environmental flows and water quality objectives for the river murray

Australian Journal of Water Resources Vol 5 No.1

61

Determining environmental flow needs and scenariosfor the River Murray System, Australia *

Christopher J GippelFluvial Systems Pty Ltd

PO Box 49 Stockton NSW 2295

Trevor Jacobs and Tony McLeodMurray-Darling Basin CommissionGPO Box 409 Canberra ACT 2601

SUMMARY: The River Murray is a “working river” in the sense that its regulation andmanagement delivers significant economic wealth and social benefits to local communities andwider Australia. Recognition of ongoing deterioration of the riverine environment has promptedseveral environmental flow initiatives, including establishment in 1999 of the “EnvironmentalFlows and Water Quality Objectives for the River Murray Project” (the Project). This paperreports progress on the main aspects of the Project to date.

A review of the impacts of flow regulation on the health of the River Murray revealed evidence fordecline, but in many instances the case for flow regulation as the sole or main cause is circumstantialor uncertain. A Basin-wide snapshot study of stream condition found evidence for extensivedegradation, with disturbance to the catchment and changes to nutrient and suspended sedimentloads being the greatest contributors. It is apparent that the rivers and streams of the Basin arebeset by multiple impacts, with flow regulation being the main problem in the River MurraySystem. The Project addresses this recognised main cause of degradation in the River MurraySystem. A profiling survey demonstrated that whilst there was unequivocal support for the principleof an environmental allocation, stakeholders were not supportive of a process that excluded themfrom involvement in decision making. Thus, establishment of an inclusive project organisationalstructure has proved to be critical, and will continue to be critical, to obtaining information andsupport across different States, and from a range of stakeholder groups.

Environmental flow needs of the River Murray were based upon the findings of two earlier ScientificPanel studies. Another Expert Reference Panel, established specifically for the Project, adopted arisked-based approach to assessment of environmental flow options. Environmental flows can bedelivered by making more water available, by altering the distribution of flows (operational changes)or by altering flow regulating structures (structural changes), or through some combination ofthese. Flow scenarios under development for consideration by the Ministerial Council in 2002are being devised on this basis. It is recognised that recovering water from existing water userswould likely involve significant social, economic, political and practical challenges. Ongoingwork to investigate and resolve these aspects of the Project is being undertaken with the samelevel of rigour as applied to the development of flow scenarios. Although the Project is in a relativelyearly stage of development, for the first time, an overall sense of the scale of what is required toachieve significant environmental outcomes in Australia’s largest and most high profile riversystem has been realised.

* Paper first presented at the seminar on environmental flows - theory, practice & management,Melbourne 2001.


62 “Determining environmental flow needs” - Gippel, Jacobs & McLeod

1 INTRODUCTION

1.1 Management of the River Murray System

The River Murray is a large river with a catchmentarea of around one million square kilometres (figure1). The River Murray (2,530 km) and its two maintributaries, the Darling (2,740 km) andMurrumbidgee (1,690 km) Rivers are Australia’sthree longest rivers. The Goulburn River (563 km),which is the largest Victorian tributary, is also animportant river. The catchment of the River MurraySystem includes one Territory and parts of fourStates.1,2 The Murray-Darling Basin (the Basin) isAustralia’s most important agricultural region,accounting for just over 41% of the nation’s grossvalue of agricultural production. While most of theBasin is devoted to pastoral and dryland farming,there are many areas where irrigation dominates thelandscape, the economy, and the society.2 The RiverMurray is thus a “working river”, in the sense thatits regulation and management delivers significanteconomic wealth and social benefits to localcommunities and wider Australia.

Development of irrigation was made possiblethrough large-scale river regulation works. Themean annual runoff in the Basin is around24,000 GL/year and the mean annual total diversionis around half this amount, of which a mean ofaround 4,100 GL/year is diverted directly from theRiver Murray System. Over 90% of the divertedwater is used for irrigation.2 The mean flow to thesea under natural conditions was around12,900 GL/year (i.e. only about 50% of runoffreached the sea), and under regulated conditions itwas 5,200 GL/year (40% of natural).3 Diversions donot match the reduction in flow to the sea, as acomponent of the water that is diverted would nothave reached the sea under natural conditions.Regulation reduces the median annual flow to thesea from the Murray Mouth to around 26% of thatunder natural conditions (figure 1, table 1).3 Thereduction in mean annual discharge is less than thereduction calculated using the median annualdischarge, because the mean is strongly influencedby large discharges in the very wet years. The RiverMurray and its catchment have a long history ofexploitation and modification, with flow regulationand increased salinity commonly recognised as thetwo main factors that have impacted (and continueto impact) negatively on the health of the Basin’saquatic ecosystems.4,5

The Murray-Darling Basin Initiative (the Initiative)is the partnership between governments and thecommunity which was established to give effect tothe 1992 Murray-Darling Basin Agreement (theAgreement).6 The purpose of the Agreement (Clause1) is “to promote and co-ordinate effective planning

and management for the equitable, efficient andsustainable use of the water, land and otherenvironmental resources of the Murray-DarlingBasin”. The Murray-Darling Basin MinisterialCouncil (the Ministerial Council) is the primarybody responsible for providing the policy anddirection needed to implement the Initiative.6 TheMinisterial Council comprises the Ministersresponsible for land, water and environmentalresources within the contracting governments. TheMinisterial Council has the power to make decisionsfor the Basin as a whole.

The Murray-Darling Basin Commission (theCommission) is the executive arm of the Murray-Darling Basin Ministerial Council.6 TheCommission’s role is to responsibly and efficientlymanaging the main course, effluents andanabranches of the River Murray downstream ofHume Dam, tributaries upstream of Hume Dam,the Darling River downstream of Menindee Lakesstorage, Commission river structures, and theMenindee Lakes storage (leased from N.S.W.) (theRiver Murray System) (figure 2). River MurrayWater is an internal business division of theCommission for the specific purpose of operatingand managing the River Murray System.6 As wellas providing advice to the Ministerial Council onmatters related to the use of the water, land andother environmental resources of the Murray-Darling Basin, the Commission is also responsiblefor implementing any policy or decision of theMinisterial Council. The Commission is anautonomous organisation, equally responsible to thegovernments represented on the Ministerial Councilas well as to the Council itself. It is neither agovernment department nor a statutory body of anyindividual government.6

1.2 Management Response to River Flow Issues

The early 1990s saw the Commission formally adoptwater quality and flow policies with the objectiveof protecting and enhancing the riverineenvironment. The Audit of Water Use followed in1995, culminating in the decision of the MinisterialCouncil to implement an interim cap on newdiversions for consumptive use (the Cap) in a bidto halt declining river health.7 The State watermanagement agencies address their own waterallocation and environmental water needs, but theyrecognise the sharing arrangement required to gainmaximum benefit for River Murray environments.The Ministerial Council decided in 1993 to allocate100 GL to water the Barmah-Millewa Forest (theBarmah Forest is Ramsar listed) (figure 2) as a singleentity.8 In 1996 more specific environmental flowmanagement opportunities for the Murray wereinvestigated by the establishment of two ScientificPanels 9,10 which commenced the investigation of

Australian Journal of Water Resources

“Determining environmental flow needs” - Gippel, Jacobs & McLeod 63

Vol 5 No.1

Figure 1: River Murray catchment, showing distribution of, and impact of regulation on, median an-nual discharge for River Murray and major tributaries.

changes in river operations that would improve theenvironment while considering the current needsof existing water users. During 1997 to 1999, theCommission also undertook a review of theoperation of Hume and Dartmouth Dams anddeveloped a number of operational changes to betteraddress the competing objectives of water supply,environmental enhancement and flood mitigation.11

The need to balance competing demands for waterthrough a single integrated approach to managingflows in the River Murray System was recognisedby the Commission in 1999 with the establishmentof the “Environmental Flows and Water QualityObjectives for the River Murray Project” (theProject). In association with the Project, RiverMurray Water has recently utilised the growingecological knowledge of the river byopportunistically managing some aspects of river

flow during natural high flow events to provideenvironmental benefits.

Determining objectives for water quality andenvironmental flows for such a large and complexriver system is not a trivial task. It requires asystematic and detailed process that draws outobjectives that are feasible, appropriate, have thesupport of the scientific, management andstakeholder communities, and which carryacceptable levels of risk. This paper reports progresson five key aspects of the Project:

(i) determining the current state of river conditionin the Basin and establishing clear evidence forregulation impacts in the River Murray System;

(ii) establishing an appropriate technical, advisoryand administrative organisational structure;

(iii) profiling stakeholders;

SYDNEY

MELBOURNE

N S W

S A

QLD

0 200 km

BRISBANE

A U S T R A L I A

V I C

Murray DarlingBasin

Murray

River

CANBERRA

M ur r umbi d g e eR

R. Murrayoutflow

AlburyYarrawonga

Current as percentageof naturalLost as percentageof natural

Excess as percentageof natural

Flow to SAUpper Darling

Murrumbidgee R.

Snowy outflow

Goulburn R.

OvensR.

Natural median annual discharge

10 00050002000500

Changes in median annual discharge

ACT

GL / year

River

Kiewa R.

Da

rlin

g

Snowy below Jindabyne



(iv) assessing environmental flow needs, and;(v) developing flow scenarios for consideration by

management.

2 CURRENT HEALTH OF THE RIVERMURRAY SYSTEM AND STREAMS IN THEBASIN

2.1 Evidence for Environmental Decline due toRegulation

One major problem faced in determining impactsof regulation on the River Murray is the difficultyin isolating changes in the aquatic environment thatare due to flow regulation from those that are dueto other factors such as changes in catchment landuse, fishing pressure, introduced species, riparianvegetation disturbance, large woody debrisremoval, and natural variations in flow regime.Another major problem in determining theenvironmental impacts of regulation is thatregulation of the River Murray occurredprogressively over a long period of time, as waterresources were developed to meet demands. Whileavailability of data allows for detailedcharacterisation of changes in the river’s hydrology,this is not the case for the ecological consequences

of these changes. This is partly because collectionof suitable data did not begin until the regulatedflow regime was well established, but also becauseecological responses are complex, often delayed, andcan manifest in a location that is distant from thesite of the hydrological disturbance.A review of the impacts of flow regulation on thehealth of the River Murray System 12 (summarisedbelow) revealed evidence for decline, but in manyinstances the case for flow regulation as the sole ormain cause is circumstantial or uncertain.Catchment and river diversions have reduced themean annual flow in the lower River Murray (belowEuston) to half the natural levels, or less.4,13 Thepercentage of runoff diverted from the majortributaries varies across the Basin, with several beinghighly committed (figure 1, table 1). The RiverMurray at Albury has more flow than natural dueto inter-basin transfers from the Snowy River.Median annual discharge (table 1) is a bettermeasure of central tendency because the mean isstrongly influenced by large but infrequent floods.

Inflows from the Darling River do not improve thesituation because this river is also highly regulated(figure 1, table 1). Regulation has generally reducedflow variability.4,9 Variation of flow through the yearis reduced through the release of relatively constant

Figure 2: The River Murray System, showing major regulating structures and river management zones.



Vol 5 No.1

flow volumes during the periods of waterharvesting (relatively constant low flows arereleased) and irrigation water supply (relativelyconstant channel capacity flows are released).9 Weirsare managed to maintain the water level at a fairlyconstant level for long periods, and this furtherreduces natural flow variability.9,14 The frequenciesof peak flows with recurrence intervals of 20 yearsor more did not change appreciably withregulation.4 The major hydrological impact of theconstruction of storages has been to reduce thefrequency of occurrence and duration of mid-rangeflows, or minor-medium floods.9 The River Murrayflows through a semi-arid environment, so it is notsurprising that prior to regulation, during times ofextreme drought, it was reduced to a chain of salineponds. Under regulated conditions, there is alwayssome flow in the river. Near the Murray Mouth,prior to regulation there was little or no flow forless than 5% of the time, but this has now increasedto around 20% of the time.4

Dartmouth and Hume Dams (figure 2) have had aprofound impact on the ecology of the river, through

release of cold water, reduction in flood frequencyand duration, seasonal flow reversal, and acceler-ated bank erosion due to extended periods of regu-lated flow at channel capacity, and altered bed lev-els9,15 Primary production, native fish andmacroinvertebrate populations have been adverselyaffected by the altered flow regime and associatedchanges in water quality.9,16,17,18,19 However, closer toYarrawonga (figure 2), fish populations are in goodcondition, probably due to the positive influence ofthe Ovens River and Lake Mulwala (the impound-ment of Yarrawonga Weir).9

Downstream of Yarrawonga, regulation has reducedthe frequency of flooding of Barmah-Millewa Forest(figure 2), but this area also suffers from unseasonal(rain rejection) flooding during the irrigationseason.9 These changes have significantly altered thequality of habitats and the distribution of vegetationtypes in the Forest.20,21,22 The river in this area isdominated by alien fish species such as carp, whichappear to be using unseasonally flooded wetlandsfor breeding.9 Despite this, the River Murraybetween Lake Mulwala and Barmah Choke (at the

Table 1Comparison of Natural and Benchmark (current) median annual flows for selected locations on the River

Murray and for major tributaries (at end of system), including the Snowy River, from which water istransferred to the River Murray System. (source: MDBC monthly simulation model).

Location

(listed upstream to downstream)

Natural

Median (GL/yr)

Benchmark (current)

Median (GL/yr)

Current as percentage of

natural

Murray @ Albury 4,324 4,832 112%

Kiewa 566 560 99%

Ovens 1,399 1,395 100%

Murray @ Yarrawonga 5,590 3,904 70%

Goulburn 3,208 1,035 32%

Broken 90 159 176%

Campaspe 242 77 32%

Loddon 188 50 27%

Murrumbidgee 2,454 764 31%

Upper Darling 1,780 1,164 65%

Murray @ S.A. border 12,385 4,827 39%

Murray @ mouth 11,084 2,857 26%

Snowy @ below Jindabyne 1,104 9 1%

Snowy @ mouth 1,960 1,160 59%



downstream end of the Barmah-Millewa Forest)contains excellent native fish populations, includingthe only remaining truly natural population of theendangered trout cod.9 Macroinvertebratecommunities appear to be adversely affected byunseasonally high summer and autumn flows.9

From Torrumbarry Weir to the Darling Riverjunction at Lock 10 (figure 2) there appears to be anaccelerated loss of in-channel benches due toprolonged regulated flows and rapid falls in waterlevel, although de-snagging is also implicated.9

Between 1927 and 1981, the river aggraded up to 3m in some locations along this zone, with the meanbeing around 1.5-2.0 m.15 There is an unequivocalincrease in turbidity between Torrumbarry andEuston Weir pool (figure 2), followed by a decreasein turbidity at Euston and a further decrease to theDarling River junction at Lock 10. This is probablypartly due to the regional geomorphic change (fromRiverine Plain to Mallee tract), but reduced velocitiesin the weir pool, and saline inflows may also beinvolved.23 Wetland and floodplain habitats havebeen adversely impacted by reduced frequency ofinundation, while the artificial elevation of waterlevels upstream of weirs has led to the permanentinundation of some wetlands, reducing theirproductivity.9 The diversity and abundance of mostaquatic biota (fish and macroinvertebrates) iscomparatively poor immediately belowTorrumbarry Weir, but improves significantlyfurther downstream.9 Weirs create severerestrictions on faunal movement, which leads topopulation discontinuities.9

From the Darling River junction to Wellington(figure 2), prior to regulation, the bed sedimentswere predominantly coarse sand, while now theyare comprised mainly of fine silts and clays. Thechannel is developing a stepped gradient associatedwith the weirs.24 Due to the operation of LakeVictoria (figure 2), the length of the period of highlyturbid Darling River water impacting significantlyon the turbidity of the River Murray has historicallybeen extended from two months to approximatelyseven months.25 The flow level currently used tosupply the minimum entitlement flow to SouthAustralia is thought to be conducive to developmentof algal blooms.26 Although there are few historicaldata, a decline in the populations of many nativefish, including Murray cod, trout cod, golden perchand river blackfish has been reported underregulated flow conditions.24 Regional extinctions arewell advanced for five native species in the lowerMurray, and another two are threatened.27 Nativefish represent only about 5% of the total fishbiomass.14

The Murray Barrages near the Murray Mouth(figure 2) comprise five low head weirs and earthen

causeways linking the islands that once formed aprevious shoreline. The Barrages block 7.6 km ofpreviously open channels, and prevent ingress ofwater to Lake Alexandrina.10,28 There is now anabrupt interface between the fluvial and tidalreaches, reducing the size of the estuarinecomponent to 11% of its pre-Barrage scale.Increasing frequency and duration of periods of verylow flow have contributed greatly to sedimentationat the Mouth and nearby channels.10,28 Althoughalgal blooms did occur before regulation, there isgeneral consensus that the incidence ofcyanobacterial blooms in the Lower Lakes hasincreased with time.10 The management of thesaline-freshwater interface over a very narrow rangehas effectively removed the habitats that representthe transition from saline to freshwater. As aconsequence, flora adapted to this transition zoneis poorly represented.10 The numbers of almost allspecies of waders and waterbirds using thewetlands of the Coorong and Lower Lakes havedeclined, particularly over the past 20 years. Theconfusion of ecological signals resulting fromhydrological and geomorphic changes interfereswith breeding/recruitment of fish andmacroinvertebrates.10

The relatively constant flow levels and unseasonalflows have resulted in an apparent lack ofmacrophytes in the lower Darling River.9 Thereduced frequency of flooding has detrimentallyimpacted the health of riparian and floodplainvegetation, and reduced the input of organic matterto the river.9 The northern sections of the GreatAnabranch (figure 2) appear to have reducedflooding frequency due to upstream diversions andthe operation of the Menindee Lakes Scheme.9 Whilethe fish assemblages in the lower Darling River arehealthy, fish movement, recruitment andrecolonisation are adversely affected by a numberof barriers, relatively constant flow levels, andreduced access to floodplain habitat. Unlike theRiver Murray, the Darling River has apredominantly native fish fauna.29

Macroinvertebrate communities in the lowerDarling River do not appear to have been impactedby regulation.9

The River Murray System has a highly diverse rangeof aquatic environments. The extensive system ofregulation of the river has impacted the hydrologyin different ways in different zones of the river(figure 2), and consequently the environmentalimpacts have been complex and spatially variable.It is important to recognise that the River MurraySystem, although degraded, retains environmentalvalues worthy of conservation and rehabilitation.12



Vol 5 No.1

this, it is clear from these studies that the rivers andstreams of the Basin are beset by multiple impacts,with flow regulation being the main problem in theRiver Murray System.

3 PROJECT ORGANISATIONALSTRUCTURE AND OBJECTIVES

The Commission’s Project Board, comprisingCommissioners and Deputy Commissioners, hasoverall responsibility for the completion of theProject. The Board is supported by a JurisdictionalReference Panel (JRP), a Community ReferencePanel (CRP), an Expert Reference Panel (ERP) ofinternationally recognised experts in the field; anda core MDBC project team that supports the abovegroups and coordinates the development of flowscenarios (figure 3).

The ultimate objective of the Project is to preparefor the Ministerial Council a Management Plan forfuture operation of the River Murray System. ThePlan will describe actions aimed at achievement ofa sustainable river environment and water quality,in accordance with community needs. The Plan willinclude an adaptive approach to management andoperation of the River.31 Two important secondaryproducts of the Project are environmental flowobjectives and water quality objectives to provide thebasis for ongoing review and modification tomanagement of the River Murray System, andimplementable flow scenarios for providing flows andwater quality which enhance the River Murrayriverine environment through achievement ofenvironmentally beneficial outcomes. The waterquality component is not the subject of this paper.

A vision and a number of high level objectivesdeveloped by the Community Reference Panel wereadopted by the Ministerial Council in March 2001.The vision was developed with the intent ofbringing communities together and bridgingcultural, economic, social and institutionaldifferences to enable cooperative progress towardsthe aim of achieving “… a healthy River MurraySystem, sustaining communities and preservingunique values”.

4 STAKEHOLDER PROFILE

A stakeholder profiling survey 32 (summarisedbelow) was undertaken to identify the range andgeographic spread of stakeholders, their prevailingattitudes and diversity of views on matters relevantto addressing environmental health of the RiverMurray. A telephone questionnaire wasadministered to a sample of more than 300stakeholders, identified by the CRP, through ascoping study, and a search of community

2.2 Snapshot of River Condition in theMurray-Darling Basin

A recent snapshot assessment of river condition 30

(summarised below) evaluated the aggregateimpacts of resource use on rivers in the Murray-Darling Basin (figure 1), and identified the prioritymanagement challenges for their maintenance orimprovement. Across the Basin, 40% of the riverlength assessed had biota that were significantlyimpaired. Ten percent of assessed river length wasfound to be severely impaired with respect to biota,having lost at least 50% of the types of aquaticinvertebrates expected to occur there. Over 95% ofthe river length assessed had an environmentalcondition that is degraded, and 30% wassubstantially modified from the original condition.Disturbance to the catchment and changes tonutrient and suspended sediment loads are thegreatest contributors to this index of degradation.Over half the reaches assessed had modifiedhydrology, with the greatest changes being apparentimmediately downstream of dams and in lowlandreaches used for irrigation supply.

An analysis that grouped river reaches with similarcharacteristics found that many reaches arethreatened by multiple stresses, principally land usechanges, damaged riparian vegetation, poor waterquality, increased bedload, and modified hydrology.The reaches most affected by this complexity ofissues are concentrated in the mid- and lower-slopesof the Basin. Habitat condition is degraded in muchof the Basin. Loss of riparian vegetation andincreased sand and gravel bedload are the twoprincipal factors causing degradation. Increases innutrient and suspended sediment loads arewidespread in the Basin. Most of the loads aregenerated in the upland and mid-slope areas of theBasin. However, most of the impact is felt in lowlandrivers, weir pools, and reservoirs where thesediment is stored.A more detailed assessment of the River Murray andlower Darling River found that overall biologicaland environmental condition is degradedthroughout, with an increasing trend in degradationtowards the river Mouth. Although the degradedcondition of the River Murray System appears tobe the consequence of multiple impacts, the mainimpacts were thought to be related to the operationof dams and weirs. Unseasonal flooding ofwetlands, loss of connection with the floodplain,habitat simplification, water quality and bankerosion were defined as significant issues.

The value of both the Basin-wide river conditionsnapshot study 30 and the review of regulationimpacts on the River Murray System 12 wasconstrained by the paucity of data for some keybiological and environmental components. Despite



directories, the internet and telephone directories.Stakeholders were from within and outside theRiver Murray region, across three States, andrepresented six main stakeholder groups.

The survey demonstrated a high level of concernfor the current state of the river, and awareness thatit would take many years to improve the situation.There was unequivocal support among stakeholdersfor the principle of an environmental allocation forthe River Murray. However the support droppedfrom 95% to less than 40% if all water users,interested people, and local people were notinvolved in the decision making process.

Stakeholders were asked to respond to twenty-sixgeneral philosophical statements on water allocationusing a five-point agree/disagree scale. There wasa high level of agreement or disagreement (>80%

agreed or disagreed) on eight of the statements, andthere was a general agreement or disagreement(60%-80% agreed or disagreed) on nine of thestatements. There was a high level of agreement thatthe natural environment and people should haveequal rights to water, that personal sacrifices wouldbe needed for effective planning, that water hasvalues other than economic values, that watershould be managed for public good, upstream usersshould consider the needs of downstream users, allsections of the community have the right toparticipate in water allocation decisions, andimmediate action was required. Respondentsgenerally disagreed with the ideas of putting wateron the market and selling it for the highest priceregardless of the intended use of the water;allocations being set by experts alone; putting theenvironment’s need for water secondary to people’sneeds; and going along with what most other people

Figure 3: Organisational structure for the Environmental Flows and Water Quality Objectives for theRiver Murray Project.

CRP



Vol 5 No.1

think about water allocation. There were ninephilosophical statements about which there was asplit opinion. These are examples of the issues wherethe greatest disagreement is likely to arise whendiscussing water allocation. These differences tendto be associated with arguments of economics, priorrights, and priority preferences betweenenvironmental and human uses of water.

A cluster analysis of the responses to the twenty-sixstatements produced a two-cluster solution.Discriminant analysis then isolated four statementsthat correctly classified 95% of the cases to theclusters. The nature of these statements was suchthat, in terms of lay philosophies on water allocation,two philosophically opposed clusters ofrespondents were defined. These clusters weredescribed as “Private Good” and “Public Good”,with Private Good people favouring the productiveand consumptive value of water more than thePublic Good people, who placed more emphasis onthe intrinsic environmental values provided bywater.32 While these two groups were equal in size,the relative proportions of these two groups in eachof the stakeholder groups varied as expected.Agriculture (65%), tourism/recreation (64%) andlocal government (57%) groups were more orientedto Private Good, while environmentalists (63%) andState government (61%) were more oriented toPublic Good. The urban group was evenly split.

It is important to note that members of the twophilosophical stance clusters were not polarised atopposite ends of the spectrum, and this is borne outby the high level of general agreement betweenstakeholder groups on many issues. Given twelvenominated uses for water from the river, allstakeholder groups ranked river health as thehighest priority, above human life support (urbansupply, irrigation and stock and domestic use),industry and recreation.

Very few respondents (7%) indicated no interest inthe river, although significantly more from outsidethe region (19%) felt this way. Significant differencesbetween states suggested localised interest indifferent zones of the river. Thirty-four percent ofrespondents were interested in only one zone of theriver, and 23% were interested in two zones. Only16% of respondents were interested in all eight zonesof the River Murray System (figure 2). This suggeststhat a whole-of-river approach to environmentalflow management may be difficult to achieve, witha focus on defined regional zones being moreappropriate.

5 ASSESSMENT OF ENVIRONMENTALFLOW NEEDS FOR THE RIVER MURRAYSYSTEM

Given the limited and uneven distribution of waterresources in Australia, governments and theresearch community have been particularly activein the area of research and development ofenvironmental flows.33 There are many techniquesand methods being applied to the problem ofenvironmental flow assessment, and their suitabilityfor Australian rivers has been reviewed in detailelsewhere.34 Most cases of environmental flowevaluation are concerned with a relatively simplesituation involving a single dam, single stretch ofriver, or particular species of interest. The size andcomplexity of the River Murray System excludedthe possibility of uniformly applying a particularenvironmental flow assessment technique across theentire river system. Rather a flexible, broad-scale,expert panel approach that examined the issuesassociated with defined regional river managementzones (figure 2) was adopted. Given thehydrological complexity of the system, modellingof flow behaviour using the Commission’s MonthlySimulation Model was essential for development ofenvironmental flow scenarios. This process wasconducted over a number of years.

The most recent review of scientific knowledge ofthe interactions between riverine ecology and flowregimes in the Murray-Darling Basin18 attempted todevelop a comprehensive conceptual model of riverfunction for the major rivers of the Basin. Theseprinciples allow qualitative prediction of the impactof regulation across the full range of situations thatoccur in the River Murray. This model is animportant tool, because some ecological andgeomorphic responses are slow, variable orotherwise difficult or expensive to measure directly.

Two important Scientific Panel investigations havebeen undertaken on the main stem of the RiverMurray: a report on the River Murray fromDartmouth Dam to Wellington, including the LowerDarling River (downstream of Menindee Lakes) 9 ,and a report on the Lower Lakes below Wellington,including the Coorong estuary.10 The methodologyemployed by these Scientific Panel studies was tocollectively pool available data and theoreticalknowledge, inspect a range of sites, glean localinformation, form judgements through workshopinteraction, conduct necessary flow modelling, andthen make recommendations for priority actions.

In January 2001 these Scientific Panels werereconvened to consider, evaluate and comment on,in a workshop format, nine flow managementscenarios that were derived from recommendationsof the original Scientific Panels.35 The deliberations



were guided by pre-determined ecologicalprinciples and by priorities for each river zoneconsidered, and performance of the flow scenarioswas evaluated against targets set for variousdesirable hydrological characteristics. Theperformance of the nine flow scenarios wasgenerally adequate. All except one met, or partlymet, their stated target. However, performance ofthe flow scenarios was less impressive when non-target effects were considered. Flow scenarios withtargets in the lower river rated poorly overallbecause of negative environmental effects upstreamof their target. Delivering flows in a highly regulatedsystem can lead to increasing levels of regulation,thus negating the effects that environmental flowsare seeking to achieve. There is a paradox in thatrelatively small-scale environmental flows targetingone part of a river system can have negativeenvironmental effects in another. Of the flowscenarios considered, only one, Cap reduction, hada modelled positive effect in all parts of the main-stem River Murray. Its success was attributed thecombination of increases in discharge, and reducedlevel of diversions. The success of this flow scenariois also related to appropriately managing the waterretrieved in a manner that reaches environmentalthresholds.

In September 2001, the Expert Reference Panelappointed to advise the Project provided anunpublished independent report35 onenvironmental flow needs for the River MurraySystem. Evidence suggests that during the 1960s or1970s, the ecological condition of the River Murrayhad deteriorated to a point where it could no longerbe considered healthy (i.e. possessing ecologicalintegrity as conventionally understood in thescientific literature).35 Taking a system levelapproach, the study 35 focussed on five eco-hydrological attributes: flow volume, flowdistribution, flow variability, connectivity, and waterquality. Using a risk-based assessment approach, thePanel determined the probability of achieving ahealthy river according to the degree that keyhydrological indicators returned towards theirnatural level (based on system modelling). Theachievement of river health through environmentalflow management requires that non-flow relatedproblems that limit the growth and survival ofnative plants and animals are also corrected (e.g.suitable habitat and water quality are available).

6 DEVELOPMENT OF FLOW SCENARIOSFOR CONSIDERATION BYMANAGEMENT

The development of flow scenarios was framedagainst the objectives adopted by the MinisterialCouncil in March 2001 (formed on the basis of

scientific and community input to that date). Thekey objectives were to reinstate ecologicallysignificant elements of the natural flow regime, keepthe Murray Mouth open to maintain navigation andfish passage and to enhance estuarine conditions inthe Coorong, and significantly improve connectivitybetween and within riverine, wetland, floodplainand estuarine environments. All flow scenariosconsidered involved some alteration to the currentflow regime. There are other ways of achieving someenvironmental outcomes that do not involvemodification of the flow regime. Providing for fishpassage through regulating structures in the riversystem, and mitigating the impact of cold waterreleases from large dams on river watertemperature, to which the Ministerial Council hasalready agreed, are examples of this approach.

A structural and operational review was undertakenof river infrastructure including major dams, locksand weirs of the River Murray System.36 Theobjectives of this investigation were to determinepossible actions for enhancing the ecology of theriverine environment through operational orstructural changes to the existing infrastructurealong the River Murray System. An extensive list ofpossible actions was developed, and then refinedthrough a workshop and systematic analysis ofvarious factors. Order of cost (pre-feasibilityaccuracy) was established for the refined list ofstructural and operational actions.

Seven key potential actions were modelled to assessthe likely costs and benefits that can be achievedthrough broad scale changes to the current operationof the River Murray System: boosting releases fromHume Dam, altered operation of the Barmah-Millewa account, boosting flows in the lower RiverMurray, raising weir pools, provision of a minimumflow through the Barrages, Cap reduction for theRiver Murray System only, and Basin-wide Capreduction

Some of the changes that were considered could not,at this stage, be effectively modelled to fully assessthe likely effects: improved management of rainrejection flows at Yarrawonga Weir, seasonallowering of weir pools, pipelining the water supplyto the Great Darling Anabranch, and providingimproved connectivity between the floodplain andthe river. These proposals have potential to realisesignificant benefits, so they were considered in apreliminary way using available information. Thereremains a need for improved modelling of the flowinteractions between the River Murray and its majortributaries. This would further enhance theefficiency and effectiveness of the flow scenariosdeveloped to date.

Some other proposals were considered to be morequestionable in relation to their feasibility and



Vol 5 No.1

practicability: decommissioning structures,proposed weir at Wellington, and a bypass channelfor the Barmah Choke. These proposals are regardedby some stakeholders as representing realisticsolutions to particular environmental problems, andwill undergo further investigation at a later date.

A range of flow scenarios are under developmentfor consideration by the Ministerial Council in 2002.The flow scenarios range from “do nothing”, betteruse and management of the water currentlyavailable for environmental purposes, through tomajor flow management policy changes (which willhave significant implications on the Cap ondiversions). All flow scenarios will includestructural and operational action components.

The approach developed by the Expert ReferencePanel 35 will be used to rate the probability of successof the flow scenarios in achieving a healthy RiverMurray System. Preliminary results indicate that theadoption of structural and operation actions alonewould result in lower overall flows passing throughthe Murray Mouth, whereas significant system wideimprovements to environmental values would bedelivered by reductions in the Cap.

The recovery of water from consumptive use forenvironmental flows is a central feature of the flowscenarios. The high value to local communities andthe Nation of existing uses of the River MurraySystem are recognised and appreciated. Recoveringwater from existing water users would likelyinvolve significant social, economic, political andpractical challenges, depending on the nature of theproposed changes and the volumes of waterinvolved. Ongoing work to investigate and resolvethese aspects of the Project is being undertaken withthe same level of rigour as applied to thedevelopment of flow scenarios. This process willinform the community and decision makers on thenature of the trade-offs involved in achievement ofenvironmental objectives.

An important issue associated with the recovery ofwater is how best to deliver the environmental waterto the desired locations on the river at the ideal time.The southern part of the Basin is much wetter thanthe north, and this is reflected in the level ofdiversions (figure 1). Diversions in theMurrumbidgee and the Goulburn Rivers accountfor around 20% and 18% respectively of total Basindiversions. Combined with diversions directly fromthe River Murray System (39% of total), these threeriver systems in the southern part of the Basinaccount for some 77% of the water diverted Basin-wide (excluding the Lachlan and Wimmera-Malleesystems), around half of which is from the RiverMurray System itself.2 Clearly, the current flowregime in the River Murray System is, in large part,a result of the high level of diversions in tributary

systems (figure 1, table 1). Accordingly, restoringthe health of the River Murray through the recoveryof water from River Murray consumptive use alonewould place a high burden on this system. Accessingwater for environmental flows from the tributarieswould relieve this burden and potentially provideadditional locations to store water prior to its releasefor environmental purposes.

Other matters that must be addressed in order toeffectively implement any change involvingsignificant retrieval of water from existing users inthe Basin include legal issues, relative costs andbenefits of implementing changed flow regimes,cost sharing, developing meaningful dialogue withcommunities, impact of potential climate change onwater availability, uncertainty in the links betweenenvironmental flow provisions and expectedenvironmental outcomes, and integration with othercatchment and river rehabilitation initiatives. Giventhe large amount of work to be carried out, and therelatively early stage of development of the Project,the findings to date are of a general and preliminarynature in many respects.

7 CONCLUSION

Based on a review of the impacts of regulation onthe River Murray System and a Basin-wide snapshotstudy of stream condition, it is clear that the riversand streams of the Basin are beset by multipleimpacts, with flow regulation being the mainproblem in the River Murray System. Theenvironmental impacts of regulation on the RiverMurray System vary according to regional zonesthat are defined in terms of the location and type ofregulation structures and also physiographiccharacteristics.

The integrated catchment management approachadopted by the Commission 6 is a necessary strategy,because problems in the lower part of the catchmentare partially related to upstream impacts. The“Environmental Flows and Water QualityObjectives for the River Murray Project” addressesthe recognised main cause of degradation in theRiver Murray System. However, the Project does notoperate in isolation, being linked to a comprehensiveand strategic framework of Commissionprogrammes and projects (the Initiative) 6 thatrecognises the interrelated and complex nature ofenvironmental issues across the entire Basin. Thelong time frames involved with natural processesare also clearly recognised. This combined with thesignificance of the changes being considered,indicates the appropriateness of a progressive, stepby step approach to implementation of agreedremedial measures and interventions.



A profiling survey demonstrated that stakeholderswere concerned about the current state of the river,and aware that it would take many years to improvethe situation. Whilst there was unequivocal supportamong stakeholders for the principle of anenvironmental allocation for the River Murray, theywere not supportive of a process that excluded themfrom involvement in decision making. Thus,establishment of an inclusive project organisationalstructure has proved to be critical, and will continueto be critical, to obtaining information and supportacross different States, and from a range ofstakeholder groups. Given that few respondentsexpressed an interest in the entire River MurraySystem, a management focus on defined regionalzones is more appropriate. This conclusion isconsistent with the regional pattern of degree andnature of regulation, and consequent environmentalimpacts. People tend to associate with their home(proximal) river zone, but these zones are also welldefined in terms of their environmental values,problems, and potential solutions.

Given the size and complexity (both in terms ofregulation and physiographic characteristics) of theRiver Murray System, a broad-scale expert panelapproach was used to assess environmental flowneeds. Over several years of investigation, generalconsensus emerged regarding the most importantenvironmental flow objectives: reinstatement ofecologically significant elements of the natural flowregime, keeping the Murray Mouth open, andsignificantly improving connectivity.

Preliminary results from the development andmodelling of flow scenarios indicate that structuraland operational actions alone will deliver relativelylocalised environmental improvements, and willresult in reduced flow through the Murray Mouth.Significant reductions in the Cap on diversions arerequired to deliver system-wide improvements tothe environment. Further development of the flowscenarios is required prior to consideration by theMinisterial Council in 2002, along with detailedassessment of the likely socio-economic impacts ofproposals. This information will permitconsideration of the trade-offs involved withachieving different environmental outcomesthrough adoption of various proposed changes.There are also numerous legal, administrative, cost,communication and uncertainty issues that need tobe resolved to further progress the project.

The work summarised in this paper represents aconcerted and cooperative effort from numerousstakeholders and experts. Although still in the earlystages of development, the project has significantlyprogressed the scope of environmental flowsresearch and development in Australia. For the firsttime, an overall sense of the scale of what is required

to achieve significant environmental outcomes inAustralia’s largest and most high profile riversystem has been realised.

ACKNOWLEDGEMENTS

This paper and the work on which is it grounded,including the supporting investigations, werecommissioned by the Murray-Darling BasinCommission as part of its commitment to deliverthe best environmental flow scenarios forconsideration by the Ministerial Council. The Projectwork described in the paper was performed by acommitted team of colleagues, and the papers andreports summarised here represent the work ofnumerous authors. All of these direct and indirectcontributions are gratefully acknowledged.

REFERENCES

1. Mackay N,Eastburn D eds. The Murray. Canberra:Murray Darling Basin Commission, 1990.

2. Crabb P. Murray-Darling Basin resources. Canberra:Murray Darling Basin Commission, 1997.

3. Based on the most recent analysis of data using theMonthly Simulation Model. Data provided by theMurray-Darling Basin Commission, November 2001.

4. Maheshwari BL,Walker KF,McMahon TA. Effects offlow regulation on the flow regime of the RiverMurray, Australia. Reg Riv: Res Manage 1995;10:15-38.

5. Gippel CJ, Collier KJ. Degradation and rehabilita-tion of waterways in Australia and New Zealand.In: deWaal LC,Large ARG,Wade PM. eds. Rehabili-tation of rivers: principles and implementation.Chichester:Wiley, 1998:269-300.

6. Murray-Darling Basin Initiative. http://www.mdbc.gov.au. (accessed November 2001).

7. Murray-Darling Basin Ministerial Council. An au-dit of water use in the Murray-Darling Basin.Canberra:Murray-Darling Basin Ministerial Coun-cil, 1995.

8. Barmah-Millewa Forum. The Barmah-Millewa For-est water management strategy. Canberra:Murray-Darling Basin Commission, 2000 June. Can bedownloaded from http://www.mdbc.gov.au.(accessed November 2001).

9. Thoms MC,Suter P,Roberts J et al. Report of the RiverMurray Scientific Panel on environmental flows:River Murray - Dartmouth to Wellington and thelower Darling River. River Murray Scientific Panelon Environmental Flows. Canberra:Murray-DarlingBasin Commission, 2000 June.



Vol 5 No.1

10. Jensen A,Good M,Tucker P,Long M eds. RiverMurray Barrages environmental flows. WetlandsManagement Program, Department of Environmentand Natural Resources. Canberra:Murray-DarlingBasin Commission, 2000 June.

11. Hume and Dartmouth Dams Operations ReviewReference Panel. Hume and Dartmouth Dams op-erations review, final report. Canberra:Murray-Dar-ling Basin Commission, 1999 May.

12. Gippel CJ,Blackham D. Review of environmentalimpacts of flow regulation and other water resourcedevelopments in the River Murray and Lower Dar-ling River system, draft report. Fluvial Systems PtyLtd. Canberra:Murray-Darling Basin Commission,2001.

13. Close A. The impact of man on the natural flow re-gime. In: Mackay N,Eastburn D eds, The Murray.Canberra:Murray-Darling Basin Commission,1990:61-74.

14. Wittington J,Cottingham P,Gawne B,HillmanT,Thoms M,Walker K. Ecological sustainability ofrivers of the Murray-Darling Basin. In: Review ofoperation of the Cap: Overview report of theMurray-Darling Basin Commission. CooperativeResearch Centre for Freshwater Ecology.Canberra:Murray-Darling Basin Ministerial Coun-cil, 2000 August.

15. Rutherfurd I. Ancient river, young nation. In: MackayN,Eastburn D eds, The Murray, Canberra:Murray-Darling Basin Commission, 1990:17-36.

16. Koehn JD,Doeg,TJ,Harrington DJ,Milledge GA. Theeffects of Dartmouth Dam on the aquatic fauna ofthe Mitta Mitta River. Arthur Rylah Institute for En-vironmental Research. Canberra:Murray-DarlingBasin Commission, 1995.

17. Pardo I,Campbell IC,Brittain JE. Influence of damoperation on mayfly assemblage structure and lifehistories in two south-eastern Australian streams.Reg Riv: Res Manage 1998;14:285-295.

18. Young WJ ed. Rivers as ecological systems - theMurray-Darling Basin. CSIRO Land and Water.Canberra:Murray-Darling Basin Commission, 2001.

19. Bennison GL,Hillman J,Suter PJ. Macroinvertebratesof the River Murray (survey and monitoring: 1980-1985). Water Quality Report no. 3. Canberra:Murray-Darling Basin Commission, 1989.

20. Dexter BD,Rose HJ,Davies N. 1986. River regulationand associated forest management problems in theRiver Murray red gum forests. Aust For 1986;49:16-27.

21. Leitch C. Towards a strategy for managing the flood-ing of Barmah Forest. Seminar on Barmah Forestorganised by the State Working Group on RiverMurray Wetland and Forest Management.Benalla:Department of Conservation Forests andLands, 1989.

22. Bren LJ. Effects of river regulation on flooding of ariparian red gum forest on the River Murray, Aus-tralia. Reg Riv: Res Manage 1988;2:65-77.

23. Mackay N,Hillman T,Rolls J. Water quality of theRiver Murray: review of monitoring 1978 to 1986.Water Quality Report No. 1, Canberra:Murray-Dar-ling Basin Commission, 1988.

24. Walker KF,Thoms MC. Environmental effects of flowregulation on the lower River Murray, Australia. RegRiv: Res Manage 1983;8:103-119.

25. Suter PJ,Goonan PM,Beer JA,Thompson TB. A bio-logical and physico-chemical monitoring study ofwetlands from the River Murray floodplain in SouthAustralia. Report no. 7/93. Australian Centre forWater Quality Research. Canberra:Murray-DarlingBasin Commission, 1993.

26. Burch MD,Baker PD,Steffensen,DA et al. Criticalflow and blooms of cyanobacterium Anabaenacircinalis in the River Murray, South Australia. In:Proc environmental flows seminar, Canberra, 25-26August. Artarmon:Australian Water and WastewaterAssociation, 1994:44-51.

27. Lloyd LN,Walker KF. 1986. Distribution and conser-vation status of small freshwater fish in the RiverMurray, South Australia. Trans Royal Soc South Aust1986;110:49-57.

28. Bourman RP,Barnett EJ. Impacts of river regulationon the terminal lakes and mouth of the River Murray,South Australia. Austr Geogr Stud 1995;33:101-115.

29. Gehrke PC,Brown P,Schiller CB,Moffatt DB,BruceAM. River regulation and fish communities in theMurray-Darling River System, Australia. Reg Riv:Res Manage 1995;11:363-375.

30. Norris RH,Liston P,Davies N. et al. Snapshot of theMurray-Darling Basin river condition. Report byCooperative Research Centre for Freshwater Ecol-ogy, University of Canberra and CSIRO Land andWater. Canberra:Murray-Darling Basin Commission,2001 September. Can be downloaded from http://www.mdbc.gov.au. (accessed November 2001).

31. Ladson AR,Argent RM. Adaptive management: en-vironmental flows: lessons for the Murray-DarlingBasin from three large North American Rivers. AustJ Wat Res 2002;5(1):89-102.

32. Nancarrow BE,Syme GJ. River Murray environmen-tal flows and water quality project stakeholder pro-filing study. Australian Research Centre for Waterin Society, CSIRO. Canberra:Murray-Darling BasinCommission, 2001 August. Can be downloaded fromhttp://www.mdbc.gov.au. (accessed November2001).

33. Gippel CJ. Australia’s Environmental Flow Initiative:filling some knowledge gaps and exposing others.Wat Sci Tech 2001;43(9):73-88.



34. Arthington AH,Zalucki JM eds. Comparative evalu-ation of environmental flow assessment techniques:review of methods. Occasional Paper No 27/98.Canberra:Land and Water Resources Research &Development Corporation, 1988:66-105.

35. Jones G,Hillman T,Kingsford R et al. Independentreport of the Expert Reference Panel on environmen-tal flows and water quality requirements for theRiver Murray System. Cooperative Research Centrefor Freshwater Hydrology. Canberra:Murray-Dar-ling Basin Ministerial Council, 2001 September (un-published).

36. Roberts J,Bourman B,Close A et al. A scientific panelassessment of modelled flow and technical optionsfor the River Murray. Canberra:Murray Darling Ba-sin Ministerial Council. 2001.

37. SMEC Victoria. Structural and operational review ofriver infrastructure including major dams and thelocks and weirs of the River Murray System, draftreport. Canberra:Murray-Darling Basin Commis-sion, 2001 September.

CHRIS GIPPELChris Gippel is a potamologist with a BSc (Hons) from the University of New-castle and PhD from the University of NSW. After a long research career at sev-eral universities, Chris now runs a private consulting firm that provides special-ist services to the water industry in the areas of geomorphology, hydrology, riverrehabilitation and environmental flows. He continues to innovate and lead de-velopment of ideas and technologies in these fields within the consulting envi-ronment. Chris has published widely, and in 1992 was recipient of an AustralianBicentennial Fellowship. He can be contacted at [email protected].

TONY MCLEODTony McLeod BE(Hons) PhD (Melbourne) is a member of the EnvironmentalFlows team at the Murray-Darling Basin Commission. Since joining the MDBCin 1998 he has been involved in the implementation of the Cap on diversionsthroughout the Basin, operation of the River Murray System and environmen-tal flows. His interests are water sharing between environmental and con-sumptive needs and management of trans-boundary water resources.

environmental flows and water quality objectives for the river murray

Documents