, 2006, 2007, Berens et al. 2007; Tan et al. 2006). The NanoTEM data have been collected in inter‐flood periods only – the bed resistivity patterns may vary during floods due to changes in the direction of groundwater‐River flux. Therefore the NanoTEM patterns represent inter‐flood periods only. The NanoTEM data have been analysed in detail in Telfer et al. (2005, 2006 and 2007) compared to the Run of River data.

Telfer et al. (2005) classifies the NanoTEM data into three classes, based on the correlations between the NanoTEM resistivity and the Run of River salt load inputs to the River, as follows:

High resistivity NanoTEM values in the riverbed (>20Ωm) are interpreted as fresh water in river bed sediments, correlating with losing stream conditions ‐ resistivity values greater than 20 Ωm are broadly correlated with salt loads of zero to less than 1 t/d/km;

Medium resistivity NanoTEM values in the riverbed (3 to 20 Ωm) are broadly correlated with salt loads of 0.5 to 2 t/d/km and gaining to losing stream conditions; and

Low resistivity values of less than 3 Ωm are strongly associated with salt loads of greater than 2 tonnes per day per kilometre.

32

Figure 17. Formation resistivity and the principles of NanoTEM (Telfer et al. 2005).

The Nanoutlinedanalysis Berri anafter SalanabranNanoTEanabran

Figure 18

(Note: D

Figure 19

noTEM riverbd above for tindicates thd Lock 4 to Mlt Interceptionches are notM surveys hanches. The Na

8. Major reach

Does not incl

9. Key reaches

bed resistivithe major reae major zoneMorgan. Noton Schemes t included inave been conanoTEM patt

hes – saline in

ude key ana

s ‐ saline inlfo

ty data have aches (Figurees of saline ie that the Nahave been im the data benducted on pterns correla

nflows and fre

branches wh

ows and fresh

been evaluae 18) and thenflow to theanoTEM rivemplementedecause not alparts of Chowate with the

esh water len

hich may hav

h water lenses

ated accordine subreachese River are Coerbed resistivd. The NanoTl anabranchewilla, Pike anAEM pattern

nses from Nan

ve saline inflo

s inferred from

ng to the ress (Figure 19).olignan to Mvity results reTEM results fes have had nd Lindsay‐Wns (Figure 20

noTEM (AWE

ows)

m NanoTEM d

sistivity criter. The sub‐re

Merbein, Lockeflect conditfor backwateNanoTEM su

Wallpolla 0).

2011).

data (AWE 20

33

ria each k 6 to tions ers and urveys.

011).

34

Figure 20. Combined AEM (AWE 2011).

35

7 Features of modern SIS design

The primary aim of SIS is to prevent saline groundwater from entering a river with the key indicator of success being a salinity reduction across the target reach. The principal focus of SIS to date has been total interception of groundwater flow however; secondary design objectives to address environmental needs are being incorporated into designs where possible within the scope of the SIS (Telfer et al. 2004).

SISs have been operational in the Mallee region since the 1970’s and a number of advances have been made in their design and operation and include:

Production bores equipped with submersible pumps. Wellpoints are found within older schemes and have a number of associated operation problems including loss of vacuum, extra pumps required to maintain vacuum, biological clogging and cracking of vacuum lines caused by the swelling of clays. The use of wellpoints often results in high maintenance costs (Telfer et al. 2008).

Bores constructed using PVC screens as these withstand highly saline environments.

Construction of midpoint monitoring bores along the scheme alignment to allow monitoring of groundwater levels as a form of performance criteria.

Near‐river monitoring can also be incorporated to monitor the formation and change in fresh‐water lenses due to scheme pumping.

Groundwater pumped by SISs generally contains iron bacteria which lead to clogging of bore screens, the aquifer and pipelines. Hardware choices as well as operations and maintenance strategies can be used to minimise the impact of iron bacteria clogging on SIS efficiency. Chlorination systems, acid dosing and pipeline pigging are commonly used maintenance methods used to control iron bacteria.

The performance of SISs is assessed using a variety of indicators which are evolving based on the use of SISs to provide additional environmental outcomes. Performance criteria for SISs include but are not limited to:

Reduction of in‐river salt load increases to zero. This can be assessed using a variety of methods including RoR analysis, continuous monitoring of in‐stream flow and salinity using pontoons (Section 6) and indirectly through successive NanoTEM surveys.

Reduction of groundwater levels at midpoint bores between production bores to density adjusted river level indicating that groundwater flow is towards the borefield rather than towards the river.

Minimising pumping and power costs.

Continuous operation.

Pumping of salt water rather than fresh.

Creating a modest buffer of freshwater adjacent the river to allow for scheme down time.

The operation of SIS during floods varies, with some being turned off during high flow events (e.g. Mildura, Mallee Cliffs), others being decommissioned due to borefields being on the floodplain (e.g. parts of Waikerie and Bookpurnong) and others operating unchanged (e.g. Woolpunda).

With new understanding of floodplain salt processes and mobilisation pathways (e.g. AWE 2011) it is likely that the operation of some SIS assets may be able to be modified to enhance benefits to the River or the floodplain environment. For example, this may be through the targeted building of

36

freshwater lenses at critical locations which may in‐turn reduce peak salt loads and enhance environmental benefits (AWE 2011).

It is suggested that a set of aims be established and in light of the greater understanding of floodplain process, that operation of the SISs be reviewed.

A key component of assessing the performance of SISs is the collection of accurate baseline data and ongoing monitoring data which may include:

Groundwater levels

Vegetation health data

Saline and fresh groundwater distributions

Aquifer properties such as transmissivity and storage data

Bore properties such as specific capacity.

37

8 Possible future SIS

SIS have already targeted gaining floodplains and gaining floodplain locations in Mallee region adjacent MMSIS and Mallee Cliffs.

The Sunraysia SIS study (AWE 2009b) identified:

There is a significant salt load inflow to the River Murray in the Red Cliffs area, extending from Psyche Bend to Mallee Cliffs.

Investigations to date have been limited but indicate the hydrogeology is very variable and the optimal scheme extent and layout is not yet clear.

Initial analysis identifies that a viable scheme is likely to be able to be developed; however several key concepts need to be tested further.

38

9 Future trends under the Basin Plan

Under the Basin Plan, and in particular the target of keeping the mouth of the River Murray open 9 years out of ten, more water will flow down the River. These additional flows mean that there is more dilutive capacity for salt inputs, and hence opportunity to dispose of floodplain salt using groundwater management to achieve floodplain benefits. One opportunity may be to use low head pumps discharging to higher river flows to improve floodplain health.

There may also be opportunities to utilise the existing SIS to manage real time salinity impacts arising from environmental watering activities, and to achieve environmental improvements directly within the extent of the SIS by managing freshwater lenses to protect river and support ecosystem values.

The current SIS salt reduction target of 61 EC may be increased in the future. An additional 41 EC has been discussed in the past. If the target was increased, new SIS would need to be built. The Red Cliffs area would be in the first tier options under consideration.

At the SIS scale, active management to emplace modest freshwater lenses along the SIS extent will almost certainly promote improved red‐gum health along the scheme extents.

The major issue affecting the River Murray is salt and SISs will continue to be the most viable solution to river salinity problems in the Basin. There is also potential to use SIS to provide secondary environmental benefits. A decline in vegetation health has been observed along the Lower Murray floodplain and is linked to reduced flooding frequency due to the regulation of the river by locks and weirs (MDBC 2003).

The common perception, that “salt accumulation is causing floodplain health decline” is not correct. A typical floodplain stores around 1000 tonnes of salt per hectare. The authors of this report have calculated that regional groundwater discharge areas (e.g. Chowilla) will accumulate only around 1 tonne of salt per hectare per annum. That is an accumulation rate of 0.1% per annum. In contrast the reduction in fresh water availability is much more severe and correlates with health decline.

It follows that the major issue for the floodplain environment is therefore a lack of available fresh water, not salt accumulation. SISs have the potential to manipulate freshwater sources to provide positive environmental outcomes for the floodplain environment.

39

10 References

Australian Water Environments 2009a, Mallee Cliffs Salt Interception Optimisation, AWE ref 47906a, prepared for New South Wales Department of Water and Energy.

Australian Water Environments 2009b, Sunraysia Salt Interception: Hydrogeology Design Inputs, prepared for Goulburn Murray Water, AWE Ref: 45682.

Australian Water Environments 2009c, Waikerie Lock 2 SIS flood recession modelling, AWE report 47913, prepared for SA Water.

Australian Water Environments 2009d, Sunraysia Salt Interception Scheme Hydrogeology and Engineering Design Input Figure Atlas, prepared for Goulburn Murray Water, AWE Ref: 45682.

Australian Water Environments 2011, River Murray Floodplain Salt Mobilisation and Salinity Exceedances at Morgan. Report to the MDBA Project Flood Recession Salt Mobilisation from Floodplain of the River Murray (MD1565).

Australian Water Environments 2012a, Mildura Merbein SIS Refurbishment: Borefield Design Model (in progress), prepared for Goulburn Murray Water, AWE Ref: 11050.

Australian Water Environments 2012b, River Murray In‐Stream Fixed Station Salinity Atlas (in progress), prepared for SA Water, AWE Ref: 11192.

Berens, V, Hatch, M, James‐Smith, J and Love, A 2007, ‘Loxton ‐ Bookpurnong instream NanoTEM survey and validation using river sediment cores’, DWLBC Report 2007/10, Government of South Australia, through Department of Water, Land and Biodiversity Conservation, Adelaide.

Brown, CM, and Stephenson, AE 1991, Geology of the Murray Basin, Southeastern Australia, Bureau of Mineral Resources, Australia.

Hatch, M, Fitzpatrick, A, Munday, T and Heinson, G 2007, ‘An assessment of ‘In‐Stream'+D47 survey techniques along the Murray River, Australia’, ASEG Extended Abstracts.

Munday, T, Fitzpatrick, A, Tan, KP, Cahill, K, Halas, L, and Shintodewi, P 2008, ‘Atlas of Sunraysia Helicopter Electromagnetic (HEM) Survey Data: Volumes 1& 2’, CSIRO EM Technical Report No: P2008/2025, CSIRO: Water for a Healthy Country National Research Flagship.

Murray Darling Basin Authority 2011, ‘Murray–Darling Basin Authority Annual Report 2010‐11’, MDBA Publication Number 218/11.

Murray Darling Basin Authority 2010, ‘Murray–Darling Basin Authority Annual Report 2009‐10’, MDBA Publication Number 110/10.

Murray Darling Basin Commission 2003, ‘Preliminary Investigations into River Red Gum decline along the Murray below Euston’, MDBC Publication 09/05.

Murray Darling Basin Commission 2002, Setting Up of MSM – Bigmod Modelling Suite for the River Murray System.

Murray Darling Basin Commission 1999, ‘Basin in a box’, Geology, hydrogeology and soil‐relief digital data, Commonwealth of Australia, released under MDB Mapping, Canberra.

Murray‐Darling Basin Ministerial Council 2001, Basin Salinity Management Strategy 2001‐2015, August 2001.

Porter, B 2001, ‘Run of River Salinity Surveys. A method of measuring salt load accessions to the River Murray on a kilometre by kilometre basis’ in, Murray Darling Basin Groundwater Workshop; Victor Harbour, South Australia, September, 2001.

SKM/AWE 2003, Review and Optimisation of SIS in the Sunraysia Region.

40

Tan, KP, Berens, V, Hatch, M and Lawrie, K 2006, ‘Determining the suitability of Instream NanoTEM for delineating zones of salt accession to the River Murray: A review of survey results from Loxton, South Australia’, CRCLEME Open File Report 192.

Telfer, A, White, G, Newman, B, Forward, P and Williams, M 2008, ‘Salt Interception Schemes: Classification by Aquifer Type in the Murray Basin, Australia’. In 2nd International Salinity Conference: 31st March‐3rd April, Adelaide.

Telfer, A, Hopkins, B and Woods, J 2004, ‘Principles of Borefield Design for Salt Interception Schemes’. In 1st National Salinity Engineering Conference: November 2004, Perth.

Telfer, A, Hatch, M, Palfreyman, C and Berens V 2005a, ‘Instream NanoTEM Survey of the River Murray 2004: Blanchetown to Mallee Cliffs’, prepared for the MDBC and MCMA, AWE Ref: 42417b.

Telfer, A, Hatch, M, Palfreyman, C and Berens V 2005b, ‘Instream NanoTEM Survey of the River Murray 2004: Blanchetown to Mallee Cliffs Figure Atlas’, prepared for the MDBC and MCMA, AWE Ref: 42417b.

Telfer, AL, Hatch, MA and Palferyman, CJ 2006, Atlas of Instream NanoTEM 2005 ‐ Wellington to Blanchetown, Australian Water Environments report 44589, prepared for the River Murray Catchment Water Management Board and the Mid Murray Local Action Planning Association.

Telfer, AL, Hatch, MA, Woods, JA and Shintodewi, PA 2007, Atlas of Instream NanoTEM 2006 ‐ Wentworth to Torrumbarry ‐ Lindsay ‐ Mullaroo, Australian Water Environments Report 45755b, prepared for the Murray Darling Basin Commission, Mallee Catchment Management Authority, Goulburn Murray Water and the North Central Catchment Management Authority.

4. Dryland salinity drivers and processes Author: Jon Fawcett1

Mallee Catchment






Copyright


Authority 2013

Disclaimer













publication.

Publication details


Chapter 4 – Dryland salinity drivers and

processes.


April 2013

Author: Jon Fawcett1


Cover images




Table of Contents

1 Introduction .............................................................................................................................................. 1

2 Why is the Mallee susceptible to land salinisation?................................................................................. 3

3 Key drivers and processes of dryland salinity........................................................................................... 7

3.1 Clearance of native vegetation ........................................................................................................ 7

3.2 Root zone drainage .......................................................................................................................... 8

3.3 Dryland management strategies to reduce root zone drainage...................................................... 9

3.4 Unsaturated zone processes.......................................................................................................... 12

3.5 Regional groundwater recharge and flow ..................................................................................... 12

3.6 Groundwater discharge ................................................................................................................. 13

4 Mapping the salinity threat in the Dryland Mallee................................................................................. 14

5 Dryland salinity statement (Victorian State Government perspective) ................................................. 18

6 Summary................................................................................................................................................. 19

6.1 State of Knowledge ........................................................................................................................ 19

6.2 The four most important points about salinity in the Mallee dryland .......................................... 19

6.3 The four most important points to consider in the future ............................................................ 19

References....................................................................................................................................................... 20

List of Figures

Figure 1: Conceptual model of salinisation processes in the Mallee (Miles et al. 2001) .................................. 1

Figure 2: Distribution of salt lakes in relation to the ancient lake Bungunnia - greyed area (after Bowler et al.

2006) ................................................................................................................................................. 3

Figure 3: The distribution of primary (natural) and secondary (induced) saline landscapes illustrated within

the estimated extents of the Lake Bungunnia (Source: Mallee CMA using Grinter & Mock 2009). 4

Figure 4: Example of Primary salinity at Cowangie (Grinter & Mock 2009)...................................................... 5

Figure 5: Example of secondary salinity at Nowingi (Grinter & Mock 2009) .................................................... 5

Figure 6: Depth to water table for the Mallee region, after SKM 2012. ........................................................... 6

Figure 7: Area of dryland cultivation in the Mallee region (Cook et al. 2001) .................................................. 7

Figure 8: Deep drainage (RZD) estimates versus clay content of the soil profile (Cook et al. 2001) ................ 8

Figure 9: General soil water content curves for a sandy soil (Tenosol) and a clayey soil (clayey Calcaresol)

(after Fawcett 2009).......................................................................................................................... 9

Table 1: Strategies to reduce RZD (Mallee CMA 2006). .................................................................................. 10

Figure 10: Groundwater levels for Bore 50349 (near Berriwillock) illustrating episodic recharge within the

Mallee dryland. ............................................................................................................................... 12

Figure 11: Distribution of land threatened by salinisation within the Mallee CMA under different climate

predictions (Bryan et al. 2007)........................................................................................................ 15

Figure 12: Risk framework adapted from Fawcett (2009) to assess risk of deep drainage. ........................... 16

Figure 13: Risk assessment of Traditional Cropping with fallow period to native vegetation........................ 17

List of Tables

Table 1: Strategies to reduce RZD (Mallee CMA 2006). .................................................................................. 10

1

1 Introduction

Dryland salinity is a significant land management issue in the Mallee region. In 2006, a survey across the

entire Mallee estimated that approximately 10 per cent of agricultural land is threatened by dryland salinity

(Mallee CMA 2006).

The basic drivers and processes for the development of dryland salinity in the Mallee are well known

(Figure 1). The clearance of native Mallee vegetation for the establishment of dryland agriculture has

resulted in additional groundwater recharge. The subsequent rise in the levels of groundwater, which is

naturally saline, has led to additional areas of land being affected by saline groundwater discharge and

waterlogging. This has also led to an increased salt load to the Murray River. These processes occur over

significant timeframes, such that the impacts of clearing native vegetation pre-1988 will likely not fully

manifest for at least another 100 years.

Figure 1: Conceptual model of salinisation processes in the Mallee (Miles et al. 2001).

Groundwater beneath irrigated areas will be the most significant contributor to salt loads over the next 30

years or so; but progressively, additional loads induced from the Mallee dryland area will begin to dominate

(Wang et al. 2005). It is estimated that the clearance of native vegetation may cause River Murray salinity

to rise by approximately 70 EC units over the next 100 years (Mallee CMA 2006).

Groundwater recharge is the key process that affects salt mobilisation and salt accumulation in the dryland.

The primary factor that influences groundwater recharge is land use. The clearance of native vegetation

and its replacement with dryland agriculture significantly increases groundwater recharge (Allison et al.

1990). Once cleared, the management of agricultural land also affects recharge rates. Superimposed on

land use are climatic drivers: variability in climate and the potential impacts of climate change.

A change in land use or climate leads to a change in root zone drainage (RZD) which is sometimes referred

to as deep drainage. RZD describes the downward movement of water beyond the root zone such that it

can no longer be lost to the atmosphere by evapotranspiration (ET). This water must percolate across the

unsaturated zone before it enters the water table and becomes groundwater recharge. Some water may

discharge laterally before it enters the water table so not all RZD contributes to groundwater recharge. The

time taken for water to cross the unsaturated zone is dependent on the depth of the water table (i.e. the

thickness of the unsaturated zone) and the hydraulic properties of the unsaturated zone. Clay layers will

2

impede the movement of water and lead to greater time lags. Additional hydraulic loads to naturally saline

groundwater will move through the saturated zone according to the nature of groundwater flow systems –

with time lags varying accordingly. The additional loads will result in additional saline discharge to streams

or as a greater area of land (on floodplains or salinas2) being subject to capillary rise and the evaporative

concentration of salts at the land surface.

2 Salinas – a saline spring or marsh that intercepts the saline water table; these discharge features are commonly scattered

throughout the Mallee dunefields (MDBC 1990).

3

2 Why is the Mallee susceptible to land salinisation?

Saline groundwater discharge sites and saline wetlands are a ‘natural feature’ of the Mallee landscape. The

expression of salinity in the Mallee landscape is associated with the geomorphologic evolution of the lower

Murray Darling Basin (Bowler et al. 2006). The numerous occurrences of saline wetlands were formed

during the final drying phases of the ancient Lake Bungunnia (Stephenson 1986) and exist predominantly in

low lying parts of the landscape. The spatial relationship between the current distribution of saline

wetlands and Lake Bungunnia is illustrated in (Figure 2). These systems act as regional discharge zones and

are subject to expansion and shrinkage as groundwater levels fluctuate (Macumber 1980).

Figure 2: Distribution of salt lakes in relation to the ancient lake Bungunnia - greyed area (after Bowler et al. 2006).

The Mallee CMA region contains around 142 206 hectares of saline land (Figure 3 - Grinter & Mock 2009).

The majority of this land (86 278ha or 60.7% of the Mallee landscape) is classified as primary salinity or

naturally occurring groundwater discharge zones. There are many well know locations in the Mallee where

these areas of primary salinity are observed including Lake Tyrrell, Raak Plains or Cowangie (Figure 4).

Secondary salinity, or induced salinity, is generally associated with the expansion of these primary saline

discharge zones and salt pans forming in low lying landscapes such as dune swales. Changes in land use

have caused an estimated additional 55 928 ha to become saline as highlighted in green (induced) in Figure

3. Examples of the secondary salinity can be observed in many places in the Mallee (Figure 5).

The Mallee CMA continues to monitor the area of primary and secondary salinity as a measure or indicator

of landscape health in the Mallee.

4

Figure 3: The distribution of primary (natural) and secondary (induced) saline landscapes illustrated within the

estimated extents of the Lake Bungunnia (Source: Mallee CMA unpublished using Grinter & Mock 2009).

5

Figure 4: Example of Primary salinity at Cowangie (Grinter & Mock 2009).

Figure 5: Example of secondary salinity at Nowingi (Grinter & Mock 2009).

6

The water balance in the Mallee landscape is very sensitive to any subtle changes. There are large areas in

the Mallee region where the water table is generally shallow and less than 10 metres below natural surface

(Figure 6). The water table is also very flat with a fall in head of less than 80 metres from Wycheproof to

Renmark, a distance of approximately 350 kilometres. Therefore only minor increases in groundwater

recharge can have large effects on the regional water balance and result in increased saline discharge at

multiple locations throughout the Mallee. While post-clearing recharge rates are reported to be 45 times

greater than pre-clearing, the magnitude of this change in recharge rate translates to only minor changes in

groundwater depths and measured in millimetres and centimetres. Low rainfall and recharge rates in the

Mallee mean that the high salinities are not flushed from the landscape and are maintained within the

regional water table aquifer, the Parilla Sands.

Figure 6: Depth to water table for the Mallee region (after SKM 2012).

7

3 Key drivers and processes of dryland salinity

3.1 Clearance of native vegetation

Widespread clearance of the native Mallee vegetation began in the 1880s and continued for a century. The

most intensive periods of clearing occurred in the 1910s and 1920s. Most of the vegetation clearance has

occurred in Victoria and South Australia and comparatively little has occurred in NSW. There has been

minimal clearance since the 1980s as the regulatory guidelines for Victoria promote the retention and

preservation of native vegetation. Figure 7 shows the extent of dryland agriculture in the Mallee which

roughly corresponds to the area of land where native vegetation has been cleared (Cook et al. 2001). This

map is considered to be representative of the current agriculture area in the Mallee.

Figure 7: Area of dryland cultivation in the Mallee region (Cook et al. 2001).

Native Mallee vegetation is very efficient at maximising the use of the available water in the root zone such

that there is little root zone drainage (RZD). As a consequence, recharge under native Mallee vegetation is

very low, and estimated to be on the order of ~0.1 mm per year. Under dryland agriculture, deep-rooted

perennial native vegetation has been replaced with shallow-rooted annual crops and considerably less soil

water is used, hence the excess water contributes to RZD. The clearance of the native vegetation and its

replacement with dryland agriculture has resulted in approximately 100-fold increase in RZD (Cook et al.

2001). The legacy of native vegetation clearance is the primary driver of dryland salinity in the Mallee.

8

3.2 Root zone drainage

Relatively minor increases in rootzone drainage can have large effects on the regional water balance and

result in increased groundwater recharge and saline discharge at multiple locations throughout the Mallee

dryland as discussed in Section 2. Measurements of RZD in dryland agricultural settings vary considerably

from less than 1 mm per year to more than 50 mm per year with a mean of approximately 10 mm per year

(Cook et al. 2001).

Compared with native vegetation RZD is substantially higher under dryland agriculture. Key factors

affecting RZD in the dryland are rainfall, soil texture and the management of agricultural land.

The timing, intensity and duration of rainfall are crucial in controlling recharge rates in the Mallee. There is

considerable variability in rainfall on yearly and decadal scales. Prolonged droughts as evident in the early

2000s, or wet periods which occurred in the 1950s and 1970s, can lead to substantial changes in recharge

rates and groundwater levels. This variability can mask the effectiveness of management strategies aimed

at combating salinity. For instance a decline in groundwater levels may result from a period of below

average rainfall, rather than serving as proof of the success of a particular salinity management strategy.

Conversely good water use efficiency practice may have limited ability to reduce saline expression in years

following high rainfall.

With increased variability expected due to climate change the impacts may only become apparent in the

longer term. It is unclear exactly what impacts climate change will have on the magnitude and timing of

rainfall in the Mallee region, but in general more infrequent and intense rainfall events are predicted. A

greater degree of accuracy in climatic modelling and monitoring of the groundwater and salinity response

would be required to be able to predict or accurately quantify the impact on dryland salinity processes in

the Mallee.

Soil texture also affects the amount and rate of RZD. The clay content of soils is an important determinant

of a soil’s hydraulic properties. A higher proportion of clay leads to greater soil water retention and

reduced permeability, such that more water is available in the soil profile over longer periods of time for

root uptake. More rapid RZD occurs on the lighter, sandy soils of dune crests, in comparison to the heavier

soils of swales. The relationship between clay content and RZD is evident in Figure 8, where RZD drainage

volumes are generally higher in soils with low clay contents compared to soils with higher clay contents.

Figure 8: Deep drainage (RZD) estimates versus clay content of the soil profile (Cook et al. 2001).

9

The amount of water that can be held by a soil also influences RZD rates (Figure 9). For example, very sandy

soils (Tenosols) have low clay content and low water holding capacity compared to Calcarosols which have

high clay contents and higher volumes of soil water storage capacity. Therefore, less rainfall is required to

fill the sandy soil profile and cause RZD compare to the clayey Calcarosol.

Tenosol

0

20

40

60

80

100

120

0 50 100 150

water content (mm)

depth (cm)

Clayey Calcarosol

0

20

40

60

80

100

120

0 50 100 150

water content (mm)

depth (cm)

Figure 9: General soil water content curves for a sandy soil (Tenosol) and a clayey soil (clayey Calcaresol). The area

under the curve (black dots and diamonds) indicates the volume of stored water (mm), the area under the curve

(hollow dots) indicates the amount of stored water not available to plants (after Fawcett 2009).

3.3 Dryland management strategies to reduce root zone drainage

Once the land becomes saline it greatly limits the productivity potential as many commercial crops are

sensitive to saline soils and cannot grow profitably in these areas. Mallee vegetation has evolved to cope

with natural saline areas however there are few plant species that are able to inhabit the high salinities

observed. The primary challenge for Mallee dryland managers is to minimise the expansion of the areas of

secondary salinity to ensure agricultural profitability and protection of native vegetation.

From a land management perspective practices are aimed at making the most efficient use of rainfall

thereby minimising RZD and accession to underlying groundwater. However it must be highlighted that

while management practices can reduce the amount of rootzone drainage and in turn groundwater

discharge, in many instances the legacy of native vegetation clearance is so great that management

practices are limited in their ability to reduce the discharge effect.

The practice of fallowing land as a means to reduce pest and disease pressures has been identified as a

significant contributor to RZD. In 2006 it was estimated that fallow land occupied only 14 per cent of the

land surface in the Mallee however accounted for 40 per cent of the average annual recharge (Mallee CMA

2006). Hypothetically the replacement of fallow land with break3 crops would reduce the future loss of land

to dryland salinisation by 50 000 ha (Mallee CMA 2006).

3 A break crop is commonly used instead of fallowing to prevent the build up of pest and disease pressures particularly in

continuous cropping scenarios. An example of a break crop may be a legume in a cereal cropping cycle or vice versa.

10

Strategies to reduce RZD and maximising on farm water use include: revegetation, strategic tree planting,

use of deep-rooted perennial crops, and use of break crops rather than fallow crops. Table 1 lists various

approaches for fallow replacement.

While the improved management of agricultural land offers several opportunities to reduce RZD and

dryland salinity, some important barriers remain in place. For instance, suitable break crops that are

tolerant of the Mallee’s dry climate are yet to be developed by plant breeders or molecular biologists.

Similarly, the annual crops currently used in the Mallee are unable to fully exploit the available water in the

soil profile due to subsoil constraints (chemical and physical). Further research efforts to better understand

subsoil constraints and the development of more salt tolerant crop varieties could lead to significant

improvements in on farm water use.

Revegetation is an effective strategy, yet it is expensive as it reduces the area of land available to

agricultural production. This strategy is best applied strategically, focussing on zones of higher than average

recharge rates, for instance on coarse textured sandy soils where the point source is identified within a

finite area.

The improved management of dryland agriculture can only partly mitigate recharge as the impacts from

removing the native vegetation are still to be expressed in the landscape. Even with the adoption of break

crops to increase water usage and reduce RZD compared with fallow, break crops are still 45 per cent less

effective than native vegetation in reducing recharge rates (Mallee CMA 2006). Without abandoning efforts

to tackle the issue, there is recognition that dryland salinity is here to stay, and thus some focus has been

directed towards the management of discharge – e.g. through salt interception schemes, the revegetation

of waterlogged areas with salt tolerant species, or the environmental watering of floodplains.

Table 1: Strategies to reduce RZD (Mallee CMA 2006).

Fallow replacement options Requirement for adoption Mechanism to achieve Options

Crops varieties with better

Mallee regional

adaptation

Plant breeding and

evaluation

Range of legumes (food

and feed)

Oilseeds (industrial and

food oils, bio-fumigation)

Multi-use crops (fodder,

green manure, grain)

Viable non-cereal crops

Suitable agronomic

practices

Research development

and extension

Crop specific agronomy

Synergy between crops

More productive pastures to

complement livestock

enterprises and cropping

Genetic improvement in

pastures

Evaluate/ select species

& cultivars

Regenerating annual

legumes

Persistent perennial

legumes

Broader range of species

(extended production

period, ephemerals etc)

11

Enhanced pasture

management

Evaluate and

demonstrate

Establishment in cropping

rotations

Weed control and

persistence

Enhanced soil N for

cropping

Increased livestock returns Select for genetic

improvement

Evaluate new sheep

breeds

Sheep husbandry

extension to increase

carrying capacity

Existing breeds – ramplan

etc

Reduced labour input, $

premium.

Lambing management,

supplementary feeding

Enhanced profitability of

the production unit/farm

Research to optimise

inclusion and

management of trees

and shrubs in the

farming system

Alley farming and shelter

belt systems

Identification of

unprofitable locations for

block planting

Expand plantings of tree

and/or shrub species

Trees and/or shrubs as a

profitable enterprise

Research to identify

appropriate species and

practices

Low rainfall silviculture

Value adding (on-farm or

regional)

Rotation systems that

increase profitability

RD&E on spatial

management of

components of farming

systems

Optimise variable rate

technology and in-

paddock guidance

systems.

Strip cropping/ pasture/

fallow systems

Sub-paddock rotation/

management systems

Novel farming systems

Identification of

alternative enterprises

and land management

New approaches to land

management.

12

3.4 Unsaturated zone processes

Dryland farming and agronomic practices are focused on the management of the soil surface to improve

crop water use of natural rainfall. Water that is not used by the crop or native vegetation must percolate

through the soil before it reaches the regional groundwater. This part of the soil profile is called the

‘unsaturated’ zone and is characterised by pockets of air between the soil particles enabling water to

percolate through. Subsurface clay layers, such as the Blanchetown Clay, can impede the vertical

movement of water causing these pockets to fill with water and the water table to rise (perched

groundwater) or discharge laterally (referred to as seepage, Figure 1). The depth of the unsaturated zone is

governed by the depth of the water table which in turn is determined by the presence and thickness of an

underlying aquitard. Each of these factors determine the rate in which water drains through the soil and

recharges the underlying regional aquifer (Parilla Sands). Cook et al. (2004) developed an approach to

estimate time lags based on drainage rates, clay thicknesses and the depth to groundwater. When applied

to areas of the Mallee that are thick and clay-rich, predicted time lags in the order of 300 years are

obtained.

3.5 Regional groundwater recharge and flow

Water that passes the root zone and impeding layers can eventually reach the regional water table as

recharge - this is often manifested as episodic pulses after larger storm events. This is illustrated within a

salinity observation bore screened in the regional aquifer (Figure 10) where several spikes in the

groundwater level occur upon a relatively flat groundwater table elevation over time. An important note is

that episodic recharge events typically occur between November and March, during the traditional fallow

period or when agricultural systems are at their lowest water use period. Thus significant recharge is likely

to occur when the plants’ ability to prevent it is low. Note that episodic recharge might achieve some

leaching of salt from the root zone, but this is only a short term occurrence - the boost to regional

groundwater levels is the main issue here.

Figure 10: Groundwater levels for Bore 50349 4(near Berriwillock) illustrating episodic recharge within the Mallee

dryland.

4 Source: Victorian Water Data Warehouse http://www.vicwaterdata.net/vicwaterdata/home.aspx

13

The flow of water through the groundwater aquifer will vary according to the hydraulic properties of the

aquifer. High recharge rates may lead to groundwater mounding which may slow water movement and in

turn create greater hydraulic pressure on the regional groundwater system increasing groundwater

discharge.

A better understanding of the connection between the Woorinen/Lowan areas with broader salinity

impacts is a significant outstanding issue for dryland salinity management.

3.6 Groundwater discharge

Groundwater discharge in the Mallee is manifested in several ways including:

• more extensive areas of waterlogged and salinised land in low lying areas or dune swales

• groundwater seepage onto floodplains or salinas that concentrate during the processes of capillary

rise and evapotranspiration

• additional flow to inland surface water features such as saline wetlands

• additional flow to the Murray River.

These discharge processes occur over a significant time frame and may occur some distance from the

source of recharge. The nature of saline discharge will also vary according to the inherent chemistry of the

salt e.g. gypsum, and concentration.

The modern era of dryland salinity management now focuses on management of discharge areas as it is

recognised that recharge areas within the Mallee are broad scale and mitigation activities such as

revegetation are likely to have minimal impact in the naturally saline landscape. With the recognition that

dryland salinity is here to stay, increased focus has been directed towards salt interception schemes, the

revegetation of waterlogged verges with salt tolerant species, and environmental watering of floodplains to

address salinity in the Mallee.

14

4 Mapping the salinity threat in the Mallee Dryland

Considerable investment has gone into projects providing prediction and assessment of the impact of RZD

or deep drainage on the Mallee landscape, for both agriculture and natural assets. The impact and threat of

RZD demanded information on what will be the future implications, so that informed management

prioritisation could be developed. Therefore, it is pertinent to provide two examples of such projects:

The first example being the Lower Murray Landscape Futures (LMLF; Bryan et al. 2007) project assessed the

impact of existing management plans resource condition targets under a range of climate and land use

scenarios. The project specifically looked at the impact of condition targets related to deep drainage. The

project provided a series of Geographical Information System (GIS) layers that described the impact to

biodiversity; productive land and carbon capture by incorporating a range of models and technologies that

included:

• Soil erosion potential

• Salt load assessment modelling (SIMPACT) of river salinity

• Agricultural Production Simulation modelling (APSIM) of deep drainage

• Climate modelling

• Land use impact modelling of the risk from deep drainage to biodiversity

• Analyses of biodiversity to develop indicators of risk.

The project assessed a range of policy options ranging from least expensive to the “Sustainable Ideal”

against a range of climate predictions. It was concluded that in relation to achieving natural resource

management (NRM) objectives i.e. biodiversity, economic gain, deep drainage, wind erosion, and

employment, a targeted approach was the most efficient and effective policy option addressing the areas

of the landscape with the highest threat of salination.

Deep drainage and depth to water table modelling provided predictions of the distribution of land

threatened by rising water tables (Figure 11); in the worst case 199 258 ha of the Mallee were predicted to

be at risk from salinisation.

15

Figure 11: Distribution of land threatened by salinisation within the Mallee CMA under different climate predictions

(Bryan et al. 2007).

The second project is one that determined the salinity risk to native vegetation induced by a range of

different farming systems as modelled within a Bayesian framework (Fawcett 2009). The project

determined the potential risk of deep drainage occurring and the consequence of it occurring in the areas

of sensitive vegetation adjacent to shallow water tables. Adjacent areas were defined as vegetation with a

high salinity sensitivity that occurs within a five kilometre radius.

Four scenarios were assessed under this framework:

1. Adjacent areas of salinity with shallow water table only

2. Adjacent areas of salinity ignoring water table depth

3. Adjacent areas of sensitive native vegetation with shallow water tables only

4. Adjacent areas of sensitive native vegetation ignoring water table depth.

The project evaluated the likelihood of a land parcel having a high rate of deep drainage that will then

cause impacts to native vegetation. The likelihood was determined by the susceptibility of the land to RZD

and the land management practices employed. The causal impact or consequence was determined by the

sensitivity of the plant to salinity/ water logging together with the value of the vegetation against its

ecological vegetation class (EVC).

16

Susceptibility Management Sensitivity Value

Likelihood Consequence

Risk

Figure 12: Risk framework adapted from Fawcett (2009) to assess risk of deep drainage.

A working example is the risk of deep drainage occurring on a property using traditional cropping methods

including a fallow period with areas of shallow water table and increasing salinity.

Risk was calculated by evaluating the likelihood of deep drainage occurring using traditional cropping and

fallow period with the consequence equated to:

• Increasing the area of pre-existing saline discharge with areas of shallow water tables

• The area of sensitive EVC native vegetation within areas of shallow watertable.

The results provided a spatial map of which land parcels with the greatest risk of deep drainage affecting

native vegetation under the traditional management regime (with fallow) if employed across the Mallee

from March to November (Figure 13).

17

Figure 13: Risk assessment of Traditional Cropping with fallow period to native vegetation (after Fawcett 2009).

• Red are the land parcels that have a very high risk (likelihood + consequence)

• Orange areas are the land parcels with a high risk (likelihood + consequence)

• Yellow areas are the land parcels with a moderate risk (likelihood + consequence)

• Green areas are the land parcels with a low risk (likelihood + consequence)

• Black – Mapped sensitive vegetation.

18

5 Dryland salinity statement (Victorian State Government perspective)

The Victorian state government approach to dryland salinity is detailed within the Victorian Dryland Salinity

(VDS) Statement 2012 (DSE 2012). The VDS statement will guide the management of dryland salinity

through Catchment Management Authorities (CMAs), the Department of Primary Industries (DPI) and other

NRM practitioners. It is pertinent to briefly consider the main overarching principles of the statement.

The document acknowledges two important changes to the approach of dryland salinity management in

Victoria, they are:

1. A shift towards asset based investment strategy

2. An increase in the importance of salinity monitoring to meet the obligations under the

Commonwealth Water Act 2007.

The Victorian Government proposes five main approaches (DSE 2012):

• Landscape or Ecosystem focus: Dryland salinity will be recognised as one of many catchment

processes that may threaten priority natural resource assets (e.g. River health outcomes).

• Risk Assessment: The risk of dryland salinity to priority assets will depend on a number of factors,

including salinity susceptibility, management practices conducted on susceptible areas, proximity of

the salinity discharge sites to assets, resilience of the asset against salinity, the value of the asset at

risk and the multiple effects of other threats.

• The Salinity Provinces Framework: Provides a structured process that will guide future investment

according to priority setting for managing dryland salinity using the assets-based approach.

• Monitoring the impact of salinity on priority assets: An effective groundwater and salinity monitoring

program will be used to gain a better understanding of potential risks, and to help measure the

effectiveness of different salinity remediation approaches.

• Reporting obligations under the Commonwealth Water Act 2007: We will continue to ensure that

Victoria progresses towards meeting revised “End of Valley Targets” and obligations under the

Commonwealth Water Act 2007.

19

6 Summary

6.1 State of Knowledge

Considerable knowledge has been gained regarding many aspects of the key processes and impact of root

zone drainage on agricultural land and native vegetation in the Mallee dryland. They address areas

including:

• The geomorphic evolution of the Mallee and why the Mallee landscape is susceptible to salinisation

• The relationship of soil type and farming system in relation to deep drainage rates

• The farming practices that are required to reduce the risk of deep drainage

• The impact of deep drainage (post land clearing) to the Mallee landscape, captured by the mapping

of secondary salinity

• The future impacts from deep drainage under a range of farming, policy and climate scenarios.

6.2 The four most important points about salinity in the Mallee dryland

• Saline wetlands are a natural feature of Mallee landscapes. The geological formations of the Mallee

region are such that small changes in the water budget can cause an increase in groundwater levels

and land salinisation.

• Under wet conditions (e.g. large rainfall events), increased recharge may not be preventable as high

rainfall events may mask the efforts of land management practices in reducing RZD.

• Greater focus on management practices that target the discharge sites to mitigate spread of

secondary salinity.

• The impact of past vegetation clearing are yet to be observed in the Mallee landscape and may take

several hundreds of years to be observed in the Murray River.

6.3 The four most important points to consider in the future

• A better understanding of the connection between the Woorinen/Lowan areas with broader salinity

impacts.

• Continue to encourage efficient farming systems to utilise soil water stores in changing climate

sequences and economic pressures.

• To maintain targeted NRM policy based around high value environmental and agricultural assets.

• To maintain monitoring of groundwater levels and the size (expansion and shrinking) of secondary

salting areas to better understand the effects of climate on dryland salinity.

20

References

Allison, GB, Cook, PG, Barnett, SR, Walker, GR, Jolly, ID, Hughes, MW 1990, Land clearance and river

salinisation in the western Murray Basin, Australia. Journal of Hydrology, vol. 119, pp. 1-20.

Bowler, JM, Kotsonis, A and Lawrence, CR 2006, Environmental Evolution of the Mallee region Western

Murray Basin. Proceedings of the Royal Society of Victoria, vol. 118 (2), pp. 161-210. ISSN 0035-9211.

Bryan, BA, Crossman, ND, King, D, McNeill, J, Wang, E, Barrett, G, Ferris, MM, Morrison, JB, Pettit, C,

Freudenberger, D, O’Leary, GJ, Fawcett, J and Meyer, W 2007, ‘Analyses of Regional Plans and Landscape

Futures for Dryland Areas’, Lower Murray Landscape Futures, vol. 2.

Cook, PG, Leaney, FW, Jolly, ID 2001, Groundwater recharge in the Mallee Region, and salinity implications

for the Murray River – a review, CSIRO Land and Water Technical Report 45/01, November 2001, pp. 133.

Cook, PG, Leaney, FW, Miles, M 2004, Groundwater Recharge in the Northeast Mallee Region, South

Australia. CSIRO Land and Water Technical Report 24/05.

DSE 2012, Victorian Dryland Salinity Statement. Department of Sustainability and Environment, Victoria.

2012.

Fawcett, J 2009, Using a Land Use Model to determine the risk of deep drainage within the Mallee.

Department of Primary Industries, Bendigo, Victoria.

Grinter, V and Mock, I 2009, Mapping the Mallee’s Saline Land. Stage 3: Classifying Mapped Salinity. Final

report for Mallee Catchment Management Authority.

Macumber, PG 1980, ‘The influence of groundwater discharge on the Mallee Landscape’. In Storrier, RR and

Stannards, ME (eds), Aeolian Landscapes of the Semi-Arid Zone of South Eastern Australia. Australian

Society of Soil Science, Riverina Branch, pp. 67-84.

Mallee CMA 2006, Victorian Mallee Salinity and Water Quality Management Plan – for Submission to

Government. Mallee Catchment Management Authority.

Miles, MW, Kirk, JA, Meldrum, DD 2001, ‘Irrigation SIMPACT: a salt load assessment model for new

highland irrigation along the River Murray in South Australia’. Environmental and Socio-Economic

Databases, Government of South Australia and Planning SA Technical Report, November 2001, pp. 59.

SKM 2012, State Wide water table geometry. Department of Sustainability and Environment, Victoria.

Stephenson, AE 1986, Lake Bungunnia: a Plio-Pleistocene megalake in Southern Australia.

Palaeogeography, palaeoclimatology and Palaeoecology vol. 57, pp. 137-156.

Wang, E, Miles, M, Schultz, T, Cook, P, Maschmedt, D, Munday, T, Leaney, T, Walker, G and Barnett, S 2005,

Targeting Dryland Areas in the Mallee for Controlling Groundwater Recharge and Salt Load to the Murray

River. Report to Client No. #/2005. CSIRO: Canberra.

5. The irrigation footprint Sunraysia Authors: Tim Cummins1 and Charles Thompson2

Mallee Catchment






Copyright


Authority 2013

Disclaimer













publication.

Publication details


Chapter 5 – Irrigation footprint Sunraysia.


April 2013

Authors: Tim Cummins1 & Charles

Thompson2

1 Tim Cummins and Associates 2 RM Consulting Group

Cover images




Table of Contents

1 Summary................................................................................................................................................... 1

2 Footprint – A careless metaphor? ............................................................................................................ 2

3 Pattern-making ......................................................................................................................................... 3

3.1 Cordwainers ..................................................................................................................................... 3

3.2 Cobblers ........................................................................................................................................... 4

3.3 Bespoke lasts.................................................................................................................................... 5

4 Nike or Psyche?......................................................................................................................................... 6

4.1 An old woman and an old shoe........................................................................................................ 6

4.2 Big shoes to fill – half empty or half full?......................................................................................... 8

4.3 The psychology of patterns – and blots on the landscape .............................................................. 9

5 Evidence at the scene of the incident..................................................................................................... 11

5.1 Deregulating textiles, clothing and footwear – and – dried fruit and citrus.................................. 11

5.2 Wine pressing (and kick-starting)................................................................................................... 11

5.3 Achilles’ heels................................................................................................................................. 12

6 Into the distance ..................................................................................................................................... 13

7 Appendix A. Pattern-making with works licences .................................................................................. 14

7.1 Siting............................................................................................................................................... 14

7.2 Construction................................................................................................................................... 14

7.3 Operating ....................................................................................................................................... 15

8 Appendix B. Pattern-making with water-use licences............................................................................ 16

8.1 Minimising salinity ......................................................................................................................... 16

8.2 Protecting biodiversity ................................................................................................................... 18

8.3 Managing groundwater infiltration ............................................................................................... 18

8.4 Managing the disposal of drainage................................................................................................ 19

8.5 Minimising the cumulative effects of water use............................................................................ 19

9 References .............................................................................................................................................. 20

List of Figures

Figure 1: The Chaffeys’ vision splendid – showing, at point A, the approximate location of the proposed

major centre, Irymple (Source: Google Maps 14 May 2012). ........................................................................... 3

Figure 2: The Red Cliffs irrigation district (SunRISE 21 2011). The red polygons were not actively irrigated in

2010/11. ............................................................................................................................................................ 4

Figure 3: Kings Billabong in the north and Psyche Bend Lagoon in the south were originally different parts of

one contiguous wetland system. ...................................................................................................................... 6

Figure 4: Scarcely 50 metres of consolidated roadway-cum-dam wall, separates Kings Billabong from Psyche

Bend Lagoon. ..................................................................................................................................................... 7

Figure 5: Actual annual water use compared with total annual use limits (Source: Mallee CMA unpublished).

........................................................................................................................................................................... 9

Figure 6: The scatter of non-irrigated (red) properties in Merbein in 2011 shows no obvious non-random

pattern (Source: SunRISE 21 2011).................................................................................................................. 10

Figure B1: Total area of irrigation in each salinity impact zone over time (Source: SunRISE 21 2012). ......... 17

Figure B2: Changes in the irrigated area within each salinity impact zone over time (Source: SunRISE21

2010)................................................................................................................................................................ 18

List of Tables

Table A1: Changes in the irrigation footprint in the private diversion area for each salinity impact zone

between 1997 and 2012 (Source: SunRISE21 2012). ...................................................................................... 17

1

1 Summary

There is more to the irrigation ‘footprint’ than the total irrigated area or the total volume of root-zone

drainage might suggest – when considered either jointly or separately. It is the offsite impacts of irrigation

that are important to public policy. Those impacts are significant, and they were not properly considered in

the design criteria for the irrigation districts. Nor were they adequately considered for the haphazard

development that preceded the Nyah to SA Border Salinity Management Plan.

A risk-based approach to minimising the offsite impacts of irrigation development was designed and

implemented as a result of the salinity management plans. This approach has been successful and it is

continuing to evolve. Everyone who has established an irrigation development since entitlement trade was

introduced has had to factor into their investment decisions the costs of minimising or offsetting the offsite

impacts.

There is scope for irrigation to continue to expand in the Mallee. However, low allocations during droughts

mean that there is a natural limit to how much perennial horticulture can be sustained. There is also a

possibility that some of the currently dried-off land will remain unirrigated.

Vigilance is still required to ensure that offsite impacts continue to be managed appropriately. It is

important for the irrigation development guidelines to continue to evolve; they need to be continuously

tested to make sure they are still appropriate for the known risks. The potential to change WUL conditions

– provided there is public support for the change – provides a safety net if any significant risks are missed.

2

2 Footprint – A careless metaphor?

This chapter was written in response to an invitation to contribute to the Mallee Salinity Statement (MSS).

The invitation included the title of the chapter. At first blush, the task seemed relatively straightforward –

we interpreted the need to describe the irrigation footprint as the need to describe the total area of

irrigation and the average volume of root-zone drainage that might be ascribed to that area.

In one sense that would be useful information; it would help to quantify the total volume of water, which,

mediated through the prism of on-farm drainage, as described in the MSS chapter: drainage, is free to

interact with the regional hydrogeology to manifest as salinity problems.

On reflection, however, we concluded that description was inadequate. Think for example of, say, 55 000

irrigated hectares transmitting a long-term average of, say, 0.75 ML per year of root-zone drainage. If that

footprint were uniformly distributed along, say, a 10-kilometre strip adjacent to the River Murray from

Nyah to the SA Border it would have quite different salinity implications to a footprint of the same

dimensions concentrated in a semi-circle around Mildura.

For one thing, in the first example there would be less incidence of what Quiggin (2001) described as

“congestion externalities”3. For another thing, the first example would also involve more water being used

in the low salinity impact zones; therefore, leaving aside the impact of salt interception schemes, it would

have less impact on river salinity.

To be sure, either of those examples could be usefully mapped with those differences explained, but

neither map would easily explain the legacy of different patterns of development at different stages of

irrigation history. For example, they would not explain how different property sizes influence the potential

to respond to changing commodity prices in the future. Similarly, they would not explain changes in crop

type, or irrigation systems, over time and how these might affect root-zone drainage. Nor would they

explain the subtly different ways in which existing irrigation interacts with a variety of different types of

wetland. Nor would they explain the likely future patterns of growth in irrigation – in the context of existing

development guidelines.

This chapter of the Mallee Salinity Statement rests on the premise that it is important to understand the

nature of the changes taking place in irrigated agriculture. That understanding should help to influence the

assumptions factored into any future analysis of groundwater trends. Groundwater systems provide the

medium through which changes taking place at human time-scales interact with changes laid down over

geological time-scales.

3 Congestion externalities arise when members of a group generate negative externalities affecting each other. Congestion

externalities frequently arise in irrigation areas. Application of irrigation water results in rising water tables, with consequent

waterlogging and salinisation. However, because of the complex hydrology of water catchments, such problems rarely display the

complete symmetry of textbook congestion problems. Activities such as tree clearance have most effect on water tables when they

take place in recharge areas, but the consequences are most evident in discharge areas. Thus, to some extent, there is a unilateral

externality that is generated by land users in recharge areas and affects land users in discharge areas (who may or may not be the

same people) (Quiggin 2001).

3

3 Pattern-making

3.1 Cordwainers

The Chaffey Brothers were the first designers to influence today’s irrigation footprint. In that sense, they

were akin to cordwainers – the people who design and make shoes. The Chaffeys’ 1887 vision-splendid

encompassed all of present-day First Mildura, Merbein and Red Cliffs irrigation districts as well as the

uncleared native vegetation that completes the square separating Mildura from dryland farming.

Figure 1: The Chaffeys’ vision splendid – showing, at point A, the approximate location of the proposed major

centre, Irymple. (Source: Google Maps 14 May 2012).

Had the Chaffeys been successful, their irrigation footprint would have consisted of three grids of four-

hectare properties radiating out from the proposed major centre of Irymple (not to be confused with

present-day Irymple). One grid would have gone north to White Cliffs now Merbein), another east to Red

Cliffs, and the third, which is extant, northeast to Mildura.

The State Rivers and Water Supply Commission (SRWSC) originally laid Merbein out in 1909 as a less rigid

grid of much larger properties. These were sized for dairying. By the time they started surveying the WWI

4

soldier-settlement scheme of Red Cliffs in 1919/20, the SRWSC engineers were trying to work with the

landscape. Rather than subduing it under a grid, they divided the district into a series of uniquely shaped

polygons of roughly equal area. Each block was optimised for the necessitude’s of furrow irrigation. Apart

from the main pumps on the river, gravity was still king.

Figure 2: The Red Cliffs irrigation district (SunRISE 21 2011). The red polygons were not actively irrigated in 2010/11.

A similar approach was followed in 1948 when the Commonwealth established the Robinvale Irrigation

District as a WWII soldier-settlement scheme. In Robinvale however, more effort was made to exclude land

deemed undrainable or otherwise unsuitable for irrigation. Nonetheless, as irrigation technologies

improved, and as irrigators terms of trade inevitably declined, this out-ground was gradually brought into

production.

3.2 Cobblers

Unlike cordwainers, cobblers patch and mend. Merbein was patched and mended after a shaky start with

dairying. After WWI it was converted into a soldier-settlement scheme with dried vine fruits as the main

commodity. Ironically, the original, larger properties would have been better suited to today’s technologies

and economies of scale.

Improvements in pumping technology and the increased availability of electrical power meant that

throughout the 1950s, 60s, 70s and 80s the irrigation footprint increased, in piecemeal fashion, outside the

irrigation districts. Such developments occurred throughout the Victorian Mallee, but the largest

aggregation of the day was in Nangiloc-Colignan.

5

Up until 1969, there were virtually no government controls on these developments – other than the fiats

involved in issuing extra water licences. The drought of 1967, and the implementation of the Lake

Hawthorn diversion scheme, which later provided the building blocks for the Mildura-Merbein salt

interception scheme, prompted concern about the salinity impacts of increased irrigation drainage to the

river.

The response was to include a standard condition, proscribing drainage to the river, on all diversion licences

issued after 1969. When the Nangiloc-Colignan Salinity Management Plan (SMP) was put in place in 1991

more than 5000 hectares were being irrigated – 84 per cent of which had been developed after 1969. The

geology of that river reach – where the Woorinen formation had blown over the former floodplain of the

north-flowing river – ensured that water tables quickly rose to cause waterlogging and drainage problems.

Some properties on the western edge of the development enjoyed good natural drainage, but that only

served to exacerbate the problem for other, relatively small, land-locked properties closer to the river.

There were no economic prospects for adequate drainage disposal on those land-locked properties. And

unlike the earlier situation inside the irrigation districts, governments initially had no appetite to help install

communal drainage infrastructure in Nangiloc.

3.3 Bespoke lasts

Tailor-made (bespoke) shoes are shaped on individually crafted lasts. For the last twenty years, since the

Nyah to SA Border SMP kicked-off the concept of irrigation development guidelines, the irrigation footprint

has grown organically. Importantly though, each incremental development represents a unique response to

a set of common rules. Each developer is required to tailor crop layouts, and irrigation layouts, to land

capability.

In deciding where to locate their developments, developers are also, in effect, guided to those parts of the

landscape where they are likely to have the least impact on biodiversity and on river salinity. The ways in

which this guidance is provided is explained in more detail in Appendices A and B.

6

4 Nike or Psyche?

Before Nike became a brand of shoes, she was the goddess of victory; but unfortunately, she seldom visited

Sunraysia in that guise.

As Greco-Roman gods go, Psyche rather than Nike has more to lend to a rich understanding of the irrigation

footprint in Sunraysia. In mythology, Psyche represented the deification of the human soul4. Certainly, the

men and women who established the irrigation footprint did not lack soul. Perhaps that is why Psyche has

been further immortalised in the name of Psyche Bend and hence Psyche Bend Lagoon – the site of an

important accountable action under the Basin Salinity Management Strategy (BSMS).

4.1 An old woman and an old shoe

At first blush, Psyche Bend Lagoon and Kings Billabong today look to represent something akin to what

Henry Lawson described as the Old Dead Tree and the Young Tree Green.

Figure 3: Kings Billabong in the north and Psyche Bend Lagoon in the south were originally different parts of one

contiguous wetland system. Human intervention has rendered them hydrologically separate while also making one a

groundwater recharge site and the other a discharge site (source: Google Maps 15 May 2012).

4 It is a long story, but Psyche’s deification stemmed from the night Cupid accidentally pricked himself when Psyche caught his gaze.

7

However, closer examination reveals that both wetlands represent different manifestations of the irrigation

footprint – outside the irrigated area per se. Psyche Bend Lagoon is exposed to the increased pressure in

the regional groundwater system caused by irrigation on the escarpment above. Kings Billabong by contrast

is off-stream storage for the First Mildura Irrigation District (FMID) supply system. As such, being kept

artificially full, it exerts pressure on the groundwater system not the other way around. This keeps salt

away from the surrounding vegetation, allowing it to thrive. On the other hand, this means that Kings

Billabong is deprived of its natural drying cycle – rendering it the billabong of eternal youth5. Meanwhile,

the Psyche of Psyche Bend Lagoon is old before her time.

This juxtaposition becomes sharper still when you consider the short distance of roadway-cum-dam wall

that separates the two. The irony is that Kings Billabong would have been decommissioned as part of the

irrigation system when electric pumps were installed in 1956 – had saline groundwater not scuppered plans

to dig a channel from the river to the central pumps on the billabong. Had those plans proceeded Kings

Billabong might now have looked much like Psyche Bend Lagoon. It is now protected from this fate by

virtue of the conditions written into LMW’s Bulk Entitlement. Nonetheless, until recently it has been

treated as something like an old shoe; so comfortable we were reluctant change it. Efforts are now being

made restore its drying cycle.

Figure 4: Scarcely 50 metres of consolidated roadway-cum-dam wall, separates Kings Billabong from Psyche Bend

Lagoon.

The point here is that the irrigation footprint extends beyond the immediate irrigated land – and even

beyond the 2000 hectares of drainage basins associated with the pumped irrigation districts. Moreover, the

effects of irrigation are played out differently in the various wetlands along the 750 kilometres of river

frontage in the Mallee CMA region.

5 To invoke Flash Nick from Jindavick (http://www.imdb.com/title/tt0071506/ 15/05/2012).

8

4.2 Big shoes to fill – half empty or half full?

The irrigation footprint is always in a state of flux; people, crops and production systems all come and go –

albeit at different temporal scales. Three major changes in the last decade stand out:

• The 100 per cent increase in the total irrigated area – brought about by water trade from 1994

onwards

• The rapid conversion from dried vine fruits to wine grapes during the 1990s

• The drying-off of previously irrigated land in response to low commodity prices and low water

allocations.

In thinking about what might happen next, it pays to remember that the small blocks and high annual water

charges associated with the pumped districts militate against any prospect of commercial cereal, pasture or

fodder production, including lucerne. The commercial future is horticulture or nothing. It is also worth

noting that waves of optimism and pessimism colour forecasting in irrigated horticulture. These waves in

turn affect the formation of price expectations and therefore investment levels. Policy makers also need to

be wary about getting caught up in these cycles; the long-run future is unlikely to be as good, or as bad, as

it is being painted at any given time.

Horticultural products are vulnerable to production cycles, and price cycles. Whenever prices are high, new

entrants are attracted, and each of them establishes expectations around the same price forecast. The long

lead times between investment and economic yields mean that those prices might hold up until the new

supplies hit the market. Depending on how many new entrants there are relative to the size of the market

(and the higher the previous price the more entrants there will be) prices may then slump. New entrants

are then discouraged until such time as the price rises high enough to encourage renewed investment

(Cummins et al. 2008).

Horticultural demand is also strongly related to consumer incomes. This is especially true of demand for

specific varieties or specific quality standards. Nonetheless, price-based substitution is ubiquitous;

consumers will buy apples if bananas are judged to be too expensive and vice versa. But taste (fashion) is

also a powerful force in horticultural industries as evidenced by the near random changes in preferences

for different varieties and styles of wine. The inflexibility of horticultural industries and shifts in demand

makes risk management increasingly difficult especially for small producers who cannot spread their output

across a number of products or varieties (Cummins et al. 2008).

The waxing and waning of horticultural production is not currently factored into the BSMS accountability

mechanisms surrounding irrigation development. Salinity accountability for expanded irrigation production

is based on the maximum volume that might be used in any given year. This is determined by adding

together the annual use limits (AULs) on every water-use licence (WUL) in each salinity impact zone. Any

change in this total from one year to the next is treated as an accountable action under the BSMS – with

coefficients used to translate each extra GL of AUL in each impact zone into ECs at Morgan. Moreover, the

people expanding the irrigation footprint in this way must, in effect, pay for the extra AUL they require.

One complication is that total actual use has historically always been lower than the total upper limit

represented by the AUL (see Figure). This raises a series of questions. Is it still appropriate to be

deliberately conservative in using AULs rather than actual water usage as the accountable action? Should

the coefficients be changed to better align the theoretical with the actual? Or will the developing market in

AULs eventually fix all this up for us if people sell their spare AUL?

9

100000

300000

500000

700000

2006-07 2007-08 2008-09 2009-10 2010-11 2011-12

Meg

ali

tres

Water Use

(annual report)

LMW AUL

LMW AUL (VWR)

Water Use (VWR)

Source: 1 Water Use: LMW and FMIT 2006-07 and 2007-08 Annual reports

2 LMW AUL: annual change from baseline - Mallee CMA region Salinity Register

3 LMW AUL: Victorian Water Register 30 June 2012

4 LMW water use: Victorian Water Register 30 June 2012

Seasonal

Allocation 35%

Seasonal

Allocation 43%

Seasonal

Allocation 100%

Seasonal

Allocation 100%

Seasonal

Allocation 98%

Seasonal

Allocation 100%

Figure 5: Actual annual water use compared with total annual use limits (Source: Mallee CMA unpublished).

It is important to note here, however, that most of the total AUL was effectively in place in the BSMS

baseline year of 1988; that component of the AUL therefore does not constitute an accountable action

under the BSMS. For that AUL component, any shortfall in use relative to total AUL might lend itself to

being incorporated into something akin to the Reduced Irrigation Salinity Impact (RISI) credit claim.

By contrast, for that component of the total AUL associated with increased development arising from water

trade, accountability based on use rather than total AUL would mean a smaller EC debit arising from the

Nyah to SA Border SMP accountable action. Note here however, that since these developers must, in

effect, buy AUL they have an incentive to hold close to what they expect to use after allowing for an

“insurance” factor. Moreover, while it would be valid to account for the claim in that way, it would require

the Victorian water register (VWR) to be able to differentiate between baseline AUL and Δ AUL. This would

add further complexity to an already complex system.

A cap on total AUL is currently being set for the L3 and L4 salinity impact zones. Future developments will

therefore be concentrated in the L1 and L2 zones. Trade in AUL, which is steadily evolving, should facilitate

any developments in the other zones. It will be important to understand how such trade interacts with the

RISI-style claims.

As with each of the accountable actions, it is important to rigorously separate out EC debits and credits

rather than simply identify net impacts. For irrigation developments that required the payment of a salinity

levy, usage less than AUL might reduce the size of the resultant EC debit. For other irrigation developments,

usage less than AUL might enable a claim for an EC credit.

4.3 The psychology of patterns – and blots on the landscape

Not just the numbers, the pictures of the 2011 Irrigation Status Report tell a challenging story. The

cumulative and current maps of irrigated and non-irrigated land have a random, almost Rorschach-like,

scatter (Watson & Cummins 2011).

It is not hard to understand why the pattern appears so random. The economics and sociology involved in

deciding to cease irrigation depend upon individual features of the irrigator. It has much to do with the

10

nature and timing of their previous financial decisions, their stage of life and their participation in off-farm

employment. It has little, if anything, to do with matters of geography and location. But the scatter is of

major policy interest for at least three reasons:

• It demonstrates the difficulty of contiguous property amalgamations

• It emphasises the potential ‘right to farm’ and externality issues when irrigation and pure residence

happen side-by-side

• It indicates the numerous planning challenges surrounding the refurbishment or reconfiguration of

irrigation infrastructure (Watson & Cummins 2011).

Figure 6: The scatter of non-irrigated (red) properties in Merbein in 2011 shows no obvious non-random pattern

(Source: SunRISE 21 2011).

11

5 Evidence at the scene of the incident

5.1 Deregulating textiles, clothing and footwear – and – dried fruit and citrus

The current irrigation footprint has much to do with decisions taken during the micro-economic reforms of

the 1980s. Many industries, including the textile clothing and footwear industries were deregulated during

that time. This helped to reduce prices for consumers and expand their choices. It brought about significant

benefits for Australia as a whole, but it also involved significant adjustment costs for those most directly

affected.

The introduction of water trade can be seen as part of the same desire to give individuals choice and limit

the role of government. The expectation was that economic efficiency would best be achieved by defining

property rights, regulating to avoid externalities (where necessary) and allowing price signals to guide

economic activity.

Deregulation of the dried fruit and citrus industries needs to be considered in this broader context. It also

created significant adjustment issues, though for a while it looked as though the wine boom might alleviate

these. Nonetheless, it also encouraged significant innovation in those industries and it freed up resources

to be deployed elsewhere.

With the benefit of hindsight, regulation can be seen as an effort to stave off the inevitable process of farm

consolidation following ‘closer settlement’. As so eloquently described by the DPI’s Neil Barr in his book,

The House on the Hill, the history of agriculture in Victoria shows terms of trade pressures, coupled with

ongoing technological improvements, driving a steady increase in the farm-scale necessary to sustain a

farming family (Watson & Cummins 2011).

Protection of the dried fruits and citrus industries gave the appearance of containing those pressures, but

they were building up nonetheless. When eventually the pressures were released, through industry

deregulation, they resulted in a shakeout in farm ownership. For dried fruit growers, however, the

shakeout was deferred because deregulation happened to coincide with the onset of the wine boom. This

itself was the result of another coincidence (Watson & Cummins 2011).

5.2 Wine pressing (and kick-starting)

Australia’s breakthroughs in winemaking technology coincided with the reform of liquor licensing laws in

the UK. Australia became capable of producing high volumes of consistent-quality cheap wines at the same

time that the UK’s few large supermarkets (then taking market share from the many small ‘off-licences’)

became capable of distributing high volumes of Australian wine (Watson & Cummins 2011).

Because the boom started as the dried fruit industry was being deregulated, there were large stores of

human capital (the grape growing knowledge held by thousands of small growers), physical capital (grape

growing plant and equipment) and natural capital (land and water) capable of being redeployed quickly

from dried fruit to wine production. That redeployment also allowed the wineries to concentrate their own

first round of capital expenditure on stainless steel rather than land, water, genetic material and grape-

growing skills. Later they invested in large-scale grape production (Watson & Cummins 2011).

Ramping up wine processing potential is no trivial matter, and matching that potential with both the supply

of grapes and the demand for wine is fraught. In later stages of the boom, and even more so in the bust,

wineries, in responding to the universal business imperative to keep reducing costs, sought to reduce their

transaction costs and their quality assurance costs by dealing with fewer growers. It was cheaper and easier

for them to deal with hundreds of large growers rather than thousands of small growers. But in any case it

was proving impossible for small-scale grape growers to compete on price with large-scale producers. And

by that time, other countries were taking advantage of the winemaking technology (Watson & Cummins

2011).

The drought-induced need to buy water allocations, and in particular the panic buying of allocations early in

the 2006/07 season added yet another shock to small-scale grape production systems and thus

12

exacerbated the underlying problem of low wine prices. The net result was much irrigated land being dried

off (Watson & Cummins 2011).

5.3 Achilles’ heels

Water trade, the wine boom and the growth of the almond industry meant that most of the modern large-

scale horticultural plantings of the past twenty years were located on green field sites outside of the old

irrigation districts. This gave them access to large parcels of land without redundant assets. It also gave

them more control over the timing of their irrigation and it helped them to avoid the inconvenience of

dealing with water authorities on a daily or weekly basis.

It is difficult for farming families to accumulate the capital necessary to fund such large activities.

Consequently, a number of other funding models were followed. Some involved direct investment from

wineries. Others involved established agricultural companies. Others were funded by managed investment

schemes (MIS) – some of which ultimately collapsed, while others endure.

The need to purchase allocations at high prices during the drought put a strain on many businesses –

especially those exposed to the wine slump. On top of this however, the business models for some, but not

all, of the MISs turned out to be akin to ‘Ponzi schemes’. That is, some of them offered abnormally high

short-term returns in order to keep enticing new investors. The high returns for those required an ever-

increasing flow of money from investors in order to keep those schemes going. When eventually the

stream of new investors dried up, those particular MIS developments were sold. As it turned out, however,

the underlying business fundamentals of horticultural production were sound, and for now, at least, those

plantings endure in the ownership of various companies (Watson & Cummins 2011). Other MISs endure in

their original form. In either case, the main message is that some horticultural crops do lend themselves to

large-scale, extensive, business models. Some of those individual developments were as large as the

individual irrigation districts established at the end of the 19th and the start of the 20th Centuries.

Importantly, as discussed below, each of the more recent developments has been subject to guidelines

designed to minimise their impact on the environment or on other people.

Apart from revealing the fatal flaw at the heart of those particular MISs, the trend to large-scale

horticulture also revealed a flaw at the heart of the part-time farming model that had built up inside the

irrigation districts. Put bluntly, it looks like any horticultural production system that lends itself to part time

farming will also lend itself to extensive, capital intensive farming systems. And economies of scale, and

superior risk management options, mean that the large-scale operations will likely out-compete the part-

time operations.

If this assessment is correct, the inference is that the commercial future for irrigation inside the pumped

districts is intensive, full-time horticultural production systems or nothing. For example, so far, there have

only been unsuccessful attempts to apply large-scale approaches to table grape production; timeliness,

attention to detail, nerves of steel, good connections and real-time market intelligence are everything

when it comes to table grapes.

13

6 Into the distance

No one knows what will happen in the future. As outlined above, if there were to be further growth in the

irrigation footprint in the Mallee it will likely be in horticulture. Irrigated perennial horticulture in semi-arid

regions offers the potential to control plant growth and deliver predictable yields.

Therefore, from this vantage point, it looks that horticulture might continue to expand in the Mallee. There

are natural limits, however, to how far it might expand. The recent experience of 30 per cent allocations on

the Murray system suggests that there is a risk of periodic catastrophic loss if perennial horticulture

expands to require more than something approaching 30 per cent of the total volume of high reliability

water shares.

The future of the pumped irrigation districts is not yet clear. Some of the previously irrigated land is likely

to become non-commercial horse paddocks or storage-cum-service points for non-permanent plant and

equipment – such as trucks and contract-harvesting equipment (both dryland and irrigation). Some of the

previously irrigated land will eventually provide housing lots for the growing city of Mildura and its

satellites. It is conceivable that most, if not all, of the rest will eventually be devoted to table grape and

vegetable production, but this is likely to happen through steady, organic growth; it will not happen

overnight. Other crops may also emerge, if they do, they will probably depend on access to the skilled and

semi-skilled labour that gives the pumped districts a comparative advantage.

In terms of the private diversion areas, the end of the drought and the return to wet conditions will test the

drainage layouts of those plantings developed over the past ten years. Changes in ownership mean that

some of the new owners may be unaware of the drainage contingencies that were identified as a

prerequisite for the granting of new irrigation licences. This may mean a return to pressure on government

to solve any drainage problems that may appear. This should be resisted. The scale of the developments

makes it easier to insist that problems be internalised. And, hopefully, the records that have been collected

by government agencies as part of the irrigation development process will help to make it clear that the

developments were allowed on the proviso of individual responsibility for any problems that might emerge.

14

7 Appendix A. Pattern-making with works licences

Works licences aim to manage the externalities associated with infrastructure developments on waterways.

The management issues cover three phases of environmental risk:

• Siting

• Construction

• Operation.

As outlined in a recent report by the National Water Commission (2012), government agencies endeavour

to provide potential developers with a wealth of geographical information even before applications for

works licences are lodged. Early in the process, agencies provide comparative, not definitive, information

about the degree of difficulty likely to be involved in gaining development approval on a site, compared to

other sites (Cummins 2004).

Communicating regulatory concepts and issues early in the process means that there is much less risk that

developers will perceive that red tape is being used to block development on an already chosen site.

7.1 Siting

Choosing the site for a new irrigation development starts with an assessment of suitable pumping sites on

the river. The shorter the distance between the pump site and the irrigation development, the lower the

establishment cost of the development. Moreover, the less native vegetation between the pump site and

the irrigation development, the less clearing is required to install the works; this lowers the environmental

costs, and the transaction costs, involved in gaining approval6. The proximity to power sources is also an

important part of the site selection process (Cummins 2004). Essentially, sites with river frontage are

prized.

In the Victorian Mallee, most river frontages are reserved as public land. Parks Victoria can grant

easements across that land. Nonetheless, it now has a policy of not allowing new pumping sites to be

developed. Instead, it seeks to consolidate pumping sites to reduce the area of disturbance associated with

pipes being laid and pumps being installed (Cummins 2004).

7.2 Construction

Works, including pump houses, must meet strict environmental and aesthetic standards (MDBC 2006).

Typically, developers must lodge siting and construction plans with their applications for works licences. As

described by the Victorian Government (2010), the plans must be fully dimensioned design plans and must

include details of:

• property boundaries

• existing native vegetation

• the location of proposed works and associated works

• a survey of the waterway channel at the site of the proposed works

• existing features, including waterways, works, buildings, power lines, easements, roads, access

tracks, fences, channels, drains, pipelines and water storages.

6 This is especially true where native vegetation has been retained on the floodplain. Vegetation retention controls in each state

may allow some trees to be cleared to install works, but only where offsets can be arranged to bring about a net gain in habitat

values. Since road reserves often contain a significant percentage of the remnant native vegetation in agricultural landscapes, it is

now common for developers to lay pipelines along easements over the private land next to the road rather than gaining approval

to lay them on the reserve.

15

Once finalised and endorsed, the plan is, in effect, a negotiated agreement on the environmental

protection measures that are a condition of the approval. Typically, successful applicants are required to

liaise with relevant Aboriginal and cultural heritage authorities to avoid or minimise impacts on any

relevant sites or objects. During construction, they must avoid or minimise disturbance to native

vegetation, particularly threatened species and communities. They must restore any native vegetation that

is disturbed with locally indigenous species in accordance with approved native vegetation offset plans.

They are also required to return soil disturbed during construction to its original profile. They must then

compact it, restore the original ground surface levels and revegetate the soil to protect it from erosion.

In order to reduce the potential loss of amenity for other river users, they are also often required to place

new power lines and delivery pipes underground. Similarly, they must ensure that pump houses are as

small as practicable and that they are coloured and screened to be compatible with the surrounding

environment.

Where practical, they are also asked to raise and secure suction pipes above bank slopes to minimise the

collection of flood debris, and to ensure that the inlet, strainer and foot valves can accommodate

fluctuations in water levels (including fluctuations below any existing weir pool minimum levels).

7.3 Operating

In operating works to take water from waterways, operators are required to keep their sites clear of

rubbish and debris at all times. They must monitor and avoid any damage, erosion or degradation to the

riparian environment resulting from the works. Importantly, they must prevent fuel, lubricants, nutrients or

any other matter used in connection with the works (including filter backwash) from entering and polluting

the environment.

Water must not be taken through the works if the relevant authority reasonably believes that that activity

is at risk of causing damage to the environment.

16

8 Appendix B. Pattern-making with water-use licences

Typically, developers apply for works licences and water-use licences at the same time. For both

instruments, the aim is to influence the choice of site early in the process so as to reduce the risk that

developers will attempt to establish new developments on environmentally inappropriate sites.

As outlined in a recent report by the National Water Commission (2012), water-use licences aim to

minimise third-party environmental impacts associated with water use. The Victorian Government (2007a)

codified those issues as minimising the impacts of water use on other persons and the environment by:

• minimising salinity

• protecting biodiversity

• managing groundwater infiltration

• managing the disposal of drainage

• minimising the cumulative effects of water use.

8.1 Minimising salinity

In areas, such as the Mallee, which are underlain by highly saline groundwater systems, excess irrigation

can add head to the groundwater system, pushing more salty water into the river, and thereby increasing

river salinity. Water trading, by changing the distribution of water use, can therefore change salinity levels

in different parts of the Mallee.

Victoria has moved away from limiting water trades into various ‘salinity impact zones’ as a way of

controlling the salinity impact resulting from trading7. Instead, every water-use licence has a condition,

called an ‘annual use limit’, which is matched with the documented irrigation requirements of the

particular crop being grown. Breaching the limit can result in the licence being suspended or ultimately

revoked. The aim is to reduce the volume of water likely to move below the root-zone and into

groundwater systems.

A system of mapped salinity impact zones (Victorian Government 2007b) is used to influence developers’

choice of sites. From the developer’s perspective, higher impact zones mean potentially higher transaction

costs and higher ongoing costs: they mean a higher capital charge on each ML of annual use limit allowed

by the water-use licence. The higher the impact zone, the higher the capital charge. At 1 July 2011, these

charges ranged from $33/ML (in the lowest impact zone, LIZ 1) to $335/ML (in the highest impact zone

where annual use limits could be increased, LIZ 4).

The charges are intended to reflect the cost to society arising from the expected increase in river salinity

associated with the development8. Their relationship to the forward-looking cost of salinity (that is, the cost

of the next most cost-effective salt interception scheme) needs to be reviewed. Nonetheless, the money

raised through the charges is available for investment in salt interception schemes. In the high impact zone,

there is also a cap on the total volume of annual use limit made available.

It is possible for proponents in the high impact zone to increase the volume of annual use limits on their

water-use licences, to expand the area irrigated or to convert to high water use crops, provided they can

arrange for other licence holders in the high impact zone to reduce their annual use limits by the same

amount. In effect, there is a market in annual use limits.

7 Victoria originally zoned different parts of the Mallee as high and low impact zones (HIZ & LIZ). Entitlement trade into HIZs was

prohibited, while trade into LIZs was permitted but levied at a varying rate per megalitre to offset the associated salinity impacts

and cover the cost of public salt interception schemes.

8 The current salinity offsetting charges were based on the costs of river salinity published in the 1988 Murray–Darling Salinity and

Drainage Strategy. They were first set in 1992 and have been adjusted for inflation each year since then (based on annual changes

in the consumer price index). Their relationship with current estimates of the cost of river salinity now needs to be reviewed.

17

Table B1: Changes in the irrigation footprint in the private diversion area for each salinity impact zone between

1997 and 2012 (Source: SunRISE21 2012).

Salinity Impact

Zone

Area

1997

Area

2003

Area

2006

Area

2009

Area

2012

% of 2012

Total

Change

1997 to 2012

L1 5760 9860 16390 26560 28375 52% +22 615

L2 6440 8670 8115 6940 8305 15% +1865

L3 1655 1350 1320 1415 1555 3% -100

L4 5635 7380 7560 6780 7175 13% +1540

Pla

nte

d

HIZ 2785 2455 2225 1775 1745 3% -1040

L1 10 210 480 2295 2155 4% +2145

L2 160 765 1750 3505 2285 4% +2125

L3 40 385 635 910 875 2% +835

L4 85 280 400 1290 1215 2% +1130

Va

can

t

HIZ 135 475 700 1140 1195 2% +1060

Total hectares 22705 31830 39575 52610 54880 100% +32 175

Figure B1: Total area of irrigation in each salinity impact zone over time (Source: SunRISE 21 2012).

18

-5,000

0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

1997 to 2003 2003 to 2006 2006 to 2009 1997 to 2009

hec

tare

sHIZ - vacant

LIZ 4 - vacant

LIZ 3 - vacant

LIZ 2 - vacant

LIZ 1 - vacant

HIZ - planted

LIZ 4 - planted

LIZ 3 - planted

LIZ 2 - planted

LIZ 1 - planted

Figure B2: Changes in the irrigated area within each salinity impact zone over time (source: SunRISE21 2010)

As evidenced by the data in Table B1 and Figure B1, the net effect of these zoning systems is that

developers concentrate their activities in the lowest impact zones. The maps, coupled with the price

signals, mean that they make those decisions early in their planning.

Under the Basin Salinity Management Strategy, the states are held accountable for all land and water

management actions, including water trading that may either individually or cumulatively affect river

salinity.

8.2 Protecting biodiversity

The Victorian Government (2007a) describes the aim of conditions in water-use licences relating to

biodiversity as being to set corrective action thresholds and procedures where limits on groundwater

infiltration and controls on drainage disposal are not sufficient to manage identified risks, associated with

water use, to specific wetlands, native vegetation stands or native animal habitats.

Development guidelines include a requirement for significant stands of remnant vegetation to be buffered

against the potential side-effects of farming activities. Buffers are generally established in one of two ways.

Fifty metres of land can be left bare between the native vegetation and the irrigated crop, or a 25-metre

biological buffer can be established between the two.

For the developer looking at ortho-photographic maps to choose between potential development sites, the

area covered by native vegetation combined with the area set aside for buffering determines the

‘maximum developable’ area of each property. The ortho-photographic maps therefore give an indication

of the relative values of two otherwise equal properties. They also give an indication of the degree of

difficulty likely to be encountered in gaining a water-use licence.

In negotiating approvals, the overall aim is for a net gain in environmental values. Vegetation may be

removed in some instances, but only if there are offsetting actions elsewhere. New South Wales and South

Australia have similar requirements to offset any permitted removal of native vegetation.

8.3 Managing groundwater infiltration

The aim of conditions in water-use licences relating to groundwater infiltration is to limit infiltration to

groundwater systems arising from irrigation so as to minimise or avoid waterlogging, land salinisation,

water salinisation and groundwater pollution.

Each state requires some form of irrigation and drainage plan to accompany an application for a water-use

licence. Accredited irrigation designers familiar with the standards specified under the approvals processes

prepare the plans. This approach had its genesis in pioneering work carried out by the Irrigated Crop

19

Management Service at Loxton in South Australia. The concepts were first given regulatory substance in the

Victorian salinity management plans completed in the early 1990s (Cummins & Watson 2007).

The irrigation plans are based on mapping and understanding the moisture-holding characteristics of the

soils that are to be irrigated. Land capability, in terms of the ‘readily available water’ that can be held in the

‘effective root-zones’ of irrigated crops, is then matched with crop layout and irrigation layout. The

matching significantly reduces the potential for water to be applied in excess of crop irrigation

requirements. That, in turn, reduces the potential to raise watertables or to mobilise saline groundwater

(Cummins & Watson 2007).

8.4 Managing the disposal of drainage

The aim of conditions in water-use licences relating to drainage disposal are to control the disposal of

drainage from irrigation so as to minimise or avoid waterlogging, salinising or eutrophying waterways,

wetlands, native vegetation, native animal habitats, groundwater and other people’s property.

New irrigation developments are required to have the capacity for internal drainage disposal

arrangements. Water-use licences are conditional on the proponent indicating which parts of the property

will be used for drainage disposal. In practice, the design requirements necessary to minimise groundwater

infiltration, coupled with modern irrigation systems and modern irrigation scheduling techniques, mean

that the vast majority of the developments brought about as a result of water trading have not yet had to

install drainage works.

This compares favourably with the developments of the late 19th and early 20th Centuries. For example,

the 17 000 hectares of irrigation in the Robinvale, Red Cliffs, Mildura and Merbein irrigation districts was

serviced by 2000 hectares of drainage basins—and even then, half the drainage went directly to the River

Murray (Cummins & Ash 1990).

It also compares favourably with developments in the second half of the 20th Century. For example, the

developments at Nangiloc–Colignan after 1969 were governed by a single regulation prohibiting drainage

disposal into the River Murray. Twenty-five years later, the Victorian Government had to construct a

communal drainage system to deal with the drainage problems that were apparent from the outset

(Nangiloc–Colignan Community Salinity Working Group 1991).

8.5 Minimising the cumulative effects of water use

A 1999 review of the various environmental protection measures (MDBC 1999) flagged the need to be

prepared to manage the cumulative effects of irrigation developments—should those effects arise. Each of

the states is keeping a watching brief on that possibility.

The conditions on WULs can be changed – provided the changes are made in keeping with a detailed

process outlined in the Water Act 1989. If there proved to be a problem with cumulative effects this

process could, for example, be used to move to communal drainage once a certain level of irrigation

intensity was reached in a given area.

20

9 References

Cummins, T 2004, Pilot Biodiversity Asset Protection Decision Support Tool. Final report prepared by Tim

Cummins & Associates with SunRISE 21 for the Mallee CMA, Mildura.

Cummins, T 2008, Irrigation Salinity Accountability – Linkages with the National Water Initiative (with

Emphasis on the Mallee Region). Final report for the Murray-Darling Basin Commission.

Cummins, T and Ash, L 1990, Salinity in Sunraysia: the community, the environment and horticultural

production: a preliminary report. Department of Agriculture and Rural Affairs, Melbourne.

http://nla.gov.au/nla.cat-vn1105227

Cummins, T and Thompson, C 2009, Capping Annual Use Limits within Salinity Impact Zones in the Victorian

Mallee – Stage 1 Final report for the Mallee Catchment Management Authority, Mildura

Cummins, T and Watson, A 2005, An Evaluation of the Interstate Water Trade Pilot Project, as at 31

December 2003. Final report for the Murray-Darling Basin Commission, Canberra .

Cummins, T and Watson, A 2007, An Evaluation of the Interstate Water Trade Pilot Project, as at 19 May

2006. Final report for the Murray-Darling Basin Commission, Canberra.

Cummins, T, Watson, A and Cooke, J 2008, ‘How Much Will Horticulturists Pay for Water?’. Acta Hort. (ISHS)

792:201-207 http://www.actahort.org/books/792/792_22.htm .

DWLBC 2010, River Murray Salinity Zoning, South Australian Government Fact Sheet 72, Adelaide.

http://www.waterforgood.sa.gov.au/wp-

content/uploads/2010/07/fs0072_river_murray_salinity_zoning.pdf Accessed on 27 September 2011.

MDBC 1999, Review of Environmental Clearances for New Irrigation Developments in the Mallee Region.

Final report for the Murray-Darling Basin Commission, Canberra.

MDBC 2006, Permanent Interstate Water Trading, How to Manual. Murray-Darling Basin Commission

Publication no. 23/06, MDBC Canberra.

http://www2.mdbc.gov.au/__data/page/114/MDB3613_Water_Trade_Man.pdf accessed 25 November

2011.

MDBA 2011, The Living Murray annual environmental watering plan 2011-12. Murray-Darling Basin

Authority, Publication no. 170/11, MDBC Canberra.

Nangiloc-Colignan Community Salinity Working Group 1991, Nangiloc-Colignan draft salinity management

plan. A salt action: joint action report for the Victorian Government, Melbourne.


National Water Commission 2012, Impacts of water trading in the southern Murray–Darling Basin between

2006–07 and 2010–11. NWC, Canberra.

O’Neill, D 2004, Review of Environmental Clearances for Permanent Interstate Water Trade. Final report for

the Murray-Darling Basin Commission, Canberra.

Quiggin, J 2001, Environmental economics and the Murray–Darling river system. Australian Journal of

Agricultural and Resource Economics, vol.45, pp. 67–94. doi: 10.1111/1467-8489.00134

SKM 2008, Market Based Instruments (MBI) for the Torrumbarry System Salt Export Mechanisms from the

Barr Creek Catchment. January 2008.

SunRISE 21 2010 , Mallee Irrigated Horticulture 1997-2009, Mallee Catchment Management Authority

Report Number: 0910/00026, Mallee CMA, Mildura.

http://www.malleecma.vic.gov.au/resources/reports/mallee-irrigated-horticulture-section1.pdf accessed

on 30 October 2011.

SunRISE 21 2012, Mallee Horticulture crop report. Final report for Mallee CMA, July 2012, Mildura.

21

Victorian Government 2007a, Water-use objectives. Victorian Government, Melbourne.

http://waterregister.vic.gov.au/Public/Documents/water_use_objectives.pdf accessed 26/11/2011.

Victorian Government 2007b, Policies for managing water-use licences in salinity impact zones. Victorian

Government, Melbourne.

http://waterregister.vic.gov.au/Public/Documents/water_use_licences_in_salinity_impact_zone_policies.p

df accessed on 26 November 2011.

Victorian Government, 2010, Policies for managing works licences, Victorian Government, Melbourne.

http://waterregister.vic.gov.au/Public/Documents/Policies%20for%20Managing%20Works%20Licences_SI

GNED_20101019.pdf accessed 27 September 2011.

Watson, A and Cummins, T 2011, Industry Adjustment in Sunraysia – 2011, Final report for the Victorian

Department of Primary Industries, Melbourne.

6. Drainage Author: Charles Thompson1 with inputs from Keith

Collett2 and Tim Cummins3

Mallee Catchment






Copyright


Authority 2013

Disclaimer













publication.

Publication details


Chapter 6 - Drainage.


April 2013

Authors: Charles Thompson1, Keith Collett2

& Tim Cummins3

1 RM Consulting Group 2 Sinclair Knight Merz 3 Tim Cummins and Associates

Cover images




Table of Contents

1 The need for drainage ............................................................................................................................... 2

1.1 To remove excess water .................................................................................................................... 2

1.2 To remove salt from the rootzone .................................................................................................... 3

2 Drainage Practices ..................................................................................................................................... 7

2.1 Historic Farm design .......................................................................................................................... 7

2.2 Modern drainage design ................................................................................................................... 8

2.3 Drainage disposal .............................................................................................................................. 8

2.4 Drainage water quality and reuse ................................................................................................... 12

3 The salinity impacts of drainage disposal ................................................................................................ 13

4 How drainage has changed according to key drivers .............................................................................. 15

5 Salinity Credits/debits from drainage disposal ........................................................................................ 17

6 Issues ....................................................................................................................................................... 20

References ....................................................................................................................................................... 21

List of Figures

Figure 1: Control of perched water table by subsurface drainage .................................................................... 2

Figure 2: Salt Transport Pathways - reproduced by CRC 2005 data from SKM 2003a (Note this includes salt loads from NSW Sunraysia also). ....................................................................................................................... 3

Figure 3: Mildura Region showing irrigation drainage disposal systems (SunRise21 2010) ............................. 9

Figure 4: Robinvale showing irrigation drainage disposal systems (SunRise21 2010) .................................... 10

Figure 5: Nangiloc-Colignan showing irrigation drainage disposal systems (SunRise21 2010). ...................... 11

Figure 6: Basin 13 now dry is showing re-establishment of vegetation after once being severely salinised. 12

Figure 7: Drainage sump replacing old drainage shaft at Bumbang (Photo courtesy RMCG). ....................... 14

Figure 8: Aerial shot showing unplanted areas (Photo courtesy RMCG). ....................................................... 14

Figure 9: Rainfall and Drain flow ..................................................................................................................... 18

List of Tables

Table 1. Drain flows and salinities over time in Mildura, Merbein and Red Cliffs, from SKM (2003a). ............ 4

Table 2. Drain flows and salinities over time in Nangiloc-Colignan, from RMCG and SKM (2008). .................. 5

Table 3. Adopted annual drain flow yield rate in the Nangiloc-Colignan district, from RMCG and SKM (2008 5

Table 4. Minimum grades recommended for the drains and plastic pipes (Poulton & Dale 2000; Table 32). . 7

Table 5. Drainage criteria minimum watertable depths in Mallee soil types (Poulton & Dale 2000; Table 33) 7

Table 6. Irrigation management eras and drainage flows ............................................................................... 15

Table 7. Estimates of Urban Garden Irrigation (SKM 2003b). ......................................................................... 16

Table 8. Drainage schemes and salinity credits/debits. .................................................................................. 17

1

Summary – Key lessons and future challenges

Important lessons are:-

1. Irrigation without drainage is unsustainable, so drainage should be planned for. 2. The first drainage schemes constructed in the Mallee were driven by the need to protect irrigated

crops from irrigation-induced water tables. The impacts of drainage disposal on neighbours, the environment and downstream users were a low priority or not well understood.

3. Irrigation leads to increased recharge to the groundwater systems and the development of groundwater mounds under the historic irrigation areas of Victoria’s Mallee. The resultant rise in the level of groundwater increases the gradient to the river and hydrogeological pressure in the underlying saline aquifers forcing groundwater into the river (irrigation-induced salinity).

4. A better understanding of the salt mobilisation processes within the Mallee irrigation areas has provided the rationale to address impacts caused by early drainage schemes and has provided a robust framework to manage future drainage impacts. With continued monitoring and review this has produced significant benefits to the region in terms of reducing the amount of irrigation-induced recharge and salt intrusion into the Murray River.

Important future challenges are:-

1. Replacement/maintenance of drainage infrastructure as it reaches the end of its life.

2. Drainage system design criteria for summer rainstorms under drip irrigation, coupled with the potential increase in the intensity of summer storms with climate change.

3. Remaining informed of the risks associated with the fate of drainage water and the fate of contaminants, especially of salt being mobilised towards the river and floodplain.

4. Specific requirements on drainage to be documented in Irrigation Drainage Management Plans as part of the Water Use License process for new development.

2

1 The need for drainage

1.1 To remove excess water

Drainage is the removal of excess water from the soil profile. Drainage occurs as both:-

- Surface drainage (across the soil surface), which usually occurs on heavy clay soils, is generally not relevant3 to the irrigated Mallee because the soil surface is a ‘wind driven’ landscape as opposed to a ‘water driven’ landscape and there are no surface drainage lines, or;

- Subsurface drainage usually occurs on sandier soils where water moves vertically down through the soil profile. This is the most common form of drainage we are concerned about in the irrigated Mallee.

In the irrigated Mallee excess water draining below the root zone tends to accumulate on underlying clay, and form perched water tables, which cause water logging, salt accumulation and crop or vegetation loss and in some cases damage to infrastructure such as roads.

Under furrow and sprinkler irrigation, a perched water table forms over the clay layer. The water table generally fluctuates between the soil surface and a depth of two metres as the result of irrigation and rainfall. In addition, hillside seepage problems occur where the deep sand of the dune crest gives way to the shallower soil further down slope.

Shallow fluctuating water tables quickly led to severe water logging and salting in the original irrigation settlement at Mildura. One of the early stories recalls that prior to channel lining and drainage the top third of the property was affected by channel seepage and the bottom third by poor drainage - leaving only the middle third to generate an income.

Control of perched water tables was first achieved by installing horizontal tile drains on a grid 13-40 m apart, with interceptor drains on the slopes.

Figure 1: Control of perched water table by subsurface drainage

Tile drains do not necessarily intercept all the water percolating past the rootzone. There is a component of natural drainage past the tile drain systems to low lying areas and through the clay layer. This results in a mound in the underlying regional groundwater system, which exacerbates groundwater discharge to the river and floodplain. This is illustrated in the diagram below reproduced from CRC 2005 using SKM (2003a).

3 historically surface runoff issues were a problem with furrow and flood irrigation and some older sprinkler

systems

3

Increased recharge to the underlying aquifers is the unavoidable consequence of irrigation in the Mallee environment and the underlying aquifers respond by saline groundwater moving to discharge zones and evaporating or moving to the river.

Figure 2: Salt Transport Pathways - reproduced by Duncan et al. (2005) from SKM (2003a) data.

Note: Figure 2 includes salt loads from NSW Sunraysia also.

1.2 To remove salt from the rootzone

Adequate drainage, removes excess water and excess salt fast enough to protect crop production. In the Mallee salt is introduced to the soil in irrigation water around 1-4 t/ha/yr4 depending on river salinity and the amount of water applied to the crop. If this salt is not removed fast enough then soil salinity will increase and reduce crop production. In recent years improved irrigation and the drying off of some properties has meant that constructed drains have not run5 until there has been significant rainfall.

The minimum required leaching fraction is the amount of drainage required to achieve a soil salinity level that is below that impacting on production. This can be expressed as the proportion of the total water applied. In many years rainfall is sufficient to provide this. But it is important for the individual irrigator to be vigilant in dry periods, as a lack of leaching creates the potential for soil salinity to accumulate6. In practice this puts a ceiling on the maximum irrigation efficiency that can be achieved and some form of deep drainage will be required.

4 At 8 ML/ha/yr and river water of 200 mg/L around 1.6 t/ha of salt is added. At 12 ML/ha/yr and 300 mg/L 3.6 t/ha salt is added.

5 Drains do not run because they are above the perched water table

6 The minimum Leaching Requirement (LR) to avoid production loss from salt accumulation in the crop root zone can be estimated

from the salinity of the applied water (ECw) and the crop tolerance to soil salinity (ECe). Where LR = ECw/(5ECe-ECw). See Ayers & Westcot (1989).

4

Leaching efficiency (Stevens 2002) has been a new point of discussion. The question is whether at high irrigation efficiencies leaching is uniform enough to protect crops from salinity. This emerged as an issue as water use efficiency dramatically improved through:-

- the widespread adoption of better technology;

- training in irrigation management;

- more responsive supply infrastructure;

- scheduling to match application rates to soil water storage capacity and crop water requirements;

- under-irrigation of crops during the drought.

This rise in irrigation efficiency means that leaching efficiency could become an important factor regarding soil salinity. The impacts of low leaching efficiency are generally confined to the irrigator’s property and can be managed if soil salinity is monitored. Collected drainage has a salinity that in theory varies with the leaching fraction i.e. the salinity of drainage water = salinity of applied water/ leaching fraction.

The River Murray upstream from Mildura provides irrigation salinity generally lower than 0.4 dS/m (or 400 EC). At 10% leaching the salinity of drainage water would be expected to be around 4dS/m. Instead it is closer to 2 dS/m, which would suggest 20% leaching. But measurements of tile drainage over recent years have shown a dramatic decrease in volume but without the expected increase in salinity. For example the “Drying of the Drains” salinity credit (SKM 2003a) showed big reductions in flow but little change in drain salinity. The same story is illustrated in Nangiloc-Colignan (RMCG and SKM 2008) in the tables below7.

Table 1. Drain flows and salinities over time in Mildura, Merbein and Red Cliffs, from SKM (2003a).

Fitted Historical 1988 Conditions 2000 Conditions

Average drain flow

(ML/month)

Average salinity

(EC)

Average drain flow

(ML/month)

Average salinity (EC)

Average drain flow

(ML/month)

Average salinity (EC)

FMIT

414702 101 2183 92 2173 49 1926

414711 16 2715 14 2675 8 2109

FMIT total 283 2239 258 2226 136 1945

MERBEIN

414701 89 1956 84 1952 51 1844

Merbein total 290 1956 274 1952 164 1844

RED CLIFFS

414703 + diversions to Cardross Basins

208 1706 200 1706 129 1782

414705 140 1726 140 1726 111 1807

414712 102 1313 91 1417 43 1589

414714 32 1748 31 1748 20 1806

Red Cliffs total 583 1651 558 1669 367 1761

7 The story is repeated in the SA Riverland where improvements in average field application irrigation efficiency (irrigation water

available to crop/water received by field inlets and is usually calculated with a daily water balance) have changed from 40-50% in the 1960s to 90% in 2008/9 Dept for Water 2011. Victorian DPI Irrigation efficiency benchmarking also provides useful data on current trends in irrigation efficiency.

5

Table 2. Drain flows and salinities over time in Nangiloc-Colignan, from RMCG and SKM (2008).

Drain Catchment Assumed Drain flow rate (ML/ha/yr)

1998 1999 2000 2001 2002 2003 2004 2005 2006

Nangiloc North 0.6# 0.58# 0.45# 0.39# 0.33# 0.34# 0.32# 0.3# 0.27#

Nangiloc (414724) 0.26 0.29 0.21 0.16 0.21 0.17 0.15 0.14 0.10

Castles Crossing 1.54 0.88 0.99 0.55 0.55 0.7* 0.7* 0.7* 0.7*

Hewetts Rd (414721) 1.40 1.16 1.09 1.18 0.70 0.87 0.82 0.78 0.62

Graces Bend 0.09 0.06 0.03 0.03 0.01 0.02* 0.02* 0.02* 0.02*

Colignan South 0.6# 0.58# 0.45# 0.39# 0.33# 0.34# 0.32# 0.3# 0.27#

Browns at Boonoonar Rd 0.6# 0.58# 0.45# 0.39# 0.33# 0.34# 0.32# 0.3# 0.27#

Browns at Reids Rd 0.6# 0.58# 0.45# 0.39# 0.33# 0.34# 0.32# 0.3# 0.27#

Kulkyne (414723) 2.55 2.86 2.03 2.30 1.77 1.88 1.70 1.63 1.20

Condos Outfall (414725) 0.71 0.98 0.70 0.73 0.32 0.41 0.36 0.28 0.49

Danes Rd 0.59 1.11 0.28 0.10 0.22 0.20 0.20 0.20 0.20

North Karadoc 0.6# 0.58# 0.45# 0.39# 0.33# 0.34# 0.32# 0.3# 0.27#

*Rate based on the average of the previous three years data for that drain catchment. # The average rate (for that year and weighted by catchment area) of all drain catchments that have reliable data (Kulkyne and Graces Bend excluded from calculation).

Table 3. Adopted annual drain flow yield rate in the Nangiloc-Colignan district, from RMCG and SKM (2008).

Drain Catchment Assumed Flow Weighted Salinity (EC)

1998 1999 2000 2001 2002 2003 2004 2005 2006

Nangiloc North 2314& 2545& 2366& 2156& 2100& 2392& 2408& 2302& 2131&

Nangiloc (414724) 2314 2545 2366 2156 2100 2392 2408 2302 2131

Castles Crossing 2187 2525 2012 2189 1741 1981* 1981* 1981* 1981*

Hewetts Rd (414721) 2182 2180 2420 2249 2121 2204 2116 1960 1932

Graces Bend 1588 1753 1347 1476 1373 1399* 1399* 1399* 1399*

Colignan South 1588^ 1753^ 1347^ 1476^ 1373^ 1399^ 1399^ 1399^ 1399^

Browns at Boonoonar Rd 1066$ 1073$ 1040$ 947$ 980$ 920$ 889$ 931$ 894$

Browns at Reids Rd 1066$ 1073$ 1040$ 947$ 980$ 920$ 889$ 931$ 894$

Kulkyne (414723) 1066 1073 1040 947 980 920 889 931 894

Condos Outfall (414725) 6937 7004 4993 5483 3920 3773 1801 2387 2654*

Danes Rd 3016 3287 4803 2760 2412 3325* 3325* 3325* 3325*

North Karadoc 3016@ 3287@ 4803@ 2760@ 2412@ 3325@ 3325@ 3325@ 3325@

* Salinity based on the average of the previous three years salinity for that drain catchment.

& Salinity as for Nangiloc (414724).

^ Salinity as for Graces Bend.

$ Salinity as for Kulkyne (414723).

@ Salinity as for Danes Rd.

6

This suggests that in practice there are a range of factors that could be influencing drainage water salinity, for example:-

- soil type - heavier soils8 tend to have lower rates of drainage, higher water tables and evaporation can create higher salinity because of local discharge;

- leakage from irrigation channels can lower drainage salinity;

- interception of regional groundwater (which is around 50 dS/m) may increase salinity;

- lower River salinities (applied salt load is lower). In recent times low river salinities coincide with reduced drainage flows.

Monitoring of drains shows relatively constant salinity and it could be inferred that irrigators are using less irrigation but are not applying it any more accurately (Poulton & Dale 2000).

Another theory is that irrigation management has improved to the extent that constructed drains now only pick up flows when water tables are high enough to reach the drainage pipes and this now only occurs intermittently following rainfall accessions or irrigation channel leakage. These events have a high leaching fraction and are low in salinity. During the majority of the time root zone drainage from irrigation is a small volume with high salinity, but little of this is collected and measured. This is because these accessions are too low to build up the water table enough to intercept the level of the drainage pipes. Root zone drainage then either slowly recharges to the regional water table below or moves along other “natural drainage lines” to other discharge areas.

8 Similarly in Colignan there are areas of very sandy soil that have very low drainage salinity.

7

2 Drainage Practices

2.1 Historic Farm design

Tile drains were installed at the depth and spacing recommended in the soil survey bulletins. Recommendations were based on research by Lyon and Tisdall (in Poulton & Dale 2000).

Drain spacing ranges from 13 m at 1.2 m depth for the heavier soils to 26 m at 1.8 m depth for the lighter soils. Where soil survey data is not available drain spacing on-farm is determined on the basis of a design drainage rate of 5 mm/day, with a water table notionally at 0.3 m depth.

In the community districts lateral drains are designed to run down the centre of planted rows. This means drain spacing options are constrained by row spacing, typically 3.4 m for grape vines and 6.8 m for citrus. Therefore drain spacing is typically 13.6 m, 20.4 m or 27.2 m (every 4, 6 or 8 rows). The minimum grades recommended are shown in Table 4 reproduced from Poulton & Dale (2000).

Table 4. Minimum grades recommended for the drains and plastic pipes (Poulton & Dale 2000; Table 32).

Type of pipe Diameter Grade Tile pipe 76 mm 0.32/100 102 mm 0.25/100 127 mm 0.18/100 152 mm 0.12/100 Plastic pipe 38-59 mm ID 0.32/100 59-73 mm ID 0.25/100

Using furrow irrigation, it was common to see a perched watertable within 20 cm of the surface after irrigation. The minimum watertable depths required for adequate plant growth are shown in Table 5 reproduced from Poulton & Dale (2000).

Table 5. Drainage criteria minimum watertable depths in Mallee soil types (Poulton & Dale 2000; Table 33).

Crop Soil type Target watertable depth (m) after irrigation 1 week 2 week 3 week Grapevines Deep sand/sandy loam 0.9 1.2 1.4 Stone fruit Loams & clay loams 0.8 1.0 1.1 Citrus Deep sand/sandy loam 1.1 1.3 1.5

Further detail on farm drainage design practices is available in Webber and Jones (1998).

8

2.2 Modern drainage design

Modern pressurised irrigation systems, particularly part-coverage systems such as drip, provide strips of dry soil to absorb rainfall and require less drainage capacity. Traditionally, drainage systems were designed for 150 mm irrigation depths for irrigation water applied with furrows.

This changes the risk from removal of irrigation accessions to the perched watertable to removal of rainfall accessions. The fact that perched water tables are lower under more efficient irrigation also provides some buffer to absorb rainfall as well.

The water logging hazard from occasional heavy storms is important, particularly as these events may become more frequent according to some climate change predictions. The problem now requires incorporating rainfall risk assessment in the design solution.

The design of the original collection system was based on removing 4.8 mm/d on a rostered irrigation system. In practice the system can only remove 2.7 mm/d if the whole area is draining9. No allowance was included for surface storm water flows, household drainage, urban runoff or sewerage effluent.

The design installed by private diverters was often much lower than this. These irrigators generally used sprinkler irrigation and, being responsible for the capital cost of their own infrastructure, generally only installed the minimum necessary. Monitoring of drainage flows in the Nangiloc-Colignan district showed that drainage flows were much lower than the community districts and the design criteria could be reduced to 1.2 mm/d. This reduced the capital cost significantly and has been applied to more recent community schemes in Boundary Bend, Tol Tol and Bumbang.

In Nangiloc-Colignan, interception drains were used to control hillside seepage, generally under citrus plantings. While between the swales on the heavier soil vines were grown with sub-surface drainage, installed in a grid pattern with fixed distance of 13.6 m. To avoid disrupting trellis, laneways and irrigation lines many properties installed mainlines for the drainage system before irrigation development began. Drain laterals were installed later as, and when, drainage problems developed. There is a proportion of undeveloped dryland within the Nangiloc-Colignan private diversion drainage catchment areas, which also reduces the need for a higher drainage capacity.

In more recent developments on some properties well-managed drip and micro systems have been used without any artificial drainage. The small leaching requirement is adequately balanced by natural drainage to the regional aquifer system or to unplanted discharge areas.

There are many irrigated areas located close to the Murray floodplain, where the perched water table discharges towards the floodplain before it is high enough to be intercepted by sub-surface drains or affect the root zone of crops. This irrigation-induced discharge occurs even during periods when there is no sub-surface drainage flow. As in all drainage systems the real test in drainage design adequacy will come after consecutive large summer storms.

2.3 Drainage disposal

Initially tile drainage systems were disposed into circa 30 m shafts that penetrated the clay into the regional aquifer below. However, building and maintaining these shafts was expensive and they were ineffective for draining large areas. So in the community districts comprehensive government schemes collected drainage from a silt box on individual properties and directed the flow into a network that disposed to the river, floodplain or to inland disposal basins. Figures 3, 4 and 5 show the location of the drainage schemes for the districts of Mildura, Red Cliffs, Merbein, Robinvale and the private diversion areas in Colignan (Sunrise21 2010).

9 http://www.lmw.vic.gov.au/html/documents/LMW_IrrigationDrainageAd.pdf accessed May 2012

http://www.lmw.vic.gov.au/html/documents/LMW_IrrigationDrainageAd.pdf

9

Figure 3: Mildura Region showing irrigation drainage disposal systems (SunRise21 2010).

In Robinvale, there is approximately 2500 ha drained, producing 3363 ML drainage water and 3275 t/yr of salt (SKM 1988a). For the 52 000 ha of area under private diverter irrigation the percentage area that has drainage installed is largely unknown.

10

Figure 4: Robinvale showing irrigation drainage disposal systems (SunRise21 2010).

11

Figure 5: Nangiloc-Colignan showing irrigation drainage disposal systems (SunRise21 2010).

Recent irrigation development has mostly been drip irrigated and without artificial subsurface drainage, but older development was based on sprinklers and is generally all artificially drained unless it is located in areas of adequate natural drainage. The disposal from these older areas (such as Nangiloc-Colignan above) is to the river, floodplain, inland disposal basins or by reuse. Many of these community disposal basins have now dried up (Figure 6).

12

Figure 6: Basin 13 now dry is showing re-establishment of vegetation after once being severely salinised (photo courtesy RMCG 2011).

2.4 Drainage water quality and reuse

Tile drainage effluent water is usually from the perched water table, and has an electrolyte concentration from 2 to 4 dS/m (2000 to 4000 EC) and a boron content of ~2 mg/L (Poulton & Dale 2000). The more saline regional groundwater is usually deeper, from 5 to 15 metres, depending on the topography and groundwater mound associated with the irrigated area. But there are isolated areas in Merbein and in Nangiloc-Colignan where the regional watertable is much closer to the surface and can infiltrate tile drainage. The regional groundwater salinity is much higher, typically from 20 to 50 dS/m and can increase the drainage water to levels above 4 dS/m especially when drainage flows are low.

The clay sub-soils are calcareous in the swale and mid-slope areas and contain high quantities of boron. The high boron concentration and the presence of nematodes in the drainage water, may constrain reuse options for drainage water on sensitive crops10.

10

Reuse on lucerne, woodlots, salt tolerant rootstocks for vines, and serial biological concentration have been proposed in the past and in some cases implemented. However, the unreliability of drainage flows, highlighted when most drains stopped during the recent drought, now makes this an unlikely option unless integrated with a normal irrigation supply.

13

3 The salinity impacts of drainage disposal

In the 1890s irrigators dug drainage systems on their properties to enable salt in the soil to drain away from the root zones of their crops. In the early 1900s they sank shafts through the Blanchetown clay layer to dispose of drainage water to the deeper groundwater system, which would have rapidly raised the regional groundwater.

In the 1930s community wide subsurface drainage systems were installed across much of the community districts disposing water to inland basins, the floodplain and the river. However, there remain some properties with private drainage in Merbein who dispose of drainage water via shafts.

In some cases disposal to the river was via regional watertable discharge areas like Lamberts Swamp and Psyche Bend Lagoon. This mobilised significant amount of salt to the River and the Sunraysia Salinity Management Plan instigated the drainage diversion scheme works that now prevent this.

When private diversion irrigation expansion occurred in the 1960s drainage problems quickly developed with most properties disposing to the River. But in 1969 there was an embargo on river disposal for new private diverters and many properties in Nangiloc-Colignan had no acceptable outlet for disposal. This led to conflict between neighbours and impacts on roads and a push for a community drainage scheme.

The then State Rivers and Water Supply Commission undertook measurements of drainage flows to identify the drainage design needed. It was found that the design criteria could be much lower, because most properties were using sprinklers and the drainage flows were much lower than in the districts. The Nangiloc-Colignan Salinity Management Plan introduced coordinated group drainage schemes to address the disposal issue.

In other private diversion areas such as at Boundary Bend, Tol Tol and Bumbang the problem was relieved by reverting to the original solution of puncturing a hole in the underlying clay layer so that the tile drainage escaped to the underlying regional aquifer.

This in turn transferred the problem to the regional water table and exacerbated the salt being discharged to the river via the regional groundwater. The Nyah to Border Salinity Management Plan introduced group drainage disposal schemes in these areas to address this problem.

14

Figure 7: Drainage sump replacing old drainage shaft at Bumbang (Photo courtesy RMCG).

The Nyah to Border Plan also reinforced the need for every new development to have adequate drainage disposal plans in place prior to approval for new development. This includes a requirement to set aside a minimum of 10%-15%11 of the land developed for future inland drainage disposal areas. All new development also requires a soil survey - the information gleaned from these surveys assists developers to avoid planting areas prone to high water tables. (Figure 8)

Figure 8: Aerial shot showing unplanted areas (Photo courtesy RMCG).

Careful selection of planted areas combined with the use of drip irrigation provided the ability to control root zone drainage from irrigation and absorb rainfall in the non-wetted zone (refer Mallee Salinity Workshop Chapter 5: The Irrigation Footprint Sunraysia). This decreased the amount of pressure on perched water tables developing and there are large areas now without artificial subsurface drainage that rely on natural drainage to discharge zones on non-planted areas on the property.

The sustainability of this will be site specific, because rainfall cannot be easily managed and some form of artificial subsurface drainage is likely to be needed after extreme rainstorms, especially summer storms when crops are most sensitive to water logging. It is worth noting that in wet years even dry land produces perched water tables. It is where those perched water tables form that is the issue.

11

10% if more than half of the catchment area is drip otherwise a minimum of 15% was required.

15

4 How drainage has changed according to key drivers

Table 6 identifies the main drivers of change that have influenced drainage management in the Mallee region over time.

Table 6. Irrigation management eras and drainage flows

Early years 1880s to 1930s

Development years 1930s to 1980s

Reform years 1980s to present

Drivers Stop crop losses, and avoid expensive hand dug shafts that proved inadequate

Increase yield and expand. Advent of electricity supplies and electric pumping, labour costs, introduction of scheduling

Water on order, tariff reform, market deregulation, water market, drip irrigation, new development, environment, increasing drip irrigation, salinity accountability, cost efficiencies

Response Build community drainage schemes with cheap labour in depression years

Yield improvements, private diverter development, pipe and riser furrows, increasing sprinkler irrigation, end of rostered irrigation, mechanical pruning and harvesting

Salinity plans, EC credits, salinity zoning, new development guidelines, detailed soil surveys, group schemes, large scale MIS, real time soil moisture monitoring, drip.

Irrigation (vines)

9 ML/ha/yr over 4-6 irrigations

9 ML/ha/yr over c. 6 -14 irrigations

8 ML/ha /yr over 40-100 irrigations

Estimated collected drainage flows

300 mm/yr + 300 mm/yr+ falling to around 200 mm/yr by the end of the 1980s

<100 mm/yr

Recharge volume passing drains

Unknown Unknown, but has been estimated in groundwater model EM2.3 for 1988 conditions to be 42 mm to 108 mm mm/yr12 depending on district

Unknown, but has been estimated for groundwater models EM2.3 to be 15 mm/yr to 23 mm/yr13 depending on district in 2007 conditions

Drainage design

2.7 mm/d14 across district or 5mm/d when rostered

1.2 mm/d private diverters15

5 mm/d on farm in district16

<1.2 mm/d ? depending on what is the acceptable rainfall risk

12

RISI Claim Table 3.7 irrigation recharge rates for districts in 2007. From Sunraysia Steering Committee (2010)

13 RISI Claim Table 3.7 irrigation recharge rates for districts in 2007. From Sunraysia Steering Committee (2010)

14 http://www.lmw.vic.gov.au/html/documents/LMW_IrrigationDrainageAd.pdf 19 mm in 7 days =2.7mm/d accessed May 2012

15 Design criteria for Nangiloc-Colignan, Boundary Bend, Tol Tol and Bumbang schemes. Pers. Comm. Lower Murray Water. 0.14

L/s/ha=c. 1.2 mm/d

16 Christen & Ayars, 2001

http://www.lmw.vic.gov.au/html/documents/LMW_IrrigationDrainageAd.pdf

16

One of the significant changes observed over the years is the estimated groundwater recharge. Recharge can be defined as the volume that passes through to the regional aquifer and was used in the EM2.3 model to calculate the salinity benefit resulting from falling regional groundwater as a result of reduced deep drainage from the perched system to the deeper regional system (Sunraysia Steering Committee 2010).

There have been numerous investigations into rootzone drainage (RZD), as it is a key determinant on recharge and the driver of salt loads to the River (Newman et al. 2009). One aspect that is particularly confusing in these investigations is that while there has been substantial effort made in calculating the volume passing the rootzone, there appears to be less emphasis on calculating what proportion recharges the underlying regional groundwater. The MDBA paper notes that “The research indicates that direct measurement of RZD at district scale is impractical, and perhaps impossible, with currently available techniques. Research on indirect methods suggests that they are informative, but insufficiently robust to provide reliable quantitative values for the purpose of conducting salinity impact assessments for the Salinity Registers.”

Another change has been urbanisation. The Sunraysia Drainage Strategy (SKM 2002) was produced in response to community concerns regarding rapid urban expansion. This Strategy provided a master plan for future surface and subsurface drainage. As well as surface drainage, the strategy recommended that some subsurface drainage be allowed for urban areas, with developers being required to undertake a risk assessment to determine the need for subsurface drainage.

Further work, SKM 2003b, scoped the impact of urban development on groundwater accessions and EC impacts. This found that areas prone to salinity were areas of low topography, close to saline water bodies, formerly irrigated land where drains have been disconnected and shallow topsoil above the Blanchetown clay. The Study expected the total urban area to double by 2050 to be 4683 ha, which would result in approximately 7% reduction in water entering the system, 29% increase in flows to receiving water bodies, 18% reduction in salt loads to the Murray and 5% reduction in groundwater accessions. The Study also estimated drainage/seepage rates for urban garden irrigation shown in Table 7. The report calculated an overall urban drainage rate of approximately 65 mm based on a drainage rate of 160 mm assuming 40% urban land is irrigated.

Table 7. Estimates of Urban Garden Irrigation (SKM 2003b).

Area of House Block (sq m) 500 800 1000

% of area watered 20% 35% 40%

Area Irrigation (ha) 0.01 0.028 0.04

% of Residential Blocks 10% 20% 70%

Total Water Use (kl) 200 500 600

Average Out of House Use (kl) 100 300 390

ML 0.1 0.3 0.39

Average Application (ML/ha) 10.00 10.71 9.75

Depth over watered area (mm) 1000 1071 975

Estimated Efficiency 70% 70% 70%

Leaching over block (mm) 78 144 153

Supply System Leakage 2% 2% 2%

Leaching over block (mm) 8.0 12.5 12.0

Total Seepage (mm) 86.0 156.5 165.0

17

5 Salinity credits/debits from drainage disposal

Since 1988 any improvements that reduced salt loads to the River have been able to be claimed under the Murray Darling Basin Salinity Management Strategy (BSMS). These are known as salinity credits. Likewise any increases in drainage to the River have created a salinity debit, requiring to be offset by a credit. Table 8 illustrates the drainage schemes in the Mallee and their relevant credits and debits.

Table 8. Drainage schemes and salinity credits/debits.

Scheme Description

EC impacts for Victoria

(BSMS Salinity Register A October 2011)

Nangiloc Colignan Implementation of coordinated group drainage schemes

0.4 EC debit

Sunraysia – Drying of the drains

Reduced drainage flows and salt loads reaching the River Murray

2.2 EC credit

Mallee disposal bores at Bumbang, Tol Tol and Boundary Bend

Removal of drainage shafts/bores and implementation of group drainage scheme with reuse

0.2 EC credit

Psyche Bend Lagoon Redirection of drainage water away from regional groundwater discharge zone before it enters River

2.1 EC credit

Lamberts Swamp Redirection of drainage water away from regional groundwater discharge zone before it enters River

3.0 EC credit

Sunraysia Reduced Irrigation Salinity Impact (RISI)

Reduced accessions to the regional groundwater through improved irrigation management and reduced leakage from irrigation supply system

4.7 EC credit

.

It is important to continue to monitor drainage so that the integrity of the claims is maintained with changing conditions. For example, the drying of the drains would have been reversed during the 2010 flooding events. The following graphs illustrate this.

18

Monthly rainfall (mm) Red Cliffs (Station 076052)

0

50

100

150

200

2501983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2008

2009

2010

2011

Mo

nth

ly r

ain

fall

(m

m)

Average daily flow Red Cliffs drain no. 1 (Barnets Rd: 414703)

0

5

10

15

20

25

18/0

6/1

983

18/0

6/1

984

18/0

6/1

985

18/0

6/1

986

18/0

6/1

987

18/0

6/1

988

18/0

6/1

989

18/0

6/1

990

18/0

6/1

991

18/0

6/1

992

18/0

6/1

993

18/0

6/1

994

18/0

6/1

995

18/0

6/1

996

18/0

6/1

997

18/0

6/1

998

18/0

6/1

999

18/0

6/2

000

18/0

6/2

001

18/0

6/2

002

18/0

6/2

003

18/0

6/2

004

18/0

6/2

005

18/0

6/2

006

18/0

6/2

007

18/0

6/2

008

18/0

6/2

009

18/0

6/2

010

18/0

6/2

011

18/0

6/2

012

Avera

ge d

ail

y f

low

(M

L/d

ay)

Figure 9: Rainfall (Source Bureau of Meteorology17) and Drain flow (Source Victorian Water Data Warehouse18) K. Collett, June 2012 SKM pers. comm.)

Rainfall and drain flow data for Red Cliffs (Drain number 1) since 1983, illustrate regional drainage trends including:-

- reduced flows in first years of drought;

- negligible flow in latter 3 years of drought (2007 to 2009);

- volume of rainfall in 2010-2011 produced a peak rate in drainage flow in response to an unprecedented single rainfall event with Red Cliffs (Station no. 076052) receiving 239.8 mm within a 30 hour period. The drain flow peak however was not as great as past drainage flows and did not as last long as historic drainage flows;

- post 2011 Rain, drain flow resumes low flow;

17 http://www.bom.gov.au/climate/

18 http://www.vicwaterdata.net/vicwaterdata/home.aspx

19

- Salinity data (not shown) for the drain suggests little change, but there have been wide variations in latter years.

This illustrates big reductions in drainage flow and salt load, but at the same time there have been a number of other influencing factors that may not be permanent. These include:-

- A large proportion (29% in the Red Cliffs irrigation district were not irrigated (Sunrise21 2012)) of plantings were dried off during the drought due to reduced water allocations and economic downturn in some horticultural industries. As these areas return to irrigation, flows would be expected to increase;

- Changing crop type from predominantly dried fruit to wine grapes and now a shift into table grapes. This could have influenced drainage flows, as some wine grapes have been deliberately water stressed to improve grape quality, while water stress is avoided with table grapes.

Improving levels of irrigation management and improved irrigation systems for all crops has been important, but there are also wider influences as well.

Another consideration for all credit claims is that with higher flows passing down the Murray, as a result of the implementation of Sustainable Diversion Limits (SDLs) under the Basin Plan, there will be more dilution. This may mean that the EC impacts (and cost associated with salinity) will be lower for a given salt load. This could mean that the impact of salt loads reaching the river will be lower, and the benefit of reducing salinity in the Mallee Region will be lower. But on the other hand, this could be offset by climate change reducing passing flows.

20

6 Issues

There are four key issues that need to be considered for the future:-

1. Age of infrastructure: The life of drains is expected to be 80 years, but many now exceed this age and at some point the cost of maintenance will exceed the cost of replacement. The actual life of drains also depends on soil characteristics, movement etc. There are some areas in Europe where drains have lasted more than 100 years.

2. Drainage system design criteria: in consideration of summer rainstorms under drip irrigation, coupled with the potential increase in the intensity of summer storms with climate change.

a. There has been a massive change in irrigation efficiency. A risk based approach to summer storms and climate change will be important in determining drainage design.

b. The need for artificial drainage19 can be minimised by:

i. using drip irrigation to provide a dryland buffer for rainfall absorption

ii. the use of ‘natural drainage pathways’ to acceptable discharge zones on the same property.

3. Drainage water quality: contaminants, particularly nitrogen, can be high in some drains and there may be other chemical residues that reach the environment. However with drains being dry this is only likely to be an issue after rainfall. Monitoring drainage water flows and quality to determine the relative risks and fate of such contaminants, especially salt mobilised towards the river and floodplain.

4. Specific requirements on drainage to be documented within the Irrigation Drainage Management Plans as part of the Water Use License process for new development, In this way when it comes time for installation (at onset or later time) there is a clear agreed plan for drain locations, disposal system, disposal area, reuse crop. There would be no confusion about where the drains go. Often the need for drainage is many years from onset, and sometimes it is triggered by an action by an adjacent land owner (e.g. neighbouring development alters natural drainage path).

19 Rain storms and change in management mean some form of artificial drainage needs to be planned for even if not implemented for all irrigation.

21

References

Ayers, RS & Westcot, DW 1989, ‘Water quality for agriculture’, FAO Irrigation and Drainage Paper 29 Rev. 1 Reprinted 1989, 1994. http://www.fao.org/DOCREP/003/T0234E/T0234E00.htm accessed 18/5/12.

Christen, EW & Ayars, JE 2001, ‘Subsurface Drainage System Design and Management in Irrigated Agriculture: Best Management Practices for Reducing Drainage Volume and Salt Load’. Technical Report 38/01, CSIRO Land and Water Griffith, NSW, Australia. http://www.clw.csiro.au/publications/technical2001/tr38-01.pdf

Duncan, R, Bethune, M, Christen, E & Hornbuckle, J 2005, ‘A Review of Salt Mobilisation and Management in Irrigated Areas of the Murray-Darling Basin’. CRC Catchment Hydrology Technical Report 05/1. March 2005.

Department for Water 2011. ‘How Efficient are we? A report on water use efficiency in the South Australian Murray Darling Basin’. Department for Water, SA Draft April 2011.

Lyon, AV and Tisdall, AL, CSIRO Bulletin No.l49 quoted in Duncan et al. 2000 above.

Newman, B, Currie, D, Evans, R & Adams, T 2009, Irrigated Agriculture in the Mallee: Estimating Root Zone Drainage. Murray-Darling Basin Authority, Canberra.

Poulton, D and Dale, M 2000, ‘Sunraysia Drainage’, in Christen, EW and Hornbuckle, JW (eds), Irrigation Insights No. 2 Subsurface Drainage Design and Management Practices in Irrigated Areas of Australia, Land and Water Australia National Program for Irrigation Research and Development.

RMCG and SKM 2008, Five Year Review of Accountable Actions under the Nyah to the South Australian Border and the Nangiloc-Colignan Salinity Management Plans. Final report to Mallee CMA, Mildura.

SKM 1988a, Robinvale Irrigation and Drainage Study. SunRISE21 Final Report to Mallee CMA, Mildura.

SKM 2002, Sunraysia Drainage Strategy. SKM June 2002.

SKM 2003a, Integration and Optimisation of Salt Interception in the Sunraysia Region. Department of Land and Water Conservation, NSW.

SKM 2003b, Mallee Urban Salinity Scoping Study Final 2 February 2003. Mallee Irrigation Environment Implementation Committee.

Stevens 2002, ‘Interactions between irrigation, salinity, leaching efficiency, salinity tolerance and sustainability’, The Australian New Zealand Grapegrower and winemaker, November, pp. 71-76. http://www.sardi.sa.gov.au/__data/assets/pdf_file/0010/46729/vineyard_irrigation.pdf

SunRISE21 2010, Mallee Irrigation Drainage Volume 1 Mildura Region, Volume 2 Colignan Region and Volume 3 Robinvale. Mallee CMA,

Sunraysia Steering Committee 2010, Sunraysia Integrated Package of Salinity management Works and Measures Business Case to the Murray Darling Basin Authority version 1 March 2010, MDBA, MCMA, G-MW, DSE, NSW Office of Water.

Webber, RTJ and Jones, LD 1998, ‘Drainage and Soil Salinity’, in Coombe BG and Dry PR (eds) Viticulture Volume 2 -Practices, Winetitles Australia.

http://www.fao.org/DOCREP/003/T0234E/T0234E00.htm

http://www.clw.csiro.au/publications/technical2001/tr38-01.pdf

7. Key tools (strengths and weaknesses) Author: Hugh Middlemis1

Mallee Catchment






Copyright


Authority 2013

Disclaimer













publication.

Publication details


Chapter 7 – Key tools (strengths and

weaknesses).


April 2013

Authors: Hugh Middlemis1

1 RPS Aquaterra

Cover images




Table of contents

Summary................................................................................................................................................................. 1

1 Background on tools ...................................................................................................................................... 2

2 Review of strengths and weaknesses of tools............................................................................................... 4

3 Wide range of tools and data for various purposes ...................................................................................... 5

4 Convergence towards multi-purpose tools? ................................................................................................. 8

References............................................................................................................................................................ 10

Figures

Figure 1. Key tools for salinity assessment and management comprise models and data..................................... 2

Figure 2. Location of the 6 numerical water trade models for Nyah-Border irrigation zoning (SKM 2008)........... 6

Figure 3. Eastern Mallee (EM) groundwater model domains (Aquaterra 2010). ................................................... 7

Figure 4. Murrumbidgee CARM project conceptual model using DHI MIKE software. .......................................... 9

Appendices

Appendix 1. Key tools – strengths and weaknesses.............................................................................................. 13

1

Summary

• The BSMS Schedules require that models be developed as predictive tools for salinity management,

and a wide range of tools have been developed for specific purposes:

- Models (surface water and groundwater)

- Data (from traditional monitoring networks of bores, stream gauging, climate etc)

- Geophysical data (AEM, nanoTEM, etc.).

• The data and modelling initiatives need to be continued into the future to support the BSMS.

• All model tools have capability for specified purposes, have usually been independently reviewed, and

have specific assumptions and limitations. Some data has assumptions and limitations (especially

geophysics and salt load estimates). Most models/data are capable of answering the questions posed

to date, although the uncertainty bounds are not small (often more than ±25%).

• No single model tool or dataset is fit for all purposes, and it is likely that at least two model platforms

would be required to serve the major purposes:

- Real time river operations with detailed groundwater and surface water interaction

- Strategic water planning for long term land, water and salinity management.

• Future studies should make best use of the insights from previous studies and recent

hardware/software advances to converge towards a ’unifying theory‘ of the key understandings and

processes (hydro-geo-logical and bio-physical-chemical), and implement that in fully

coupled/integrated modelling tools of surface water and groundwater systems, noting that:

- salinity impact assessment and management involves surface water and groundwater

investigations and modelling (salinity impacts are mainly due to saline groundwater

interactions with the surface) and

- high value ecosystems are concentrated on the floodplain where complex interactions occur

between groundwater and surface water, which requires integrated tools.

• Groundwater and surface water interactions play a major role in determining the extent and

magnitude of river salinity impacts. For example, river dynamics and flood inundation recharge are

major inputs, and evapotranspiration from shallow soils and water tables on the floodplain is the major

(natural) discharge/interceptor of fluxes towards the River. The tools (data and models) should

represent interaction processes to an adequate degree of detail, particularly for future needs, where

environmental watering is becoming important. The suite of key tools in the Mallee includes data and

models that generally have a basic/adequate degree of complexity for surface and groundwater

interaction processes. Improvements are warranted (especially on broad floodplain areas), and there

are examples where lessons learned (e.g. Lindsay-Wallpolla model EM4) could be extrapolated to other

areas.

2

1 Background on tools

The Basin Salinity Management Strategy (BSMS) 2001-2015 (MDBMC 2001) requires an explicit estimation of

the salinity impacts for actions that have a significant River Murray salinity effect (defined as 0.1 EC at Morgan).

As groundwater (GW) and surface water (SW) interactions play a major role in the extent of river salinity

impacts, modelling is a key part of the salinity assessment process. In fact, the BSMS Schedules require that

models be developed as predictive tools for salinity management (Evans & Middlemis 2008).

The MDBA has a hydrological model (MSM-BIGMOD) of daily flow and salinity in the River Murray which is

used (among other applications) to calculate salt loads entering river reaches and predict flow, salinity and salt

load (Close 1996). There are also a number of groundwater models for the Mallee groundwater zone, as

described herein. These modelling tools are underpinned by a range of data types including traditional

hydrological monitoring as well as remotely sensed geophysical data (e.g. airborne electromagnetic (AEM)

surveys). Together, the data and the models are considered to be key tools for salinity assessment and

management (Figure 1).

Figure 1. Key tools for salinity assessment and management comprise models and data.

Groundwater Models Surface Water Models

Geophysics

•AEM, nanoTEM, Sebal, imagery, topography

Traditional Data

•Monitoring networks (GW, SW, climate, SIS pumping)

•Crop reports (land use change, water/drain volumes)

•Veg & soil surveys

3

Examples of the use of MSM-BigMod and/or groundwater modelling in the Mallee Zone include:

• Salt Interception Scheme (SIS) investigations and construction approval – Joint Works investments

decisions (e.g. Benefit/Cost ratios)

• SIS validation of Salinity Register entries after commissioning (A Register Entries)

• Investment contributions between MDBA and States for ‘shared works’

• The future scale of the salinity ‘problem’ (B Register predictions)

• Benefits claimed for improved irrigation practices (IIP) or reduced irrigation salinity impacts (RISI)

• Impacts of new irrigation development resulting from water trading

• Claims for salinity credits for retiring irrigation

• 5-year reviews of all of the above (as required under the BSMS Operation Protocols)

• Scenario planning for Natural Resources Management (NRM) investments (e.g. market-based

investments (MBI) or subsidies for land use changes)

• Targeted water acquisitions

• Irrigation planning zoning

• The Living Murray (TLM) and environmental flows options assessments (e.g. Chowilla, Lindsay-

Wallpolla).

The way models are formulated, the complex nature of groundwater and surface water interaction (particularly

in the presence of a significant floodplain area), and the requirements of the BSMS Protocols, may result in a

larger than desirable level of uncertainty in the estimation of salinity impacts and the expectations around

model accreditation. The BSMS prescribes that salinity assessment efforts should be commensurate with the

risk and that decisions can be made and then regularly updated (under the 5-year review process), so it is not

unreasonable to adopt relatively simple models in the anticipation that improvements will be made later.

Provisional assessments and register entries are used when there is considered to be excessive uncertainty.

The BSMS Operation Protocols are regarded as guidelines providing advice about how models might be used.

However, there remain questions of detail around input assumptions, validation criteria and the level of

sophistication available to simulate complex processes. An example of the decisions about the level of

sophistication required can be found in the difference between the MDBA’s hydrologic model (MSM-BIGMOD),

which incorporates daily flow, and groundwater models, which simulate much longer time scales. The Quality

Assurance (QA) process for model accreditation often involves an impartial peer review of each model against

criteria which have not necessarily been developed explicitly with groundwater modelling objectives in mind

(unless the MDBC Groundwater Flow Modelling Guidelines (MDBC 2001) have been invoked specifically, which

has not always been the case). These issues are discussed in detail in Evans and Middlemis (2008).

The BSMS Operational Protocols which are endorsed by the MDBA provide broad direction on technical

matters associated with the implementation of the BSMS, notably regarding models and data. The Operation

Protocols were originally endorsed by the MDBC in 2003 and subsequently updated in 2005 and following the

2007 mid-term review. The BSMS and Operation Protocols will presumably be subject to further review in the

lead up to 2015 (the nominated review date for the BSMS in its current form), during which process it is

envisaged that some of these technical issues of modelling guidelines/methods should be addressed.

4

2 Review of strengths and weaknesses of tools

A brief review of the known modelling tools for salinity impact assessment in the Mallee CMA region has been

undertaken for the purpose of the Mallee Salinity Workshop. The tools include groundwater and surface water

models, and the data that underpins them, notably including drilling and testing, monitoring and trend analysis,

Airborne Electromagnetic (AEM), nanoTEM and other geophysical surveys, Run of River (RoR) surveys,

irrigation and drainage water balance analyses, recharge models, vegetation and soils surveys.

Appendix 1 summarises the review findings, identifying key issues, learnings, understandings, knowledge and

future issues, and considering the purpose/objective, complexity, scientific basis; tool/model performance and

capability/limitation. Some tools identified include:

• latest updates to EM2 model under the Sunraysia Eastern Mallee Model Project (report in press)

• the EM3 model for the entire Mallee CMA that was developed by Aquaterra in 2009-10 for the DSE

under the ecoMarkets initiative (not necessarily used for salinity impact assessment, but certainly

suitable for it)

• the EM4 model of the Lindsay-Wallpolla floodplain developed by Aquaterra in 2009 for the DSE and

CMA (and related Mike-Flood hydrodynamic model by Water Technology)

• SIMRAT model for the rapid assessment of the salinity impacts of water trade that was developed by a

consortium of URS, AWE, SKM and the SA Department of Environment and Heritage

• Buronga numerical groundwater flow and salt transport model developed by Hugh Middlemis and Noel

Merrick (this is notable as it is the only salt transport groundwater model in the Mallee)

• eWater “Source Catchments and Source Rivers” hydrological modelling tools developed in recent years

and destined to replace MSM-BigMod and REALM/IQQM, and

• Murrumbidgee Computer Aided River Management System (CARMS) being developed by Danish

Hydraulic Institute (DHI) for NSW State Water, comprising a fully integrated surface water and

groundwater modelling system (a future option for the Mallee).

5

3 Wide range of tools and data for various purposes

The outcome of the project investment in tools and related data is a wide range of modelling and assessment

tools and datasets developed for various purposes and on behalf of various funding organisations. From

personal experience, it is known that, at times, organisations with funding, and sometimes the funders

themselves, are not mindful to invest in further refining an existing tool or database that has been developed

under a different funding program. Rather, each one wishes to own the intellectual property outright, which

seems less than wise use of resources.

The current status is that we have a wide range of tools, and each tool thus has its own assumptions, strengths

and weaknesses, suited to the specific purpose. It would be possible, however, to identify and collate the

strengths and key understandings from the range of tools and studies. Essentially this would identify a

fundamental conceptualisation of the key hydrological processes involved in salinity impacts from its various

sources, and the related key datasets and analysis/software tools. This fundamental conceptualisation could

then be implemented in an integrated multi-purpose modelling tool (discussed further later) that would

simulate fully coupled surface water and groundwater processes, preferably with a spatial zoom capability, and

applied to any site. The data layers within existing models would essentially be exported for direct import into

the integrated model, as has occurred in the Murrumbidgee CARM project

(www.dhigroup.com/News/2011/07/12/ImprovingRiverEfficiencyAComputerAidedRiverManagementSystemFo

rTheMurrumbidgeeRiver.aspx).

One result is that there is currently a confusing range of model tools, and no comprehensive conceptualisation

or database, that has been accepted as being capable of quantifying all the key hydrological processes/sources

(dryland agriculture, irrigation, drainage, SIS, floodplain processes) to meet the various land and water

management requirements (Basin Salinity Management Strategy, SIS design and optimisation, The Living

Murray and other environmental watering initiatives, catchment management).

For example, Figures 2 and 3 show the patchwork of groundwater modelling tools that have been developed

for various purposes across the Mallee (e.g. EM1 was developed for legacy of history assessments (mainly

dryland), EM2 for irrigation and SIS, EM3 for ecoMarkets, EM4 for floodplain processes (Aquaterra 2010), Nyah

to Border for high/low impact zoning (HIZ/LIZ) for irrigation development and water trades (SKM 2008)). It

would be quite feasible for a single model platform to be developed to represent all these purposes and

processes to an adequate degree of detail.

For surface water models, the picture is clearer, with MSM-BigMod as the key salinity assessment model.

However, there is poor integration between the surface water and groundwater modelling tools and poor

understanding of groundwater in the design of the BSMS Operation Protocols (Evans & Middlemis 2008). The

BSMS and Operation Protocol framework requires the review and accreditation of a specific tool for a stated

purpose, which hinders the potential for developing tools that can be applied to a range of purposes.

6

Figure 2. Location of the 6 numerical water trade models for Nyah-Border irrigation zoning (SKM 2008).

With regard to the datasets that underpin assessment tools (see Table 1 for references and summary

information), we are beginning to see some acceptance of the value of investment in certain areas, notably

AEM (spatial salinity distribution and input to flood inundation recharge), nanoTEM (gaining/losing streams),

Run of River (salt loads), and other geophysical and remotely sensed information (e.g. Modis and Sebal

evapotranspiration methods, satellite imagery). Other monitoring initiatives are providing key data, including

irrigation area crop reports, and related water deliveries and drainage volumes, and there is the traditional

groundwater and surface water monitoring networks and soils/vegetation surveys. These key data initiatives

should be maintained into the future, as the data is fundamental to the modelling tools.

Figure 1 illustrates the three main themes in the suite of key tools and how they inter-relate:

• Models (surface water and groundwater)

• Data (from traditional monitoring networks of bores, stream gauging, climate etc.)

• Geophysical data (AEM, nanoTEM, etc.).

7

Figure 3. Eastern Mallee (EM) groundwater model domains (Aquaterra 2010).

Historically, projects have usually been undertaken in an isolated manner, with little cross-fertilisation of

insights/methods between tools, especially when different consultants are undertaking different projects.

Where independent reviews are required, the result is a multiplicity of reviews and not all review findings are

carried forward into subsequent developments. This is clearly wasteful on resources, and does little to develop

and improve a common understanding of the key elements and tools. As a minimum, it is recommended that

future studies be directed to apply the key learnings from the wide range of field investigations, data analyses

and modelling (e.g. using the findings of this initiative), especially when updating a certain tool for a specific

purpose. That would at least be a cost-effective approach consistent with best practice principles to improve

project outcomes.

EM3 Model Domain

EM1

EM4EM4

EM2

EM3

8

4 Convergence towards multi-purpose tools?

Perhaps we are now in a good position to make best use of the insights from previous studies to converge

towards a ‘unifying theory’ of the key understandings and processes (hydro-geo-logical and bio-physical-

chemical). The outcomes from the recent workshop on surface and groundwater interactions are relevant,

given that:

• salinity impact assessment and management involves surface water (SW) and groundwater (GW)

investigations and modelling (salinity impacts are mainly due to saline groundwater interactions with

the surface).

• high value ecosystems are concentrated on the floodplain where complex interactions occur between

groundwater and surface water.

The SW-GW workshop held in Canberra in March 2012 hosted by CSIRO and the National Water Commission

and the MDBA (proceedings in press, but should be available from: http://www.csiro.au/en/Organisation-

Structure/Flagships/Water-for-a-Healthy-Country-Flagship/Publications-WfHC.aspx) identified that there is a

wide range of modelling approaches now available. However, because the time-scales involved are different

(between surface water and groundwater processes), different models are often used for river management

(fast, high volumes, generally fresh), groundwater assessment (slow, low volumes, generally salty in the

Mallee), salinity management or environmental watering purposes. New products for coupled surface and

groundwater modelling are available on the market to address this shortcoming, but uptake by practitioners

remains slow (partly because of budget challenges and partly due to learning curves). There are notable

examples of fully coupled surface water and groundwater models at the catchment scale (e.g. WA: Murray

River MIKE-SHE model developed by Joel Hall at the Department of Water; NT: Daly River FEFLOW-MIKE11

model developed by Anthony Knapton of Natural Resources, Environment, The Arts and Sport (NREATS); NSW:

Murrumbidgee CARM), and this is considered to be an appropriate trajectory for future tool development for

the Mallee. The industry has identified the need to improve resources management and develop a more

integrated approach that manages surface water and groundwater as the one resource, which demands

integrated modelling tools.

Mallee CMA (and presumably other stakeholders) will need to consider whether or not they would prefer the

status quo of a range of models for a range of purposes (with related potential for management confusion), or

whether they would like a single (ideally) modelling platform that can be applied to a range of purposes. A

single (ideally) modelling platform approach would involve reduced costs in terms of reducing the need for

multiple model development project and multiple peer reviews of multiple tools. It would also involve

increased costs in tool development (compared to the current specific purpose models) as well as tool

warehousing, data sharing agreements, maintenance/upgrades and so on.

The recent SW-GW workshop in Canberra identified that there is no single/ideal model tool (‘silver bullet’), and

thus it is likely that at least two model platforms would be required to serve all purposes:

• Real time river operations with detailed SW-GW interaction.

• Strategic water planning for long term land, water and salinity management.

It is certainly feasible with current software, and likely cost-effective overall, to implement a

comprehensive/unified understanding in a complex modelling tool, although as indicated above, it is likely that

at least two tools would be required, and probably more. Such tools could have a high level of complexity

(surface water, groundwater and floodplain processes), and could be semi-regional to regional in scale (feasible

to cover the entire Mallee CMA). The tool(s) should preferably have a suitable basic scale (e.g. 100m), and a

grid-flexible zoom capability (in space and time) such that it would be suitable for application to a range of

purposes. It is the zoom capability that is the most problematic with current technology in complex fully

coupled models of surface and groundwater systems.

9

The tool could be developed using the eWater ‘Source Rivers’ and ‘Source Catchments’ hydrological modelling

platform (www.ewater.com.au/products/ewater-source/for-rivers), with the groundwater linkage models.

However, eWater developers themselves emphasise that these tools do not replace the need for detailed

numerical modelling platforms where the complexity is warranted (i.e. it is questionable whether this model

would be capable of representing the detailed interactions between the irrigation mounds, the floodplain/river

and the SIS). One key issue is that the Source software has a hydrological basis (not hydraulic or

hydrodynamic), incorporating empirical relationships. Where complex flood inundation is involved, a

hydrodynamic model is required to quantify the flow dynamics in a hydraulic sense (velocities, volumes,

inundation depths). Integrated hydrodynamic and groundwater models provide the basis for developing a

detailed understanding of the dynamics and optimisation of management approaches. A specific study would

be required to scope the strengths and weaknesses of each approach for the specific needs of the Mallee,

perhaps considering the outcomes from the current CARM project in the Murrumbidgee

(http://www.carmproject.com.au/).

Figure 4. Murrumbidgee CARM project conceptual model using DHI MIKE software.

(www.dhigroup.com/News/2011/07/12/ImprovingRiverEfficiencyAComputerAidedRiverManagementSystemForTheMurrumbidgeeRiver

.aspx)

10

References

Aquaterra 2006, Hydrogeological Modelling for B Register “Legacy of History” assessments in the Mallee Zone

of Victoria and NSW. Eastern Mallee “EM1” Model. Aquaterra presentation, September 2006.

Aquaterra 2009a, ‘Groundwater Modelling of the Living Murray Scenarios for Lindsay Island.’ Aquaterra report

to SKM, October 2009. Ref: A54/C1/R001c.

Aquaterra 2009b, ‘Mallee Zone 5-Year Rolling Salinity Review-B-Register ‘Legacy of History’ Assessment.’

Report to MDBA by Aquaterra, October 2009.

Aquaterra 2009c, ‘Sunraysia Sub-Regional Groundwater Flow Model (EM2.3) Final Report’. Report to Goulburn-

Murray Water and Murray Darling Basin Authority. October 2009.

Aquaterra 2010a, ‘BSMS Five Year Review – Sunraysia Drying of Drains’, Final report to Mallee Catchment

Management Authority, June 2010. No. A112/600/Final/Drains.

Aquaterra 2010b, ‘Eastern Mallee Version 1.2 (EM 1.2) Model. Paper to Address the Impartial Peer Review

Comments.’ Submission by Aquaterra to Murray Darling Basin Authority, September 2010.

Aquaterra 2010c. ‘Mallee CMA Groundwater Model (EM3) - Transient Calibration Development Report’. Report

prepared for Department of Sustainability and Environment, June 2010. Reference A53B/B2/R004b.

Aquaterra 2010d, ‘Sunraysia Integrated Packaged of Salinity Management Works and Measures’, Business Case

to the Murray-Darling Basin Authority, February 2010.

Close, A 1996, ‘A new daily model of flow and solute transport in the River Murray’, 23rd

Hydrology and Water

Resources Symposium 21-24 May 1996. The Institution of Engineers, Hobart, Australia..

Crosbie, R, Jolly, I, Leaney, F, Petheram, C and Wohling, D 2010, ‘Review of Australian

Groundwater Recharge Studies.’ CSIRO: Water for a Healthy Country National Research Flagship, pp. 81.

Evans, R and Middlemis, H 2008, ‘Groundwater Modelling associated with BSMS Implementation’. Issues paper

prepared for MDBC, January 2008.

Ginnivan, J, Mathers, K, Munday, T, Pfeiffer, P, Sutherland, G, Tatnell, B, Amoafo, B, Telfer, A, Fitzpatrick, A

2008, ‘Supporting the development and implementation of salinity management initiatives in the Sunraysia

region in Victoria and NSW by enhancing our understanding of the regional hydrogeology through airborne

geophysical data’, in ‘2nd International Salinity Conference: 31st March-3rd April 2008’, Adelaide.

Lawrie, K 2008, ‘To what extent can recent advances in salinity mapping and assessment create new salinity

management and policy opportunities?’ in ‘2nd International Salinity Conference: 31st March-3rd April 2008’,

Adelaide.

Lawrie, K, Clarke, JDA, Tan, KP, Pain, C, Brodie, R, Edwards, D, Apps, H, Wong, V and Cullen, K 2008, ‘An

airborne electromagnetic survey used to address salinity and land management issues in the River Murray

corridor, SE Australia,’ in '2nd International Salinity Conference: 31st May-3rd April 2008'. Adelaide.

Merrick, NP, Middlemis, H and Williams, RM 2002, ‘Buronga Salt Interception Scheme: Groundwater Flow,

Solute Transport, and Optimisation Modelling. Dept of Land and Water Conservation’, Centre for Natural

Resources Report CNR 2002.044.

Merrick, NP, Middlemis, H, and Williams, RM 2005, ‘Dynamic river-aquifer interaction modelling and optimal

interception of saline groundwater discharge.’ Proceedings, NZHS-IAH-NZSSS Conference "Where Waters

Meet", Auckland, Nov-Dec, 2005.

Merrick, NP 2010, ‘Peer Review of the Eastern Mallee [EM2.3] Groundwater Model,’ Report for MDBA by N P

Merrick of Heritage Computing, January 2010.

11

Murray-Darling Basin Ministerial Council (MDBMC) 2001, Basin Salinity Management Strategy 2001-2015.

Murray-Darling Basin Commission (MDBC) 2001,‘Groundwater Flow Modelling Guideline.’ Prepared by

Aquaterra for MDBC. January 2001.

MDBC 2004, ‘In-stream NanoTEM Survey of the River Murray. Blanchetown to Mallee Cliffs.’ Report and Atlas

for Murray-Darling Basin Commission. November 2004.

MDBC 2007, ‘In-stream NanoTEM 2006. Wentworth to Torrumbarry. Lindsay-Wallpolla.’ Report and Atlas for

Murray-Darling Basin Commission, June 2007.

Prathapar, SA 2010, ‘Assessment of Aquaterra’s Response to Peer Review of EM1.2.’ Report by S A Prathapar,

NSP Pty Ltd. Baulkham Hills NSW, September 2010.

Prathapar, SA 2010, ‘Eastern Mallee Model Version 1.2. Impartial Peer Review.’ Report by S A Prathapar, NSP

Pty Ltd. Baulkham Hills NSW, March 2010.

Passfield, G, Weatherill, D, Middlemis, H and Sutherland, G, 2009, ‘Advances in groundwater modelling of

floodplain inundation recharge and evapotranspiration, with application of AEM data (Lindsay-Wallpolla,

Victoria and NSW).’ In 3rd Australasian Hydrogeology Research Conference 1-3 December 2009, Perth, WA.

RMCG 2008, ‘Five Year Review of Accountable Actions Under the Nyah to the South Australian Border and the

Nangiloc Colignan Salinity Management Plans.’ Report for Mallee CMA April, 2008. 6-M-29.

Sharma, P, Close, A and Mamalai, O 2003, ‘Biggest Bang for the Salinity Buck for the River Murray?’ in: Boyd,

MJ (ed.) et al. 28th International Hydrology and Water Symposium: About Water. 10-13 November 2003,

Novotel Northbeach, Wollongong, NSW, Australia.

SKM 2001, ‘A Proposed Method for Accounting for the EC Impacts of Water Trade in the Victoria Mallee.’

Report for Department of Natural Resources and Environment, November 2001. WC01497.

SKM 2002, ‘Lindsay River Groundwater Interception Scheme – Groundwater Modelling.’ Report for Department

of Natural Resources and Environment, June 2002. WC00817.002.

SKM 2003, ‘Sunraysia Drying up of Drains - Sunraysia EC Credit Claim,’ Report for Department of Sustainability

and Environment, July, 2003. WC02252.205,

SKM 2005. ‘Murray River Floodplain Salt Storage in Riparian Environments Near Mildura: Completion Report.’

Report for Mallee Catchment Management Authority, October 2005,WC02934.

SKM 2005, ‘Numerical Water Trade Models: Model Calibration Report.’ Report for the Mallee Catchment

Management Authority, August 2005, WC02917.

SKM 2006a, ‘Hydraulic Modelling of the Hattah Lakes.’ Report for the Mallee Catchment Management

Authority, May 2006. WC03226.

SKM 2006b, ‘Murray River Floodplain Salt Storage – Stage 2.’ Report for the Mallee Catchment Management

Authority, July 2006, WC03546.

SKM 2006c, ‘Regional Floodplain Salt Storage and Mobilisation Processes to the Murray River: Stage 3 Report –

Salt on the Floodplain.’ Report for Mallee Catchment Management Authority, December 2006.WC03727.

SKM 2006d, ‘Sunraysia Regional Disposal Strategy – Modelling of Hydrogeological Impacts of Using Mourquong

as a Disposal Basin,’ March 2006. Final report for the Department of Natural Resources, WC03228.

SKM 2006e, ‘Sunraysia Regional Disposal Strategy- Salt and Water balances for the Mourquong Basin, October

2006.’ Final report for the Department of Natural Resources, WC03228.

SKM 2007a, ‘Hattah Lakes: Additional Hydraulic Modelling.’ Report for the Mallee Catchment Management

Authority, July 2007. VW03981.

12

SKM 2007b, ‘Modelling of Murray Rock Bar’, File Note for the Mallee Catchment Management Authority,

November 2007, VW03981.

SKM 2007c, ‘Numerical Water Trade Models: Interim Report.’ Report for Mallee Catchment Management

Authority, June 2007, WC03700.

SKM 2007d, ‘Salt on the Floodplain Stage 4: Autumn 2007 Monitoring Report.’ Report for the Mallee Catchment

Management Authority, August 2007. VW03947.

SKM 2008a, ‘Numerical Water Trade Models: Nangiloc – Colignan Model.’ Report for the Mallee Catchment

Management Authority, July 2008, VW04080.

SKM 2008b, ‘Numerical Water Trade Models: Red Cliffs to Yelta.’ Report for the Mallee Catchment

Management Authority, June 2008, VW04080.

SKM 2008c, ‘Numerical Water Trade Models: Robinvale Wemen Model.’ Report for the Mallee Catchment

Management Authority, July 2008, VW04080.

SKM 2008d, ‘Numerical Water Trade Models: Model Development – Yelta to South Australian Border.’ Report

for the Mallee Catchment Management Authority, July 2008, VW04080.

SKM 2008e, ‘Understanding the Impacts of Water Trade and Water Application on Groundwater: Victorian

Mallee Numerical Water Trade Model Refinement – Numerical Modelling Summary Report.’ Report for Mallee

Catchment Management Authority, September 2008, VW04080.

SKM 2010a, ‘10/840 Dryland Salinity Contribution to the Murray: Refinement of the Reforecast Groundwater

Trends in the Mallee Region for 2030 and 2050.’ Report for Mallee Catchment Management Authority,

December 2010, VW05141.

SKM 2010b, ‘10/836 Dryland Salinity Contribution to the Murray – Risk Assessment of Policy and Accounting for

Assessing Salinity Impacts in the Mallee: Background Report.’ Report for Mallee Catchment Management

Authority, December 2010, VW05140.

SKM 2011, ‘Victorian Mallee Salt Procedures Manual: Discussion Papers.’ Report for Mallee Catchment

Management Authority, March, 2011, VW05804.

URS Australia, AWE, DEH and SKM 2003, ‘Tools for assessing salinity impacts of interstate water trade in the

Southern Murray-Darling Basin. SIMRAT a spatially distributed rapid assessment tool for Nyah to Lake

Alexandrina. Scoping of a rapid assessment tool for the Riverine Plains.’ Final Report prepared for the Murray-

Darling Basin Commission, October 2003. URS Project A1691.

Water Technology 2009, ‘Lindsay and Mulcra Island hydraulic model calibration report.’ Report prepared by

Water Technology for Mallee Catchment Management Authority, January 2009.

13

Appendix 1. Key tools – strengths and weaknesses.


Tool Purpose/ObjectivesComplexity & Scientific Basis of Tool

Capability/Performance Limitations Findings - Learnings - KnowledgeFuture Issues (BSMS, data/monitoring, software, research) - key tools highlighted

Eastern Mallee EM1.2 Model Final Report (Aquaterra 2009b)

MODFLOW model for 5-year review (in Aquaterra 2009) of Legacy of History (LoH)

Medium-High complexity Modflow model with 3 layers and 300m grid; uses data/ information available up to 2009.

Accredited tool for LoH, but could be improved with learnings from studies since 2009.

Improvements warranted: dryland recharge rates and time lags; floodplain process complexity; irrigation recharge and calibration performance in some areas.

Used data available in 2009 to develop accredited tool for LoH, with acknowledged limitations. Model predictions on salt loads accurate to +/-25%. Independent review finds 'fit for purpose'.

Key tool. Improvements are warranted, but rather than updating EM1.2 tool, consider developing integrated model tool to address all issues from one platform for LoH and irrigation and SIS and floodplain processes. Should also consider coupled surface and groundwater model.

Eastern Mallee EM2.3 Model Final Report (Aquaterra 2009c)

MODFLOW model tool to investigate irrigation development and SIS

Medium-High complexity Modflow model with 4 layers and 125m grid. Irrigation District water balance RZD. AEM for salinity. Floodplain evap complexity.

Accredited tool for irrigation and SIS, with features for river/floodplain processes. Now superseded by EM2.3.1

Dryland recharge effectively ignored; evidence now challenges SIMRAT time lag/rate assumptions. Floodplain processes need further improvement (EVT parameters, river dynamics, salinity variations with time).

Independent review of EM2.3 finds 'fit for purpose' in high confidence areas (low confidence areas are Redcliffs to Mallee Cliffs, which were upgraded in subsequent EM2.3.1).

Key tool. Improvements are warranted, but rather than updating EM2 tool, consider developing integrated model tool to address all issues from one platform for LoH and irrigation and SIS and floodplain processes (including environmental watering). Should also consider coupled surface and groundwater model.

Sunraysia Eastern Mallee EM2.3.1 Model (Aquaterra 2012)

MODFLOW model to investigate irrigation development and SIS (Sunraysia Eastern Mallee Model Project).

Medium-High complexity Modflow model with 4 layers and 125m grid, refined further in SIS areas. Irrigation District water balance RZD. AEM for salinity. Floodplain evap complexity.

Reviewed tool for irrigation and SIS, with features for river/floodplain processes.

Dryland recharge effectively ignored; evidence now challenges SIMRAT time lag/rate assumptions. Floodplain processes need further improvement (EVT parameters, river dynamics, salinity variations with time).

Independent review of EM2.3 finds 'fit for purpose' across domain.

Key tool. Improvements are warranted, but rather than updating EM2 tool, consider developing integrated model tool to address all issues via one platform for LoH and irrigation and SIS and floodplain processes (including environmental watering). Should also consider coupled surface and groundwater model. Integrated tool could be used as basis for ecological responses, Basin Plan issues, operational/strategic analysis tool.

Eastern Mallee EM3 groundwater model of entire Mallee CMA (Aquaterra 2010)

MODFLOW model developed for DSE ecoMarkets initiative.

Medium-High complexity Modflow model with 4 layers and 200m grid. Ensym recharge data modelling (similar to WAVES) by DSE. Floodplain processes simple.

Calibrated 1990-2005, with comparison to about 80 bores and SRMS <5%. Reviewed tool for evaluating changes to land and water management to inform ecoMarkets initiative. Suitable for application to many purposes, but needs further calibration/refinement to improve performance. Ensym model suitable for climate variability recharge inputs.

General calibration performance needs improvement. Ensym recharge needs further refinement/validation, such as checking against WAVES modelling by CSIRO (Crosbie et al. 2010). Floodplain processes need further improvement (EVT parameters, river dynamics, flood recharge).

Independently reviewed by Julliette Woods (AWE). Model tool available under data sharing agreement from DSE.

Key tool. Improvements are warranted, but rather than updating EM3 tool, consider developing integrated model tool to address all issues via one platform for LoH and irrigation and SIS and floodplain processes (including environmental watering). Should also consider coupled surface and groundwater model. Integrated tool could be used as basis for ecological responses, Basin Plan issues, operational/strategic analysis tool.

Eastern Mallee EM4 Lindsay-Wallpolla Groundwater Model (Aquaterra 2009a, Passfield et al. 2009)

MODFLOW model to assess TLM environmental watering effects.

Medium-high complexity MODFLOW model with 4 layers and 50x100m grid extending across entire floodplain (Vic and NSW) from Wentworth to SA border, including Lake Vic.

Calibrated 1980 to 2008. SRMS of 5% indicates good performance; 70 bores on 14 transects. High complexity floodplain processes (recharge and EVT), informed by AEM.

Model covers entire floodplain from Wentworth to SA border. But, complex floodplain processes applied to Lindsay River area only. Needs further calibration to improve performance in long term after flood events (i.e good performance to 3 years after flood, and increasingly divergent after that)

Key tool with regional coverage and high complexity floodplain processes (recharge and EVT), informed by AEM and benchmarked to groundwater levels. Learnings could be incorporated into other models or integrated tool for future.

Key tool. Regional model tool covering entire floodplain from Wentworth to SA border. Learnings could be incorporated into other models or integrated tool for future.

Lindsay-Wallpolla Hydrodynamic Model (Mike-Flood) (Water Technology 2009)

Hydrodynamic model developed to identify flood inundation extent/duration, for input to EM4 groundwater model.

Mike-Flood hydrodynamic model of Lindsay River area only.

Calibrated to known floods with good performance. Lindsay River area only. Does not extend upstream to Wallpolla. Does not cover entire floodplain from Wentworth to SA border.

Key tool to identify flood inundation extent/duration, for input to groundwater model

Established surface water modelling tool. Hydrodynamic modelling a key requirement for groundwater or integrated surface water and groundwater modelling, where floodplain inundation and recharge identified as key processes

Hattah Lakes Modelling (SKM 2006)

Mike-Flood hydraulic model (1D/2D) and water balance model of Hattah Lakes

Medium complexity hydrodynamic surface water modelling tool

Calibrated to 1956 flood and Nov. 2000 flood events. Limited groundwater interaction processesComplex systemreceiving less water than under natural conditions

Established surface water modelling tool. Hydrodynamic modelling a key requirement for groundwater or integrated surface water and groundwater modelling, where floodplain inundation and recharge identified as key processes

Hattah Lakes Mike-Flood model scenarios (SKM 2007)

Mike-Flood hydrodynamic (1D/2D) model of Hattah Lakes

Medium complexity scenario modelling

Application of model to scenario modelling Limited groundwater interaction processesScenarios tested various options for environmental watering of lakes

Demonstrated surface water scenario modelling tool

Buronga SIS groundwater flow and salt transport model (Merrick et al. 2002, Merrick et al. 2005)

Groundwater flow and salt transport model of local area around Buronga SIS and Mourquong disposal basin.

Medium-High complexity Modflow and MT3D model with 2 layers and 20m grid.

Culmination of model development since the mid 1980s, initially analytical model, then finite element numerical flow model, then finite difference numerical flow and solute transport model. All designed, developed and calibrated in a manner that meets the requirements of the MDBA modelling guidelines (although most of the models were developed prior to the guidelines).

Local scale

Concluded that the traditional method of calculating salt loads by multiplying modelled groundwater fluxesto river by the near river salinity is adequate for BSMS purposes.

Concluded that solute transport approach is a level of complexity that is not warranted.

SIMRAT model for the rapid assessment of the salinity impacts of water trade. Developed by a consortium of URS, AWE, SKM and the SA Department of Environment and Heritage (URS 2003)

Rapid assessment of the salinity impacts of water trade.

Applicable to the Pilot Interstate Water Trading Project (from Nyah to Goolwa), extending 15km either side of the River Murray in the Mallee Zone. Primary purpose to allow MDBC to adjust Registers due to (one or more) permanent water trades to greenfield irrigation areas within the interstate trading zone.

Independently reviewed and found to be suitable for application, in the absence of more detailed and agreed methods, to meet the key design objective of a simple tool, using the rapid assessment philosophy to explain with the smallest set of variables what would be the maximum amount of the salinity impact on the Murray River due to surface water entitlement trading.

Designed for rapid assessment of trade impacts on an annual audit basis. Practical application of the rapid assessment tool to individual trades could be used to inform decisions in a semi-quantitative manner, and not as the prime justification for the decision. It is suggested that SIMRAT could be used for decision-making (in the absence of any other agreed approach; e.g. a detailed numerical model), and in the event that the initial decision is disputed, the onus could be put back on the applicant to undertake expert hydrogeological review (under “non-ideal” situations) to prove their case.

Demonstrated that simple, rapid assessment tools can be developed with available data for specific purposes, and supported by extensive and detailed investigations. Some data from the Millennium drought indicates that the recharge time lag algorithmmay be over-estimating time lags in certain areas (not everywhere).

Key tool in that vertical recharge algorithms used to determine lag times from clearing of vegetation and application of irrigation to greenfields sites until the recharge is manifest at the water table (i.e.informs numerical groundwater flow models). Some data from the Millennium drought indicates that the recharge time lag algorithm may be over-estimating time lags in certain areas (not everywhere).

Modelling Tools and related reports




Mallee Impacts of Water Trade - HIZ/LIZ (SKM 2001)

Outline of analytical modelling approach to enable rapid assessment of salinity impacts of irrigation

Medium complexity analytical modelling approach defined

Proposed method, adopted by MDBC with the condition that more detailed numerical modelling wouldbe developed to support the model. The model is applied within the Mallee as a planning tool enforced with market mechanisms (tools and trading rules) to direct new development away from areas of highest impact. Not implemented to assess individual trades but annual cummulative EC impact across the region.

Designed as a cost-effective, rapid assessment, analytical modelling tool with limitations typical for such an approach

Innovative approach, designed as medium complexity and using available data to conservatively evaluate salinity impacts of irrigation development. Lead to the development of the series of Numerical models from Nyah to the SA Border from 2005 to 2008, believed also to have lead to the development of the SIMRAT modelling tool.

Key tool used by Mallee CMA to calculate and report the annual cumulative EC impact to DSE and MDBA to inform the update of the MBDA BSMS Register A item Nyah to SA Border SMP. Water trade has been superceded with Annual Use Limits (maximum allowable water application per year as a condition of use on a water licence) as the unit for salinity impact calculations.

Lindsay River SIS Groundwater Modelling (SKM 2002)

Numerical model tool to investigate groundwater and floodplain processes and assess concept designs for salinity management options, notably SIS bores

Medium-High complexity Feflow model with 5 layers and grid of 50-200m generally. Dynamic river and floodplain recharge features.

Calibrated 1985 to 1999. Equivalent freshwater head correction. SRMS of 5% indicates good performance, but time series not presented.

Limited extent to Lindsay Island area. Northern boundary at River Murray, southern boundary just south of floodplain. Fixed fluxes upwards through deep base. Fixed EVT flux.

Demonstrated that Feflow models can be developed with available data and with some features that are better than the typical Modflow models. However, some features are very simple compared to features in existing Modflow models (notably evaporation, important for floodplain).

Key tool in that innovative features could inform upgrades to model development in region in future. Limitation in that direct applicability is limited to Lindsay Island local area.

Numerical models - Summary (SKM 2008)

Summary report on the MODFLOW numerical model suite used to evaluate effects of water trade in specific irrigation areas

Suite of 5 medium complexity numerical models with limited spatial extent

Calibrated 1975-2000. SRMS of 5-10% generally indicates good performance

Limited to local areas, but together cover most of the area from Nyah to the SA border (questionable whether large enough extent to fully evaluate Mallee clearing). Low complexity flood inundation recharge and evapotranspiration processes, noting that EVT is major interceptor on the floodplain.

Used as basis for salinity impacts assessment of irrigation/trade including HIZ / LIZ

Key tool. Good tool for small local areas that together cover most of the area from Nyah to the SA border, and underpins HIZ / LIZ

Report: 5 yr Review – N2B and N/C SMPs (RMCG 2008)

5-year review of accountable actions from Nyah to the SA Border, and also Nangiloc-Colignan Salinity Management Plans

Not a tool, but a review of accountable actions

N/A

Not a tool as such, but a review of accountable actions, and related practices andprocedures for irrigation, drainage and water trade (but not SIS, not dryland and not environmental flows).

Identifies limitations with current approaches of assessing salinity impacts relating to irrigation, drainage and water trade, and recommends actions to improve performance.

A range of recommendations were made re the various guidelines and rules applied to irrigation, drainage and water trade (but not SIS and not dryland and not environmental flows).

Numerical models - Nangiloc-Colignan and Robinvale (SKM 2005)

MODFLOW numerical models to evaluate effects of water trade in specific irrigation areas

Medium complexity numerical model with limited spatial extent

Calibrated 1975-2000. SRMS of 5% to 10% indicates good performance

Limited extent to specified areas.Used as basis for salinity impacts assessment of irrigation/trade including HIZ / LIZ

Good tool for small local areas. Underpins HIZ / LIZ

Numerical models - Robinvale-Piambie and Piambie-Nyah (SKM 2007)



Calibrated 1975-2000. Good performance indicated Limited extent to specified areas.Used as basis for salinity impacts assessment of irrigation/trade including HIZ / LIZ


Numerical models - Red Cliffs to Yelta (SKM 2008a)



Calibrated 1975-2000. Good performance indicated by SRMS <4%

Limited extent to specified areas around Mildura



Numerical models - Yelta to SA (SKM 2008b)


Medium complexity numerical model with regional spatial extent

Calibrated 1975-2000. Good performance indicated by SRMS 3%

Lindsay-Wallpolla area, but low complexity flood inundation recharge and evapotranspiration processes



Numerical models - Nangiloc-Colignan update (SKM 2008)



Calibrated 1975-2000. SRMS of 8.8% indicates adequate performance

Floodplain area, but low complexity flood inundation recharge and evapotranspiration processes



Numerical models - Robinvale to Wemen (SKM 2008)



Calibrated 1975-2000. SRMS of 5% indicates good performance

Limited extent to specified areas around Robinvale



e-Water Source modelling softwarehttp://www.ewater.com.au/products/ewater-source/for-rivers/groundwater-surface-water-link-model/

Hydrological modelling tools: Source Catchments for predicting water yield and constituents fromupland un-regulated catchments. Source Rivers for assessing long term impacts of water resourcepolicy on system storages, flows and water shares in regulated rivers. Source Catchments provides the un-regulated (upland) surface water inflows (including base flow) to Source Rivers.

Groundwater-Surface Water Interaction Tools (GSWIT) link to Source models. GW-SW Link is a reach-scale model that determines the exchange flux of water betweena river and the underlying aquifer. Perfect-GW Lag is a catchment-scale model that provides output of daily flows and salt loads at a gauging station of interest

GW-SW Link model has simple capability to dynamically model groundwater pumping, diffuse, irrigation & flood recharge, bank storage exchange, & evapotranspiration, and is designed for use with Source-Rivers (eg. also allows fluxes/heads from external groundwater models (such as MODFLOW) to pass to/from Source Rivers along main river reaches/floodplains). Perfect-GW Lag model utilises groundwater flow & salt transport concepts from 2CSalt model, predicts timing of groundwater discharge to upland streams, accounts for lateral flow (quick) and groundwater discharge (slow), handles gaining/losing streams and improves low flow (base flow) prediction (designed for upland catchments and linking with Source Catchments)

Medium complexity tools designed for working with Source software, but not a replacement for detailed numerical models. Groundwater models that have been calibrated for GW-SW exchange should always be the first preference (eg. Modflow/Feflow).

The influence of GW-SW exchange can now be explicitly accounted for in the new generation catchment and river models. Should assist paradigm shift whereby river and groundwater modellers work together. New functionality enables: - improvement in catchment-scale prediction of baseflow and how it can be impacted by climate change, land use change and groundwater development - removal of the GW-SW exchange fluxes out of the unaccounted loss/gain parameters in river models, thus improving their calibration - explicit accounting of the time lags associated with groundwater processes, thus enhancing forecasting capability of river models

Likely key tool for future, esp if Source Catchments/Rivers eventually replaces MSM and/or BigMod as the operational and strategic surface water modelling platform for the River Murray (and replaces REALM/IQQM for tributaries).




Murrumbidgee CARM project (Computer Aided River Management)http://www.dhigroup.com/News/2011/07/12/ImprovingRiverEfficiencyAComputerAidedRiverManagementSystemForTheMurrumbidgeeRiver.aspx

Hydrodynamic model of river system day to day operations, using forecasts of river inflows and real time water orders, coupled with simulation of river behaviour and interactions with groundwater and floodplain systems, to optimise the operation of the dam releases and downstream re-regulation weirs, to meet all water demands while minimising releases from the headwater storages.

Fully integrated surface water and groundwater modelling tool that reproduces the key catchment runoff and river flow processes: tributary inflows; continuously variable river flow travel times; in-channel storage dynamics; evaporation; evapotranspiration from riparian vegetation and near-river groundwater exchange.

MIKE 11 hydrodynamic river simulation model (over 2000km of river channels and floodplains), including near-river bank and groundwater exchanges (previously unaccounted) and evapotranspiration simulated using MIKE-SHE integrated surface groundwater interaction model, fully coupled to the MIKE 11 river model. Continuous dynamic coupling between groundwater behaviour in the alluvium of the river and the dynamic water levels in the river.

TBA

Demonstration of capability of fully coupled/integrated modelling of surface water and groundwater systems at river basin scale with benefits in terms of mathematically optimised water savings and real time system operations.

Likely key tool for future. To be delivered in late 2012. Demonstration of capability of fully coupled/integrated modelling of surface water and groundwater systems at river basin scale with benefits in terms of mathematically optimised water savings and real time system operations.

Report: Peer Review of EM2.3 model (Merrick 2010)

Report: on peer review of EM2.3 model to assess fitness for purpose.

Report finds EM2.3 model is fit for purpose of assessing salinity impacts of irrigation development and SIS in the Sunraysia.

All issues identified on EM2.1 model were addressed by EM2.3 upgrade. Issues identified from EM2.3 peer review were addressed in the subsequent development of EM2.3.1 model.

Not a tool as such, but a review of a tool that identifies the limitations of the tool.

Identifies strengths and weaknesses of EM2.3 model.

Review confirmed value of AEM information to inform groundwater model & salinity impact assessment, and recommended future AEM survey after major flood event (which would mean 2012 or 2013, given end of La Nina events). Recommended further application of EM2 modelplatform to investigate flood dynamics, climate change and environmental watering.

Report: Peer Review of EM1.2 model (Prathapar 2010)

Peer Review re technical modelling issues.

Not a tool, but a review of a model N/ANot a tool as such, but a review of a tool that identifies the limitations of the tool.

Documentation on complex issues of model capability, limitations and work plan for improvement

Outlines areas for EM1.2 model improvement

Paper: Response to EM1.2 Peer Review (Aquaterra 2010)

Response to Peer Review on technical modelling issues.

Not a tool, but a discussion paper N/ANot a tool as such, but consideration of a review of a tool that focuses on the limitations of the tool.


Identifies work plan for EM1.2 model improvement

Paper: Response to Response to Peer Review of EM1.2 model (Prathapar 2010)

Response by Peer Reviewer of the response by consultant to the Peer Review re technical modelling issues.

Not a tool, but a discussion paper N/ANot a tool as such, but a review of a tool that identifies the limitations of the tool.


Reviews work plan elements for EM1.2 model improvement

Presentation: EM1 model (Aquaterra 2006)

Summary on tool development and results (2006)

Not a tool, but a presentation, and about a superseded tool as at 2006

Useful background on EM1 model Note EM1 tool superseded by EM1.2Identified sensitivity to recharge rates; EM1.2 update assumed smaller rates

Refer to EM1.2 tool

Sunraysia Regional Disposal Strategy - Mourquong Impacts (SKM 2006)

MODFLOW numerical model to investigate impacts of using Mourquong as regional disposal basin

Low complexity MODFLOW model Calibrated 1970-2003. Limited to local Mourquong area Some insights into local scale seepage effectsCould be used to inform detailed features for Mourquong in more regional scale accredited models (eg. EM1, EM2, EM3)

HECRAS model of rockbar in Murray River (SKM 2007a)

Investigate options to raise rockbar in Murray River and thus effect environmental watering of Chalka Creek

HECRAS model of a short specific area of Murray River at Chalka Creek

Calibrated to conditions 24 July 2007short specific area of Murray River at Chalka Creek

Raising rock bar would not improve flows

Report/Atlas: NanoTEM Blanchetown to Mallee Cliffs (MDBC 2004)

Detailed Report and Atlas on NanoTEM survey of River Murray

High complexity geophysical survey and modelling approach to develop complex Atlas tool.

Identifies: where gaining and losing stream conditions occur; the locations of regional clay aquitards beneath the river; where SIS have been effective in preventing saline groundwater inflows.

Geophysical models based on statistical correlations that are mostly quite robust. Some inferences may not be comprehensively sound.

Provides objective and quantified insights into streamaquifer interactions and saline/fresh water interfaces. A key tool in multi-disciplinary investigations and management of salinity issues.

Improvements envisaged in future re. geophysical inversion methods, field survey methods, ground truthing and interpretation of results. No work program identified as such.

Report/Atlas: NanoTEM Wentworth to Torrumbarry (MDBC 2007)

Detailed Report and Atlas on NanoTEM survey of River Murray

High complexity geophysical survey and modelling approach to develop complex Atlas tool.

Identifies: where gaining and losing stream conditions occur; the locations of regional clay aquitards beneath the river; where SIS have been effective in preventing saline groundwater inflows.

Geophysical models based on statistical correlations that are mostly quite robust. Some inferences may not be comprehensively sound.

Provides objective and quantified insights into streamaquifer interactions and saline/fresh water interfaces. A key tool in multi-disciplinary investigations and management of salinity issues.

Improvements envisaged in future re. geophysical inversion methods, field survey methods, ground truthing and interpretation of results. No work program identified as such.

Paper: Airborne Electromagnetic Survey (Lawrie et al. 2008)

Short technical paper describing AEM survey

Not a tool, but a paper. Comprehensive report and data on River Murray Corridor AEM is now available here: www.ga.gov.au

Not a tool. Documents key scientific basis for salt store estimates. AEM work to date, go to: www.ga.gov.au

Could apply algorithms to historical or future AEM datasets.

Paper: Using geophysics in SIS development (Ginnivan et al. 2008)

Short technical paper on using AEM, RoR, EC Transects in Salt Interception Scheme design/optimisation

Not a tool, but a paper. N/A Not a toolOutlines how geophysics can help design/optimise SIS.

Demonstrates value of investing in scientific methods

Paper: Recent advances in salinity mapping (Lawrie 2008)

Short technical paper on salinity mapping and policy implications

Not a tool, but a paper. N/A Not a tool Outlines how science can help inform policy. Insights to improve evidence-based policy

Geophysical Data and Related Reports/Tools

Data-Driven Assessments and related reports/tools




Salinity Risk Assessment (SKM 2010)

Salinity risk assessment of technical, policy and capacity issues regarding irrigation and dryland salinity

Not a tool. Literature review and analysis of risks, considering legacy of history and future development, and HIZ / LIZ

Excellent risk analysis that identifies priority areas for further investigation/treatment. Appendices provide very good summary of model tools and capability

Tendency to emphasise the positives in SKM work and the limitations/uncertainties in others' work, but generally an excellent analysis and assessment

Excellent compilation of work to date, register complexities, model tools and risk implications

Key tool. Identifies MDBA BSMS Register A as bigger issue than Register B

Paper: Biggest Bang for the Buck (Sharma 2003)

Short technical paper on high priority of SIS in Sunraysia

Not a tool, but a paper. N/A Not a toolOutlines how engineering, science and modelling candeliver salinity management benefits via SIS, especially in Sunraysia

Demonstrates economic value of investing in science and engineering

Report: Sunraysia Integrated Package (Aquaterra 2010)

Joint Victorian-NSW Business Case to MDBA on Sunraysia BSMS issues

Not a tool, but a report. Includes info on EM2.3 model framework.

Although not a tool, it does summarise very well the inter-relationships of various resources and salinity management initiatives and the technical tools to support investment (including summary of the suite of EM model tools).

Not a toolBusiness case to support & prioritise investment on a range of initiatives under a cross-border framework

Identifies work plans for investigations from 2008 through to around 2015

Sunraysia Drying up of Drains (Original) (SKM 2003)

Data-driven statistical analysis of reduced drainage from irrigation, to support a credit claim

Generalised Additive Model (GAM) statistical analysis tool

Data driven toolNot a process-based tool, so valid for historical assessments only (not suitable for predictions).

Cost-effective and sound technical tool for historical hind-casting

Can help justify assumptions about historical improvements in irrigation efficiency.

Report: Drying of Drains at Mildura, Redcliffs, Merbein and Yelta (Aquaterra 2010)

Technical analysis to support salinity register claim.

Data-driven statistical analysisDetailed and well-documented analysis, with good recommendations for monitoring.

Data-driven, not process-basedEstablishes basis for register claims and identifies monitoring data needs and protocol reviews.

Recommended improved monitoring and water balance analysis, updates to protocols and related models, business case to establish whether unsaturated zone modelling complexity is required.

Mallee Salt Procedures Manual (SKM 2011)

Establish procedures for technical calculations relating to salinity impact assessments

Technical/analytical methods (not software tools)

Sound methods, clearly presented, to help standardise procedures

Various, relating to specific methods Helps standardise procedures Helps standardise procedures

Dryland Salinity Contribution to Murray (SKM 2010)

Reforecast GWL trends 2030 - 2050

Mallee HARRT trend analysis, with multi-criteria analysis and geostatistical mapping tool, upgraded with CSIRO climate variability

Sound method, with good data availability and good tools

Regional analysis (not suited to specific property scale), best suited to data with long term time series and good spatial distribution, so limitations where this does not apply

Produced a 2030 and 2050 depth to water table map for average-wet-dry conditions. Also produced a 1960 depth to water table map, which could help inform other studies.

Provides input to help rationalise monitoring programs and also provides useful information for other studies (notably 1960 DTW map).

Salt Storage on Floodplain, S1 (SKM 2005)

Scientific investigations to estimate salt stored on floodplain

Not a tool but a set of field investigations (surveys of vegetation, soils, EM), imagery collation, drilling & sampling

Data driven analysis Limited to Mildura areaData driven methods that can underpin modelling tools and optimise monitoring programs

Sound data-driven methods that could be augmented with latest techniques and used to underpin model tools.




Data driven analysisLimited to Kings Billabong, Iraak South and Wallpolla Island

Data driven methods that can underpin modelling tools and optimise monitoring programs








Salt Storage on Floodplain, S4 (SKM 2007c)

Scientific investigations to estimate salt stored on floodplain -Sept 2007 monitoring report





Sunraysia RDS – Salt and Water Balance Mourquong (SKM 2006e)

Excel spreadsheet of Salt & Water balance analysis to evaluate salt disposal operations and capacity

Excel spreadsheet with salt and water balance processes

Data driven analysisMourquong only. Many assumptions in salt/water balance model

salt loss exceeds salt harvesting; max./min. elevations estimated

Disposal at Mourquong has identified local scale effects

8. Policy and regulatory environment Authors: Charles Thompson1 and Tim Cummins2

Mallee Catchment






Copyright


Authority 2013

Disclaimer













publication.

Publication details


Chapter 8 – Policy and regulatory

environment.


April 2013

Authors: Charles Thompson1 & Tim

Cummins2

1 RM Consulting Group 2 Tim Cummins and Associates

Cover images




Table of Contents

Key messages..................................................................................................................................................... 1

1 Precursors ................................................................................................................................................. 2

1.1 The 1966-7 drought – Salinity is serious ........................................................................................... 2

1.2 Chowilla and Dartmouth - Tensions over Chowilla and the development of a shared solution ...... 3

1.3 Mineral Reserves Basins – The cost of not including the community .............................................. 4

2 Foundations .............................................................................................................................................. 5

2.1 Murray-Darling Basin Agreement (1987) – States work together on NRM...................................... 5

2.2 The Salinity and Drainage Strategy (1988) and Basin Salinity Management Strategy (2001) – States

become accountable......................................................................................................................... 5

2.3 Salt Action: Joint Action (1988) – Community takes charge of planning.......................................... 6

2.4 Mallee Area Review - Land Conservation Council – Protects the use of public land........................ 7

2.5 Vegetation Retention – Protects native vegetation and implements ‘net gain’ .............................. 7

2.6 The Water Act 1989 – Provides property rights to water................................................................. 7

3 Community-driven plans address real salinity problems ......................................................................... 9

3.1 Nangiloc-Colignan SMP- addresses a history of poor drainage disposal .......................................... 9

3.2 Sunraysia SMP- reduces drainage impacts and lifts irrigation management ................................... 9

3.3 Nyah to SA Border SMP- protects the environment from water trade ............................................ 9

3.4 Mallee Dryland SMP- reduces recharge and contamination of the freshwater aquifer ................ 11

4 National and Basin wide reforms............................................................................................................ 12

4.1 The Cap on Diversions - prevents the erosion of water security .................................................... 12

4.2 COAG Water Reform - driving water reform .................................................................................. 12

5 Broadening the scope - some interesting asides.................................................................................... 14

5.1 The Murray-Darling Basin Natural Resources Management Strategy (1989) and the Integrated

Catchment Management Policy (2001) – The MDBC gets more involved...................................... 14

5.2 Floodplain Wetlands Management Strategy for the Murray-Darling Basin (1998) – Wetlands get

recognised....................................................................................................................................... 14

5.3 The Living Murray (2002) – The First Step - a healthy working river and no further decline ......... 15

6 Contemporary settings ........................................................................................................................... 16

6.1 The Catchment Land Protection Act 1994 – The CMA role is established ...................................... 16

6.2 White Paper: Our Water Our Future (2004) – Water use licenses with conditions ....................... 16

6.3 Northern Region Sustainable Water Strategy – refining salinity zones and AUL trading............... 17

6.4 Environment Protection Act 1970 – Protecting surface water quality............................................ 17

7 Where to now? ....................................................................................................................................... 19

7.1 2007 Water Act (Commonwealth) - The legislation behind the Basin Plan, MDBA and the

Commonwealth Environmental Water Holder ............................................................................... 19

7.2 The Basin Plan – Implementing the Water Act 2007 ...................................................................... 19

7.3 Future Policy.................................................................................................................................... 19

References....................................................................................................................................................... 20

List of Figures

Figure 1: Site of Chowilla Dam (from McCoy 1988). ......................................................................................... 3

Figure 2: Total area of irrigation in the private diversion areas for each salinity impact zone over time

(Source: SunRISE 21 2012)............................................................................................................................... 10

List of Tables

Table 1: Changes in the irrigation footprint in the private diversion area for each salinity impact zone

between 1997 and 2012 (Source: SunRISE21 2012). ...................................................................................... 11

1

Key messages

The drivers that have shaped policy and regulation relevant to salinity management in the Mallee have

been:

• The 1967 drought and high river salinity

• The tensions over Chowilla and the shared solution in Dartmouth

• From government solutions to community solutions

• National Competition Policy and water reform

• The need to address environmental decline of the river and wetlands

• The development and adoption of new technology

• Policy reviews in response to the changing footprint of irrigation.

Current and future drivers are:

• Commonwealth influence in natural resource management

• The need to effectively implement environmental flows

• Moving to active environmental management by establishing objectives for environmental

maintenance, rehabilitation or restoration

• Adapting to climate change.

The Policies relevant to the future are:

• The Basin Plan under the Water Act 2007 (Commonwealth)

• The Regional Catchment Strategy and underpinning State legislation for natural resource

management (e.g. Water Act 1989 (Vic.)

• Taking a risk based approach to salinity management. This means focusing on salinity processes and

making sure policy continues to recognise it is a sensitive system and poor management costs dearly.

2

1 Precursors

1.1 The 1966-7 drought – Salinity is serious

The severe drought of 1996/7 caused very high salinities along the River Murray.

In the South Australian Riverland crop yields were greatly affected by high salinity and in 1967, during

drought, some 30% of the permanent plantings were lost due to excess salt. This brought the salinity issue

into focus and resulted in intensive hydrogeologic investigations (Newman 2012).

Victoria identified the Sunraysia area and the Barr Creek Catchment near Kerang as the largest Victorian

contributors to salinity in the Murray (McCoy 1988). With Commonwealth grants under the National Water

Resources Development Program, salinity interception schemes were installed at both locations. In

Sunraysia this was the Lake Hawthorn diversion scheme, which diverted drainage water inland to the

Wargan Basins rather than have Lake Hawthorn continually transport salt from drainage water and

intercepted groundwater flow into the Murray.

Further investigations were carried out in a landmark study for the River Murray Commission (Gutteridge et

al. 1970). The consultants recommended, amongst other things, that works be installed to intercept

groundwater flowing into the River Murray. Working parties were set up and in 1975 the State Rivers and

Water Supply Commission (SRWSC) produced ‘Salinity Control and Drainage: A Strategy for Northern

Victorian Irrigation and River Murray Water Quality’ (SRWSC 1976). This was referred to the Parliamentary

Public Works Committee, which until 1980 approved individual works in the Strategy.

Following approval the Mildura-Merbein groundwater interception scheme was installed in 1979-80. This

scheme intercepts groundwater between Mildura and Merbein with disposal to Lake Ranfurly and the

Wargan Basins, inland.

The impacts of high salinity during the drought also resulted in the State Rivers and Water Supply

Commission putting an embargo on all new sub-surface drainage being returned to the river. This had

important ramifications for private diverters and for Nangiloc-Colignan in particular, which was rapidly

developing. After 1969 the new developers had to dispose of their drainage water inland. This started to

create major disposal problems.

Later on, in 1984 the Rural Water Commission decided to only reissue license for 4 years instead of 15

years, for the pre-1969 properties that were draining to the river. Irrigators who disposed of drainage via

disposal bores had licenses extended for only two-year terms (NCCSWG 1991).

3

1.2 Chowilla and Dartmouth - Tensions over Chowilla and the development of a shared solution

In 1960, the South Australian Government opened the Waikerie irrigation district with plans to provide a

storage of 5900 GL3 straddling the NSW/Victoria border near Chowilla. South Australia (SA) felt the need for

more water and more control of its water. The dam would encompass 1036 square km and be nearly 100

kilometres long as shown in the sketch below.

Figure 1: Site of Chowilla Dam (from McCoy 1988).

Estimated costs spiralled from the original $17m estimate and by 1968 after tenders were called they had

reached $68m. The River Murray Commission (RMC) re-examined the project and was alarmed by a 50%

increase in the revised evaporation predictions. It recommended shelving the project. The South

Australians were furious and some even accused Victoria of wanting to have its own big dam in the upper

Murray and of sabotaging the project by a timed release of salt from Barr Creek into the Murray (Powell

1989).

The RMC technical committee in March 1968 recommended a site at Dartmouth – high in the headwaters

of the Mitta Mitta River – as an alternative that would serve the needs of all States better than Chowilla.

Nonetheless, there was still a lot of protest from South Australia, with some arguing the State was doomed

without Chowilla, and that both storages were needed. In 1969 the RMC technical committee

recommended that Dartmouth be built and the proposal for Chowilla be abandoned. However, it was not

until 1972 that the four governments completed the legislation necessary to enable construction at

Dartmouth to proceed (Powell 1989).

Salinity had an influence on the decision. The 1966/67 drought had revealed that a flow of 2200 ML/day

was required below Mildura to keep salinity within safe limits in South Australia. There were concerns that

3 It was originally announced as 3,700 GL

4

Chowilla would actually increase salinity and there were grave concerns about the environmental impacts

of flooding the Lindsay River wetlands and surrounding area4. The RMC technical committee had also

revised the evaporation estimates upwards from 740 GL/yr to 1130 GL/yr (McCoy 1988).

As a result of Dartmouth, additional water was made available to all States. The allocation for Nyah to

Border was an entitlement of 8000 ML. This prompted the Rural Water Commission to initiate the Nyah to

the South Australian border hydrogeological project (Thorne et al. 1990) to determine where that water

might be used for irrigation in the Victorian Mallee with the least impact on river salinity.

Managing the offsite impacts of this new water, and those of the sleeping and dozing (unused and partially

unused) entitlements expected to be activated by water trade, was the main driver for the development of

the Nyah to SA Border Salinity Management Plan.

1.3 Mineral Reserves Basins – The cost of not including the community

As mentioned above, the Barr Creek diversion scheme was built in the 1960s. This involved pumping salty

water out of Barr Creek into Lake Tutchewop for evaporation instead of allowing it to flow into the Murray.

But taking Lake Tutchewop out of the Kerang Lakes system meant that flood storage was lowered meaning

that flood peaks would be higher. There were also risks regarding salt accumulation in Tutchewop and

leakage into surrounding water tables.

Tutchewop was meant to be the first of a series of planned evaporation basins, the next in the series being

the Mineral Reserves Basins adjacent to the Tresco irrigation district and the final one being Lake Tyrrell.

Local landholders were so strongly opposed to the use of the basins they took out a class action against the

Rural Water Commission. Shortly after this in December 1986 (Langford 1999) the Victorian Government

announced it was cancelling the project.

The legacy of this conflict was that the Victorian Government then changed its policy on salinity

management; it started asking local communities to help find acceptable solutions for the salinity problems

that had been getting worse across the State after the heavy rains of 1974 and 1975. The Kerang Lakes Area

Working Group (KLAWG) and other salinity working groups were formed as part of Salt Action: Joint Action

a partnership between Government and Community (KLAWG 1992).

In the Mallee this led to the Nangiloc-Colignan, Sunraysia, Nyah to SA Border and Mallee Dryland Salinity

Management Plans.

4 There was local community agitation against the proposal led by Mr. Jack Seekamp from Renmark who drew support from

irrigators and local government representatives in Sunraysia and the Riverland.

5

2 Foundations

2.1 Murray-Darling Basin Agreement (1987) – States work together on NRM

The purpose of the Murray–Darling Basin Agreement is to ‘promote and co-ordinate effective planning and

management for the equitable, efficient and sustainable use of the water and other natural resources of

the Murray-Darling Basin, including by implementing arrangements agreed between the Contracting

Governments to give effect to the Basin Plan, the Water Act and State water entitlements.’

The first Murray–Darling Basin Agreement was signed by the governments of the Commonwealth, New

South Wales, Victoria and South Australia in 1987. This was an amendment, the final one, to the River

Murray Waters Agreement, which had been in place since 1915. Five years later in 1992, a new Murray–

Darling Basin Agreement was signed by the same governments, replacing the River Murray Waters

Agreement.

Queensland became a signatory in 1996, and then in 1998 the Australian Capital Territory participated

through a memorandum of understanding. The Agreement is now Schedule 1 of the Water Act 2007

(Cwlth).

2.2 The Salinity and Drainage Strategy (1988) and Basin Salinity Management Strategy (2001) – States become accountable

Like the Murray Darling Basin Agreement, the Basin Salinity Management Strategy (BSMS) is now a

schedule (Schedule B) to the Water Act 2007 (Cwlth), but it had its origins in the adoption of the Murray

Darling Basin Salinity and Drainage Strategy in 1988. It influenced the development of salinity plans across

Victoria, enabling drainage and salt disposal from land affected by salinity and benefits to be created where

salt was reduced from entering the river.

In 2001 the Murray-Darling Basin Ministerial Council approved the publication of the BSMS 2001–2015 that

took into account the 1999 Basin Salinity Audit and the National Land and Water Resources Audit, which

predicted large increases in dryland salinity.

The objectives of the BSMS are to:

• Maintain the water quality of the shared water resources of the Murray and Darling rivers for all

beneficial uses—agricultural, environmental, urban, industrial and recreational.

• Control the rise in salt loads in all tributary rivers of the Murray-Darling Basin and, through that

control, protect their water resources and aquatic ecosystems at agreed levels.

• Control land degradation and protect important terrestrial ecosystems, productive farmland, cultural

heritage and built infrastructure at agreed levels.

• Maximise net benefits from salinity control across the Basin.

The Strategy attaches no blame to anything that happened before 1 January 1988. But each state is now

fully accountable for anything it does to increase (or decrease) river salinity by 0.1 EC units. ‘EC units at

Morgan5’ are the units of account. And registers are maintained of accountable actions (Register A) and for

any the legacy of history impacts that have not reached the river from actions taken prior to 1988 (Register

B). The MDBA keeps a baseline of river flows for testing the size of an accountable action in a computer

model of the river system known as MSM BigMod.

5 the units are based on the salinity cost effects of salt all along the river, but are expressed as equivalent EC at Morgan

6

The Strategy outlines formulas for sharing the costs, and the benefits, of works and measures to reduce

river salinity. In defined circumstances State Governments are entitled to increase river salinity, subject to

strict accountability procedures. These entitlements are often referred to as EC credits.

It enabled Governments to invest in the most cost effective salt interception schemes regardless of State

borders.

For the Mallee, EC credits were generated by: drainage diversion works, groundwater interception schemes

and through improved irrigation management. On the other hand, the Mallee required EC credits to offset

the salinity impact of water transfers into the region, as well as the impact of drainage disposal schemes

constructed after 1988. The main use of salinity credits in the Mallee has been to underwrite new irrigation

developments whose river salinity impacts are calculated by the salinity hazard zones under the Nyah to SA

Border Salinity Management Plan.

When it was released the Salinity and Drainage Strategy created some fear in the Sunraysia community that

it would be faced with deteriorating river salinity. It was downstream of the areas where credits were to be

used (installing drainage in the Riverine Plains) and upstream from where most of the credits were being

generated – salt was going to be extracted by the South Australia Salt Interception Schemes.

This was reflected in the River Murray Management Program proposed by the Sunraysia Salinity

Management Plan (Sunraysia Community Salinity Working Group (SCSWG) 1991). The community was

asking for warning of salt slugs and coordination of drainage disposal so that no unexpected peaks

occurred. In response the Murray Darling Basin Commission started to make available river salinity

forecasts.

2.3 Salt Action: Joint Action (1988) – Community takes charge of planning

In May 1988, the government released the Victorian Salinity Strategy, Salt Action: Joint Action, for tackling

the growing salinity problems in the state. This strategy set out a systematic program for developing

community-led Salinity Management Plans (SMPs) for salt affected regions.

Communities in salt-affected areas worked with Government agencies to develop and implement regional

Salinity Management Plans. The original objectives of Salt Action: Joint Action focused on the long term

commitment required by Government and the community for implementation of integrated land and water

management plans over 30 years.

Salt Action: Joint Action set a framework for action, identifying the role of government and the community

in planning and implementing salinity control measures; salinity management plans were established to

identify in greater detail the priorities for action across salinity control regions. It noted that long-term

climatic changes would likely influence the observed trends in salinisation; however insufficient

understanding of the processes and the impact of weather patterns did not enable the net impact on

salinity to be reliably predicted at that stage.

Plans were instigated in Nangiloc-Colignan, Sunraysia, Nyah to SA Border and Mallee dryland. A community

working-group was appointed to develop each plan with secretarial support provided by the lead agency

(Department of Primary Industries (DPI)6 for Sunraysia, RWC for Nangiloc and Nyah to the SA Border and

Department of Sustainability and Environment (DSE)7 for the Dryland). The Mallee Region took the unusual

approach of coordinating agency inputs through a common project manager so that salinity staff reported

to one manager (Mr. Tim Cummins) regardless of agency. This led to a team approach across agency

boundaries.

6 Actually the Department of Agriculture and Rural Affairs (DARA) at the time.

7 Actually the Department of Conservation and Natural Resources (CNR) at the time

7

2.4 Mallee Area Review - Land Conservation Council – Protects the use of public land

In 1989 the Land Conservation Council (LCC) produced a series of recommendations for every parcel of

public land in the Mallee. Government approved and implemented these recommendations through

‘Orders in Council.’ In 1997 the Environment Conservation Council replaced the LCC, but it gave continuing

operation to previous LCC recommendations.

The LCC defined ‘public land’ to include reserved or unreserved Crown land, State forest, parks and other

areas under the National Parks Act 1975, land managed and controlled by Parks Victoria, and land vested in

public authorities other than municipal councils.

In the context of irrigation development, the LCC recommendations now mean that future irrigation

development can only take place on private land and drainage disposal is now limited to private land and

specific parcels of public land previously identified for that purpose.

For the Mallee, the bottom line of the LCC recommendations is that public land will no longer be alienated

for irrigation or dryland agriculture; there is a finite amount of land available for irrigation development

(Cummins & Cooke 2006).

2.5 Vegetation Retention – Protects native vegetation and implements ‘net gain’

Vegetation clearing on private land in Victoria is controlled through regulations in the Planning and

Environment Act 1987 and Native Vegetation Framework. Victoria introduced controls on broad- scale

clearing of native vegetation in the late 1980s (VNPA 2012).

By the mid-1990s the annual clearing rate of woody vegetation in Victoria had dropped to about 1500 ha

per year, compared to 9407 ha a year in 1987-1990, and 10 766 a year between 1972 and 1987 (Victorian

Catchment and Land Protection Council Annual Report 1995/96, pp. 15 & 16 quoted in VNPA 2012).

This was an important move for protecting biodiversity and reducing salinity. It is well established that

remnant vegetation allows much less groundwater recharge through rainfall than does cleared land (Mallee

Salinity Workshop Chapter 4: Dryland Salinity Drivers and Processes).

The concept of ‘net gain’ was introduced in Victoria’s first biodiversity strategy in 1997. It adopted the

current net gain goal that there should be “a reversal, across the entire landscape, of the long-term decline

in the extent and quality of native vegetation, leading to a net gain”. The first target was ‘no net loss by the

year 2001’ (NRE 1997).

This was further developed and adopted in Victoria’s Native Vegetation Management – a Framework for

Action (‘the Framework’). This was adopted as government policy in August 2002 and became statutory

policy in July 2003, when it was incorporated under Clause 81 of all planning schemes.

This framework provided the flexibility for new irrigator developers to clear agreed parcels of land provided

a net gain through offsets was properly established and approved (Cummins & Cooke 2006).

2.6 The Water Act 1989 – Provides property rights to water

The Water Act 1989 introduced a range of water reforms and flagged many more. From a Mallee

perspective, the most important reforms the Act flagged were the intention to introduce water trade, the

intention to establish ‘bulk water entitlements’ (BEs) and specific environmental responsibilities for water

authorities.

Clear definition of existing rights to water, in terms of both volume and seasonal reliability, helps to

implement the cap on diversions. It helps to protect the environment, prevent erosion of existing rights to

water, set rules about how water is to be shared in droughts, and provides a strong basis for water trade.

8

Agreement on the Murray BEs was extremely hard fought. The Murray Water Entitlement Committee

(MWEC), a group of approximately 40 people representing a range of irrigator groups, conservation groups,

water authorities, catchment management authorities and government agencies, negotiated it in good

faith. The Murray BEs were formalised through community consultation around ‘Sharing the Murray’

(MWEC 1997).

All parties were united in their determination to ensure the health of the river system. All recognised that

sacrifices had to be made, but none were willing to allow their constituency to suffer more than any other

group. They were determined to share the pain fairly.

Mallee irrigators made two major sacrifices. The first was to assume the same exposure to drought

rationing as others. Mallee irrigators consequently had to cope with allocations as low as 30 per cent of

their entitlements during the recent drought. The second was to relinquish their previously unlimited

access to ‘sales’ water. This means anyone wanting to move from say grapevines to citrus now had to buy

the extra water required to meet crop requirements.

These major sacrifices were partially offset by a series of compensating measures. The most important of

these was to ensure that everyone downstream of Nyah had the same basic right of 9.1448 megalitres per

hectare. Irrigators with high-use crops like citrus and almonds were granted more (up to 12 megalitres per

hectare) in a one-off gesture.

The bottom line is that the total volume of water entitlements in the Mallee is now clearly specified. So too

is the reliability of those entitlements. The only way this volume can change is through water trade

(Cummins & Cooke 2006).

8 This is the metric equivalent of three acre-feet per acre.

9

3 Community-driven plans address real salinity problems

3.1 Nangiloc-Colignan SMP- addresses a history of poor drainage disposal

The Nangiloc Colignan Salinity Management Plan was developed by a community working group chaired by

Cr. Ron Vine between 1987 and 1991. The Plan proposed programs for:

• Irrigation management

• Coordinated group drainage scheme

• Environmental rehabilitation

• Carwarp domestic and stock pipeline.

This was to be supported by community education, monitoring and an implementation program. Following

government support for the main components of the Plan, the coordinated group drainage scheme was

constructed and completed by 2002.

There had been five previous proposals for drainage schemes developed for the area since 1969 (NCCSWG

1991).

3.2 Sunraysia SMP- reduces drainage impacts and lifts irrigation management

The Sunraysia Salinity Management Plan covering the community districts of First Mildura, Merbein, Red

Cliffs and Robinvale was released in 1991. The Plan was developed by a community working group chaired

by Mr Owen Lloyd and proposed programs for:

• River Murray management

• Water supply management

• Irrigation management

• Drainage management

• Environmental rehabilitation.

All of this was supported by monitoring and implementation programs.

Following Government support many of the Plan’s programs and targets have been implemented and in

most cases exceeded. Key components were the drive to convert to pressurised irrigation, introduce water

metering, better supply systems and manage drainage disposal better (create EC credits).

3.3 Nyah to SA Border SMP- protects the environment from water trade

The Nyah to SA Border Salinity Management Plan, covering the private diversion areas, was released in

1992. The Plan was developed by a community working group chaired by Mr Rodney Hayden and proposed

programs for:

• Encouraging water transfers (a premium was to be offered for those selling out of high salinity

impact zones)

• Minimising river salinity (by only allowing new development in low impacts zones)

• Protecting the natural environment (by requiring a checklist to be completed for new development)

• Watering efficiently

• Improving drainage disposal (including disposal bores)

• Protecting the natural environment from existing irrigation.

10

An implementation program and a program for further investigations supported the plan.

With Government support many of the Plan’s programs and targets have been implemented and exceeded.

There was an expectation that there would be 45 000 ML (the volume unused in the sub-region at the time)

activated through water trade to create an additional 4500 ha this proved to be greatly understated. Trade

from the Goulburn-Murray Irrigation District upstream was not envisaged and when this came about as a

result of later water reform there was a huge expansion. For example from 1997 to 2009 the total area

irrigated between Nyah and the SA Border increased from 40 225 ha to 72 455 ha (SunRISE 21 2012).

The Plan enables and supports water trade whilst also protecting the environment and minimising the

impact on river salinity. It provides the basis for accounting for irrigation development, as well as a

framework to avoid or minimise the known side effects of irrigation development. Salinity impact zoning

and levies based on the salinity impact underpin the Plan and allows the setting of rigorous standards to

apply to new irrigation developments.

One way it does this is to guide irrigation development. First, it guides developers away from ‘High Salinity

Impact Zones’ (HIZ) to ‘Low Salinity Impact Zones’ (LIZ). Then, it guides developers to avoid damaging

environmental values at the development site. Finally, it guides developers to design their plantings and

irrigation systems around land capability (Mallee Salinity Workshop Chapter 5: The Irrigation Footprint

Sunraysia).

Trading rules originally prevented water being traded into the HIZ. The only source of additional water

available for individual irrigators within the HIZ was water already being used elsewhere within the HIZ. In

2007, this approached was changed; water entitlements can now be traded freely, but annual use limits on

water-use licences will not be increased in the HIZ unless they are reduced, by corresponding amount on

another licence in the HIZ.

In 2012 SunRISE 21 mapped irrigation expansion by salinity zone (SunRISE 21 2012). The results are shown

in Figures2 and Table 1 below and show that irrigation expansion in the private diversion areas has been

predominantly in the Low Impact Zones.

Figure 2: Total area of irrigation in the private diversion areas for each salinity impact zone over time (Source:

SunRISE 21 2012).

11

Table 1: Changes in the irrigation footprint in the private diversion area for each salinity impact zone between 1997

and 2012 (Source: SunRISE21 2012).

Salinity Impact

Zone

Area

1997

Area

2003

Area

2006

Area

2009

Area

2012

% of 2012

Total

Change

1997 to 2012

L1 5760 9860 16390 26560 28375 52% +22 615

L2 6440 8670 8115 6940 8305 15% +1865

L3 1655 1350 1320 1415 1555 3% -100

L4 5635 7380 7560 6780 7175 13% +1540 Pla

nte

d

HIZ 2785 2455 2225 1775 1745 3% -1040

L1 10 210 480 2295 2155 4% +2145

L2 160 765 1750 3505 2285 4% +2125

L3 40 385 635 910 875 2% +835

L4 85 280 400 1290 1215 2% +1130

Va

can

t

HIZ 135 475 700 1140 1195 2% +1060

Total hectares 22705 31830 39575 52610 54880 100% +32 175

In the context of future irrigation development within the Mallee, the Nyah to SA Border Plan’s bottom line

is that it limits the land available for irrigation development, because high impact zones cannot be

developed and caps are proposed for other zones.

It also provides an accountability mechanism for the Salinity and Drainage Strategy. It does this by

recording the irrigation footprint (the Annual Use Limit) change for each salinity zone and has the

hydrogeology to calculate the change in salt loads and river salinity associated with water trade.

However the salinity zoning did need to respond to the large areas of new development and in 2001 the

original two zones were replaced with four and a more sophisticated method for salinity accounting was

introduced. In 2007, as a result of unbundling, accounting was based on Annual Use Limits rather than

water entitlements.

Rolling caps on the low impact zones are being implemented as a result of the Northern Regional

Sustainable Water Strategy (NRSWS). See Section 7.3 below.

Increased understanding of groundwater systems and the changing cost of salinity to downstream users

shows the need for policy and regulation to be responsive to the risk posed by changing demands.

In Nyah to Border the extraordinary growth of vegetable production, olives, wine grapes and almond

plantings have meant that while the original foundations and zoning system were very good, they needed

strengthening as new information came to light.

3.4 Mallee Dryland SMP- reduces recharge and contamination of the freshwater aquifer

The original Mallee Dryland Salinity Management Plan was developed by a community group chaired by Mr

Leo Fuller. It was released in 1992. The original Dryland Salinity Management Plan focused on what were

thought to be the main point-sources of groundwater recharge. Its support for the pipelining of the

Wimmera Mallee Stock and Domestic Supply System was ultimately successful. As was the reshaping of

eroded dunes and replanting them with crops and trees. The original plan also encouraged the adoption of

lucerne to control recharge. A significant achievement was the sealing of disused and corroded bores in the

Duddo Limestone. Previously these bore were at risk of leaking saline Parilla Sands water and thereby

contaminating the freshwater supplies below.

12

4 National and Basin wide reforms

4.1 The Cap on Diversions - prevents the erosion of water security

Water taken out of the rivers and streams of the Murray-Darling Basin has grown to over 10,000 gigalitres a

year. This is about 80 per cent of natural flow.

In June 1995 the Murray-Darling Basin Ministerial Council recognised that without changed policies total

diversions were heading for, a clearly unsustainable, 90 per cent of natural flow. The Ministerial Council

called for an immediate moratorium on growth in total diversions.

In December 1996 a permanent cap was imposed. It is defined as “the volume of water that would have

been diverted under 1993/94 levels of development.” Under this Victoria is allowed to divert some 1620

gigalitres a year on average. In 1997 there were about 100 gigalitres of unused ‘sleeper’ and ‘dozer’

entitlements. As these were taken up ‘sales’ water reliability was steadily diminished.

In 1997 permanent interstate water trade was enabled in the Mallee regions of NSW, South Australia and

Victoria. In the process each state adopted environmental guidelines based on those used in Victoria. This

fulfilled inter-governmental agreements to ensure that where cross-border trading is possible, trading

arrangements must be consistent. In 2006 permanent interstate trade was introduced into the rest of the

Murray-Darling Basin.

For the Mallee, the bottom line for the cap on diversions is that there is a finite volume of water that can

be traded into the Mallee. In reality the amount likely to be pumped in the Mallee is probably governed

more by economics of pumping. At some point the distance from the River is too great to make pumping

infrastructure worthwhile (Cummins & Cooke 2006).

4.2 COAG Water Reform - driving water reform

As a result of the Council of Australian Governments (COAG 1994) key reforms were required to be

implemented by States regarding:

• Consistent water charging

• Removal of impediments to water trade in water entitlements

• The separation of water entitlement from land title

• Institutional reform

• Water quality

• Maintenance of the health and viability of river systems and groundwater basins

• Environmental requirements were to be determined on the best scientific information available.

The principal COAG water policy agreement is the 2004 National Water Initiative (NWI), which is Australia's

blueprint for water reform. Under the NWI, governments have made commitments to:

• Prepare water plans with provision for the environment

• Deal with over-allocated or stressed water systems

• Introduce registers of water rights and standards for water accounting

• Expand the trade in water

• Improve pricing for water storage and delivery

• Meet and manage urban water demands.

13

The overall objective of the National Water Initiative is to achieve a nationally compatible market,

regulatory and planning based system of managing surface and groundwater resources for rural and urban

use that optimise economic, social and environmental outcomes. It set up the framework for the National

Water Commission, the Commonwealth Water Act 2007, which established the Murray Darling Basin

Authority, and the Commonwealth Environmental Water Holder.

It also set the scene for the $10 billion Water for the Future Program, which provided investment in a range

of water reform programs including the ‘Sustainable Rural Water Use and Infrastructure Program’, the ‘On-

farm Irrigation Efficiency Program’, and water purchasing under the ‘Restoring the Balance’ program.

Water savings created have been allocated to the Commonwealth Environmental Water Holder to help

meet the Sustainable Diversion Limits proposed in the Draft Basin Plan.

14

5 Broadening the scope - some interesting asides

5.1 The Murray-Darling Basin Natural Resources Management Strategy (1989) and the Integrated Catchment Management Policy (2001) – The MDBC gets more involved

The Ministerial Council objectives for the 1989 Murray-Darling Basin Natural Resources Management

Strategy were, to promote and coordinate the effective management of land, water, environment and

cultural resources. An integrated approach was taken regardless of state and territory boundaries.

The principles adopted were equity, economic efficiency and sustainability. The Natural Resource

Management Strategy implemented management programs on vegetation, groundwater, land, off-stream

and in-stream management, riverine environment and incorporated the salinity and drainage strategy.

It led to the creation of the Integrated Catchment Management Policy (ICM Policy) in 2001.

The ICM Policy produced a framework through which natural resource management within the Murray

Darling Basin was managed during the period between 2001 and 2010.

The policy included goals, values and principles to guide the community, government and industry through

the decision making process, in order to achieve catchment targets for water quality, water sharing, river

health and terrestrial biodiversity.

This was in an effort to improve the overall health of the Basin and reduce the stress placed on Basin

resources. Timeframes for achieving each of the catchment goals were included within the policy.

Individual strategies addressing particular resource issues were also developed under the ICM Policy. The

first of these was the Basin Salinity Management Strategy released in 2001. The Murray-Darling Basin Flood

Plain Management Strategy was subsequently released in 2003.

5.2 Floodplain Wetlands Management Strategy for the Murray-Darling Basin (1998) – Wetlands get recognised

The objectives of the Floodplain Wetlands Management Strategy closely align with those of the Water

Reform Principles put forward by COAG. The strategy also helped achieve the aspirations of the Natural

Heritage Trust.

The goal of the strategy is to maintain and enhance the wetland ecosystems within the Murray-Darling

Basin. Eight objectives were identified in the strategy:

• Support community initiatives in the management of floodplain ecosystems

• Develop scientific understanding of the processes operating within the wetlands

• Evaluate and manage river flow regimes to maintain and restore floodplain wetlands

• Develop sustainable-use guidelines and prepare wetland management manuals, to support

floodplain and dependent wetland rehabilitation

• Improve management of introduced species

• Develop standards for information gathered through monitoring and mapping of floodplain wetlands

• Improve understanding of social, cultural, economic and environmental values of wetland systems

• Increase awareness of wetland values and management issues.

15

Close cooperation between policy-makers, agency staff, researchers and the community was a key feature

of the strategy. Through the strategy the Murray-Darling Basin Commission has funded investigations into

the:

• Chowilla Floodplain

• The health and water requirements of the Macquarie Marshes

• The relationship between flooding and water bird breeding within the wetlands of the

Murrumbidgee River

• The functioning of the major mid-Murray wetlands in Victoria.

The Murray-Darling 2001 program supported projects, which aim to rehabilitate wetlands within the

catchment. Some examples included:

• The management and rehabilitation of the Bullock Swamp, as a part of the Nangiloc-Colignan salinity

management plan in Victoria

• The management of River Murray wetlands, as a part of the Mallee Water Management Plan in

Victoria.

5.3 The Living Murray (2002) – The First Step - a healthy working river and no further decline

The Living Murray initiative was the precursor to the Basin Plan. It identified the need for 500 GL of water

to be returned to the Murray as a first step to maintaining ecosystem health at six icon sites. The icon sites

included the Hattah Lakes and the Chowilla Floodplain and Lindsay-Wallpolla Islands and the River Murray

Channel. This was the first step for preventing further decline in floodplain health and flagged the need for

further volumes that later were identified in the Basin Plan.

16

6 Contemporary settings

6.1 The Catchment Land Protection Act 1994 – The CMA role is established

Following a review of catchment management the Victorian Government passed the Catchment and Land

Protection Act 1994.

The purposes of the Act include setting up a framework for the integrated management and protection of

catchments; to encourage community participation in the management of land and water; to set up a

system of controls on noxious weeds and pest animals. Catchment Management Authorities (CMA) arose

from the Act and it also provided the framework for Regional Catchment Strategies. The Regional

Catchment Strategy was developed and endorsed many of the previous strategies and action plans.

The Mallee CMA was delegated responsibility by the State for coordinating salinity management in the

Mallee. Its second-generation salinity management plan for the Victorian Mallee was followed more

recently by a land and water management plan (Mallee CMA 2012). Both aimed to further improve the

efficiency of salinity management activities. This was possible because key planks of the original plans in

effect reduced the differences between the planning areas and the remaining issues were very similar

across the salinity plans.

6.2 White Paper: Our Water Our Future (2004) – Water use licenses with conditions

The White Paper was Victoria’s response to implementing the National Water Initiative, which led to

unbundling. Its actions aimed to:

• Repair rivers and groundwater systems - the natural source of all our fresh water - by giving them

legal water rights and conducting restoration works

• Price water to encourage people to use it more wisely

• Permanently save water in our towns and cities, through commonsense water saving and recycling

measures

• Secure water for farms through pioneering water allocation and trading systems

• Manage water allocation to find the right balance between its economic, environmental and social

values.

It set up three tiers for water allocation. Rights held by the Crown, rights held by the environment and

authorities and caps, and individual rights.

It established environmental water reserves, created low reliability water shares from sales, with 20% of

this being allocated to the environment.

It also established the water register and unbundled water rights into water shares, water-use licences with

annual use limits and delivery shares. The water-use licence conditions have an overriding purpose of

minimising adverse side effects to the environment and third parties.

The Paper proposed investigations with regard to trade-able permits for salinity impacts, and a

commitment to training and incentives to promote best practice irrigation.

New irrigation development or redevelopment needed to meet standards close to best practice. Existing

irrigators had standards set that were equivalent to minimum common standards or brought across from

pre-existing diversion licenses or conditions of earlier transfer of water rights. Licences were given ongoing

tenure, and made transferrable with the property (tied to the land) while at the same time standards

conditions could be altered by a locally drafted plans endorsed by the Minister.

17

The White Paper paved the way for Pricing regulation through the Essential Services Commission. It

foreshadowed the merger of the Sunraysia Rural Water Authority and Lower Murray Water. It also

provided a process for Water Authorities to reconfigure their delivery networks, which included the

potential to stop providing services to individual customers if that process was followed.

The broad functions of the CMA in river health, floodplain management and drainage management and on-

ground river and water protection and restoration were also confirmed.

6.3 Northern Region Sustainable Water Strategy – refining salinity zones and AUL trading

The Northern Region Sustainable Water Strategy (NRSWS) was developed in the face of insufficient water

to meet the Region’s needs. It provided forecasts of the impact of climate change and actions regarding

water sharing arrangements, water reserve, rights to water, carryover and establishment of a Victorian

Environmental Water Holder.

In terms of salinity the Strategy’s actions included:

• Updating the Victorian Manual of Salt Disposal in the MDB to account for unbundling, the Basin

Salinity management Strategy Review and the Basin Plan

• Improving salinity accounting and reporting using change in Annual Use Limits that are held on water

use licenses in salinity impact zones

• Capping of salinity impacts by establishing a rolling cap on the total annual use limit in Low Impact

Zones 3 and 4 in the Mallee Region

• Investigating the need for salinity impact zones upstream of Nyah

• Investigating further refinements to salinity impacts zones and the ability to trade annual use limits

• Continuing support for Sustainable Irrigation Program

• Leading Victoria’s inputs to the review of the Basin Salinity management Strategy, and the Water

Quality and salinity components of the Basin Plan

• Implementing the recommendations of the review of Victoria’s irrigation drainage program.

6.4 Environment Protection Act 1970 – Protecting surface water quality

The State Environment Protection Policy (Waters of Victoria)9 [SEPP (WoV)] requires water businesses with

responsibilities for irrigation provisions and drainage to implement the waste hierarchy to reduce the

impact of irrigation drainage on receiving water environments.

DPI, DSE, Environmental Protection Authority (EPA), CMA and water authorities are required to work

together to minimise pollutants entering drains by developing and implementing Government endorsed

land and water management plans, working with irrigators to implement efficient irrigation, ensuring new

developments incorporate efficient practices, facilitating research into efficient practices and benchmarking

water delivery and water use efficiency. Water authorities need to implement practices to minimise

9 This Policy:

(1) applies to all businesses, non-government agencies, community groups, individuals and State and local government agencies

that use, plan, manage or derive benefit from Victoria’s surface waters;

(2) applies to each person responsible for making legal decisions in relation to Victoria’s surface waters; and

(3) is an instrument of the Environment Protection Act 1970, and is administered by the Environment Protection Authority, which is

responsible for ensuring its overall implementation.http://www.epa.vic.gov.au/about_us/legislation/water.asp#sepp_waters

18

pollutants generated, monitor on a priority basis impacts on surface waters, work with DPI, DSE, CMA, EPA

to audit the impact of irrigation drainage on surface waters.

The waste hierarchy includes measures to:

• Conserve water

• Avoid contaminated irrigation runoff to irrigation drains (and seepage to groundwater) by working

with landholders, CMAs and government agencies to implement the most efficient on-farm water

use and recycling practices

• Avoid the generation of pollutants from within channels and drains (that is to ensure infrastructure is

maintained to reduce erosion, avoid sediment suspension and ensure that chemicals are used in a

manner that does not impact on natural ecosystems); and as a second order measure (after

avoidance opportunities have been maximised) recycle irrigation water on-farm and then recycle

remaining irrigation drainage water to minimise irrigation runoff entering natural waterways (that is

rivers, streams, wetlands etc.).

These measures (and associated priorities, targets and timelines) should be clearly identified in regional

catchment strategies and sub-ordinate plans. EPA requires relevant water businesses to have plans for

implementing the waste hierarchy and to have implemented those plans by 2013, building on the previous

water plans.

The SEPP (WoV) also requires relevant water businesses to monitor the impact of irrigation drains on

receiving environments and as part of that program, ensure that these impacts are independently audited.

In particular, over the 2008–2013 regulatory period, EPA requires water businesses to further develop and

implement programs for independently auditing the impact of irrigation drains.

It does not necessarily mean that every drain needs to be monitored, but there should be enough

representative drains monitored to meet the satisfaction of the independent audit (which involves working

with DSE, DPI, CMA and the EPA).

19

7 Where to now?

7.1 2007 Water Act (Commonwealth) - The legislation behind the Basin Plan, MDBA and the Commonwealth Environmental Water Holder

As mentioned previously, the Act establishes the Murray-Darling Basin Authority (MDBA) with the functions

and powers, including enforcement powers, needed to ensure that Basin water resources are managed in

an integrated and sustainable way.

It requires the MDBA to prepare the Basin Plan for the integrated and sustainable management of water

resources in the Murray-Darling Basin. It also establishes a Commonwealth Environmental Water Holder to

manage the Commonwealth's environmental water to protect and restore the environmental assets of the

Murray-Darling Basin, and outside the Basin where the Commonwealth owns water.

It provides the Australian Competition and Consumer Commission (ACCC) with a key role in developing and

enforcing water charge and water market rules10 along the lines agreed in the National Water Initiative. The

Act gives the Bureau of Meteorology water information functions that are in addition to its existing

functions under the Meteorology Act 1955.

States will still need to be actively involved as they have broader responsibilities (e.g. in land management)

and also prepare the Water Resource Plans under the Basin Plan (See Section 8.2 below).

7.2 The Basin Plan – Implementing the Water Act 2007

The Draft Basin Plan (MDBA 2011) is a high-level plan to ensure the water resources of the Murray–Darling

Basin are managed in an integrated and sustainable way. It is proposed to be implemented as state

governments revise or renew their water resource plans leading up to 2019. The Draft or Proposed Basin

Plan (November 2011) includes the following components:

• Long-term average sustainable diversion limits

• Environmental Watering Plan

• Water Quality and Salinity Management Plan

• Water trading rules

• Water resource plans

• Monitoring and evaluation.

7.3 Future Policy

Future challenges are, by definition, uncertain. This means it is difficult to predict future policy drivers.

We have learnt that the landscape, river and floodplain are part of a sensitive system with a high cost

associated with poor management and a high dividend from improved management and sound policy.

Future policy development will need to consider future challenges and catchment processes. Taking a risk-

based approach to salinity will be important.

10 http://www.environment.gov.au/water/topics/markets-trade.html

20

References

COAG 1994, ‘The Council of Australian Governments water reform framework’. Extract from Council of

Australian Governments Communiqué. Environment Australia, Hobart, 25 February 1994.

http://www.environment.gov.au/water/publications/action/pubs/policyframework.pdf

CSIRO 2008, ‘Water Availability in the Murray-Darling Basin’. CSIRO for the Australian Government.

Cummins, T and Cooke, J 2006, Foundations for Sustainable Irrigation Development in the Mallee. Report

for the Department of Sustainability and Environment to present to an OECD delegation.

Gutteridge, Haskins and Davey 1970, Murray Valley Salinity Investigation. River Murray Commission.

Canberra, 1970.

Kerang Lakes Area Working Group, 1992. The Kerang Lakes Area Draft Management Plan. The Kerang Lakes

Area Working Group, March 1992.

Langford, JK, Forster, CL & Malcolm, DM 1999, ‘Towards a Financially Sustainable Irrigation System –

Lessons from the State of Victoria, 1984-1994’. World Bank Technical Paper No. 413. Washington DC 1999.

http://publications.worldbank.org/index.php?main_page=product_info&cPath=0&products_id=21365

Accessed 17/5/12.

Mallee CMA 2012, Victorian Mallee Irrigation region: Land and Water Management Plan. Mallee

Catchment Management Authority, Mildura, pp. 129.

MDBA 2011, Chapter 3 Key elements of the draft Basin Plan. Murray-Darling Basin Authority webpage -

http://www.mdba.gov.au/draft-basin-plan/delivering-healthy-working-basin/ch03 Accessed 16/5/12.

McCoy, CG 1988, The supply of water for irrigation in Victoria from 1881 to 1981. Rural Water Commission

of Victoria, 1988.

MWEC 1997, Sharing the Murray: proposal for people's entitlements to Victoria's water from the

Murray. Murray Water Entitlement Committee, Melbourne. http://nla.gov.au/nla.cat-vn168852.

Newman, R 2012, ‘River Murray salinity management and irrigation’ in Australian Regolith and Clays

Conference, Mildura 7-10 February 2012.

http://www.smectech.com.au/ACMS/ACMS_Conferences/ACMS22/Proceedings/PDF/S7_5%20ARGA2%20

Newman.pdf Accessed 16/5/12.

NCCSWG 1991, Nangiloc Colignan Draft Salinity Management Plan. The Nangiloc Colignan Community

Salinity Working Group (NCCSWG), February 1991.

NRE 1997, Victoria's Biodiversity: Our Living Wealth. Department of Natural Resources and Environment.

pp. 34.

Australian Government National Water Commission 2012 website accessed 15/5/12 from

http://www.nwc.gov.au/home/water-governancearrangements-in-australia/victoria/water-planning-and-

management/water-policies-and-plans.

Powell, JM 1989, Watering the Garden State: Water Land and Community in Victoria 1834-1988. Allen and

Unwin 1989. pp. 319.

SRWSC 1976, Salinity Control and Drainage: A Strategy for Northern Victorian Irrigation and River Murray

Water Quality. Engineering and Water Supply Department. Adelaide.

Sunraysia Community Salinity Working Group 1991, Sunraysia Draft Salinity Management Plan, Volume 1.

Salt Action Victoria, 1991.

SunRISE 21 2010, Mallee Irrigated Horticulture 1997 -2009, Final report to Mallee CMA, February 2010.

21

SunRISE 21 2012, Irrigated Horticulture Crop report. Final report to Mallee CMA, July 2012.

Thorne, R & Hoxley, G & Chaplin, H 1990, Nyah to the South Australian border hydrogeological project.

Investigations Branch, Rural Water Commission of Victoria, Armadale, Vic.


Victorian National Parks Association 2012.

http://vnpa.org.au/admin/library/attachments/PDFs/Reports/Victoria-state%20of%20decline.pdf Accessed

16/5/12.

9. Community Involvement Author: Tim Cummins1 with significant input from Charles Thompson2

Mallee Catchment






Copyright


Authority 2013

Disclaimer













publication.

Publication details


Chapter 9 – Community involvement.


April 2013

Authors: Tim Cummins1 & Charles

Thompson2

1 Tim Cummins 2 RM Consulting Group

Cover images




Table of Contents

Summary................................................................................................................................................................. 1

1 Introduction ................................................................................................................................................... 2

2 Building the support system .......................................................................................................................... 3

3 Empowering the community ......................................................................................................................... 5

3.1 An overview .......................................................................................................................................... 5

3.2 Nangiloc-Colignan SMP ......................................................................................................................... 5

3.3 Sunraysia SMP....................................................................................................................................... 6

3.4 Nyah to the South Australian Border SMP............................................................................................ 7

3.5 The Mallee Dryland SMP....................................................................................................................... 9

4 The legacy of community involvement in salinity management plans ....................................................... 10

References............................................................................................................................................................ 11

1

1 Summary

Properly done community engagement processes produce much more successful and more robust

approaches to problem solving than central planning could ever achieve. The buy-in from such planning

processes also makes successful implementation much more likely.

Knowing then what we know now, we could have completed the four community-driven salinity

management plans more efficiently – but if we did overinvest in this for salinity per se we ended up with a

store of social capital that has proven invaluable in helping to deal with a host of other natural resource

management issues since then.

We need to make conscious efforts to maintain the social capital built up through these plans. We also

need to be wary of processes that corrode social capital – unfortunately that is one of the risks associated

with the Basin Plan. On the other hand we also need to avoid being captured by communities of self-

interest.

2

2 Introduction

Community involvement in salinity management goes back a long way in the Mallee. The men and women

who did so much to bring about improvements are too numerous to mention in this document. This

chapter will therefore serve as an overview of this important part of our history and some of those who

were involved.

In that vein, let us start with the citation given to Jack Seekamp when he received the Medal of the Order of

Australia in 1991. Jack died in 2007, aged 85. Many in Sunraysia credit him with stopping the Chowilla Dam.

Seekamp OAM, Mr. Jack Victor (AD1991).

For service to conservation and the environment.

Mr. Seekamp has been active in conservation and environmental issues in the Renmark/Sunraysia

area since the middle 1940s when he acted part-time as a research officer for the CSIR (later CSIRO).

He was technical officer for committees concerned with salinity and drainage from the early 1960s

and from 1966 was a Foundation member of the Sunraysia Salinity Committee. In 1967 he

photographed and produced a film ‘Salinity in the Murray Valley’. He was a Foundation member of

the Renmark Soil Rehabilitation Committee in 1974, the Murray Valley League Working Party on

Water Quality and Supply in 1978, and the Sunraysia and Riverland Committee on Salinity in 1979.

Mr. Seekamp was [a] member and Deputy Chairman of the SA River Murray Water Resources

Advisory Committee between 1979 and 1990 and has acted as an expert witness for the SA

Government. He was a Foundation member of the SA Save The Murray Campaign in 1981 and a

member of the SA Advisory Board of Agriculture for three years from 1986. He is currently a

Foundation member of the Murray River Reserves Working Group, the Chowilla Rehabilitation

Working Committee, the SA River Murray Wetlands Management Committee, and several other

community organisations concerned with water resources and the environment. Mr. Seekamp has

also produced numerous pictorial reports on environmental issues in the region, addressed school

and community groups, and appeared on radio and television in support of this cause.

Ever mindful of this rich past, this chapter concentrates on the achievements that rose out of the

cooperation between governments and the community that started with Salt Action: Joint Action in 1988. It

concentrates therefore on the development and implementation of community-driven salinity

management plans.

It is worth noting however that the public servants employed to help develop those plans regularly

attended meetings of the Sunraysia and Riverland Committee on Salinity (SARCOS) with Jack and several

other local stalwarts. SARCOS continued to meet for at least 15 years (MWWG 2008). Though one

particular meeting did seem longer than that. The people of Sunraysia owe a debt to the foresight and

perseverance of SARCOS.

3

3 Building the support system

In 1986, the Victorian Government recruited fifty or more new staff across several agencies, the

Department of Conservation, Forests and Lands (CFL), the Department of Agriculture and Rural Affairs

(DARA) the Rural Water Commission (RWC) and the Department of Water Resources (DWR). It also created

a coordinating agency, the Salinity Bureau within the Premier’s Department.

The present author, who had been indoctrinated by the Sun News Pictorial’s halt the salt campaign during

the 1970s, and who had done his undergraduate thesis on salinity management in horticultural crops of the

Murray Valley, was one of those inducted. He was enticed away from a promising career with a Queensland

fertiliser company, and a company car, by a simple ad in the paper.

A key feature of the induction process was three separate weeklong interdisciplinary training sessions-cum-

symposia at Dookie College. Fellow inductee, Bill O’Kane, often played the role of symposiarch. Luminaries

such as Phil Macumber, Ray Evans and Phil Dyson gave competing views of hydrogeology. People as diverse

as Sharman Stone (then with RWC) and Gyn Jones offered their views about working with the community.

Gyn (“as in pop”) also painted memorable word pictures of feedback loops in natural resource

management – citing for example the mine shafts around Ballarat filling with water as trees were cleared

for the diggings; the temporary solution involved steam-driven pumps fuelled by more trees cleared from

the diggings.

Later a core team of 12 people across three government agencies was assembled at the regional level to

provide secretarial and technical support to four community working-groups in the Victorian Mallee. The

induction processes at the regional level were not, at first, as polished as those at Dookie. For example, a

young Charles Thompson spoke in public for the first time ever when he agreed, at a moment’s notice, to

deliver a presentation to a small group of farmers in the Red Cliffs pub. Ever fearless, Charles was on that

one occasion also almost speechless.

A lead agency was appointed to supply secretarial support to each group and to coordinate the technical

input into each group:

• RWC for Nangiloc-Colignan

• DARA for Sunraysia

• RWC for Nyah to South Australian (SA) Border

• CFL for the Mallee Dryland

The regional managers for each of these agencies agreed to pool their resources for each plan through a

common project manager employed by DARA. In performing that role, I answered for each individual plan

to the regional manager of the lead agency. I also coordinated input from a project officer dedicated to

each group (employed by the lead agency), a technical assistant and an economist employed by DARA a

community education officer employed by RWC and an environment officer for each plan employed by CFL.

Outside this central structure, but integral to it, were other positions dedicated to salinity management (a

planning officer in CFL, a community education officer and an extension officer in DARA and a technical

specialist in RWC). Crucial technical input was also provided by enthusiastic youngsters such as Greg Hoxley

and Geoff Linke at RWC in Armadale. Guidance, managerial oversight and technical input were also

available from John Cooke of CFL, Mark Dale of DARA and Brent Godkin of RWC.

From John we learnt how to handle difficult people in meetings. We also learnt that if someone keeps

banging on about something you don’t understand, it is quite likely important. Moreover, you should do

your level best to understand it; even if the issue turns out to be not quite what the difficult person thought

it was, it will, more often than not, still turn out to be important. John also taught us how to take an

economic approach to environmental decision making. On that front, he was, and is, ahead of his time.

From Mark we learnt important social skills. For example, you should never wear a safari suit into the public

bar of a hotel – especially not at 5.00 pm on a working day. Mark also taught us important management

skills; the first task is to make people’s strengths productive and their weaknesses irrelevant. For example,

4

if you ever employ a bright young thing with strong people skills, strong technical skills, and a low aptitude

for managing budgets and preparing ministerial briefing notes, you should resist the temptation to train

them in the arts of bureaucracy. Rather, you should give them a free rein to do what they are good at while

shielding them from the things for which you have a comparative advantage.

From Brent we learnt that work finishes when you knock off for the day. It is important to clear your mind

at the end of the day; it is important to smell the flowers. When you are at work, however, you must give

the important things your undivided attention. You must also maintain eternal vigilance against what might

go wrong. You must not worry about what might go wrong, but you must be prepared for it.

From that wafer-thin document “Guidelines for the preparation of salinity management plans”, we learnt

most of what we now know about economics and environmental management. I don’t think it taught us

much about managing social problems.

5

4 Empowering the community

4.1 An overview

Wilkinson and Barr (1993) provide the definitive reference regarding the salad days of Salt Action: Joint

Action. The main things to note here is that in those early days the chairs of the different community

working-groups (in theory at least) had direct access to the members of a cabinet sub-committee. The main

effect of this purported access was to ensure that previously rival government agencies would successfully

work together. In practice, open access to senior public servants such as Peter Sutherland, Campbell

Fitzpatrick, Graham Hunter, Keith Collett, and Graeme David helped to fine-tune the cooperation that was

engendered by this threat.

The four salinity management plans (SMP) in the Mallee can be summarised as follows:

• Nangiloc-Colignan was about cure; it was about overcoming community divisions and institutional

failure

• Sunraysia was ostensibly a mopping-up exercise; the drainage systems of the 1930s had ‘solved’

problems with on-farm waterlogging and salinity, but they had left residual problems with river

salinity and apparent problems with a series of unnatural drainage basins totalling 2,000 hectares

servicing nearly 17,000 hectares of irrigation – with half that area draining to the river

• Nyah to the SA Border was about prevention rather than cure

• The Mallee Dryland was about dealing with uncertainty – and doing so with appropriate imprecision.

4.2 Nangiloc-Colignan SMP

To this day, more than twenty years after it was completed, the Nangiloc-Colignan Salinity Management

Plan remains the single most difficult project I have ever been involved with. There were times in the

Nangiloc football club or the Nangiloc Hall that I would rather have been anywhere else.

On the other hand, someone had to act as a lightning rod when necessary. In a small community, complex

familial relationships can sometimes get in the way of efforts to respond directly to someone you disagree

with – especially if that person is shouting in a small room. Superimposed on all this in Nangiloc were the

strained relationships between corporate farmers (who seemed to have arrived just before the drainage

problems and environmental problems first emerged) and family farmers (whose relationships with the

district stretched back to the days when Boonoonar used to play Carwarp at cricket).

Bullock Swamp and Carwarp Creek were always the flashpoints regarding the corporate farms. Let the

record show however that the patience and generosity of spirit shown by the employees of those corporate

farms was pivotal to the success of the Nangiloc-Colignan SMP. With two, or perhaps three, notable

exceptions, most of those involved with that plan became skilled in the art of copping it sweet.

The chair, Councillor Ron Vine was a difficult but likeable man – as evidenced by the fact that in his dying

days he was nursed both by his wife and his ex-wife. Provided you could head off his propensity to react

against perceived threats, Ron was a selfless representative of his local community. I doubt anyone else

could have done the job.

Ron did not like surprises. If ever you wrong-footed him by giving him new information just before, or

worse, during, a meeting, it would be interpreted as an effort to undermine his authority. Authority was

very important to Ron. If ever you made a mistake, he was quick to let you know about it. And his forensic

accounting skills meant that he was dynamite when it came to any mistakes in your calculations.

Once, early in the process, Charles used his initiative to arrange a couple of cars to transport working group

members to the launch of Salt Action: Joint Action in Bendigo. Ron had asked for a bus, but Charles felt the

numbers going could be more easily managed in two cars. Ron was furious. He told Joan Kirner, then the

Minister for CFL: “my project officer is out of control”. The regional managers of both RWC and CFL were

6

asked to counsel Charles; he was advised that this was a community-driven process and that in future he

would do exactly as Ron asked.

What forced everyone to the negotiating table in Nangiloc was Brian Kiley’s decision to renew some

irrigation licences for only two or four years instead of the anticipated fifteen (Mallee Salinity Workshop

Chapter 8: Policy and Regulatory Environment). Brian, the RWC regional manager shared Ron’s concerns

with authority, but he was more good-natured about it. He made all the right noises about community

consultation, but was seemingly unconvinced. Nonetheless, he was happy enough to stay out of the way if

it looked like it might work.

The key to success in Nangiloc was to evaluate, patiently and diligently, every single option put forward by

the community. Nonetheless, there were two people on the working group were never going to be happy

with whatever was proposed. But in presenting the plan to the rest of the community, while those two

were yelling at you, you had to be able to look everyone else in the eye and say: “I understand exactly what

they think we should do instead, we have studied those proposals closely, but unfortunately the numbers

do not add up.”

Having said that, I must add, that both of the recalcitrants were great blokes in their own right. I will never

forget a day Charles Thompson and I spent with one of them on the river, in a tinny, in flood, looking at the

marvels of Tarpaulin Creek. It was a day of hearty good cheer punctuated with companionable silences.

Charles, only recently emigrated from England, was warmly taken to heart by many members of the

working group. He tells me for example that he ate lambs’ brains for the first time at Bryan Noyce’s kitchen

table in Karadoc. He enjoyed them too; at least while he thought he was eating scrambled eggs on toast.

4.3 Sunraysia SMP

Owen Lloyd, as he and I have discussed, is technically one of the world’s worst chairmen. Rambling,

tortuous, elliptical discussions would be allowed to run on seemingly forever … and then, through some

miracle, a profound point would be revealed. Actually, it wasn’t always a miracle. Often it was Richard

Wells interjecting to cut through to the heart of the matter. Richard, himself no slouch at rambling, had an

uncanny ability to identify the few key things that were important when the time came.

After the profound point was revealed, Owen would make sure that everyone had their chance to have a

say about it. This might include anything from the delightful Angus Cameron politely agreeing with

everything that had been said or Ted Lawton providing a critical historical insight. Other times it might

include Ted telling us again about how much water it took to grow one orange. Ted was ahead of his time

when it came to virtual water.

Somewhere in the world, there is footage of Jean-Michel Cousteau interviewing Owen on the shores of

Basin 13 in the Cardross drainage basins. I know, because I saw it once on daytime television in Huntsville,

Alabama. In it, Owen proudly boasts that the people of Sunraysia are planning to dry the basins out.

Imagine his shock then when there was an environmental panic once the Basins did indeed start to dry up.

It turned out that they were acting as a refuge for small fish species that had disappeared from the river

system. Lesser men would have been offended, that they were being treated as environmental vandals for

trying to do the right thing. Owen simply helped work out how to get fresh water into the system to keep

the fish alive.

Owen has a remarkable track record in steering people through very difficult issues. He did so with the

Sunraysia SMP, the First Mildura Irrigation Trust (FMIT), a Cardross Lakes committee and probably many

more issues of which I am unaware. Peter Hammond, a former chair of the FMIT told me once that he

planned to nominate Owen for an Order of Australia award. As far as I know, he has not done that yet. But

he should. Or I should.

The Sunraysia Plan was very resource intensive. I am still not entirely sure that was justifiable or justified at

the time. But I have form in this regard; I can point to one particular meeting of that group, at Trentham

Cliffs, where I singlehandedly added perhaps a year to the process through a bungled effort at facilitation.

The working group’s meetings were always at night and they always went late into the night. I don’t know

7

about anyone else, but I was always abuzz afterwards and could seldom get to sleep before 2.00 or 3.00

am. Mostly because of something akin to ‘staircase wit’, I would think of things I should have said if only I

had thought of them early enough. And this went on, once a fortnight – for years!

Once a fortnight! What were we thinking?

We, the support staff, took our job seriously. This was an era when people inside the pumped districts still

had an expectation that governments should do things for them. For them the answer was obvious;

government should give everyone drip irrigation systems and fix up the delivery system at the same time so

that it was capable of servicing everyone with drip irrigation. It was our job to patiently explain that nothing

in their plan would be supported if it didn’t achieve a benefit cost ratio of at least 1.04 to 1. It was our job

to help them make it easier for their negotiating partner, the government, to say yes.

The working group members were convinced that improvements in irrigation management would reduce

the groundwater mound and stop the drains flowing. We would work and rework the numbers for them,

and Geoff Linke of Hydro-Technology would redo the hydrogeology before coming back and patiently

explaining to the working group, once again – using his considerable gifts for communication – that

improved irrigation was unlikely to have a significant impact on the groundwater mound. In effect, the

received wisdom was that the system was then charged up to the point where it would only take a

teaspoon of water to get past the root-zone to maintain the head in the system. John Martin of RWC could

be relied on to disagree with Geoff.

To put it bluntly, the working group was telling us that, what now constitutes two Accountable Actions

under the Basin Salinity Management Strategy (the Reduced Irrigation Salinity Impact action and the

Sunraysia Drying of the Drains action) should be used to strengthen an economic argument for supporting

improved irrigation management and technology. We were telling them that it would never happen. In the

end they were able to justify partial support on the basis of a partial drying of the drains, but only for half

the irrigators – the half that drained into the river. They were then incredibly innovative in developing a

tariff scheme to tax themselves to raise funds for the other half. Personally, I was always lukewarm about

government support for improved irrigation, but I could see that they would have no credibility with the

broader community if they did not include it as part of their plan. It was the obvious answer after all.

I did not mind being proved wrong occasionally. My proudest boast in salinity management is that I am the

person who said: “great idea, too bad no one will do it”. This was in response to Richard Wells’ suggestion

that incentives for irrigation improvements should be linked to a requirement to do an irrigation

management course. More than 2,500 people have done that course so far. With hindsight, it was the most

important part of the plan. Certainly, no one could accuse us of not treating seriously the ideas put forward

by the community.

When Lyndall Ash of DARA and I finally finished writing the draft plan, I remember looking at the summary

and wondering out loud that how it could have taken us more than a fortnight to sort that out. I knew then

that we had a good plan – it just seemed to make so much sense.

To his great credit, Keith Collett, then of RWC, spent a lot of time on the phone to me when he was crafting

the government response to the plan. He suggested some subtle changes in interpretation that he thought

would help get the plan across the line. I had Owen’s trust and I was confident that he would agree with

what Keith was suggesting. As good public servants, Keith and I were both fastidious in making sure the

plan was consistent with the guidelines.

4.4 Nyah to the South Australian Border SMP

The Nyah to the SA Border Plan was intellectually stimulating and satisfying from start to finish. All the

support staff enjoyed working on it for that reason, and I am sure that was a big motivator for the working

group as well. And what a delight they were to work with. No sensitive egos, no expectations about what

governments should do and only a couple of ramblers – to keep us on our toes about how the plan might

go down with the broader community as Peter Forbes of RWC once wisely observed.

8

Unlike Sunraysia, or Nangiloc-Colignan for that matter, the working group members were not used to

governments taking much interest in their activities. In keeping with the spirit of the times they were

enthusiastic about small government, but they could see the worth of putting regulations in place to try to

avoid repeating the mistakes of the past once water entitlements were made tradable.

Their main concern at the outset had to do with the wisdom of selling the extra 8,000 ML being made

available out of Dartmouth. They argued that more than enough water had already been made available

for irrigation, surely it would be better to leave that for the environment. Brian Kiley forcefully made the

point that the RWC was not for turning. It was after all, less than one day’s flow and a lot of the water in

Dartmouth had already been earmarked for the environment. This water was going to be important in

helping to kick the market off. I went along with him I am afraid.

It took us all a while to get our minds around the hydrogeological information that the urbane and youthful

Greg Hoxley put in front of us. But he was convincing and we were convinced. The main issue then became

whether to have two salinity impact zones or three. The working group opted for simplicity.

The next issue was to decide whether to rule out trade into the high impact zone altogether or whether

instead to allow it only if drip irrigation was used. This chestnut was revisited many times. The argument

ultimately swung on the magnitude of the differential between the high and the low zones. It was bigger

than could reasonably be achieved with even the best of irrigation practices, and there were no guarantees

that irrigation standards could be maintained in perpetuity.

It still fascinates me that this issue was revisited so many times. I think it says a lot about the underlying

dynamics of the working group. There were some very deep thinkers amongst them and they had some

interesting choices to make. At one end of the spectrum they didn’t want to invite government into their

lives any more than was absolutely necessary. At the other end of the spectrum, they did think it was vital

to have regulations to protect the health of the river and they thought it was reasonable for people to be

expected to take care of their own drainage.

They were also resolute in their desire (rightly I believe) to avoid government having any say whatsoever in

what crops were to be grown or what irrigation systems were to be used. They were similarly resolute in

their desire to ensure that any regulations they did put in place were practical and enforceable. The worst

of all possible worlds for them would be to introduce regulations that complicated people’s lives for no

benefit. This was the point of dissonance in their thoughts about trade into the high impact zone.

On one hand, they felt uneasy about cutting off options for people in the high impact zone. There must be

some way we could get around this? What if people were doing all the right things, surely we wouldn’t stop

them then? But wouldn’t that mean stipulating a particular type of irrigation system? And wouldn’t we be

putting in place regulations without any real prospect of enforcing? Better, simply, to rule it out.

Rodney Hayden, the chairman, walked us deftly through this minefield. He was thoughtful, patient,

humorous, laconic and eloquent (if that is not an oxymoron). Like all members of the working group he

found the whole process intellectually stimulating, and he was more than up to the challenge.

A similarly dissonant chord was struck the day John Cooke had the temerity to suggest that perhaps we

should be thinking about river users and the aesthetics of pumphouses; perhaps in fact we should think

about regulating the colour of pumphouses. A couple of members initially looked fit to start a riot. Those

individuals never really warmed to the idea, but most eventually came to the conclusion that it wasn’t too

much to ask of people making use of public land.

One fundamental premise of the Mallee plans is worth noting here. The government members of those

working groups (John, Mark and Brent) never voted on anything that went to a vote. What’s more, none of

the government employees ever sought to influence a vote. When options were presented, we would give

our views (based on the guidelines) about the degree of difficulty likely to be encountered in getting the

government to say yes, but that was it.

I think we engendered more trust that way and I suspect the working group members accordingly gave

more weight to our assessments of the degree of difficulty involved in getting the government to say yes.

9

This approach worked however only because the government of the day never sent us any signals about

what they thought the plans should look like – other than to reaffirm the guidelines.

In one sense we trusted we would get another say when the machinery of government was considering

whatever draft plan the community saw fit to put forward. Balanced against this however was our

understanding that once the plan was put forward, we were honour-bound to explain to government why

the working group thought the way they did – just as we had been honour-bound to explain to the working

group why the government had crafted the guidelines the way they had.

Fortunately, this was a complete non-issue for the Nyah to SA Border Plan. Everything that working group

put forward made so much sense that it was accepted holus bolus.

4.5 The Mallee Dryland SMP

Having gotten progressively more efficient at running community-driven planning processes, we took the

government seriously when they said they wanted to do dryland plans as well, but they didn’t think they

warranted the same level of investment in time or resources as the irrigation plans. My memory is that we

were given 14 months to complete the Mallee Dryland plan and we delivered in that time frame.

Predictably enough, however, when it came time for the government to respond the reviewers kept looking

for the level of detail that would have taken two or three years to collect – the other dryland plans were

indeed developed over those timeframes.

On reflection, I still think the Mallee dryland plan was fit for purpose. More time and effort would not have

significantly reduced the uncertainty surrounding the potential for human activity to make a significant

difference.

John Cooke’s long history of involvement in the dryland was the key to us delivering on time. His first

suggestion was that we should make use of an existing group. Consequently, the Land Protection Regional

Advisory Committee (LPRAC) took on another guise as the community working-group for the Dryland Plan.

No sooner would an LPRAC meeting close than they would reconvene as the working group with some

additional input from DARA at Walpeup.

To describe Leo Fuller, the chairman, as one of nature’s gentlemen is to transcend the cliché. He was

gentle, strong, considered and considerate. He ran a tight meeting while keeping the lightest of touches on

the reins. He was also very knowledgeable. And he had a wonderful working relationship with John.

Their first job was to consider John’s suggestion that the plan concentrate on the potential point sources of

groundwater recharge as well as the potential point-sources of contamination for freshwater Duddo

Limestone aquifer. After some discussion, they thought this was sensible, without the benefit of any

detailed understanding of the benefits in salinity terms, they did know the costs and they reasoned that the

risks involved in not addressing them were commensurate with the costs. The proposed actions also had

other non-salinity benefits that were in keeping with the costs.

The point sources taken care of, they then concentrated on the thornier issues that revolved around

different cropping systems and to what extent they might each affect recharge. This was fertile ground for

debate and there was, and still is, strong opinion about continuous cropping versus various systems of

rotation. Tangled up in that debate are various artefacts of the collapse of the wool reserve price scheme as

well. Fortunately for me, and my humble horticultural background, Darren Herpich of CFL was able to walk

me through all this. Darren was also a fine writer and between the two of us, we were able to write the

plan and layed out for printing using WordPerfect 5.1.

With hindsight, I think we were appropriately inconclusive about the cropping systems; salinity is just one

part of the mix of things that a cropper must take into account and for most it, is a very small part. John

was wise to focus us on the point sources.

10

5 The legacy of community involvement in salinity management plans

Looking back we can see a generation of public servants and consultants who are still willing to talk

meaningfully to local community members about practical problems – in notable contrast to the approach

taken by Commonwealth Government in the development of the initial Guide to the Basin Plan.

Also we have had a generation of well-informed community members willing to jump in and help us out

with successive natural resource management problems – we need to keep nurturing this.

In short the process developed a lot of social capital, provided we keep maintaining that we should

continue to be well placed to continuously improve our natural resource management.

There is one thing from those exhilarating pioneering days that might never be seen again – a Committee of

Ministers pro-actively driving the process and securing a $32 million per year budget. Not only that, but

then overseeing that budget to ensure that the resources – drilling, monitoring, modelling, support

personnel were available to the community to see their planning through to implementation, no matter

how long it took.

11

6 References

Wilkinson, RL & Barr, NF 1993, ‘Community involvement in catchment management : an evaluation of

community planning and consultation in the Victorian salinity program’. Department of Agriculture, East

Melbourne.

MWWG 2008, ‘Vin Byrnes – MWWG Executive Member Profile’. NSW Murray Wetlands Working Group.

http://www.mwwg.org.au/pdf/aboutVinByrnes.pdf accessed 17 May 2012.

Mallee Salinity Workshop May 30, 2012

Documents

Transcript of Mallee Salinity Workshop May 30, 2012