Environmental Water Requirements for Groundwater Dependent … · 2015. 4. 27. · Project DF006-1...

Environmental Water Requirements for Groundwater Dependent Ecosystems of the Adelaide Plains and McLaren Vale

Adelaide and Mount Lofty Ranges Natural Resources Management Board 205 Greenhill Road EASTWOOD SA 5063

February 2012

ECOLOGICAL ASSOCIATES REPORT NO. DF006-1-C

This report may be cited as:

Ecological Associates and SKM (2012). Environmental water requirements for groundwater dependent ecosystems of the Adelaide Plains and McLaren Vale. Ecological Associates Report DF006-1-C prepared for Adelaide and Mount Lofty Ranges Natural Resources Management Board, Eastwood.

Ecological Associates 5, 235 Unley Rd Malvern SA 5061 Ph. 08 8272 0463 Fax 08 8272 0468 [email protected]

Adelaide and Mount Lofty Ranges Natural Resources Management Board 205 Greenhill Road EASTWOOD SA 5063 Ph. 08 8273 9100 [email protected]

Project DF006-1 Document Control

Report Title Report Ref. Version Issued Issued to Issued by


DF006 1-B 25 January 2012

Jenny Awbery Marcus Cooling


DF006 1-C 2 February 2012

Jenny Awbery Marcus Cooling

Report authors: Marcus Cooling Dougal Currie

Contents

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1! Introduction-------------------------------------------------------------------------------------------1-1!

1.1! Introduction 1-1!1.2! Background 1-1!1.3! Study Area 1-1!1.4! Scope of Work 1-2!1.5! Adopted Approach 1-2!1.6! Overarching Objectives 1-4!

2! Geology and Hydrogeology of the Study Area--------------------------------------------------2-1!2.1! Origins of the Mount Lofty Ranges and Adelaide Plains 2-1!2.2! Aquifer Systems 2-1!

3! Nature and Extent of GDEs-------------------------------------------------------------------------3-1!3.1! Introduction 3-1!3.2! Sources of Information 3-1!3.3! Results 3-3!3.4! Existing GDE Typology 3-5!3.5! New GDE Types 3-7!3.6! GDE Typology for this Study 3-8!

4! Water Requirements of Dependent Flora and Fauna-----------------------------------------4-1!4.1! Fish 4-1!4.2! Aquatic Macroinvertebrates 4-4!4.3! Plants 4-6!

5! Fractured Rock Aquifer Springs-------------------------------------------------------------------5-1!5.1! Occurrence 5-1!5.2! Ecology 5-4!5.3! Functional Groups Present 5-6!5.4! Groundwater Dependence 5-6!5.5! Proposed Environmental Water Requirement 5-7!5.6! Threat Assessment 5-7!

6! Groundwater Dependent Streams ----------------------------------------------------------------6-1!6.1! Distribution 6-1!6.2! Ecology 6-4!6.3! Functional Groups Present 6-7!6.4! Groundwater Dependence 6-7!6.5! Proposed Environmental Water Requirement 6-8!6.6! Threat Assessment 6-9!

7! Terrestrial Vegetation at the Base of the Hills ------------------------------------------------7-1!7.1! Distribution and Occurrence 7-1!7.2! Ecology 7-3!7.3! Functional Groups Present 7-5!

Contents

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7.4! Groundwater Dependence 7-5!7.5! Proposed Environmental Water Requirement 7-6!7.6! Threat Assessment 7-6!

8! Measuring EWRs --------------------------------------------------------------------------------------8-1!8.1! Measurement of EWRs 8-1!

9! Conclusions -------------------------------------------------------------------------------------------9-1!9.1! GDE Typology 9-1!9.2! Fractured Rock Aquifer Springs 9-1!9.3! Groundwater Dependent Streams 9-1!9.4! Terrestrial Vegetation at the Base of the Hills 9-2!

10! References----------------------------------------------------------------------------------------- 10-1!

Figures and Tables

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Tables

Table 1. GDE composition .........................................................................................................................3-3!Table 2. Revision of GDE types proposed by SKM (2010).......................................................................3-8!Table 3. Groundwater requirements of fish................................................................................................4-3!Table 4. Macroinvertebrate community types relevant to GDEs in the study area....................................4-5!Table 5. Groundwater conditions to support macroinvertebrate ecological functions...............................4-6!Table 6. Group 1 plant species ...................................................................................................................4-7!Table 7. Group 1 groundwater requirements..............................................................................................4-7!Table 8. Group 2 plant species ...................................................................................................................4-8!Table 9. Group 2 groundwater requirements..............................................................................................4-8!Table 10. Group 3 plant species .................................................................................................................4-9!Table 11. Group 3 groundwater requirements............................................................................................4-9!Table 12. Group 4 plant species ...............................................................................................................4-10!Table 13. Group 4 groundwater requirements..........................................................................................4-10!Table 14. Group 5 plant species ...............................................................................................................4-11!Table 15. Group 5 groundwater requirements..........................................................................................4-11!Table 16. Fractured rock aquifer springs example sites .............................................................................5-4!Table 17. Example Sites of Groundwater Dependent Streams ..................................................................6-3!Table 18. Assessment of measurement approaches for EWRs ..................................................................8-2!

Figures

Figure 1. Identification of springs from historic cadastral maps................................................................3-2!Figure 2. Identified GDEs in the study area ...............................................................................................3-4!Figure 3. The extent of the outcropping basement (in general) and Stoneyfell Quartzite (in particular) as a

guide to the potential distribution of springs in the study area....................................5-1!Figure 4. Conceptual hydrogeological model of fractured rock spring discharge .....................................5-3!Figure 5. Fractured rock spring discharge GDEs in Cleland Conservation Park .......................................5-3!Figure 6. Site Photo Heptinstalls ................................................................................................................5-5!Figure 7. Consequences of lower water tables for fractured rock aquifer spring.......................................5-8!Figure 8. Classification of groundwater dependence, with confidence levels based on DWLBC aerial

videography of watercourses and an analysis of stream-aquifer interactions (adapted from SKM 2011) .........................................................................................................6-2!

Figure 9. Conceptual model of a groundwater dependent stream ..............................................................6-4!Figure 10. Site Photo Wilsons Bog ............................................................................................................6-6!Figure 11. Site Photo Coats Gully ..............................................................................................................6-6!Figure 12. Stream baseflow exceedance curves for records for Brownhill Creek (1991-2011) and First

Creek (1976-2006) based on their entire monitoring records......................................6-8!Figure 13. Consequences of lower water tables for groundwater dependent streams..............................6-10!Figure 14. Schematic representation of the dependence of terrestrial vegetation at the base of the hills on

shallow groundwater....................................................................................................7-1!Figure 15. Terrestrial vegetation at the base of the hills. ...........................................................................7-3!Figure 16. River red gum (Eucalyptus camaldulensis) in Hazelwood Park, Burnside ..............................7-4!Figure 17. Groundwater level monitoring for the Q1 aquifer at Hazelwood Park.....................................7-6!Figure 18. Consequences of a lower water table on terrestrial vegetation .................................................7-7!Figure 19. Groundwater extraction in the vicinity of Hazelwood Park .....................................................7-8!

SECTION 1 Introduction

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1 Introduction

1.1 Introduction

Ecological Associates and Sinclair Knight Merz (SKM) were engaged by the Adelaide and Mount Lofty Ranges Natural Resources Management Board (the Board) to recommend environmental objectives and water requirements for the groundwater dependent ecosystems (GDEs) of the Adelaide Plains and McLaren Vale Prescribed Wells Areas (PWAs).

Understanding environmental water requirements (EWRs) is a key part of the water allocation planning and licensing for the PWAs. This report details the EWRs of the GDEs and outlines the process that determined these EWRs.

1.2 Background

GDEs are ecosystems (both saline and fresh) that rely on groundwater for some or all of their water requirements. There are typically five types of GDEs: wetlands, river baseflow, terrestrial vegetation, estuarine/marine and subsurface.

GDEs typically rely on specific attributes of groundwater in different environments, these being groundwater level, quality and flux. The impact of changes in groundwater attributes on GDEs is determined by the degree and nature of their groundwater dependency.

The Adelaide and Mount Lofty Ranges Natural Resources Management Board (the Board) is currently preparing a draft Water Allocation Plan (WAP) for the Dry Creek and Central and Northern Adelaide Plains PWAs. The Board also has responsibility to review the WAP for the McLaren Vale PWA.

The Natural Resources Management Act 2004 requires that the needs of groundwater dependent ecosystems are assessed when determining the quantity of water available for water users. The WAP will detail how groundwater is to be allocated for consumptive use and for the environment, based on the best available knowledge of the water requirements of potential GDEs.

In 2010 the Board commissioned a review of GDEs including their functions and values, levels of threat and the nature of their dependency on groundwater (SKM 2010). This investigation provided an initial assessment of the location and level of risk to GDEs across the area, including GDEs dependent on the Quaternary, Tertiary and fractured rock aquifers.

This study was commissioned to build on this review through fieldwork and more detailed examination of GDEs to determine the water requirements of GDEs for inclusion in the Water Allocation Plan.

1.3 Study Area

The study area comprises the Adelaide Plains and Willunga Basin extending from beyond the Gawler River in the north to the Sellicks Hill Range in the south, including the Noarlunga Embayment. The study


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area includes the minor catchments of the Mount Lofty Ranges that drain into this area, such as First through to Sixth Creeks and Brownhill Creek.

It excludes catchments which lie substantially east of the western scarp of the ranges including the Gawler, Little Para, Torrens, Sturt and Onkaparinga catchments. The water requirements of these catchments has been undertaken separately as part of the Western Mount Lofty Ranges Prescribed Area (VanLaarhoven and van der Wielen 2009). The EWRs determined in the Western Mount Lofty Ranges Water Allocation Plan have been taken into consideration in this study.

The Mount Lofty Ranges component of the study area was identified as a high priority area for GDE investigations by the SKM (2010) study. In this area the water table is frequently shallow and interacts with ecosystems of high conservation significance. Importantly, groundwater is part of an aquifer that is subject to current or potential use that must be managed if ecosystems to be protected. In constrast, in the Northern Adelaide Plains, Dry Creek and Kangaroo Flat regions, the aquifers that interact with ecosystems are typically too restricted in extent or too saline to be subject to use. These areas are a lower priority for investigation.

1.4 Scope of Work

The overall objective of this project was to recommend environmental objectives and water requirements of GDEs in the combined Northern and Central Adelaide PWAs, Dry Creek PWA and McLaren Vale PWA.

The specific objectives were to:

• establish overarching environmental objectives for the GDEs of the region;

• document the EWRs that are likely to achieve these objectives at a low level of risk; and

• develop draft ‘agreed environmental outcomes’ that will be reflected in the WAP principles.

For the McLaren Vale PWA the specific objectives were to:

• review and update existing information on GDEs and their EWRs to recommend appropriate management responses for the review of the McLaren Vale WAP.

1.5 Adopted Approach

This project seeks to specify the environmental water requirements of GDEs with sufficient detail to allow effective protection of water requirements, while also comprehensively representing GDEs that occur in the study area.

There is little existing information on the location of GDEs, their ecology and the role of groundwater in their water requirements. Therefore an approach was required that used available information in a general and consistent framework to define water requirements in a way that was scientifically defensible.


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The approach adopted in this project followed the approach used in the study to determine EWRs for the Mount Lofty Ranges prescribed water resource areas (VanLaarhoven and van der Wielen 2009).

Central to this process was the contribution of an expert panel comprising ecologists and water resource managers. The expert panel reviewed the findings of the consultancy team and contributing knowledge about species and sites. The panel helped develop conceptual models of the role of groundwater in ecosystems, which were used to make predictions about the nature and extent of groundwater dependence in the study area. The panel comprised:

• Jenny Awbery (Adelaide and Mount Lofty Range Natural Resources Management Board);

• Jason VanLaarhoven (Department for Water);

• Jason Nicol (South Australian Research and Development Corporation);

• Paul Wainwright (Department for Environment and Natural Resources);

• David Schmarr (South Australian Research and Development Corporation);

• Paul McEvoy (South Australian Water Corporation);

• Michelle Bald (Department for Water);

• Grant Lomman (Adelaide and Mount Lofty Range Natural Resources Management Board);

• Marcus Cooling (Ecological Associates);

• Dougal Currie (SKM); and

• Stuart Richardson (SKM).

The methodology involved the following three stages.

Defining Ecosystems

A review was conducted of the aquifers in the study area and their interactions with surface systems. This is is summarised in Section 2.

A previous investigation by SKM (2010) reviewed the GDEs known to occur and likely to occur in the study area based on existing information. A classificaiton of nine GDE types was identified and examples, where possible, located. This classificaiton was reviewed based on advice from an expert panel and field assessments. This process is presented is Section 3.


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Hydrological Requirements of Component Biota

In seeking to define the water regime required to sustain the flora and fauna that depend on GDEs, the flora and fauna they support was investigated. Field survey records, expert advice and known species distributions were used to identify fish, macroinvertebrates and plants that are likely to depend on GDEs.

The hydrological tolerances of these species was reviewed based on their life histories, published physical and chemical tolerances and the range of conditions they are known to tolerate.

Determine EWRs Based on Component Biota

Conceptual models were developed of the interaction between groundwater and flora and fauna at GDE sites to predict EWRs. The models considered the requirements of all the component flora and fauna to provide an integrated assessment of the water requirements of the ecosystems and the consequences of change in the groundwater environment.

1.6 Overarching Objectives

Environmental water requirements have been defined as ‘the water regime needed to sustain the ecological values of ecosystems, including their processes and biological biodiversity, at a low level of risk’ (DWLBC 2006).

In this project this definition has been applied to determine the environmental water requirement of GDEs as:

“the water regime required to maintain self-sustaining populations resilient to drought”.

As far as the available evidence allows, water requirements are based on the water regimes that sustain intact ecosystems which retain more intact plant communities and fauna habitat values. It is recognised that water requirement may be less in ecosystems that have been degraded through vegetation clearance or other disturbances.

It is a policy decision, and a task for later investigations, to determine whether it is appropriate to provide water to ecosystems in order to maintain their current (and possibly degraded) condition or to enable their recovery to a more intact state.

SECTION 2 Geology and Hydrogeology of the Study Area

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2 Geology and Hydrogeology of the Study Area

2.1 Origins of the Mount Lofty Ranges and Adelaide Plains

The geology of the study area is comprised of outcropping basement geologies in the Mount Lofty Ranges (Adelaide Hills) and sedimentary basins along the plains and coast. The Mount Lofty Ranges forms the central portion of the Adelaide Geosyncline, which consists of a thick sequence of meta-sedimentary and minor igneous rocks of Cambrian to Pre Cambrian age. The Adelaide Plains are underlain by unconsolidated sediments of the St Vincent Basin which overlie the basement rocks that are exposed in the Ranges. The sediments increase in depth with distances from the Ranges. They are comprised of Quaternary age interbedded sands and clays (up to 100 m thick near Adelaide Airport) that are underlain by limestone and sands of Tertiary age, which are approximately 150 m thick southeast of the Para Fault and increase to almost 500 m in thickness to the northwest of the study area.

2.2 Aquifer Systems

Fractured Rock Aquifer

In the Mount Lofty Ranges, fractured rock aquifers occur in the basement rock geologies with some shallow alluvial aquifers occurring in valley floors. The groundwater flow systems associated with the fractured rock aquifers are local in scale and complex due to the variability in fracture networks. This complexity is compounded by geological faults, which are widespread throughout this region. Recharge occurs in upland areas and tends to be localised where fractures outcrop. Discharge occurs where impermeable layers are encountered or where fractures outcrop, and constitutes the baseflow of streams in the ranges. Discharge (as groundwater through flow) also occurs at depth to the adjoining sedimentary aquifers of the Plains, particularly in fault zones, such as along the Para, and Eden-Burnside fault lines. The fractured rock aquifer is believed to be the primary source of recharge to the Quaternary and Tertiary aquifers (Gerges, 2006). Groundwater salinity in the fractured rock aquifers is generally good (< 750 mg/L) with higher salinity noted in less permeable units (such as the Woolshed Flat Shale) and in the lower reaches of the catchment where rainfall recharge is less (Gerges, 2006).

Quaternary Aquifers

Quaternary aquifers typically form where there is thick Quaternary cover (e.g. over much of the Adelaide Plains), but may also occur as shallow alluvial aquifers in gullies and along the coastal margins in young, Holocene age sediments.

In the St Vincent Basin, the Quaternary sediments generally comprise silts, clays and floodplain sediments, and there are multiple aquifers in a varying sequence. The Quaternary Aquifers are commonly labelled Q1-Q6, with the Q1 aquifer being closest to the surface and Q6 being the deepest. These aquifers have varying extents and interconnections, being separated by aquitards of variable thickness and vertical hydraulic conductivities. Due to the clayey nature of the soils and lower rainfall on the plains, recharge to the shallow watertable is generally limited. However, the alluvial aquifers which surround the streams

SECTION 2 Geology and Hydrogeology of the Study Area

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receive recharge from surface water through permeable alluvial sediments (Gerges, 2006). Groundwater salinity is variable. In the Q1 aquifer, it can be relatively fresh (<1500 mg/L) surrounding streams to the southeast of the Para Fault and tends to increase to the northwest (Gerges, 2006). Some perched aquifers can occur in the coastal zone, particularly along the Le Fevre Peninsula, where higher recharge can occur through dune sands, which are underlain by the low permeability Hindmarsh Clay unit.

Tertiary Aquifers

In the St Vincent Basin, tertiary sediments host several aquifer systems designated T1, T2, T3 and T4 in order of increasing depth. They are mostly confined. The Tertiary aquifers are typically more transmissive and often contain better quality groundwater than the overlying Quaternary aquifers. The bulk of groundwater extraction occurs from these aquifers. The main source of recharge is thought to be lateral through-flow from the fractured rock aquifer (Gerges, 2006). In regions where the Tertiary aquifer outcrops recharge occurs via direct rainfall infiltration. The Tertiary aquifer discharges along the coastline into the Gulf St Vincent or via upward leakage to the Quaternary aquifers (Gerges, 2006).

Tertiary aquifers occur below the Quaternary aquifer systems and are typically confined, but in parts of the study area (such as the upper parts of the Golden Grove and Noarlunga Embayments) Tertiary sediments will contain the watertable aquifer where they outcrop.

SECTION 3 Nature and Extent of GDEs

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3 Nature and Extent of GDEs

3.1 Introduction

Although springs, soaks and permanently flowing stream reaches are known to be widespread in the study area, little work has been done to collate information describing these sites. A range of sources was consulted to collate as complete a database as possible (within the resources of this project) of the extent of GDEs in the study area, the hydrological characteristics of the sites, their ecological composition and condition.

Based on existing information sources and consultation with ecologists with field expertise in the study area, a GIS database was created of known groundwater discharge sites. The database is preliminary and generally only identifies the location and nature of the sites and the source of information. The focus of data collection was freshwater discharge sites that are likely to be related to productive aquifers and are potentially threatened by groundwater use. Less emphasis was given to saline groundwater discharge environments along the coast where groundwater is unlikely to be used and is therefore of less importance to the Water Allocation Planning process.

The database could be expanded by further research to:

• identify additional GDEs;

• provide more detailed information on the condition, structure and hydrology of the sites; and

• expanding the database to address saline sites related more comprehensively.

3.2 Sources of Information

Information was primarily sourced from field ecologists with expertise in the study area through interviews or written correspondence.

Information was also sourced from historic maps. A collection of hand-drawn cadastral maps dating from before 1840 to the 1970s have been digitised and orthorectified by DENR. These maps were reviewed to find marked springs (Figure 1). The Centenary Map of the Belair National Park identifies springs in the upper Minno Creek catchment and was an important information source.


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Figure 1. Identification of springs from historic cadastral maps


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Other information sources include:

• fish records held by Michael Hammer;

• Survey and museum records from the SA Freshwater Fish Action Plan 2009;

• WaterRAT layers for large and small permanent pools and baseflow;

• existing reports; and

• review of aerial photography.

3.3 Results

The review identified 92 groundwater discharge sites in the study area (Table 1). Approximately 50% of these were new sites that were identified through interviews and were not recorded in other existing information sources. Most of the sites were springs, which represent localised, permanently boggy areas and may be located on hillsides or near watercourses. Few stream reaches were reported to have flow sustained by groundwater discharge. Most notable were the streams of Brownhill Creek catchment, First Creek, Second Creek and the Ironbank tributary of Sturt River. Two wells were identified from early cadastral maps and were included as indicating the presence of shallow groundwater.

Table 1. GDE composition

Site Type Number of Sites

Spring 63

Stream Reach 25

Well 2

Coastal Perched Aquifer 2

The highest concentration of identified sites is in the Mount Lofty Ranges between Ansteys Hill and Coromandel Valley, a region which also supports the highest rainfall and the most extensive area of remnant vegetation in the study area. The concentration of sites in this region may reflect the interests of ecologists and natural resource managers, as it supports ecologically intact sites that are accessible by the public. Staff from the City of Playford identified three sites in the north of the study area on private land.


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Figure 2. Identified GDEs in the study area


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Few GDE sites were reported on the plains. The deeply incised landscape of the ranges and outcropping fractured rock contributes to the prevalence of GDEs. In contrast the plains has a low-relief landscape with few areas where the ground surface intercepts the water table.

3.4 Existing GDE Typology

GDEs in the study area have previously been classified by SKM (2010) on the basis of the landform, hydrology, hydrogeology and ecology. The nine types were reviewed in this project to evaluate their usefulness in determining EWRs.

These GDE types are reviewed below with respect to the determination of EWRs in this study.

Fractured Rock Aquifer Spring Discharge and Fractured Rock Aquifer Watercourses

The discharge of groundwater from the fractured rock aquifer supports the majority of GDEs in the study area. Discharge occurs where fractures outcrop or changes in permeability (often associated with changes in lithology) promote the discharge of groundwater. Discharge may occur at isolated locations (as springs) on hillsides or near watercourses. Discharge may also occur over extended reaches of watercourses that intersect the aquifer; this is most likely to occur where watercourses are set deep into the landscape, so that the watercourse is lower than the water table in the surrounding hillsides.

Break of Slope GDEs

At the base of hill slopes, particularly where high relief fractured rock basement grades to sedimentary foothills and plains, the water table can frequently intersect the surface topography, creating groundwater discharge sites. Examples of break of slope GDEs are the base of Chapel Hill and Blewitt Springs in the McLaren Vale PWA. Break of slope GDEs have not been identified in the Adelaide Plains.

Groundwater Discharge on Plains

Little evidence has been found of extant sites of GDEs on the Adelaide Plains. Historically, soaks have been recorded along the River Torrens and were most likely maintained by bank recharge from the river (Shanahan et al. 2010). Baseflow and permanent pools have also been identified on watercourses on the Adelaide Plains in aerial videography by the Department for Water, Land and Biodiversity Conservation in 2003. However, reported groundwater levels are generally too low to suggest that watercourses are groundwater dependent and it is most likely that permanent pools are sustained by local intermittent rainfall events and bank recharge.

Bank recharge would occur along all watercourses crossing the Adelaide plains and would have maintained riparian vegetation, including Eucalyptus camaldulensis and soaks. Bank recharge is created


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by stream flow and does not appear to maintain persistent or widespread aquifers that could be considered GDEs.

Groundwater data indicate the potential for discharge from the Quaternary Aquifer to the Gawler River between Gawler and Virginia. In this reach the water table is within 10 m of the surface and potentially contributes to stream flow and the water requirements of deep-rooted vegetation such as Eucalyptus camaldulensis.

Coastal Perched Aquifer

Prior to drainage improvements across the Adelaide Plains, watercourses did not flow out to sea in every year. In most years, flow across the plains was depleted through evaporation and recharge and terminated in a series of wetlands that extended from Glenelg to the Port River. Known as the Reed Beds, the wetlands comprised areas of permanent water of varying salinities and depth. Species reported from the Reed Beds include Eucalyptus camaldulensis, Melaleuca halmaturorum and Phragmites australis (Kraehenbuehl 1996). Aldinga Scrub is a well-preserved wetland where a perched aquifer forms in the permeable Semaphore Sands over the low-permeability Hindmarsh Clay (Ecological Associates 2002).

A similar system occurs at the mouth of the Gawler River where alluvial sediments have been deposited to form a delta. The functioning river mouth was blocked in the 1920s to detain water and create a farm water supply. Now known as Buckland Park Lake, flood water from the Gawler River creates a lens of fresh water over saline groundwater.

Here, regular surface water inflows created a shallow perched freshwater system over a shallow saline water table that is strongly influenced by the marine environment. While the Reed Beds have been lost to development, Buckland Park Lake remains (Smith 2010).

Estuarine GDEs

Watercourses with well-defined discharge points to the coast include Field River, Christies Creek, Onkaparinga River and Pedler Creek. Each of these sites features estuarine sediments that are recharged by stream flow, forming a localised aquifer. In the Field River, Christies Creek and Pedler Creek sands are saturated with brackish water that maintains stands of Phragmites australis and Bolboschoenus caldwellii.

Coastal Wetlands

The landscape in the vicinity of Barker Inlet is characterised by a low-lying topography and a shallow saline watertable. Groundwater in the Quaternary Aquifer flows towards this region and discharge creates saline mudflats that merge into the Avicennia marina woodlands of the Port River, Barker Inlet, St Kilda and Port Gawler areas.


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Prior to European settlement, sand plains ran along the eastern bank of the Port River, creating a supratidal samphire saltmarsh. The building of tidal levees in the mid 1900s to prevent seawater incursion changed the hydrological regime of the area.

The area consists largely of low-lying marshland underlain by poorly consolidated marine sediments. Natural elevation ranges from -1.0 m in creek channels to 1.5 m AHD on undulating mounds between tidal creeks. Most of this area comprises prograded Holocene St Kilda Formation sediments which are overlain in places by modern intertidal and swamp deposits. It consists of unconsolidated coastal marine muds, spongy peat or shelly or clayey sands.

Shallow regional aquifers containing saline / hypersaline groundwater underlie the area (Thomas et al. 2001). Recently deposited coastal sediments usually have saline groundwater because seawater covered the area during the deposition phase. There may be hydraulic connections to saline water bodies such as the Port River Estuary. The water table is influenced by the tide and is generally less than 1 m below the surface. The average groundwater hydraulic gradient is of the order of 0.095% and produces very low seepage rates of 0.3 to 0.6 m/year. Consequently evaporation from the water table is an important component of the groundwater discharge. The surface aquifer is underlain by the Hindmarsh Clay, an aquitard that provides a uniform impermeable barrier throughout the area.

Marine GDEs

The discharge of groundwater off the coast potentially creates a salinity or nutrient regime which is important to marine flora and fauna. There is little data to evaluate the influence of groundwater on the marine environment, or its importance.

3.5 New GDE Types

This study identified one GDE type in the Adelaide region that was not recognised in the previous review by SKM (2010).

Terrestrial Vegetation at the Base of the Hills

Watercourses draining the Mount Lofty Ranges cross a steep scarp where the Eden-Burnside Fault marks the commencement of the Adelaide Plain. Alluvial fans have formed at the foot of the ranges where material eroded from the catchments in the ranges are deposited as streams lose power on the lower gradient Adelaide Plain. Alluvial fans are evident at the base of the ranges where Brownhill Creek, First Creek, Second Creek and other tributaries enter the plains. These Quaternary sediments support the Q1 aquifer which is recharged by stream flow from the catchments to the east as well as groundwater through-flow from the fractured rock aquifer across the Eden Burnside Fault. The aquatic habitat and vegetation in these areas have been extensively modified through the development of the eastern suburbs, but support significant stands of Eucalyptus camaldulensis. Historically, a stand of Leptospermum


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lanigerum, which depends on permanent waterlogging was known from Brownhill Creek in Mitcham, and this probably represents reliance on shallow groundwater within this system.

3.6 GDE Typology for this Study

The water requirements of GDEs must be considered in the Water Allocation Plan where they are potentially impacted by use of the groundwater resource. The table below evaluates the importance of GDE types for the determination of environmental water requirements (Table 2).

Table 2. Revision of GDE types proposed by SKM (2010)

Proposed GDE Types for the Adelaide Plains and McLaren Vale PWAs (SKM 2010)

Occurrence within the Adelaide Plains PWA

Revised GDE Type Requirement to Determine EWRs

Fractured Rock Spring Discharge

Numerous examples found in the Mount Lofty Ranges

Fractured Rock Springs Required

Fractured Rock Baseflow Numerous examples found in the Mount Lofty Ranges

Fractured Rock Baseflow

Required

Break of Slope GDEs No examples found within the Adelaide Plains PWA

Groundwater discharge on Plains

No extant examples found within the Adelaide Plains PWA

Coastal Wetlands This type is represented by the Barker Inlet, St Kilda and Port Gawler region

Coastal Wetlands Not required. Aquifer is saline and not subject to use.

Coastal Perched Aquifer Most sites have been drained, but Buckland Park is an example

Coastal Perched Aquifer Not required. Aquifer is poorly defined, localised ephemeral and not subject to use.

Estuarine GDEs Examples located at Field River, Christies Creek, Onkaparinga River and Pedler Creek

Estuarine GDEs Not required. Aquifer is poorly defined, ephemeral, localised and not subject to use.

Marine GDEs It is hypothesised that groundwater discharge off the coast may contribute to ecological water requirements of marine ecosystems.

Marine GDEs Not required. Hydrogeology and ecology is poorly known and EWR cannot be evaluated using existing information.

Terrestrial Vegetation at the Base of the Hills

This group previously referred to overbank recharge on the plains in general, which does not appear to support GDEs Shallow groundwater systems in the quaternary aquifer west of the Eden-Burnside Fault contribute to the water requirements of River Red Gum.

Terrestrial vegetation at the base of the hills

Required

SECTION 4 Water Requirements of Dependent Flora and Fauna

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4 Water Requirements of Dependent Flora and Fauna

4.1 Fish

The fresh reaches of watercourses in the study area potentially support 10 native fish species (Hammer 2005a). Of these, common galaxias, climbing galaxias and mountain galaxias remain in largely natural aquatic habitats and can be used to interpret the water requirements of groundwater dependent streams (Table 3).

Migratory freshwater species

Climbing galaxias has a very restricted distribution in the study area. Extant populations are known only from Brownhill Creek (Hammer 2005a) and the Onkaparinga River at Clarendon (Schmarr and McNeil 2010). However, recent sampling has failed to find climbing galaxias in Brownhill Creek (pers. comm. David Schmarr, SARDI). It is located in deeper pools where there is a permanent flow of cold water and a high degree of habitat heterogeneity that includes rocks, snags and dense emergent macrophyte growth. Climbing galaxias is also known from the Upper Torrens catchment, also in spring fed pools with similar habitat complexity.

Climbing galaxias is generally known to be diadromous with a marine larval phase that involves migration back to freshwater habitats. It is known to substitute the marine environment for lentic (standing) waterbodies like lakes and reservoirs, suggesting larvae and juveniles depend on some form of a pelagic phase. If the climbing galaxias in Brownhill Creek are diadromous, juveniles need to negotiate the long stretch of urbanised drains to either reach the sea or the lentic environment of the Patawalonga. This would require connecting flows to be sustained over the migratory periods.

Climbing galaxias tends only to be found where rainbow trout is absent and the two species are likely to compete for space and food. Hydraulic features within streams that isolate the species are therefore important for the survival of climbing galaxias. Permanently flowing riffles can provide habitat too shallow for rainbow trout but suitable for climbing galaxias. Permanent pools that are isolated by sills also provide opportunities for climbing galaxias to survive in the absence of rainbow trout.

Within the study area, common galaxias is known from the from large, flowing pools in the lowland reaches of Sturt Creek. They are associated with shallow riffles flowing either over rock or through stands of Typha. Elsewhere, this species is more commonly associated with open waters and its restriction to shallow and sheltered habitat probably reflects a retreat to areas from which the larger predators trout and redfin are excluded. Flows that provide these habitats are required throughout the year.

Similar to climbing galaxias, common galaxias appears to be diadromous in the Sturt River and would migrate to the Patawalonga or St Vincent Gulf. Connecting flows would be required along the urbanised reaches of the Sturt River to sustain common galaxias.

Both species are tolerant of high salinities in certain circumstances. Common galaxias has been found in estuaries and watercourses with salinities up to 80,000 EC (Morgan et al. 2006) and an acute LD50 of 45 g/L has been reported for the species (Chessman and Williams 1975). The larvae of climbing galaxias


4-2

tolerate marine salinities. However, their range includes freshwater habitats such as the upland regions of the Great Dividing Range where low salinities are encountered (Allen et al. 2002). Salinities in the watercourses of the study area are generally less than 1,000 EC (Hammer 2005b).

Obligate, freshwater, stream specialist

Mountain galaxias is widespread in the watercourses of the Mount Lofty Ranges and is common in Brownhill Creek. In the study area populations are fragmented and restricted to smaller streams and tributaries such as lower Fifth Creek and the main channel of Sixth Creek. It is also known from First, Second and Fourth Creeks and the Sturt River. It is present in a small groundwater-fed reach of upper Minno Creek above the Railway Dam.

Mountain galaxias is found in a variety of habitats including small still pools, large deep pools and fast flowing riffles. Sites where mountain galaxias are most common have cool, permanent flowing habitat in chains of connected pools. Shade and flowing water are likely to be important in maintaining cool water that the fish require over summer.

Mountain galaxias tend to be absent from sites where their predators brown trout, rainbow trout and redfin are present. Their use of available habitat is often limited by these species, and mountain galaxias are restricted to riffles connecting larger pools or reaches above small barriers that exclude the larger fish. The population in Coats Gully illustrates this situation, where a sill near the junction with the Sturt River appears to exclude the predators from the tributary.

This species is particularly dependent on baseflows that maintain habitat extent and flows of sufficient discharge to provide low water temperatures and maintain dissolved oxygen concentrations in pools and riffles. Since the introduction of exotic predatory fish, flows that activate sills and riffles have become more important in protecting local populations. Mountain galaxias is a mobile species within river systems, but its ability to disperse and colonise new habitat is threatened by low baseflows; small and isolated populations are at risk of elimination.

A problematic interaction with sills can be that large numbers of mountain galaxias accumulate downstream of the barrier where they are vulnerable to predation.

Mountain galaxias is a freshwater fish whose range extends to alpine regions of the Great Dividing Range. It tolerates low salinities that are associated with ‘freshwater’ environments in the Mount Lofty Ranges, up to 1,000 EC (Hammer 2005b).


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Table 3. Groundwater requirements of fish

Flow Season Flow Component Ecological Functions Relevant Species Groundwater Requirements

Low Flow Season Low Flow Maintain pool depth and flow across riffles as habitat as refuge habitat

climbing galaxias

common galaxias

mountain galaxias

Groundwater discharge to maintain baseflow

Discharge sufficient to maintain low water temperatures and oxygenated conditions

climbing galaxias

common galaxias

mountain galaxias


High Flow Scour pools to export organic matter and prevent de-oxygenation

climbing galaxias

common galaxias

mountain galaxias

Groundwater discharge to maintain pool volumes and wetted channel to increase channel response to catchment runoff

Reconnect pools to support dispersal to new habitats

climbing galaxias

common galaxias

mountain galaxias


High Flow Season Low Flow Maintain pool depth and flow across riffles as habitat as refuge habitat

climbing galaxias

common galaxias

mountain galaxias


High Flow Provide connecting flow to the sea to permit downstream migration of larvae and upstream migration of juveniles

climbing galaxias

common galaxias



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4.2 Aquatic Macroinvertebrates

Fauna

The aquatic invertebrate fauna of a groundwater-fed stream in the study area was characterised by Towns (1985). Towns found that despite the permanence of aquatic habitat, the macroinvertebrate fauna exhibited strongly seasonal patterns in composition and life history. This most likely reflects the changes in water quality which occur over the year. Permanent pools are subject to the accumulation of organic matter over low flow periods, which provides for a high biological oxygen demand. In summer high water temperatures reduce oxygen solubility and support higher rates of microbial decay which further reduce dissolved oxygen concentrations. These conditions are only alleviated by flushing flows which refresh the water and may also remove accumulated organic matter. Periods of low pH and high conductivity occur when the season breaks with the first catchment runoff in late autumn or early winter. Salinities in farm dams in the Mount Lofty Ranges are generally higher in autumn than in spring and typically in the range of 1,000 to 2,000 EC, which is indicative of water quality that would occur in stream pools (Lundstrom 2008).

So while permanent pools provide aquatic habitat throughout the year, the aquatic fauna shows strongly seasonal life cycles although the composition of the fauna remains relatively constant throughout the year. In contrast, intermittently flowing reaches exhibit a strongly seasonal successional cycle that most likely reflects the colonisation of newly flowing habitats in winter and spring and the gradual development and maturation of individuals. The permanent pools provide a source of colonists to intermittent stream reaches, such as the leptophlebiid mayfly Atalophlebia inconspicua which was abundant in areas of permanent flow.

The environments of standing water and flowing water described by Towns (1985) are reflected by the two macroinvertebrate functional groups defined by (VanLaarhoven and van der Wielen 2009): those that require flowing water (found in riffles, runs and cascades) and those with a distinct preference for still or very slow flowing water (found in pond or pool habitats, and slow flowing lowland streams) (Table 4).

Within these two broad groups, six different community types can be identified, depending on the type of habitats and the persistence of the flow regime. The same species can be found in a number of different community types and it is difficult to identify specific indicator taxa that are restricted to just one community. Often the difference between types is in degrees of species diversity and relative abundance of different species from each group, with fewer or more still water or flowing water taxa found in particular habitat types.

Groundwater discharge makes a strong contribution to two of the six broad community types of macroinvertebrates:

• flowing water, riffle in reaches with permanent or seasonal flow; and

• still water, persistent ponds and pools in reaches with permanent or seasonal flow (Table 4).


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The cobble/boulder habitats of riffles or the gravel habitats that characterise runs provide a wide diversity of microhabitats, so that these areas are generally the most diverse communities in stream systems. Cascade species are still present in riffles, living on the upper surfaces of rocks but other taxa present can use other microhabitats. With significant subsurface refuge habitats, most species can survive short periods of no flow (although diversity is highest in permanently flowing streams).

The diversity of macroinvertebrates is highest among the still-water communities in ponds or pools where water is present throughout the year. The diversity and abundance of plants in permanent ponds and pools ensure a wide range of microhabitats.

A third component, not specified by VanLaarhoven and van der Wielen (2009) is the hyporheos – the flooded interstices of the stream bed that support a specialist hyporheic fauna and provide a refuge for surface-dwelling invertebrates during periods of low flow (Boulton and Brock 1999).

Table 4. Macroinvertebrate community types relevant to GDEs in the study area

Macroinvertebrate Community Types

Significance of Groundwater Discharge

Flowing water

Flowing water, cascade Not Significant

Flow in cascade habitats is dominated by rainfall runoff.

Flowing water, riffle Significant

Groundwater discharge can generate perennial flow and contribute to the duration and persistence of flow generated by rainfall-runoff.

Still water

Still water, persistent ponds and pools

Significant

Groundwater discharge can maintain permanent pools.

Still water, lowland streams

Not Significant

Lowland streams in the study area are generally losing streams and aquifers do not contribute significantly to flow. Groundwater levels indicate that the water table is generally well bellow the stream surface. Permanent pools reported from this area are likely to reflect intermittent inflows from local rainfall runoff.

Still water, temporary pools

Not Significant

The hydrology of temporary pools is dominated by runoff.

Still water, floodplain wetlands

Not Significant

There is little floodplain development in the upland reaches of watercourses in the study area where groundwater influences hydrology.

These habitats are disconnected by groundwater by definition.


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Water Requirements

Groundwater discharge to surface waters supports two important ecological functions. It contributes to the persistence of aquatic habitat and provides the connecting flows that allow fauna to disperse and colonise new areas.

The groundwater conditions that contribute to these processes can, in general, be defined by the presence of the water table at or near the surface or the discharge of groundwater to the surface (Table 5).

Table 5. Groundwater conditions to support macroinvertebrate ecological functions

Habitat Component Ecological Functions Groundwater Requirements

Permanent Pools Maintain persistent aquatic habitat conditions

Water table at or near the surface throughout the year

Perennial Riffles Allow movement to recolonise vacant habitats


Persistent Pools Maintain persistent aquatic habitat conditions

Groundwater discharge to the watercourse upstream of the site throughout the year

Persistent Riffles Allow movement to recolonise vacant habitats

Groundwater discharge to the watercourse upstream of the site throughout the year

Shallow Groundwater Maintain hyporheos

Provide refuge for predominantly surface-dwelling macroinvertebrates


4.3 Plants

VanLaarhoven and van der Wielen (2009) used the concept of functional groups to classify the water requirements of streams. Functional groups represent species with similar requirements and tolerances of water levels and flow. A similar approach has been taken in this study, but more new, more narrowly defined groups were used to represent the precise hydrological environments that are influenced by groundwater. Hydrological objectives were developed by the expert panel.

Group 1 Perennially Saturated, Intolerant of Flow

Conditions of perennial saturation, but without any significant flow, occur in groundwater seeps in the Mount Lofty Ranges. These conditions are found in Heptinstalls Spring, Eagle Hill Quarry and Harford Spring, all of which are associated with the Stonyfell Quartzite – Basket Range Sandstone contact. The sites are located near the crest of a ridge where there is no significant surface water catchment or drainage lines contributing to wetland hydrology. The saturated soil conditions are sustained entirely by groundwater discharge, supplemented by local rainfall. The absence of drainage features means that flooding is limited to a depth of less than 0.2 m.


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These seeps are vegetated by plants adapted to permanently saturated conditions while being intolerant of flow (Table 6, Table 7).

The salinity of the wetlands was not sampled, but wetlands supporting similar vegetation were sampled in the Fleurieu Peninsula Wetland Inventory where almost half the 138 wetlands reported salinities of less than 200 EC and almost 90% of wetlands had salinities of less than 500 EC (Harding 2005).

Table 6. Group 1 plant species

Group 1.

Permanent waterlogging No or shallow (<0.2 m) flooding Intolerant of strong flow Headwater wetlands & High-order creeks

Baumea tetragona

Baumea gunnii

Gleichenia microphylla (also occurs on seasonal seeps)

Viminaria juncea?

Todea barbara

Gahnia sieberiana

Blechnum minus

Table 7. Group 1 groundwater requirements

Season Ecological Function Hydrological Objective Groundwater Requirements

Winter Plant growth and survival Continuous shallow flooding, 0 to 0.2 m

Water table above the ground surface

Spring Asexual reproduction and growth

Continuous shallow flooding, 0 to 0.2 m


Summer Germination and growth Waterlogged Water table at or above the ground surface

Autumn Plant growth and survival Waterlogged Water table at or above the ground surface

Group 2 Perennially Waterlogged, Tolerates Flow

Watercourses that receive groundwater discharge are perennially waterlogged and are also subject to flow. The plant species in this habitat have adaptations to tolerate flow such as narrow, flexible stems which readily collapse during floods and stabilising root systems. The vegetation is intolerant of drought and consequently has a limited distribution in watercourses where groundwater discharges (Table 8, Table 9).

This group includes species that occur in a wide range of salinities ranging from the fresh wetland habitats of the Fleurieu Peninsula (Harding 2005) to moderately saline areas (Maslin et al. 1998).

In the study area these species are found on Brownhill Creek and on the Coats Road tributary.


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Group 2.

Permanent waterlogging

Tolerant of stream flow

Seasonal flooding related to stream flow, but no sustained standing water

Acacia provincialis

Carex appressa

Cladium procerum

Carex fascicularis

Hypolepis rugulosa Senecio minimus


Season Ecological Functions Hydrological Objective Groundwater Requirements

Winter Plant growth and survival. Waterlogged stream bed.

Ready transmission of flow from rainfall events.


Spring Asexual reproduction.

Growth, flowering and fruit maturation.

Waterlogged stream bed.



Summer Seed set, germination and growth.

Adult plant growth and survival.

Damp stream bed.


Water table at or above the ground surface

Autumn Adult plant growth and survival.

Juvenile plant maturation.

Damp stream bed.



Group 3 Perennially Saturated, Seasonally Flooded

Along watercourses which receive groundwater discharge, pools and swamps can form. A shallow water table creates perennially saturated soils, and flow or a seasonally elevated water table provides seasonal flooding. Flooding can persist for several months and these habitats support species adapted to inundation of up to 0.5 m for some or most of the year. In undisturbed areas Gahnia sieberiana and Leptospermum lanigerum and L. continentale are common species. Habitats that have been cleared of native vegetation may be recolonised by Phragmites australis and Typha spp. This habitat is found in the watercourses of the Brownhill Creek catchment, First Creek catchment, Second Creek catchment and many other locations.

The species in this group occur in a wide range of conditions from freshwater (Harding 2005) to saline marshes (Taylor 2006) (Table 10, Table 11).


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Group 3.

Permanent waterlogging

Shallow (<0.5 m) flooding

Weak/Low flow (or seeping water)

A) Disturbed Areas Phragmites australis

Typha spp. B) Undisturbed Areas Gahnia sieberiana

Leptospermum lanigerum

Leptospermum continentale

Baumea tetragona



Winter Plant growth and survival. Continuous flooding up to 0.5 m




Continuous flooding up to 0.5 m




Continuous flooding up to 0.5 m or receding to 0 m.




Continuous flooding up to 0.5 m or receding to 0 m.


Group 4 Alternately Waterlogged and Drained Sites

Groundwater discharge supplements the stream flow created by rainfall runoff, creating more persistent flow. With distance, the influence of groundwater declines as the relatively small contribution of groundwater is lost to evaporation and seepage and rainfall runoff becomes the dominant component. Within this zone, seasonally waterlogged conditions occur. Soils around watercourses are waterlogged while streamflow persists in winter and spring, but dry out in summer and autumn as evaporation rates increase and rainfall becomes more intermittent.

A wide range of plants are adapted to seasonally waterlogged conditions (Table 12, Table 13). Eucalyptus camaldulensis and Acacia melanoxylon are tree species that tolerate seasonal waterlogging but occur in well-drained environments as well. Understorey species with similar tolerances include Carex tereticaulis and Chorizandra enodis.


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This group includes species which occur in environments subject to some salinisation. Chorizandra enodis, Cyperus gymnocaulos and Lepidosperma laterale occur in coastal wetlands. However these species also occur in well-drained environments with low salinities.


Group 4.

Alternately waterlogged and drained soils

Prolonged flooding rare or absent

Acacia melanoxylon

Pteridium esculentum

Eucalyptus camaldulensis

Carex tereticaulis

Chorizandra enodis

Cyperus gymnocaulos

Lepidosperma laterale s.str.



Winter Plant growth and survival. Continuous flow Groundwater discharge to watercourse upstream



Continuous flow Groundwater discharge to watercourse upstream



Persistent baseflow Shallow water table upstream readily transmits flow in summer rainfall runoff events



Persistent baseflow Shallow water table upstream readily transmits flow in autumn rainfall runoff events

Group 5 Shallow water table below drained soils

A shallow water table can contribute to the water requirements of deep-rooted vegetation while the overlying soil remains well-drained and supports plants intolerant of waterlogging. Aldinga Scrub is formed on the sandy soils of the Semaphore Formation and supports a shallow perched aquifer that contributes to the water requirements of Eucalyptus fasciculosa and E. camaldulensis (Table 14). Along the Eden-Burnside Fault a shallow aquifer is interpreted to occur that also supports scattered large E. camaldulensis. The aquifer is recharged by flow across the fault and from stream draining the ranges.

Eucalyptus camaldulensis is moderately tolerant of high salinities with growth affected by salinities as low as 2,000 ECe (Benyon et al. 1999). However, trees tolerate much higher temporary salinities, albeit with severe impacts on canopy cover and growth (Thorburn and Walker 1994).


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Eucalyptus camaldulensis is the most widespread eucalypt in Australia and occurs in a wide range of environments (Table 15). Groundwater dependence has been demonstrated at various sites on the River Murray (Thorburn and Walker 1994), however this species also occurs along watercourses in areas with deep water tables, more than 20 m below the surface, where groundwater dependence is unlikely (Ecological Associates 2008). These strongly contrasting conditions make it difficult to predict soil and water conditions on the presence of this species, or to estimate tolerance to environmental change.

Eucalyptus camaldulensis are moderately tolerant of salinity. Benyon et al. (1999) reports that growth rates of Eucalyptus camaldulensis are impacted at soil salinities of 2 dS/m, while Mensforth et al. (1994) note trees on the Chowilla floodplain accessing groundwater with salinities as high as 40 dS/m, albeit under some stress. Gerges (2006) reports groundwater salinities of less than 1,500 mg/L occurring in these parts of the Q1 aquifer (near First to Fifth Creeks downstream of the Eden-Burnside Fault). As Eucalyptus camaldulensis has adapted to these native groundwater salinities, the EWR should be defined as the maintenance of the historical groundwater salinities.


Group 5.

Shallow watertable

Eucalyptus camaldulensis

Eucalyptus fasciculosa



Winter Tree growth.

Germination and juvenile growth

Very high soil moisture in the root zone.

Shallow water table

Spring Tree growth.

Flowering and fruit maturation.

Very high soil moisture in the root zone.

Shallow water table

Summer Flowering, fruit maturation and seed set.


Well drained surface zone above deeper zone of high soil moisture.

Shallow water table


Germination and juvenile growth.

Well drained surface zone above deeper zone of high soil moisture.

Shallow water table

SECTION 5 Fractured Rock Aquifer Springs

5-1

5 Fractured Rock Aquifer Springs

5.1 Occurrence

Fractured rock aquifer springs are defined as localised areas of groundwater discharge from the fractured rock aquifer on hillslopes or at the head of first order watercourses. They receive little inflow from catchment runoff and are not subject to the erosion and deposition processes that influence the structure of watercourses.

Figure 3 illustrates the potential distribution springs based on the extent of the outcropping fractured rock aquifer. Known springs are laregly confined to the outcropping basement, with a high density reported from in the vicinity of the Stoneyfell Quartzite.

Figure 3. The extent of the outcropping basement (in general) and Stoneyfell Quartzite (in particular) as a guide to the potential distribution of springs in the study area


5-2

Fractured rock aquifer groundwater discharge to the surface occurs where fractures or other weaknesses or cavities outcrop at the surface or where an aquitard underlying or low permeability unit impedes groundwater flow, causing it to discharge to the surface. The networks of fractures that support springs are complex, making it difficult to interpret the recharge area for a known spring or to anticipate where springs will occur based on hydrogeological data. Springs occur throughout the Mount Lofty Ranges where the bedrock outcrops.

A number of important springs are associated with the outcropping Stonyfell Quartzite between Cleland Conservation Park and Eagle Hill. The quartzite, which caps the range, is underlain by the relatively impermeable Basket Range Sandstone and Woolshed Flat Shale. The Stonyfell Quartzite, near Mount Lofty, hosts a perched aquifer above the Woolshed Flat Shale (Stewart and Green, 2010). Springs in this region tend to occur at the contact between the Stonyfell Quartzite and underlying strata, suggesting the change in permeability is causing groundwater to discharge at the surface. Significant springs include Heptinstalls, Wilsons Bog, Chinamans Bog Harford and Eagle Hill Quarry, each of which support species threatened at a state and national level.

Elsewhere, the main process to create springs is most likely to be outcropping fractures. Fractures which outcrop low in the landscape in relation to the water table will tend to be more persistent, while springs positioned at or near the water table will flow seasonally where the water table is high (late winter / spring). Fractures also drain the unsaturated zone, and can discharge over several weeks after a period of rainfall without being connected to an aquifer. In all cases, the greater duration and reliability of saturated soil conditions will influence the plant communities present and their habitat values. Intermittent springs tend to support species which are relatively widespread and may also occur in watercourses and sheltered slopes that are not influenced by groundwater. Perennial springs tend to support specialised species that are only associated with groundwater discharge.

Figure 4 presents a generic conceptual model of fractured rock aquifer discharge, where the presence of a low permeability unit (e.g. Woolshed Flat Shale) in the geological strata may lead to the formation of a perched aquifer in the overlying unit. Springs tend to occur where the junction of these strata outcrops, which is evident in Figure 5 where the springs occur at the edge of the Stonyfell Quartzite.


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Figure 4. Conceptual hydrogeological model of fractured rock spring discharge

Figure 5. Fractured rock spring discharge GDEs in Cleland Conservation Park


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Table 16. Fractured rock aquifer springs example sites

Example Sites Notes

Heptinstalls Spring Heptinstalls Spring is a permanent soak at the head of a first order tributary of First Creek near the crest of Mount Lofty Ranges. The wetland vegetation contrasts strongly with the surrounding Eucalyptus obliqua woodland and supports a range of species dependent on permanent waterlogging including Gleichenia microphylla, Leptospermum lanigerum, L. continentale and Baumea tetragona.

Eagle Hill Quarry Wetland at the head of a first order tributary of Brownhill Creek (Ellis Creek) that supports Leptospermum lanigerum, Blechnum minus and Gleichenia microphylla.

Harford Spring Wetland at the head of a first order tributary of First Creek near Reynolds Drive, Crafers

Horsnell Gully Deeply incised first-order watercourses in Horsnell Gully Conservation Park receive groundwater discharge that supports wetland vegetation including Blechnum nudum, . B. nudum and Todea barbara.

Joseph Fisher Picnic Area Localised damp area on the lower slopes of the Minno Creek gully that supports a stand of Phragmites australis within a Eucalyptus obliqua woodland.

5.2 Ecology

The water regimes created by fractured rock aquifer springs vary in relation to the amount of discharge of the spring, and proximity to the spring. Springs on hillsides at Coats Gully, Wilsons Bog and Heptinstalls Spring become progressively wetter at lower parts of the slope, and there is a corresponding change in plant communities and fauna habitat along this gradient.


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Figure 6. Site Photo Heptinstalls

The upper fringe of the spring is most likely to be near the water table and will therefore experience seasonal waterlogging as the water table rises and falls on a seasonal basis. This area tends to support terrestrial species that tolerate, or benefit from, waterlogging but which also occur outside the influence of groundwater. Overstorey vegetation includes Acacia melanoxylon, Eucalyptus obliqua or E. viminalis and the understorey will include species such as Baumea juncea, Poa umbricola, Lepidosperma semiteres, Lindsaea linearis and Pteridium esculentum. These conditions can occur at the fringes of wetlands and watercourses and this plant assemblage is not exclusively associated with groundwater discharge.

Lower slopes of hillside springs are perennially saturated and have deeper, sometimes peaty, soils. These conditions only occur in locations of groundwater discharge and therefore support a plant assemblage that occurs in small, isolated patches and supports many species of conservation significance. The fern Gleichenia microphylla tends to replace Pteridium esculentum and is associated with Goodenia ovata, Derwentia derwentiana and Juncus subsecundus. The tree fern Todea barbara can occur, particularly in areas sheltered from the sun. Trees do not persist into these areas and the shrubs Leptospermum continentale and L. lanigerum (in the wetter areas) become the dominant overstorey species.

Water may pool in the lower slopes creating conditions of perennial inundation and seasonal inundation that supports a third plant assemblage. Gahnia sieberiana or Leptospermum lanigerum may be present as


5-6

the dominant overstorey species, but a more open form may also be present, dominated by Gleichenia microphylla, Blechnum minus, B. wattsii and B. nudum. A range of other herbs and sedge-form species occur, such as Baumea tetragona and Baumea gunii.

In degraded areas, where native vegetation has been cleared, springs in the fractured rock aquifer will be recolonised by the native species Phragmites australis or Typha domingensis, or a range of exotic species including blackberry and periwinkle.

The aspect of the site also influences the water regime of the spring and the plant species it supports. Todea barbara is generally only known from perennially damp areas with deep soils that are usually found in the floor of gullies in the highest rainfall areas of the Mount Lofty Ranges. However, a small population is known near Montacute high on a hillside, but in a location that is sheltered from direct sunlight for most of the day by a southerly aspect.

There are few fauna that are exclusively associated with fractured rock aquifer springs, but a number of species are require the sort of dense, damp conditions that springs provide. Swamp rats and bandicoots both favour dense vegetation cover and soft soil for digging. A number of bird species benefit from the dense shrubby vegetation including scrub wren, heath wren and southern emu wren (Mount Lofty Ranges subspecies). Damp areas can support a high density of insects which attract swallows and martins. Dense vegetation can provide shelter for the cryptic Lewin’s Rail.

As isolated springs are not connected to watercourses and do not generally pond water, they do not provide significant habitat for native fish.

5.3 Functional Groups Present

Vegetation

• Group 1: Perennially saturated, intolerant of flow

• Group 2: Perennially saturated, seasonally flooded

Macroinvertebrates:

• Still water, persistent ponds and pools

Fish

Not present

5.4 Groundwater Dependence

Given that many of the springs have small surface catchment areas (Heptinstalls Spring is located within 400 m of the Mount Lofty summit) and consequently receive limited input from surface runoff, groundwater is likely to provide a substantial proportion of their water supplies. Groundwater may


5-7

support these ecosystems in several different ways, depending on the site. The functions of groundwater, listed in order of decreasing groundwater contribution, are:

maintenance of inundation (permanent or seasonal)

maintenance of waterlogged conditions (permanent or seasonal)

provision of shallow watertables that phreatophytic vegetation can access

If, at a particular site, the groundwater contribution is such that permanent inundation is maintained, then it follows that the remaining functions will also be provided. There is significant variability in springs throughout the study area and the nature of groundwater dependency will vary, but as a minimum groundwater will maintain waterlogged conditions and support phreatophytic vegetation in fringing areas.

The primary aspect of groundwater in supporting the ecology at the site is the depth of the watertable. This controls the extent and persistence of waterlogging and inundation. The springs are also dependent on the rate at which water is supplied to the site (i.e. groundwater flux) to sustain evapotranspiration and any throughflow. The rate of groundwater supply is controlled by the hydraulic gradient into the spring.

5.5 Proposed Environmental Water Requirement

The proposed EWR for fractured rock springs is:

“Groundwater levels shall be maintained above the pool level (where permanent inundation occurs), above the base of the bog (where permanently waterlogged conditions are located), or above the rooting depth of phreatophytic vegetation (where shallow watertables are required) to maintain permanent inundation where currently permanent, seasonal inundation where currently seasonal or ephemeral where currently ephemeral”.

The influence of groundwater on vegetation declines with increasing distance from the spring. The edges of these sites supports vegetation that depends on deeper groundwater than described above. It is assumed that by specifying groundwater discharge to the surface, the fringing vegetation will necessarily be protected. This assumption should be tested when groundwater impacts on ecosystems are being evaluated.

5.6 Threat Assessment

Consequences of groundwater change

A reduction in groundwater levels will affect fractured rock aquifer springs by reducing the rate of groundwater discharge and the surface area of the wetland that is affected by inundation, waterlogging or shallow groundwater (Figure 7). Wetland plant communities will contract to the remaining waterlogged parts of the site and terrestrial plants will colonise the wetland fringes.


5-8

The perennially saturated, non-flowing, freshwater conditions provided by fractured rock aquifer springs have a very limited occurrence in the Mount Lofty Ranges and therefore support specialised plant species that are not found elsewhere. Consequently, the wetlands support many species that are rare or endangered such as Drosera binata (rare Cwth Environment Protection and Biodiversity Conservation Act 1999), Thelymitra circumsepta (SA endangered) and Shizaea fistulosa (SA vulnerable).

Even minor changes to the groundwater environment of fractured rock aquifer springs can have significant consequences for species distribution and persistence, as illustrated in Figure 7.

Figure 7. Consequences of lower water tables for fractured rock aquifer spring


5-9

Threats

The sensitivity of groundwater conditions to pumping is likely to be high given the small hydrogeological capture zones and the limited storage associated with fractured rock aquifers. A small capture zone is indicative of a small water budget, and the limited storage means that water tables tend to be drawn down more acutely in such settings. Given the dependence of these ecosystems is linked to water table and the rate of groundwater discharge, the ecosystems are considered to be sensitive to pumping if initiated.

The current level of groundwater pumping in the vicinity of springs in the Mount Lofty area is limited (see Figure 5). A spring water bottling plant captures natural spring discharge and some domestic extraction occurs to the south of the Mount Lofty summit, along the ridge towards Crafers. However, there is no pumping in the immediate vicinity of these sites (i.e. within their hydrogeological capture zones).

SECTION 6 Groundwater Dependent Streams

6-1

6 Groundwater Dependent Streams

6.1 Distribution

Groundwater dependent streams systems occur where the hydrology or water quality of a watercourse is influenced by groundwater discharge. It includes the groundwater discharge point as well as the watercourse downstream where the influence of groundwater persists.

Figure 8 presents the distribution of groundwater dependent stream systems based on regional spatial information. Stream-aquifer connectivity was analysed by SKM (2011) based on topography, depth to the water table, water quality, isotope data and baseflow separation analysis, and classifies streams as gaining, variable gaining-losing and losing streams with high, medium and low levels of confidence. Aerial videography flown in autumn 2003 by the Department for Water, Land and Biodiversity Conservation identified dry season pools and baseflow reaches. Gaining streams are reported mostly from the incised landscape of the Mount Lofty Ranges with losing and variable gaining-losing streams dominant on the plain. Baseflow and dry season pools are identified on the plain, but generally with a lower level of confidence. An exception is the reach of the Gawler River between Gawler and Virginia where a high level of confidence is assigned to the groundwater interaction.

Overall, it can be concluded that groundwater interactions with watercourses occur predominantly in the Mount Lofty Ranges and that watercourses on the plains are typically losing streams.


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Figure 8. Classification of groundwater dependence, with confidence levels based on DWLBC aerial videography of watercourses and an analysis of stream-aquifer interactions (adapted from

SKM 2011)

Watercourses may receive groundwater from isolated locations, such as fractured rock aquifer springs which discharge to the slopes in or near watercourses. This frequently occurs in first or second order watercourses with steep gradients. Outcropping fractures or outcropping strata which direct groundwater


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to the surface provide a point source of groundwater which contributes to stream flow. Isolated areas of discharge occur in First Creek at Wilsons Bog, Chinamans Bog, Harford Spring and Waterfall Gully Reserve (among other locations) and contribute to persistent, but not perennial, flow in First Creek to the foot of the ranges. Similarly, in Minno Creek upstream of the Railway Dam in Belair National Park, a series of isolated springs contribute to flow.

Discharge may also occur along a reach of a watercourse, and this occurs where a stream channel intersects the water table. The evidence for this is strongest when streams are deeply incised into the surrounding landscape and is interpreted to occur between steep spurs in the two northerly-flowing streams in Horsnell Gully Conservation Park and in Coats Gully in Ironbank.

Where the water table is close to the surface, groundwater may contribute to the water requirement of riparian vegetation, even if groundwater does not always discharge to the surface. Groundwater is within 10 m of the surface for part of reach between Gawler and Virginia. Eucalyptus camaldulensis growing along the river may meet part of their water requirement from groundwater. The discharge of groundwater to the surface at this location may only be intermittent.

Figure 9 illustrates typical features of streams influenced by groundwater. The intersection of the stream bed and the water table can create groundwater-fed perennial pools and permanently flowing reaches. Impermeable strata frequently delimit the extent of groundwater discharge. Downstream of gaining reaches, groundwater may supplement surface flows and create more persistent flows even though the stream may be losing and the hydrology may be dominated by surface runoff.

Table 17. Example Sites of Groundwater Dependent Streams

Example Sites Notes

First Creek Catchment First Creek catchment receives groundwater discharge in the headwaters of the catchment from a number of springs including Wilsons Bog and Chinamans Bog. Groundwater fed baseflow contributes to perennial flow in the upper reaches of the catchment and contributes to sustained, but not perennial, flow in Waterfall Gully. Supports mountain galaxias.

Second Creek Catchment Slapes Gully is the narrow gorge Second Creek passes through just before discharging to the plain. Slapes Gully has perennial flow which extends to Michael Perry Reserve in Burnside. The baseflow maintains pools and riffles in the reserve which provide habitat for mountain galaxias.

Brownhill Creek Catchment Localised springs and reaches of perennial baseflow are recorded throughout the catchment including the lower reaches of Brownhill Creek. The catchment supports one of only two populations of climbing galaxias in the study area. The first and second order tributaries are steep with shallow alluvium but the main creek on the valley floor has rather deeper channel alluvium.

Coats Gully, Ironbank A tributary flowing 1.5 km from Coat Road to Sturt River near Pole Road features permanent flow. Creek flows through deeply incised bedrock with a narrow corridor of channel alluvium featuring permanent pools separated by riffles. Supports mountain galaxias.

Minno Creek, Belair National Park The upper reaches of Minno Creek are perennially waterlogged and provide trickle flow. Vegetation has been modified by clearance and replacement by exotic species but remnants. Supports mountain galaxias. Channel gradient is relatively low and channel alluvium is deeper than other examples.

Gawler River Shallow groundwater beneath the stream channel may contribute to the water requirements of riparian Eucalyptus camaldulensis


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Figure 9. Conceptual model of a groundwater dependent stream

Outside of the stream channel, the springs will share the same characteristics as fractured rock aquifer springs described above. Within the channel, the springs and the watercourse downstream are structured by the movement of water and associated sediment erosion and deposition.

6.2 Ecology

The flow in watercourses varies according to seasonal rainfall and the intensity of individual storm events. These structure plant communities and aquatic habitat by eroding channels, forming stream benches, sorting and reworking bed material and knocking-down and removing vegetation. Even though severe storms may be rare, they have lasting effects on stream ecosystems. They prevent the accumulation of peat and other erodible bed material and secondly they have the potential to remove and effectively eliminate slow-growing plants that are intolerant of hydraulic force.

Within the study area, watercourses in the Mount Lofty Ranges tend to be deeply incised with steep gradients. The alluvium in the stream channel tends to be shallow and underlain directly by bedrock. This alluvium stores water from catchment runoff and groundwater flow and is a storage that supports vegetation and maintain pools between flow events.


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Fractured rock aquifer baseflow streams tend to have an open channel, which is periodically disturbed by high flows. Fast-growing, colonising species such as Phragmites australis and Typha domingensis may establish in this zone between major disturbances. Stream flow will erode pools, creating structural diversity and providing a variety of depths and flow environments. Pools may support semi-emergent and aquatic species such as Triglochin procerum or Haloragis brownii and riffles may support low growing, flow-resistant species such as Isolepis fluitans.

Benches adjacent to the primary channel will support species which depend on permanent waterlogging but are well-anchored, with strong root systems that tolerate flow. Streams with persistent or perennial baseflow will support Acacia provincialis, Leptospermum lanigerum, Carex appressa, Gahnia sieberiana, Cladium procerum and Pteridium esculentum. Where an established population is present, Gleichenia microphylla and Hypolepis rugulosa readily recolonise damp areas after disturbance.

Streams with seasonally waterlogged benches will support species more tolerant of dry conditions such as Carex tereticaulis, Juncus pallidus and Cyperus appressa. Eucalyptus camaldulensis is more likely to be present as the dominant overstorey species.

The persistent flow created by groundwater discharge is important for maintaining the depth and extent of pools, which are required by native fish. Discharge must be sufficient to replace losses to seepage and evaporation to maintain pools through periods without rainfall runoff events. Of most significance in the study area are mountain galaxias, common galaxias and climbing galaxias. Under natural conditions deep permanent pools would have supported these species. With the introduction of brown trout and rainbow trout, mountain and climbing galaxias are restricted to pools that are too small for these larger predators (Hammer 2005b). They tend to occur in pools less than 0.3 m deep but with a surface area of more than 2 m2. Pools this small are vulnerable to drying out in summer and autumn, so sustained groundwater-fed baseflow is critical to the survival of these species.

Baseflows contribute to the magnitude and duration of riffle flows which connect pools. Riffle flows enable fish to disperse new pools, which reduces the vulnerability of local populations to disturbances at any one site. Dispersal is particularly important for climbing galaxias which is an anadromous species. Found only in Brownhill Creek in the study area, climbing galaxias migrates downstream to spawn, at least to the Patawalonga but possibly to Gulf St Vincent (Hammer 2005b). Since the introduction of brown trout and rainbow trout, riffles have become important habitat for native galaxias fish. Populations survive throughout the year if there is access to riffles. Shallow riffles are a barrier to the movement of brown and rainbow trout, and the presence of mountain galaxias but not trout in Coats Gully is attributed to the riffles that isolate the tributary from the Sturt River.

The perennially damp soil and dense understorey vegetation provides habitat for similar birds and mammals as for fractured rock aquifer springs.


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Figure 10. Site Photo Wilsons Bog

Figure 11. Site Photo Coats Gully


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Vegetation:

• Group 2: Perennially Waterlogged, Tolerates Flow

• Group 3: Perennially Saturated, Seasonally Flooded

• Group 4: Alternately Waterlogged and Drained Sites

Macroinvertebrates:

• Flowing water, riffle

• Still water, persistent ponds and pools

Fish:

• Migratory freshwater species (climbing galaxias, common galaxias)

• Obligate, freshwater stream specialist (mountain galaxias)


Depending on the site, groundwater may support these ecosystems in several different ways. The functions of groundwater are listed in order of decreasing groundwater contribution:

Maintenance of permanent flow

Maintenance of permanent pools

Maintenance of waterlogged conditions within the riparian zone

Provision of shallow watertables that phreatophytic vegetation can access within the riparian zone

If, at a particular site, the groundwater contribution is such that permanent flow is maintained, then it follows that the remaining functions will also be provided.

There is significant variability among the streams of the study area and the level of groundwater contribution. There are a few stream reaches in the study area where permanent flows are maintained (for instance those listed in Table 5). At other sites, only permanent pools, waterlogged conditions or shallow watertables may be maintained by groundwater. It is beyond the scope of this study to map where such conditions are present, but it is acknowledged that the application of EWRs should be tailored to reflect the variability.

Streamflow data provides a means to assess groundwater discharge to streams on a catchment scale to inform the derivation of EWRs. Baseflow separation filters can be applied to the gauged data to estimate the volume of groundwater discharge. Figure 12 shows baseflow exceedance curves for Brownhill Creek


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and First Creek. The gauge at Brownhill Creek is located at Scotch College and represents its mid- to upper-catchment, including a section of the stream at the base of the Adelaide Hills where it passes over geological faults and loses water to sedimentary aquifers of the Adelaide Plains (Green et al., 2010). The gauge on First Creek is located in Waterfall Gully representing its headwaters solely within fractured rock geologies.

Due to their different locations in their respective catchments, these gauges display different baseflow characteristics. The Brownhill Creek catchment (upstream of Scotch College) is larger than the First Creek catchment and has greater high and moderate flows. But the trend is reversed for low flows. Flow is permanent at the First Creek gauge, while Brownhill Creek ceases to flow at Scotch College for 10 % of the historical record despite there being permanent reaches upstream of the gauge.

Figure 12. Stream baseflow exceedance curves for records for Brownhill Creek (1991-2011) and First Creek (1976-2006) based on their entire monitoring records.


The baseflow separation data from the historical record can be used as a benchmark to quantify EWRs on a catchment scale. Recognising that low flows are critical for the maintenance of GDEs, the EWRs should be defined in terms of low flow requirements. For instance, the EWR for First Creek may specify that flows need to be maintained above 1 ML/month at gauge 5040517. Similarly, the EWR for Brownhill Creek may be that it needs to flow for at least 90 % of the time at gauge 5040901.

The use of gauging data is appropriate for a catchment, but further detail is required that links the ecology of the stream to the flow regime. For instance, the EWR for Brownhill Creek should specify (in addition


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to the flow requirements listed above) that permanent flows and permanent pools need to be maintained in sections of the stream where climbing galaxias have been identified.

Where the ecology depends on waterlogged conditions or shallow watertables, the EWR can be defined in terms of groundwater levels. To maintain waterlogged conditions, a minimum groundwater level is defined by the capillary fringe of the watertable below land surface. To maintain the accessibility of groundwater for phreatophytic vegetation, the EWR is defined by a groundwater level that roots can access (i.e. a maximum depth and/or rate of change).

Along a reach defined as gaining (as identified in SKM 2011), the environmental water requirement is:

• the baseflow component of streamflow must be sufficient to maintain permanent flow (where identified) or a minimum number of no flow days (where flow is seasonal); and,

• the adjacent groundwater levels must be above the stream/pool level (where permanent flow/pools are located), above the base of the stream (where permanently waterlogged conditions are located), or within access of the roots of phreatophytic vegetation (where shallow watertables are required).



A reduction in groundwater levels will affect groundwater fed watercourses by reducing the persistent or perennial hydrological influences of groundwater discharge and increasing the intermittent and seasonal influences of rainfall runoff (Figure 13).


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Figure 13. Consequences of lower water tables for groundwater dependent streams

Groundwater-fed pools would become shallower, more vulnerable to poor water quality and more prone to drying out in summer or during droughts. A reduction in the persistence of pools would threaten the survival of native fish populations and will alter the structure of macroinvertebrate communities.

Reaches where groundwater maintains saturated conditions or perennial flow would contract, reducing the habitat available for plants dependent on waterlogging. The extent of reaches that provide perennial flowing riffles would contract, reducing an important habitat component for climbing, mountain and common galaxias.


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Losing reaches downstream of groundwater discharge sites will be affected by a reduction in the persistence of flow. The seasonal availability of aquatic habitat will decrease, providing fewer or shorter opportunities for macroinvertebrates, frogs and fish to complete their life-cycles. Plant species tolerant of seasonal flow are likely to become more abundant.

Threats

The groundwater catchments associated with fractured rock baseflow are significantly larger than for fractured rock spring discharge. Local pumping will have an acute and immediate impact on springs, whereas the impacts to baseflow from pumping will be spread over a greater area. Any pumping within the groundwater catchment will impact baseflow, but the timeframe between pumping and the impact to streamflow will vary with the distance from the stream. As such, total extraction as opposed to the location of extraction is of more significance to fractured rock baseflow.

Currently there is little commercial groundwater extraction activity within fractured rock aquifer, with most extraction confined to stock and domestic use. SKM (2009) estimated a total groundwater extraction of 632 ML/y from the fractured rock aquifer within the PWA, with a more recent estimate by AGT (2011) somewhat higher at 742 ML/y for non-commercial extraction.

SECTION 7 Terrestrial Vegetation at the Base of the Hills

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7 Terrestrial Vegetation at the Base of the Hills

7.1 Distribution and Occurrence

The Adelaide Plain is formed of Tertiary and Quaternary sediments overlying the down-thrown block of the Mount Lofty Ranges along the Eden-Burnside and Para Faults. The topography contrasts strongly either side of the Eden-Burnside fault, where deeply incised streams with steep bed gradients in an erosional environment to the east flow to a broad, low-gradient plain to the west. The loss of stream power associated with the change in topography provides a depositional environment, and streams have formed a series of alluvial fans at the foot of the ranges north from the Sturt River, Brownhill Creek, First to Sixth Creeks up to the Gawler River (Bourman et al. 2010).

Figure 14. Schematic representation of the dependence of terrestrial vegetation at the base of the hills on shallow groundwater


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These sediments form the Q1 Quaternary Aquifer of the Adelaide plain. The aquifer is recharged mainly by surface water flow from catchments in the Mount Lofty Ranges. Green et al. (2010) found that groundwater discharges from fractured rock aquifers into surface streams above the Eden-Burnside Fault (Figure 14). It then traverses the fault zone via the surface water system before recharging the sedimentary aquifers below the fault zone. There is also potential for lateral recharge across the Eden-Burnside fault from the fractured rock aquifer.

Ecosystem interactions are predicted to occur on the western side of the Eden-Burnside fault in the region shown in Figure 15. The Q1 aquifer in this region receives groundwater through-flow across the fault as well as recharge from streams as they reach the alluvial fans at the base of the range. The prinicpal ecosystem component in this region is the large Eucalyptus camaldulensis trees. These are not mapped as urban areas are not included in native vegetation mapping and in any case exist mainly as scattered trees. The level of confidence that groundwater contributes to the water requirements of these trees in this region is moderate: i.e. while it can be confidently predicted that shallow groundwater is present and it known that the species Eucalyptus camaldulensis utilises groundwater when available,

• there is no empirical evidence of groundwater use by trees in this region;

• the distribution of Eucalyptus camaldulensis has not been mapped; and

• groundwater level data in the Q1 aquifer is very limited.


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Figure 15. Terrestrial vegetation at the base of the hills.

7.2 Ecology

The plains along the foot of the range have been modified extensively, initially for agriculture and later for urban development. There is little evidence of extant groundwater dependent ecosystems. Springs are described in this region from historical documents such as The Register (31 October 1885) which describes a perennial spring at Burnside formed where “a gravel bed resting on a subsoil of clay” discharged to the surface and supported Stylidium despectum, Cyperus tenellus, Crassula decumbens, Juncus caespiticius and Isolepis cernua.

The most widespread indicators of ecosystem dependence on groundwater are Eucalyptus camaldulensis. This species occurs predominantly along watercourses which provide water to support growth over spring


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and summer. However at the base of the ranges they are distributed outside watercourses, suggesting that shallow groundwater is available to support their growth.

Figure 16. River red gum (Eucalyptus camaldulensis) in Hazelwood Park, Burnside

Eucalyptus camaldulensis are important habitat trees in the urban landscape. They support a range of vertebrate fauna by providing nesting and sheltering habitat in hollows, fissures and bark for bats, birds, possums and reptiles. Insects that feed on nectar, pollen, leaves and decaying organic matter provide prey for insectivorous birds, bats and reptiles.

There is little other information to characterise this ecosystem. There are records of plants that depend on perennial waterlogging at other locations at the foot of the ranges, specifically Leptospermum continentale and Leptospermum lanigerum at Greenglades Council Reserve at Paradise (Kraehenbuehl 1996) and Leptospermum lanigerum on Brownhill Creek downstream of Old Belair Road (pers. com. Tom Hands, botanist, May 2011).


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Vegetation:

• Shallow water table below drained soils

Macroinvertebrates:

Not Present

Fish

Not present


Groundwater supports these ecosystems by providing a shallow watertable that roots can access, such that the vegetation is able to maintain photosynthesis in summer when soil moisture stores are depleted. To support this ecological function the groundwater regime must be maintained at depths that are accessible to plant roots and be of a tolerable salinity.

The EWRs is defined based on the needs of Eucalyptus camaldulensis as it is the key species within this GDE type. Eucalyptus camaldulensis is known to be able to access groundwater from deep within the soil profile. White et al. (2000) reported root water uptake from the capillary fringe at 6 m below the ground surface in the WA wheatbelt, and Horner et al (2009) reports that root water uptake from a watertable at 15 m deep in the Barmah-Millewa Forest. It is probable that even greater rooting depths can be attained in the absence of soil physical or chemical constraints. Despite their ability to access groundwater from depth and their drought tolerance, Eucalyptus camaldulensis can be sensitive to changes in groundwater level. Horner et al. (2009) showed a high incidence of tree mortality within high density stands of the Barmah-Millewa Forest that coincided with a watertable decline of 0.25 m/y between 1998 and 2007. In this regard, the EWR for Eucalyptus camaldulensis is based on a rate of change of the watertable as opposed to a fixed groundwater level.

Figure 17 shows a groundwater level hydrograph for the shallow Q1 aquifer at Hazelwood Park. The historical record shows groundwater levels in a state of dynamic equilibrium – i.e. aside from seasonal fluctuation there is no long term trend of rising or falling groundwater levels. A decline in summer water levels was apparent until 2010, yet that appears to be a result of the recent drought with higher water levels noted in 2011 in response to wetter conditions. The data provides a benchmark for the derivation of EWR of this GDE functional group. Given that the Eucalyptus camaldulensis at Hazelwood Park have adapted to these conditions and were resilient during the recent drought, the EWR could be defined by rate of decline in groundwater levels that occurred over this period (March 2006 - March 2010). That is, the recovered (spring) groundwater levels need to be maintained near the long-term average and the summer groundwater levels must not decline by more than that evident during 2006 – 2010.


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Figure 17. Groundwater level monitoring for the Q1 aquifer at Hazelwood Park


The EWR can be defined as:

• maintenance of the long-term average recovered (spring) groundwater levels; and

• summer groundwater levels must not decline by more than the rate of change from 2006 to 2010 as measured a nearby observation bore that was not influenced by groundwater use over this period.



A reduction in groundwater levels will affect the productivity and health of vegetation dependent on the water table. The most likely species to be affected will be Eucalyptus camaldulensis (Figure 18).


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Figure 18. Consequences of a lower water table on terrestrial vegetation

The water requirements of E. camaldulensis are likely to be met by a combination of rainfall infiltration, capillary rise of water from the water table and direct access to water in the saturated zone of the aquifer. A lower water table reduce the availability of groundwater and trees will become more dependent on the less persistent, less abundant and less reliable water provided by rainfall infiltration. This is likely to lead to slower growth in trees and reduced productivity of leaves, flowers, nectar and wood. Trees will become less resilient to drought.

Threats

In this part of the St Vincent geological basin, the presence of faults creates strong hydraulic connection between the deeper, more productive Tertiary aquifers and the shallow Quaternary aquifers that host the watertable. Extraction from any aquifer in this region may impact the watertable, but that which occurs from the Q1 aquifer will have the most significant impact.

Domestic water users take water from backyard bores tapping into the Quaternary aquifers. Since 1990 about 2,600 backyard bores have been drilled into these aquifers on the Adelaide Plain and 2000 are thought to be operational. Bores have low rates of extraction, 3 L/s (Barnett et al. 2010).

In contrast to the fractured-rock aquifers, extraction from the sedimentary aquifers has more diffuse impacts that occur over a longer timeframe. Because storage is limited in a fractured rock setting, extraction can result in sharp groundwater level declines over a small area of influence near the point of extraction. In the sedimentary aquifers, particularly the deeper Tertiary aquifers, storage is high and


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groundwater level declines resulting from extraction will be less significant but will occur over a greater area of influence.

Figure 19 shows groundwater extraction in the vicinity of Hazelwood Park. Most extraction is for domestic purposes with there being only minor commercial extraction activity. Compared to other parts of the PWA, the level of extraction is categorised as low.

It is unlikely that groundwater extraction activities in the vicinity of these GDEs will impact the salinity of the groundwater. In certain settings, extraction can cause the upward or lateral migration of high salinity groundwater. However at this location, the salinity of underlying and surrounding layers is typically less than 1500 mg/L (Gerges et al., 2006) and does not constitute a threat.

Recharge processes will also play a major role in influencing groundwater levels, particularly as this is a major recharge zone for the sedimentary aquifers. Changes in rainfall and streamflow are likely to exert significant influence on the depth of the watertable.

Figure 19. Groundwater extraction in the vicinity of Hazelwood Park

SECTION 8 Measuring EWRs

8-1

8 Measuring EWRs

8.1 Measurement of EWRs

EWRs are more useful in water planning when they are measurable. The EWRs proposed in this report specify groundwater conditions which could be measured through further investigations, even if they cannot be quantified using existing information.

The methods used to measure EWRs has implications for the management of the resource. The more site-specific and precise methods are, the more they will be able to inform water management decisions. However, this level of detail comes at a cost of intensive data collection. Furthermore, there may be limited potential to generalise about multiple sites from the information of a well-described few.

Table 18 presents the strengths and weaknesses of approaches available to measure the EWRs proposed in this report. The terms used to define EWRs in this report are:

• the baseflow component of the stream (groundwater dependent streams);

• the groundwater level in the vicinity of the ecosystems (fractured rock aquifer springs and groundwater dependent streams); and

• the regional groundwater level and its rate of change (terrestrial vegetation at the base of the range).

Methods which measure the baseflow component of streams include water quality, isotope and baseflow separation approaches (Table 18). These can be applied regionally to evaluate the overall influence of groundwater in a catchment. These methods are attractive because they can report on groundwater requirements for multiple GDEs or complexes of GDEs upstream of the monitoring site. However, they have limited usefulness in providing information on the eco-hydrogeological processes influencing individual ecosystems, because they cannot distinguish where in a catchment changing conditions have contributed to the monitoring result. These methods may be valuable as an early warning of groundwater change as a change in the groundwater signature would identify a change in groundwater contributions at some location in the catchment and could trigger further, more site-specific investigations. These methods may also be valuable when applied more intensively, such as upstream and downstream of a stream reach where groundwater discharge occurs and changes in the relationship between monitoring stations would indicate a change in the groundwater environment.

Methods which monitor individual sites provide more reliable and accurate data on the interactions between the aquifer and ecosystems. These can include monitoring bores adjacent to watercourses or wetlands that report levels and can be related to measurements of groundwater discharge or wetland water level to develop models of groundwater flux. However, these methods require a significant monitoring effort and are likely to be suitable only at high priority sites.

Regional monitoring bores are likely to be effective in detecting change in the Q1 aquifer at the base of the range. At present monitoring bores are sparse and the aquifer is poorly characterised in this area.


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Table 18. Assessment of measurement approaches for EWRs

Approach Requires Strengths Limitations

Baseflow separation

Specify EWR as a baseflow regime (i.e. the volume and timing of groundwater discharge across a catchment).

- gauges on watercourses at the foot of the range or below high value reaches within the range

- several years of records

- hydrological analysis

- indicates proportion of flow derived from a persistent source (groundwater)

- integrates whole of catchment

- does not distinguish between groundwater and subsurface flow or regulated releases (e.g. Heathfield WWTP)

- integrates whole of catchment – provides no information on groundwater discharge at localised groundwater discharge areas within the catchment

- expensive to set up

- not feasible for every watercourse

- we do not know what the baseflow signature should be in reaches without gauges – cannot set a quantitative EWRs for ungauged reaches until more gauges are installed years of data is collected

Representative groundwater bore

Specify EWR as the groundwater level at a location

- install monitoring bore that reports aquifer conditions in the vicinity of a GDE

- provides a simple indicator that is easy to manage

- local aquifer characteristics can be related directly to local GDE water regime

- conditions reported by bores are very localised, and conditions vary enormously between localities

- would need numerous bores and a long-term data record to comprehensively relate aquifer conditions to GDEs

- bores located near the GDE are a lagging indicator - aquifer depletion may have already affected ecosystems by the time monitoring bores respond, so placement of bores near points of extraction also required.

- does not indicate flux; this would require a network of bores

- without existing data we do not currently know what a suitable range of groundwater levels should be – cannot set a quantitative EWR until bores are installed


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Isotopes

Specify EWR as an isotope signature

- test stream water for strontium, radon or other isotopes to indicate the proportion of groundwater in surface water and to identify the locations and times of groundwater discharge

- collect water over several seasons and years to build up a signature

- good mapping tool

- can be used at the catchment scale, reach scale or tributary scale

- not comprehensive: can only be applied at sites where data has been collected

- difficult to set a signature as a quantitative threshold for an EWR – ratios change from season to season, time since last runoff event

- subject to sampling errors

- expensive to analyse samples

- cannot be automated

- bank storage and interflow can complicate the apparent groundwater contributions

- we do not currently know what the isotope signatures should be – cannot set a quantitative EWR until years of data is collected

Salinity

Specify EWR as a salinity range in low flow periods as an indicator of groundwater contribution.

- regular sampling of stream salinity, particularly in low flow periods

- cheap and simple to collect data

- could be used at the catchment scale or tributary scale

- not comprehensive: can only be applied at sites where data has been collected

- salinity is influenced by evaporation, dilution, bank storage and interflow so it is difficult to develop a quantitative threshold for low flow periods

- probably better as a descriptive indicator than as an EWR specification

- we do not currently know what the salinity signature should be: cannot set a quantitative EWR until years of data is collected


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Conceptual statement of hydraulic gradient

Specify EWR as a gaining hydraulic gradient at locations where GDEs have been mapped

- mapping or predictive mapping of where GDEs occur

- comprehensive and site specific – covers all known and predicted GDEs

- the level of detail in the EWR specification matches the current level of knowledge

- testable: methods can determine if the gradient is positive or not.

- a range of complimentary measurement methods can evaluate the hydraulic gradient

- readily improved: local monitoring data at high value sites would develop more specific and quantitative EWRs in the future, i.e. what the groundwater gradient should be

- very general: does not quantify the hydraulic gradient other than it is ‘positive’

- not sufficiently protective: groundwater levels could fall and significantly impact on GDEs before the hydraulic gradient is neutral or negative

SECTION 9 Conclusions

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9 Conclusions

9.1 GDE Typology

This study determined that three GDE types in the study area are relevant to the development of the Water Allocation Plan:

• fractured rock aquifer springs;

• groundwater dependent streams; and

• terrestrial vegetation at the base of the hills.

These ecosystems are associated with shallow groundwater or the discharge of groundwater to the surface from aquifers that are subject to use.

9.2 Fractured Rock Aquifer Springs

Fractured rock aquifer springs occur in the outcropping basement of the Mount Lofty Ranges. They occur as isolated features where fractures, topography or stratigraphic features promote the discharge of groundwater to the surface.

The springs are small in extent and consequently often provide a specialised plant habitat for species with a very restricted distribution. The springs therefore support a high proportion of rare and threatened plant species and generally have a very high conservation value.

The threat of current groundwater use to fractured rock aquifer springs is likely to be low as there is little development of groundwater resources in aquifers maintaining these systems. However there may be sites where local groundwater use in close proximity to springs, even if small, affects spring hydrology.

The proposed environmental water requirement for fractured rock aquifer springs is:

“the adjacent groundwater levels must be above the pool level (where permanent inundation occurs), above the base of the bog (where permanently waterlogged conditions are located), or above the rooting depth of phreatophytic vegetation (where shallow watertables are required)”.

9.3 Groundwater Dependent Streams

Groundwater dependent streams occur in the Mount Lofty Ranges where springs contribute to stream flow or where the stream bed intersects the water table. Groundwater influences stream hydrology by contributing to the persistence or permanence of pools, flowing reaches and waterlogged channel beds.

Groundwater contributions to stream hydrology are important in maintaining native fish populations in the study area. Common galaxias, mountain galaxias and climbing galaxias all occur in reaches that are strongly influenced by groundwater and depend on permanent pools and riffles to maintain populations

SECTION 9 Conclusions

9-2

and escape predators. Perennial pools and flowing reaches also contributes to macroinvertebrate diversity and supports specialised native plants.

The threat of current groundwater use to groundwater dependent streams is likely to be low as there is little use of groundwater from the fractured rock aquifer in the study area. However, there may be localised areas of groundwater use in close proximity to groundwater dependent streams that have an effect.

The proposed environmental water requirement for groundwater dependent streams is:

“along a reach defined as gaining, the environmental water requirement is:

• the baseflow component of streamflow must be sufficient to maintain permanent flow (where identified) or a minimum number of no flow days (where flow is seasonal); and,

• the adjacent groundwater levels must be above the stream/pool level (where permanent flow/pools are located), above the base of the stream (where permanently waterlogged conditions are located), or within access of the roots of phreatophytic vegetation (where shallow watertables are required).”

9.4 Terrestrial Vegetation at the Base of the Hills

Shallow groundwater in the Quaternary aquifer at the base of the hills between Yatala Vale and Springfield is coincident with a population of large Eucalyptus camaldulensis. This species is known to make use of groundwater when available, and this region is interpreted to be represent a groundwater dependent ecosystem.

Groundwater may contribute to the water requirements of these trees by providing elevated soil moisture in the capillary zone above the water table or providing tree roots with water directly from the saturated zone. Trees are likely to also access rain infiltration above the water table, but groundwater is likely to supplement tree growth, increasing productivity and growth rates, and thereby tree habitat value.

The threat of current groundwater use to terrestrial vegetation at the base of the hills is likely to be moderate. There has been increasing use of groundwater from domestic bores on the Adelaide plain and groundwater levels have been shown to decline. Groundwater monitoring data from the shallow aquifer in this region is very sparse and this threat assessment can only be made with a low level of confidence.

The proposed environmental water requirement for terrestrial vegetation at the base of the hills is:

• “maintenance of the long-term average recovered (spring) groundwater levels; and

• summer groundwater levels must not decline by more than the rate of change from 2006 to 2010.”

SECTION 10 References

10 References

Allen, G. R., S. H. Midgeley, and M. Allen. 2002. Field Guide to the Freshwater Fishes of Australia. Western Australian Museum, Perth, Western Australia.

Barnett, S. R., E. W. Banks, A. Love, C. T. Simmons, and N. Z. Gerges. 2010. Aquifers and groundwater. Pages 92-102 in C. B. Daniels, editor. Adelaide Water of a City. Wakefield Press, Kent Town.

Benyon, R. G., N. E. Marcar, D. F. Crawford, and A. T. Nicholson. 1999. Growth and water use of Eucalyptus camaldulensis and E. occidentalis on a saline discharge site near Wellington, NSW, Australia. Agricultural Water Management 39:229-244.

Boulton, A. J. and M. A. Brock. 1999. Australian Freshwater Ecology Processes and Management. Gleneagles Publishing, Glen Osmond.

Bourman, R. P., N. Harvey, and S. Bryars. 2010. Catchments and Waterways. Pages 69-89 in C. B. Daniels, editor. Adelaide Water of a City. Wakefield Press, Adelaide.

Chessman, B. C. and W. D. Williams. 1975. Salinity tolerance and osmoregularity ability of Galaxias maculatus (Jenyns) (Pisces, Salmoniformes, Galaxiidae). Freshwater Biology 5:135-140.

DWLBC (2006). State Natural Resources Management Plan. Department of Water, Land and Biodiversity Conservation, South Australia.

Ecological Associates. 2002. Investigation of Groundwater Dependent Ecosystems in the McLaren Vale Prescribed Wells Area. Report prepared for the Onkaparinga Catchment Water Management Board, Adelaide.

Ecological Associates. 2008. Determination of Environmental Water Requirements for Mosquito Creek Catchment and Bool and Hacks Lagoon - Issues Paper South East Natural Resources Management Board, Mount Gambier, South Australia.

Gerges, N. 2006 Overview of the hydrogeology of the Adelaide metropolitan area. South Australia. Department of Water, Land and Biodiversity Conservation. DWLBC Report 2006/10

Green, G., Watt, E., Alcoe, D., Costar, A. and Mortimer, L. (2010). Groundwater flow across regional scalle faults. Technical Report DFW 2010/15, Department for Water, South Australia.

Hammer, M. 2005a. The Adelaide Hills fish inventory. Adelaide. Hammer, M. 2005b. The Adelaide Hills fish inventory. Distribution and conservation of freshwater

fishes of the Torrens and Patawalonga catchments, South Australia. August 2005. Patawalonga and Torrens Catchment Water Management Boards, Adelaide.

Harding, C. L. 2005. Wetland Inventory for the Fleurieu Peninsula, South Australia. Department for Environment and Heritage, Adelaide, South Australia.

Horner, G.J., P.J. Baker, R. MacNally, S.C. Cunningham, J.R. Thomson and F. Hamilton. 2009. Mortality of developing floodplain forests subjected to a drying climate and water extraction. Global Change Biology 15: 2176-2186.

Kraehenbuehl, D. N. 1996. Pre-european vegetation of Adelaide: a survey from Gawler River to Hallett Cove. Nature conservation Society of South Australia, Adelaide.

Lundstrom, G. 2008. Farm dam salinity audit of the Eastern Mount Lofty Ranges South Australia. South Australian Murray-Darling Basin Natural Resources Management Board, Adelaide.

Maslin, B. R., L. A. J. Thomson, M. W. McDonald, and S. Hamilton-Brown. 1998. Edible wattle seeds of southern Australia: a review of species for use in semi-arid regions. CSIRO Australia, Canberra.

Mensforth L.J., Thorburn P.J., Tyerman S.D. and Walker G.R. 1994. Sources of water used by riparian Eucalyptus camaldulensis overlying highly saline groundwater. Oecologia, 100: 21-28.

Morgan, D. L., A. Chapman, S. J. Beatty, and H. S. Gill. 2006. Distribution of the spotted minnow (Galaxias maculatus) (Jenyns, 1842) (Teleostei: Galaxiidae) in Western Australia including range extensions and sympatric species. Records of the Western Australian Museum 23:7-11.

Schmarr, D. and D. McNeil. 2010. Ecological responses to environmental water provisions in the Onkaparinga River. SARDI Aquatic Sciences Report F2010/000637-1 prepared for the SA Department for Water, The Adelaide and Mount Lofty Ranges Natural Resources Management Board and e-water Cooperative Research Centre, Adelaide.

Shanahan, M., D. S. Jones, and S. Hughes. 2010. A History of Water in the City. Pages 155-174 in C. B. Daniels, editor. Adelaide: Water of a City. Wakefield Press, Adelaide.

SECTION 10 References

SKM. 2010. Groundwater-dependent environmental assets of the Adelaide Plains and McLaren Vale. Sinclair Knight Merz report VE323416. Adelaide and Mount Lofty Ranges Natural Resources Management Board, Eastwood.

SKM. 2011. Adelaide Plains Groundwater Investigation Projects. Part 3: Surface water / groundwater interactions. Sinclair Knight Merz report VE23530. Adelaide and Mount Lofty Ranges Natural Resources Management Board, Eastwood.

Smith, K. 2010. The Biodiversity of Buckland Park. Page p. 67 Adelaide: Water of a City. Wakefield Press, Adelaide.

Stewart, S. and Green, G. (2010). Groundwater flow model of Cox Creek catchment, Mount Lofty Ranges, South Australia. Department for Water, South Australia.

Taylor, B. 2006. Wetland Inventory for the Lower South East, South Australia. Department for Environment and Heritage, Mount Gambier, South Australia.

Thomas, B., R. Fitzpatrick, and R. Merry. 2001. Literature Review of Acid Sulfate Soils and the Environment in the Barker Inlet / Gillman Area. Appendix A of Demonstrating Amelioration of Acid Sulfate Barker Inlet / Gillman Area, South Australia. Report prepared for Barker Inlet Port River Estuary Committee by CSIRO Land and Water, Urrbrae.

Thorburn, P. J. and G. R. Walker. 1994. Variations in stream water uptake by Eucalyptus camaldulensis with differing access to stream water. Oecologia 100:293-301.

Towns, D.R. (1985). Limnological characteristics of a South Australian intermittent stream, Brown Hill Creek. Australian Journal of Marine and Freshwater Research, 36(6): 821-837.

VanLaarhoven, J. and M. van der Wielen. 2009. Environmental water requirements for the Mount Lofty Ranges prescribed water resources areas. Department for Water, Land and Biodiversity Conservation Report 2009/29 and South Australian Murray-Darling Basin Natural Resources Management Board, Adelaide.

White, D.A., Turner, N.C., and Galbriath, J.H. 2000. Leaf water relations and stomatal behaviour of four allopatric Eucalyptus species planted in Mediterranean south west Australia. Tree Physiology 20. pp. 1157-1165.Wilkinson, J., J. Hutson, E. Bestland, and H. Fallowfield. 2005. Audit of contemporary and historical quality and quantity data of stormwater discharging into the marine environment, and field work programme. South Australian Environment Protection Authority, Adelaide.

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