No. 6 Daily extraction management .in unregulated rivers (2002 … · 2015-03-06 · important for...

13 AUGUST 2002

NSW Government

No. 6 Daily extraction managementin unregulated rivers (2002 version)

Development of this policy

This policy advice was initially released in late2001, and guided water sharing committees in thedevelopment of the initial round of Water SharingPlans in 2001/02. However, the design and analysisof daily extraction limits for these plans raised anumber of issues regarding the appropriatenessand practicality of adopting full daily extractionmanagement in some rivers. In particular:

the high cost of monitoring and administrationmeans that moving to full daily flow sharescannot be justified in some rivers withrelatively few users and low water use demand,

the high variability in flows across some watersources means that the water source must besubdivided to ensure that daily extractionlimits reasonably reflect local wateravailability,

inadequate flow data, particularly when thewater source is subdivided, means that thedaily extraction limits cannot be reliablydetermined.

This indicated that in some water sources or partsof the water sources, it might be more appropriateto introduce an interim management option over theterm of the first Water Sharing Plan. This option,while seeking to protect at least the very low flowsand move toward daily extraction management, willrecognise the limitations and risks identified above.

The policy advice was revised in mid-2002 toreflect a more flexible approach to theintroduction of daily extraction management. Italso clarifies some of the ambiguities in the earlierversion.

Why daily extraction management isneeded

During 2000, most irrigation licences onunregulated rivers were converted from an areabasis to a yearly volume known as a shareentitlement. All other river licences are also beingconverted to a yearly volume entitlement. Thisbegan the process of more clearly defining users’rights to access water.

The volumetric conversion provides water users withgreater business flexibility and establishes a betterbasis for managing river flows. However, the shareentitlement does not, on its own, fully define users’access to water. Nor is there in place sufficientprotection of the river flow needed to maintain theenvironmental health of our rivers.

Under the Water Management Act 2000, watermust be specifically allocated for environmentalneeds. So while the establishment of shareentitlements is a critical first step, it will benecessary in many unregulated rivers toprogressively move to provide greater protectionfor river health. This will involve establishing riverflow levels below which licensed water users mustcease to pump, and defining access to wateraccording to the share of the actual flow which isavailable.

In Australia our rivers are naturally variable,changing frequently from flood to droughtconditions and our native flora and fauna areuniquely adapted to these conditions.

However, in most unregulated rivers, it is duringdrier periods when flows are naturally low tomoderate, that there is generally greatest concernfor the health of the river. This is when poolscontract, water quality deteriorates rapidly, algae

13 AUGUST 2002

blooms, oxygen levels decline and fauna competefor the reducing food supplies. This is also whendemand for water for human uses is often at itshighest.

If river extraction is allowed to proceedunrestricted, upstream pumpers could potentiallyremove all the water. This would not only leaveinsufficient water to provide drought refuge orrelief for native aquatic plants and animals but alsoaffect the water users downstream. In somesystems, particularly where there is a large amountof storage relative to flow, water extraction canalso threaten high flows and freshes that areimportant for river and estuary ecosystems.

We need a way of establishing the amounts of flowthat should stay in the river and the volumes thatcan be extracted, through all of these flow levels.

River flow objectivesThe Government has agreed to broad river flowobjectives (see below) aimed at safeguarding river

flows for environmental health. Not all of theseflow objectives are relevant to all rivers - many ofthese relate to rivers that are controlled by majordams.

The river flow objectives are based on theprinciple of mimicking the key characteristics ofthe natural flow regime.

River flow regimes can be characterised by thesize and duration of various flow levels. How oftena flow of a particular size is likely to occur is bestillustrated by a flow duration curve. A flowduration curve plots the volumes of flow(megalitres per day) against the percentage ofdays that such a flow will be equalled or exceeded.

Figure 1 shows a typical flow duration curve.

If our rivers are to be sustainable to meet currentand future water needs, we must retain certainproportions of river flow to maintain thebiodiversity and health of our rivers.

River Flow ObjectivesObjective 1 protect natural water levels in pools of creeks and rivers and wetlands during

periods of no flow

Objective 2 protect natural low flows

Objective 3 protect or restore a proportion of moderate flows, “freshes” and high flows

Objective 4 maintain or restore the natural inundation patterns and distribution offloodwaters supporting natural wetland and floodplain ecosystems

Objective 5 mimic the natural frequency, duration and seasonal nature of drying periods innaturally temporary waterways

Objective 6 maintain or mimic natural flow variability in all rivers

Objective 7 maintain rates of rise and fall of river heights within natural bounds

Objective 8 maintain groundwaters within natural levels, and variability, critical to surfaceflows or ecosystems

Objective 9 minimise the impact of in-stream structures

Objective 10 minimise downstream water quality impacts of storage releases

Objective 11 ensure river flow management provides for contingencies

Objective 12 maintain or rehabilitate estuarine processes and habitats

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Figure 1EXAMPLE FLOW DURATION CURVE FOR

AN UNREGULATED RIVER

What are daily extraction limits?

Establishing cease to pump (CTP) flow levels on theunregulated rivers will protect the very low flows.Establishing daily extraction limits are a means forboth protecting river health and for sharingavailable flows above the CTP between competingwater users. These extraction volumes willultimately enable a portion of the natural riverflows to be protected for environmental needs.

The daily extraction limits will enable licenceholders’ extractive rights to be specified andprotected to a greater degree than currentlyexists - that is, when and what amount can beextracted from a river will be clearly specified.

These extraction volumes may be converted intolicence conditions advising individual water users ofthe minimum river flow level at which they canpump, and the maximum rates at which they canextract water (in litres per second or megalitresper day) depending on flow. This is referred to asthe daily extraction entitlement. Water users canconvert these rates into the equivalent number ofpumping hours a day relevant to their pumps andirrigation set ups. This will allow them to betterplan their extraction patterns and/or watering

schedules to fit in with the likely volumes of wateravailable to them at critical times.

Daily extraction limits will not overcome local watersupply constraints (eg small creeks whichfrequently cease to flow) or the competition forwater that occurs when available flows are lessthan the daily extraction limit.

However, they will ensure that when there is amoderate flow through the catchment, then alllicence-holders have the right to a fair share of it.

Equitable sharing of available flows that are lessthan the daily extraction limit should aim to beachieved by way of rostering.

The Department may choose to announce apercentage of daily extraction entitlement accessduring these competition periods if rostering failsto equitably share these flows.

Where will daily extractionmanagement be applied?

Ultimately all unregulated rivers should move to adaily extraction management to ensure that:

environmental flows are protected across thewhole flow regime

13 AUGUST 2002

property rights to water are established whichmakes transparent and protects the share ofthe flow available to individual licence holders

licence holders are better able to assess theirsupply reliability in terms of frequency ofaccess and thus make informed investment andtrading decisions

water transfer rules are consistent andobjective

a market in individual daily extractionentitlements can operate so that individualscan adjust their supply reliability to suit theirenterprises and infrastructure

rostering can occur between any number ofindividuals based on the sum of their pooleddaily extraction entitlements.

However, establishing and implementing dailyextraction management will require additionalinfrastructure and management effort including:

actual or simulated streamflow data,

operational gauges providing daily flowinformation,

announcements to all users of daily flow class,

daily pumping/metering information,

improved data storage and management,

audit and compliance.

This will impose significant additional costs forwater resource management and administrationthat may not be justifiable in some systems duringthe term of the current Water Sharing Plan.

It is likely that at least some of these costs will bepassed on to water users so implementation needsto be set at realistic levels for each system.

Therefore in the shorter term, daily extractionmanagement should only be established andreflected in Water Sharing Plans for those riverswhich have some or all of the followingcharacteristics:

stressed (high level of current extractivedemand relative to low to median flows)

extractive demand is likely to threatenidentified conservation values, in particularthreatened species

likely to have high levels of competition foraccess to water in the short to medium term

likely to have high demand for water transfers

likely to have high potential for development ofinactive entitlement

having reasonable historic flow record

having a suitable operational gauging station(s).

Even where daily extraction management isestablished, it may take several years to fullyimplement the necessary management andcompliance arrangements such as:

installation or upgrade of gauging station(s)

installation of meters and/or pump diaries

establishment of a data storage andmanagement system

automated flow class announcements.

For other rivers, an interim management strategymay be adopted. The choice of managementstrategy will depend on what flow information isavailable, the degree of environmental water andproperty rights required, and the potential cost ofmanagement relative to the water use demand.

All options should aim to improve the current flowregime resulting from the visible flow pumpingconditions that exist on the majority ofunregulated licenses.

Selecting the appropriatemanagement strategy

Where it is determined that daily extractionmanagement is not appropriate for a water source(i.e. does not meet the characteristics listedabove), one of the following alternate types ofmanagement may be considered: Cease and/or commence to pump thresholdsonly.

In this case there is no daily limit on extractiononce the commence to pump threshold has beenexceeded. It has the benefit of requiring a lowerlevel of management in that:i) it can be implemented in a shorter time frameii) it can be managed using a low flow staff gauge

onlyiii) cease to pump (CTP) levels can be established

with or without a historic flow record.However, no flow record will also mean that theimpact of the CTP on water users’ will bedifficult to assess.

13 AUGUST 2002

iv) compliance considerations are limited todetermining whether or not there are anypumps operating illegally during cease to pumpperiods.

Its disadvantages, however, are that:i) it can only protect very low flows and

potentially does not protect flow variability. ii) it establishes a property right to a lesser

degree than the daily extraction managementoption.

iii) the reliability of the water resource is moreunclear when it comes to making decisions inrelation to investment and trade.

iv) there is no quantitative limit, which whenreached, would trigger refusal of any furthertransfers into a water management zone

v) depending upon the level that it is set at, it mayonly achieve a small improvement in theprotection of environmental flows and theimplementation of the river flow objectives.

Cease and/or commence to pump thresholds,plus daily extraction limits.

In this case daily extraction limits are establishedfor flows above the CTP, but are not distributed toindividual licence holders as a daily extractionentitlement.

The daily extraction limit can be specified in theWater Sharing Plan and used as solely a basis formanagement of trade with no on groundimplementation. Alternatively all extractions can bemonitored by the Department and collectivelymanaged by the users to ensure that usage stayswithin the amount specified by the daily extractionlimits.

The approach has the advantages that:i) it does formalise environmental rights to water

throughout the flow range.ii) it ensures that any water transfers are

consistent with the daily extraction limits. iii) if daily extraction limits are implemented the

audit requirements are that all waterextractions stay within the daily extractionlimit.

For many rivers, the low level of active use shouldkeep current extraction within the daily limits. Onothers, water users may need to roster and beaudited in critical periods if there is any risk theymay jointly exceed the daily limit. Failure tocomply would require resolution at the local level.

If this can’t be achieved the introduction ofindividual daily extraction entitlements may benecessary.

Its disadvantages are:i) it does require a reliable and representative

historic flow record to enable the dailyextraction limits to be determined and theirimpacts assessed

ii) where the extractions are managed to the dailyextraction limit a fully operational gaugingstation(s) is required to inform the water usersof the access class

iii) in addition, it will require compliance audits onthe daily extraction but these can be done atthe group level (sum of metered extractionsduring any audit period) to ensure thatenvironmental flows are protected.

The methodology for establishing CTP levels anddaily extraction limits is outlined in detail in theAttachment.

Management Options

Six management options based on the strategies ofthe previous sections can be established. Theseare:

1a Common cease and commence to pump thresholds onlybased on field verification.

1b Common cease and commence to pump thresholds only,based on analysis of historic flow data, and fieldverification.

2a CTP thresholds set based on streamflow record andfield verification. Daily extraction limits set but notdistributed to individuals as a daily extractionentitlement with compliance on CTP only.

2b CTP thresholds set based on streamflow record andfield verification. Daily extraction limits set but notdistributed to individuals as a daily extractionentitlement with compliance on CTP and dailyextraction limits.

3a CTP thresholds set based on streamflow record andfield verification. Daily extraction limits set anddistributed to individuals as daily extractionentitlements for some or all flow classes. Complianceon CTP, and daily extraction limits. (partialimplementation of daily extraction management)

3b CTP thresholds set based on streamflow record andfield verification. Daily extraction limits set anddistributed to individuals as daily extractionentitlements. Compliance at individual levels according

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to the group register. (full implementation of dailyextraction management)

Figure 2 Guidelines for selecting an appropriate extraction management option

Note #1: Selection of appropriate option should consider identified conservation values and threatened species.

Note #2: The occurrence of a catchment with no suitable gauging site will be extremely unlikely. Selection of a visible flowcommence/cease to pump condition as the primary method of pumping access should only be adopted in instances where no otheralternative exists. This would be when no gauge site can be established or if establishment of the gauge site is considered to bedetrimental to the environment.

These options are presented in Table 1, togetherwith their implementation requirements andmanagement implications. An example of a typicalassessment process that may take place whendeciding on a management option for each watersource area or management zone is shown in Figure2.

When Should a Management OptionBe Changed ?

The decision to move to a more detailed form ofextraction management, and whether this will occurduring the duration of the current Water SharingPlan or in subsequent plans will be based upon ofnumber of factors. These include;

The time taken to obtain new information. Forexample streamflow information needs to becollected for some time before it can beassumed to be climatically representative.

The likelihood of the proportion of flow usedfor extraction reaching unacceptable levelsduring the life of the plan.

The degree of competition for the resourcebetween existing users.

The time required to install the necessaryadditional operational infrastructure for analternate option.

The cost and resourcing implications of movingto a alternative option in the short term

Any decision to move to a more detailed form ofextraction management during the duration of thecurrent Water Sharing Plan should be specified inthe plan.

Stream height and extraction data should becollected regularly for any of the options chosen.Collection of this data will assist in any futuresocio- economic assessment, analysis of planperformance indicators, and in determining when tomove to a more detailed management option.

Movement from one management option to anothercan be prompted by a number of triggers: Forexample:

PoorStreamflow

Record/Estimate

No Gauging StationCurrent Gauging Station

Stressed

Option 3aor 3b

Unstressed

ReliableStreamflow

Record/Estimate

Stressed

Unstressed

Option 3a or 3b

Option 1b,2b,3a,3bSee Note #1

Visible FlowCTP

See Note #2

High risk of growth

Low Risk of Growth

Suitable gauging

site

No suitable gauging

site

Option 1a

Selected Water Source or Management Zone

Option 3aor 3b

High risk of growth

Low Risk of Growth

No suitable gauging

site

Visible Flow CTP

See Note #2

Suitable gauging

site

Option 3a or 3b

Suitable gauging

site

No suitable gauging

site

Option 1b,2b,3a,3bSee Note #1

Visible FlowCTP

See Note #2

Suitable gauging

site

No suitable gauging

site

Visible Flow CTP

See Note #2

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A decision to move from option 1a to 1b may bebased on obtaining streamflow informationwhich indicates that the frequency ofexceedence of the CTP is unacceptable interms of either impact on the environment orextractive use.

A decision to move from 1b to 2a may beprompted by large amounts of trade movinginto the catchment or large amounts of unusedshare entitlement activating. This would createthe need formally establish the environmentalrights to water in terms of daily extractionlimits.

Movement from option 2a to 2b could be as aresult of daily extractions exceeding the dailyextraction limits set in 2a.

Movement from 2b to 3a could be prompted byusers desiring to know what their individualdaily extraction entitlement will be in order toprepare their businesses to operate under afull daily extraction regime. Alternatively itcould be prompted by the need to establish adaily extraction trading market.

Note: Option 2b and 3a are similar the onlydifference being that in option 3a users arenotified of their individual daily extractionentitlement for some or all classes.Management of daily flow access remainsidentical to that of option 2b.

Movement from either option 3a to 3b or forthat matter option 2b to 3b would be promptedby usage failing to remain within the dailyextraction limit. This would result the issuingof individual daily extraction entitlements forall classes and compliance to either individualentitlement or group registers.

Establishing management zones

Most unregulated river catchments have beendivided into subcatchments based on considerationof hydrology, location of gauging stations, andwater user associations. These subcatchmentsformed the basis for the 1998 Stressed RiversAssessment and have more recently defined thewater source areas of Water Sharing Plans.However in some cases these subcatchments arelarge and the flow characteristics across thesubcatchment are not sufficiently uniform to forma sensible basis for defining a common CTP or dailyextraction limits.

In such cases the water source or subcatchmentshould be further subdivided into managementzones and an appropriate management option and“end of system” streamflow reference siteselected for each zone.

The delineation of management zones should beguided by the following criteria:

flow travel times from the top reaches of thesubcatchment to the end-of-zone referencepoint should preferably not exceed 1 day

streamflow should be relatively homogenousacross the management zone – ie when a lowflow occurs at the end of system, low flowsshould also be occurring upstream. Preferablyflow should be homogeneous on at least 90% ofdays when flows are in the low to median flowrange

existing and/or potential stream gauging sitesshould be available at or close to the end ofthe designated management zone to ensure endof system targets are met

Upstream gauges with appropriate downstreamextraction rules to ensure end of system flowtargets can also be used in the absence of asuitable gauge near the end of the managementzone

the larger the number or volume of licensedentitlements within a zone the morehomogeneous the zone should be.

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Table 1 Flow Management Options for Unregulated Rivers

No Management Option Prerequisites for development andimplementation of Water Sharing Plan

Implications

1a Common cease andcommence to pumpthresholds only -based on fieldverification

• No reliable streamflow estimates(NB only qualitative assessment ofimpacts on flow/licence holders canbe made)

Implementation:• Staff gauge read daily• Daily announcements of access • Exception compliance against CTP

• May not protect basic domestic, stock, and native title rights • Protects very low flows• Theoretically does not protect low to moderate flows• Theoretically does not protect flow variability above the CTP• No consistent basis for water transfers• Investment and trading decisions based on limited information• Establishes very basic property rights, but not separate,

tradeable entities1b Common cease and

commence to pumpthresholds only -based on analysis ofhistoric flow data andfield verification

• Reliable streamflow estimatesImplementation:• Staff gauge read daily• Daily announcements of access• Exception compliance against CTP

• Can be set at a volume adequate to protect basic domestic, stock,and native title rights

• Protects very low flows• Theoretically does not protect low to moderate flows• Theoretically does not protect flow variability above the CTP• No consistent basis for water transfers• Investment and trading decisions based on limited information• Establishes very basic property rights, but not separate,

tradeable entities2a Daily extraction limits

set but notdistributed toindividuals as a dailyextractionentitlement.Compliance on CTPonly

• Reliable streamflow estimates• Estimated peak daily demandImplementation:• Staff gauge read daily• Daily announcements of access• Exception compliance against CTP

• Can be set at a volume adequate to protect basic domestic, stock,and native title rights

• Does not protect flow regime above CTP in practice• Provides a consistent basis for water transfers which protects

the environmental water• Formally establishes the environmental rights to water • Establishes very basic property rights, but not separate,

tradeable entities2b Daily extraction limits

set but notdistributed toindividuals as dailyextractionentitlement.Compliance on CTPplus daily extractionlimits

• Reliable streamflow estimates• Gauging station and/or suitable site• Estimated peak daily demandImplementation:• Operational gauging station read

daily• Daily announcements of access• Exception compliance against CTP

and group compliance with the dailyextraction volume

• Can be set at volume adequate to protect basic domestic, stock,and native title rights

• Can protect the flow regime in practice• Provides a consistent basis for water transfers which protects

the environmental water• Formally establishes the environmental rights to water• Establishes very basic property rights, but not separate,

tradeable entities• Relies on rostering during critical periods to keep use within daily

limits3a Partial implementation

of daily extractionmanagement. Dailyextraction limits setand distributed toindividuals as dailyextraction entitlementfor some or all flowclasses. Compliance onCTP and dailyextraction limits

• Reliable streamflow estimates• Gauging station and/or suitable site• Estimated peak daily demand

Implementation:• Daily announcements of access• Daily audit of metering data and

group compliance with the dailyextraction limit

• Exception reporting against CTP



the environmental water• Formally establishes the environmental rights to water• Better establishes a more exclusive property right, which is a

separate, tradeable entity• Assumes rostering during critical periods to keep use within daily

extraction limits

3b Full implementation ofdaily extractionmanagement. Dailyextraction limits setand distributed toindividuals as dailyextractionentitlements for allflow classes.Compliance atindividual levels

• Reliable streamflow estimates• Gauging station and/or suitable site• Estimated peak daily demandImplementation:• Operational gauging station read

daily• Daily announcements of access class• Individual audits of metering data

and compliance with the dailyextraction limit in accordance withthe group register

• Exception reporting against CTP



the environmental water• Formally establishes the environmental rights to water • Establishes a more exclusive property right, which is a separate,

tradeable entity• Allows for group registration & rostering

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The cease to pump and daily extraction limitsshould be calculated for each zone independentlybased on the selected “end of zone” reference site.The cumulative impact of the individual zoneextraction limits on the end of water source flowsshould also be assessed.

Establishing the CTP and daily extraction limitsbased on management zones will ensure that thetriggers for access better coincide with the actualflows passing the pumps, and therefore that theimpact assessed in their design also fairly reflectsthe future probability of access and environmentalflow outcomes. However, this also significantlyincreases establishment, implementation andmanagement costs.

The requirements for each management option areshown in Figure 3.

Government Role

The DLWC and other agencies will provide thecommittee with:

relevant flow data including examples of wet,average and dry years and long term statistics;

environmental considerations, includingthreatened species considerations;

assessment of the water requirements forbasic domestic and stock rights;

information on the number of licensed waterusers, current pumping conditions, the currentlevel of development and the water users totalannual share entitlement;

assessment of the appropriate flowmanagement options and management zones,including proposals for cease to pumps, flowclasses, and daily extraction limits whereappropriate;

assessments of the impacts of these optionson licensed water users.

The government agencies will also prepare draftplan provisions that reflect general requirementsand the Committee’s strategies andrecommendations.

On approval of the Water Sharing Plan, the DLWCwill prepare an implementation program. This willbe done in close consultation with the local wateruser community.

It is expected that the appropriate operationalarrangements will be phased in over a number ofyears.

The timetable for this, will be developed as part ofthe Implementation Program.

Figure 3: Steps Required To Implement Chosen Management Option

Option 1a

(no gauge & no streamflow

record)

Option 2b

(gauging station orsuitable site plus

reliable streamflowestimates)

Option 3a

(gauging station or suitable site plus

reliable streamflow estimates)

Option 2a

(no gauge but reliable streamflow

estimates)

Determine CTP from streamflow

record & field investigation

Verify newgauging site if

required

Install gauge& establish CTP level

Assess & determine dailyextraction limits from streamflow

record

Verify new gauging site

Verify new gauging site if

required

Licence notification

of CTP

Determine CTPfrom

field assessment

Option 1b

(no gaugebut reliable streamflow estimates)





Verify newgauging site if

required




record



of CTP


of CTP




Install gauge & establish CTP plus

classes

Option 3b

(gauging station or suitable site plus

reliable streamflow estimates)


record


of CTP & Daily ExtractionEntitlements for selected classes




record

Install gauge& establish

CTP plusclasses

Install gauge& establish

CTP plusclasses

Selected Management Zone


of CTP


of CTP & Daily ExtractionEntitlements for

all classes

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Committee Role

The Committee is to consider the agreed river flowobjectives for their water sources and provide amore detailed interpretation for their priority sub-catchment(s). These are to form the basis fordetermining the appropriate management optionsand associated management criteria.

The Committee is to then recommend, depending onthe management options selected and inconsideration of the social and economic costs, oneor more of the following:

very low flows to be protected (all managementoptions)

flow classes and daily extraction limits in eachdefined class (management options 2a,2b &3a,3b)

what part of those daily extraction limits areto be issued to licences as daily extractionentitlements initially (management options3a,3b)

the remaining unallocated daily extraction limitpart which may be allocated during the term ofthe plan (management options 2a,2b & 3a,3b).

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ATTACHMENT – ESTABLISHING CEASE TO PUMP FLOWLEVELS AND DAILY EXTRACTION LIMITS

Determining the Cease to PumpThe cease to pump (CTP) establishes the thresholdat which licensed pumping must stop. It thereforeprotects the very low flows, and the supply to basicright pumpers during dry periods. The CTPthreshold should address river flow objectives 1 &2, and include an explicit allowance for basicdomestic and stock rights.

The starting point for establishing the CTP is the95th percentile of the annual daily flow durationcurve (ie 95% of days of the year will have flowgreater than this threshold) or the flow thresholdthat protects the lowest 5% of days with flow inintermittent rivers. Until field verification takesplace, this should be used as a guide. In all cases,the CTP threshold will also be determined fromfield assessment of pool habitats, low flowconnectivity, etc.

For some rivers, the whole of the year 95th

percentile may be a relatively high volume andsetting the CTP at this level could have significantconsequences on irrigation or other commercialpurposes. For example, the whole of the year 95th

percentile could be higher than the 80th percentilecritical month flow and would therefore eliminateany A class flow access.

In any event, an assessment of pool habitats andlow flow connectivity must be conducted to verifythat the proposed flow limit is actually achievingthe required environmental objectives. Thisassessment could be based on expert and localopinion and include field validation.

In some cases different cease to pump andcommence to pump thresholds may be established.Setting the commence to pump threshold higherrecognises that the initial flow after a dry periodis more important to the replenishment andrecovery of the in-river environment than themaintenance of flows after a period of higherflows. Different cease to pump and commence topump thresholds can also help to prevent “flowhunting” ie turning access off and on too frequentlyif the flows hover around the threshold for anyextended period. Varying cease to pump andcommence to pump levels during different seasonsof the year has also been used as a management

option in some unregulated subcatchments. Forexample, where higher flow protection is requiredfor threatened species at certain times of the year(e.g. breeding/migration), while allowing lower verylow flow protection during other times of the year(e.g. peak irrigation demand period).

In determining a CTP it is critical that thestreamflow reference site used for the assessmentis the same as that which will be used as theoperational gauging site. Otherwise the impact on“end of system” environmental flows and on waterusers access will be different from that assessedfor the Water Sharing Plan.

Establishing daily flow extractionclasses River flow regimes can be characterised by thesize and duration of various flow levels. How oftena flow of a particular size is likely to occur is bestillustrated by a flow duration curve. A flowduration curve plots the volumes of flow(megalitres per day) against the percentage ofdays that such a flow will be equalled or exceeded.It should be noted that the flow duration curvesbased on historic flow data do not representnatural conditions because the data on which theyare based is, to varying extents, affected bychanges in land cover and water extraction inrecent years. Provided they are developed over aclimatically variable period, they should provide anapproximation of the flow probabilities that are anadequate basis for flow sharing (noting that thelonger the streamflow record the closer it is tonatural).

Figure A1 (see next page) is a sample flow durationcurve for a typical perennial unregulated river. Thecurve shows that for this particular river:

for most of the time, eg 80% of days, dailyflows exceed 50 ML/day - this is called the80th percentile flow (Low Flow)

for 50% of days, daily flows exceed 200ML/day - this is called the 50th percentileflow (Moderate Flow)

for 30% of days, daily flows exceed 470ML/day - this is called the 30th percentileflow (High Flow).

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This flow duration curve also illustrates how in aperennial river of this type, water extractiontypically has the most marked effect on themoderate to low flow regimes. During high flowperiods, water demands and therefore the volumepumped from a river, tend to be low.

This situation is typical for rivers that have someflow all of the time. However, in ephemeral orintermittent rivers that typically have no flow for asignificant percentage of days, the percentilethresholds that define high, moderate and lowflows may differ. Furthermore, water users maypump into off-river storages during high flowperiods to overcome the lack of supplies in drytimes

To simplify the determination and implementationof daily extraction limits, it is recommended thatflows above the CTP be divided into three classesas follows:

Class A - low flows - generally from CTP to 80th percentile.

Class B - low to moderate flows - generally 50th to 80th percentile.

Class C - moderate to high flows, freshes and floods - generally 0 to 50th percentile- may be subdivided if water demands are high.

In setting the flow range for the A, B and Cclasses, either the flow duration curve based on alldays of the year or that based on only the days ofthe month when demand most exceeds wateravailable (the critical month) may be used. While awhole year flow duration curve ranks the flows onall the days in the period of record, a particularmonth flow duration curve only ranks the flowsthat occurred during that particular month in theperiod of record.

In river systems where extraction is focussed on afew months and the flows are highly seasonal, acritical month curve is recommended as thisreflects the probability of flows occurring duringthe times of greatest competition for flow. Insystems where demands and flows are more evenlyspread across months then the annual curve may beused to determine the flow classes.

Figure A1FLOW DURATION CURVE FOR AN

UNREGULATED RIVER

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Flow classes are intended as a means to deliverriver flow objectives; in particular protection oflow flows and mimicking of natural flow variability,while keeping the day to day changes in usersaccess to a practical level. For each sub-catchment/management zone there will be a needto revise the class boundaries to take into accountlocal hydrology, identified conservation values,specific environmental requirements and practicalconsiderations. For example:

additional classes above the Class C could beestablished where there is a significantdemand during high flows;

A and B classes could be combined if thedifference in flow levels is not significant ormeasurable;

A or B classes may be omitted because theriver does not flow much of the time (ie 50thto 100th percentile flows are zero); and

the top of B class could be adjusted upbecause the 50th percentile flow correspondsto a critical level for watering a wetland

Determining daily extraction limitsThe first stage of the process for setting flowextraction volumes is to decide on the amount offlow in each class which can be sustainablyextracted without threatening river health orreducing the access to existing users belowreasonable levels. This amount of flow is called thedaily extraction limit. Water sharing plans willneed to specify a daily extraction limit for eachdefined flow class in each water management zone(or the whole water source where appropriate).

The daily extraction limit may be defined as aproportion of the upper limit in each flow class. Following are the recommended flow thresholds forthe generic flow classes.

Class Recommended Flow Threshold

A 80th percentile

B 50th percentile

C 30th percentile

For water sources or management zones that areidentified as high conservation value, the dailyextraction limits should be set at a level thatrestricts future increases in water extractions,and protects conservation values. For managementzones, which have no licences, daily extractionlimits may be set at zero.

Daily extraction limits should be set inconsideration of environmental sustainability andextractive demand. They should generally be in therange 0 to 30% of the flow threshold. Theexception is where demands are already very highin the flow class and the economic impact of asignificant reduction in access would be high, thevolumes may be set at up to a maximum of 60% ofthe threshold.

For other water sources or management zones, thestarting point for determining daily extractionlimits, whose current peak daily demand exceeds30% of the flow index, should be current peak dailydemand of the licences less 10%, up to a maximumof 60% of the flow sharing index.

Where the current peak daily demand is less than30% of the flow sharing index, and the watersource is not classed as high conservation value,the daily extraction limit may be increased to up to30% to allow for full development of existinglicences, transfers of licences into the sub-catchment, new (unembargoed) licence applications,or other considerations consistent with the WaterSharing Plan’s objectives and strategies.Committees are not encouraged to recommend aBEV beyond the 30% and to do so will require cleardemonstration of significant socio-economicbenefits and minimal impact on the health of thewater source.

The peak daily demand is the theoretical maximumamount of water needed on any day by licensedwater users to meet their production requirements.It assumes no restrictions on access, typicalwatering systems and good practice watermanagement. It should be calculated for currentand full development of licences.

Peak daily demand for irrigation is calculated usingthe seasonal and daily watering requirements ofthe crops in the sub-catchment taking account ofthe local climatic conditions. The total peak dailydemand for the river is this irrigation demand plusa daily allowance for other licensed purposes.

In calculating peak daily demand for C Class orhigher, an allowance may also be added for waterextraction into off-river storages. This will needto be determined on a case by case basis,depending on annual entitlement, total volume ofstorages and hydrological characteristics of theriver and the plan diversion limit.

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In assessing impacts it should be remembered thatoptions such as voluntary rostering or groupsregistrations and managing diversions to the totaldaily extraction limit, can help water users tominimise the impacts of reducing daily flow access.The government’s Water Reform StructuralAdjustment programs can also provide educationaland financial assistance to individual licenceholders. Also it could take up to 4 years to fullyimplement daily extraction limits, which gives timefor rostering and other adjustments to be made.

The guidelines discussed above have been based onthe findings of the 1998 Stressed RiversAssessment, which found that in the majority ofunregulated sub-catchments less than 30% of thelow flow index is currently extracted. Relativelyfew sub-catchments had extraction between 30-60% of low flow index. In the remaining sub-catchments, over 60% of the low flow index arecurrently extracted during the peak demandmonths. These sub-catchments are showingsignificant signs of environmental stress and wereclassified as hydrologically stressed systems. Thissuggests that extraction of more than 60% of lowflow is unsustainable.

On the other hand, in most stressed rivers, itwould not be possible to reduce extraction muchbelow 60% in low flows in the short term withoutserious socio-economic impacts.

In assessing the economic impact of proposed dailyextraction limits, the following should be used as aguide:

comparison of peak daily demand estimatesagainst any field usage data that is available toassess its appropriateness

comparison of current peak daily demand forcritical month and daily extraction volume. Ifthe extraction volume is significantly lowerthan the current demand then the economicimpact is likely to be significant

comparison of full development peak dailydemand for critical month and daily extractionlimits. If the daily extraction limit issignificantly lower than the full developmentdemand but more than the current demand,then the economic impact will only be felt asand when the inactive entitlements areprogressively developed. Care needs to betaken to ensure that this scenario is comparedto what would have happened under fulldevelopment without the daily extractionlimits.

Where available, any modelled assessment ofdays of i) nil pumping, ii) days when the amountpumped is less than the demand.

Distributing Daily Extraction Limitsto Individual LicencesThe lesser of the full development peak dailydemand or the daily extraction limit for each flowclass should be distributed to individual licences inproportion to their annual entitlement.

Where the full development peak daily demand oflicences is less than the daily extraction limit in aflow class, the remainder of the daily extractionlimit may be set aside as unallocated.

This situation will generally occur in unstressedsystems or in the higher flow classes of stressedsystems. The remaining undistributed extractionvolume is then defined as unallocated.

Unallocated daily flow volumesUnallocated daily flow volumes are available to beissued during the term of a plan but should only beissued in the following cases:1. where annual share entitlement is transferred

into the sub-catchment;2. to new licences which are issued under

embargo exemptions;3. to new licences issued if the sub-catchment is

not embargoed;4. to existing licence holders where the plan so

provides as part of a strategy to reduce lowflow stress or adjust to reduced low flowaccess.

Worked ExampleAs an example, we can consider how this could beapplied to a perennial river with a flow durationcurve shown in Figure A1.

The assessed very low flow is 10 ML/day. Thecalculated current peak daily demand is 80 ML/day.An additional 20 ML/day is used for pumping to offriver storages when opportunities arise. Fulldevelopment peak daily demand is an additional 15ML/day.

Based on the proposed method:Very low flows. A field assessment shows 7ML/day is required to maintain connectivitybetween pools in the river and provide for otherlow flow environmental requirements. An additional3ML/day is assessed as being needed to provide

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for basic water rights, giving a total of 10ML/dayto be protected before licensed pumping is allowed.

A Class. For low flow periods when flows arebetween 10 ML/d and 50 ML/d (80th percentile).Current peak daily demand less 10% is well inexcess of the maximum allowed daily extractionlimit of 60% of the 80th percentile flow (50 ML/d),or 30 ML/day. The daily extraction limit shouldtherefore be 30ML/day, all of which would beinitially allocated to licences.

B Class. When median flows occur, ie between 50ML/d (80th percentile) and 200 ML/d (50th

percentile).Current peak daily demand less 10% is 72ML/dwhich is between 60 ML/day (30% of the 50th

percentile flow of 200 ML/d) and 120 ML/d day(60% of the 50th percentile flow of 200 ML/d).The daily extraction limit should therefore be72ML/day, all of which would be allocated tolicences.

C Class. When moderate to high flows occur, ieabove 200 ML/d (50th percentile).Current peak daily demand (including the 20ML/daypumping to off river storages) less 10% is 90ML/dwhich is well below 144 ML/day (30% of the 30th

percentile flow of 480 ML/day). In this case, 144 ML/d could be determined as thedaily extraction limit to allow full peak dailydemand of 95 ML/d plus 20ML/d for those whopump to off river storage to be allocated tolicences, and 29 ML/d to remain unallocated fornew (embargo exempted) licence applications andsome growth in town water usage.

For an individual licence:A licence in this sub-catchment has an annual shareentitlement of 110ML (2%) out of a total of5,500ML of entitlement in the sub-catchment. Thelicence currently has full flow range access anddoes not pump into off river storage.

As a result of implementation of the plan thelicence would have the following conditions:

no pumping permitted when the river flow isless than 10ML/day;

pumping of up to 0.6 ML/day when the flow isin A class (daily flow share of 2% of theallocated daily extraction limit of 30 ML/day);

pumping of up to 1.4 ML/day when the flow is inB class (daily flow share of 2% of the allocateddaily extraction limit of 72 ML/day); and

pumping of up to 1.8 ML/day when the flow is inC class (daily flow share of 2% of the allocateddaily extraction limit of 95 ML/day).

It should be noted that these daily extractionlimits are not cumulative, eg when the river isflowing in the ‘B Class’ range then the licensee cantake up to 1.4 ML/day, not 2 ML/day (1.4 Bclass+0.6 A class).

The steps required to determine and implementdaily extraction rules will depend on themanagement option adopted, and whether a suitablegauging station and/or historic flow record isavailable. Figure 2 sets out the necessary steps,which should be followed to establish themanagement rules depending on which option isselected.

Other considerationsTown water suppliesUnder the Water Management Act, local waterutility licenses (for town water supply) havepriority when access to water is limited. Where alocal water utility has on-river storage dams,extraction of water from those dams is excludedfrom daily extraction management butrequirements for these dams to pass some inflowsmay be considered as a separate exercise.

Where a local water utility pumps from the river,essential town requirements will need to be metbefore the remaining daily extraction limit volumesare distributed to irrigation, industrial and otheraccess license users. The local water utility licencemay also have a different cease to pump level togeneral licences.

Where a local water utility has recently augmentedits supply infrastructure and adopted morestringent extraction conditions, these will need tobe reflected in the sharing formula.

Where a committee is considering proposingalterations to a local water utility’s daily flowaccess or on-river dam release rules to provide foressential environmental or conservation values,there will need to be careful consideration of theimpacts on town water supply. The DLWC willconsult with the utility on a range of accessarrangements together with options for the utilityto provide for its needs in alternative ways. Thisconsultation will also identify the ability of theutility to manage proposed changes, and how longsuch changes would take. This assessment shouldthen be reflected in any recommendations made bythe committee.

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Licensed damsLicences which extract from farm or other dams on1st and 2nd order non-permanent watercourses areexcluded from daily extraction management; willnot be issued with daily extraction entitlement andwill not be subject to pumping restrictions based onriver gauge levels. This is because flow durations ongullies and minor rivers is so different to riversthat applying the same rules would not be sensible.Daily extraction management is also inapplicable tolicences for dams not associated with licensedextractive use (eg passive recreation dams,instream dams only used for basic rights).

Extractive licences associated with all otherinstream dams should be issued with dailyextraction entitlements in all classes, and should beincluded in assessment of peak daily demand. Forthese licenses the Water Sharing Plan should statethat, despite daily flow class pumping limits,pumping from these dams is not restricted at anytime when:1. there is no inflow to the dam, or 2. all inflows to the dam are being passed or at

least up to the A class equivalent at that point.

Special cease to pump conditionsIf there is a small part of the sub-catchmentwhere the cease to pump level on the operationalgauge does not provide for adequate protection ofcritical low flows locally, a supplementary localcease to pump condition may be considered.

Highly interactive surface and groundwaterIn some cases extraction from groundwater near ariver is effectively the same as extracting fromthe river. In these cases it is appropriate to linkmanagement of these particular groundwaterlicences to the management of the river to ensuremaintenance of critical river flows.

Strategies to reduce stressWhere extraction is greater than 30% of flow in aclass (or less in a high conservation value sub-catchment) a plan could provide for strategies toreduce extraction. Such strategies could includesuch things as:

not allowing transfers into the sub-catchment staged contraction of daily extraction limits

during the period of the plan;

allowing licence holders affected by reducedlow flow access to apply for unallocated C classdaily extraction volume;

providing for licence holders to ‘hand in’ Aclass daily extraction entitlement in return fordaily extraction entitlement of greatermagnitude in C class.

Any such strategies should consider carefully theimpacts on licence holders and trading markets andwhat rate of exchange is appropriate (in terms ofthe incentive they represent). They may alsoconsider how the existing government WaterReform Structural Adjustment programsadministered by the Department of Agriculturecould be linked in.

Strategies involving issue of greater annual shareentitlements in return for retirement of low flowaccess are not an option in the Murray-DarlingBasin. Water sharing plans for coastal sub-catchments may include such strategies where theimpact on downstream sub-catchments andestuaries is clearly understood. Where this is notthe case the plan may provide for these strategiesto be added during the term of the plan once thenecessary assessment is completed.

No. 6 Daily extraction management .in unregulated rivers (2002 … · 2015-03-06 · important for...

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