Transcript
Page 1: The Murray - Home Enviro Data SA | EnviroData murray mouth...The Murray Mouth is an important cultural and spiritual place for the Ngarrindjeri people. The growing environmental degradation
Page 2: The Murray - Home Enviro Data SA | EnviroData murray mouth...The Murray Mouth is an important cultural and spiritual place for the Ngarrindjeri people. The growing environmental degradation

TTTTThhhhhe Murre Murre Murre Murre Murraaaaay My My My My Mooooouthuthuthuthutheeeeexxxxxploploploploplorrrrriiiiinnnnng thg thg thg thg the ime ime ime ime implipliplipliplicccccaaaaatttttioioioioionnnnns os os os os of cf cf cf cf closloslosloslosururururureeeee

ooooor rr rr rr rr resesesesestrtrtrtrtriiiiicccccttttteeeeed fd fd fd fd f lololololowwwww, 2002, 2002, 2002, 2002, 2002

Murray-Darling Basin CommissionLevel 5, 15 Moore StreetCanberra City ACT 2600

Department of Water, Land and Biodiversity Conservation25 Grenfell StreetAdelaide SA 5000

Project Co-ordinator: Tiffany InglisEditing: Naomi Goodwin and Sandra Bennett

Design: Lavaworks

Cover photograph and photograph on opposite page supplied byMAPLAND Environmental and Geographic Information,

Department for Environment and Heritage.

TTTTThhhhhe e e e e MMMMMurrurrurrurrurraaaaayyyyyMMMMMooooouthuthuthuthuth

Exploring the implications of

closure or restricted flow

JuJuJuJuJullllly 2002y 2002y 2002y 2002y 2002

c

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The land and waters is a living bodyThe land and waters is a living bodyThe land and waters is a living bodyThe land and waters is a living bodyThe land and waters is a living body.....

WWWWWe the Ngarrindjeri people are a part of its existence.e the Ngarrindjeri people are a part of its existence.e the Ngarrindjeri people are a part of its existence.e the Ngarrindjeri people are a part of its existence.e the Ngarrindjeri people are a part of its existence.

The land and waters must be healthy for theThe land and waters must be healthy for theThe land and waters must be healthy for theThe land and waters must be healthy for theThe land and waters must be healthy for the

Ngarrindjeri people to be healthyNgarrindjeri people to be healthyNgarrindjeri people to be healthyNgarrindjeri people to be healthyNgarrindjeri people to be healthy.....

WWWWWe are hurting for our countrye are hurting for our countrye are hurting for our countrye are hurting for our countrye are hurting for our country.....

The LThe LThe LThe LThe Land is dyingand is dyingand is dyingand is dyingand is dying,,,,,

the River is dyingthe River is dyingthe River is dyingthe River is dyingthe River is dying,,,,,

the Kthe Kthe Kthe Kthe Kurangk (Coorong) is dyingurangk (Coorong) is dyingurangk (Coorong) is dyingurangk (Coorong) is dyingurangk (Coorong) is dying

and the Murray Mouth is closingand the Murray Mouth is closingand the Murray Mouth is closingand the Murray Mouth is closingand the Murray Mouth is closing.....

What does the future hold for us?What does the future hold for us?What does the future hold for us?What does the future hold for us?What does the future hold for us?

TTTTTom Tom Tom Tom Tom Trevorrowrevorrowrevorrowrevorrowrevorrow, Ngarrindjeri elder, Ngarrindjeri elder, Ngarrindjeri elder, Ngarrindjeri elder, Ngarrindjeri elder, Camp Coorong, Camp Coorong, Camp Coorong, Camp Coorong, Camp Coorong, 2002, 2002, 2002, 2002, 2002

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1 Foreword4 Summary

7 I I I I Innnnntrtrtrtrtrodododododuuuuuccccctttttioioioioionnnnnby Paul Harvey

The MurrayThe MouthA Modest HistoryPutting Current Conditions in Perspective

PPPPPerererererspspspspspeeeeeccccctttttiiiiivvvvveseseseses13 Ngarrindjeri Culture

by Steve Hemming, Tom Trevorrow and Matt Rigney

21 Fishing Industryby Garry Hera-Singh

25 Tourism and Recreationby Freya Higgins-Desbiolles and Glen Jones

33 Water Qualityby Justin Brookes

53 Fish and Invertebratesby Jason Higham, Michael Hammer and Michael Geddes

65 Migratory Wadersby David Paton

73 Aquatic Plant Communitiesby George Ganf

81 Coastal Processesby Murray Townsend and Doug Fotheringham

85 WWWWWhhhhhaaaaat it it it it is Ps Ps Ps Ps Pososososossssssiiiiibbbbbllllleeeee: Hyd: Hyd: Hyd: Hyd: Hydrrrrrooooololololologggggy ay ay ay ay annnnnd Md Md Md Md Mooooorrrrrphphphphphooooololololologggggyyyyyby David Walker

Estimating Mouth OpeningModelling Mouth OpeningOptimising Barrage Releases

93 Glossary95 Abbreviations

Contents

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I M P L I C AI M P L I C AI M P L I C AI M P L I C AI M P L I C A T I O N S O F M U R R AT I O N S O F M U R R AT I O N S O F M U R R AT I O N S O F M U R R AT I O N S O F M U R R A Y M O U T H C LY M O U T H C LY M O U T H C LY M O U T H C LY M O U T H C L O S U R EO S U R EO S U R EO S U R EO S U R E

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ForewordIn the 1930s the Government made the decision to construct barrages at theMouth of the River Murray to prevent salt water intrusion into the LowerLakes. This was in response to demand for increased freshwater diversionsfrom the Lakes themselves and upstream users. As a consequence, reducedflows and barrage construction has altered the morphology of the Murrayestuary and Mouth, increasing the threat of Murray Mouth closure. This hassignificantly impacted on the environmental, social and economic values ofthe region, including the Coorong.

Over the last sixty years, we have worked with this modified River system andare now trying to address the challenges that arise from the altered flowregime. This compilation of papers presents the complexity of the issuesfaced by a closure of the Murray Mouth - social, economic andenvironmental impacts, as seen through the eyes of community membersand scientists. The papers are intended to inform the debate leading tobetter management of, not only this reach of the River, but more generallythroughout the Murray-Darling system.

The Murray-Darling Basin Commission, together with South Australianagencies, is investing significant resources to increase our understanding ofthe broad range of issues facing the Murray Mouth. In 2001, The Murray-Darling Basin Ministerial Council adopted 15 objectives to attain a healthyRiver Murray. Keeping the Murray Mouth open to maintain navigation andfish passage and to enhance estuarine conditions in the Coorong is one ofthese objectives. The papers in this compilation provide a comprehensivespringboard for future projects and management possibilities to achieve thisobjective.

Don BlackmoreDon BlackmoreDon BlackmoreDon BlackmoreDon BlackmoreMurray-Darling Basin CommissionMurray-Darling Basin CommissionMurray-Darling Basin CommissionMurray-Darling Basin CommissionMurray-Darling Basin Commission

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I M P L I C AI M P L I C AI M P L I C AI M P L I C AI M P L I C A T I O N S O F M U R R AT I O N S O F M U R R AT I O N S O F M U R R AT I O N S O F M U R R AT I O N S O F M U R R A Y M O U T H C LY M O U T H C LY M O U T H C LY M O U T H C LY M O U T H C L O S U R EO S U R EO S U R EO S U R EO S U R E

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Justin BrookesJustin BrookesJustin BrookesJustin BrookesJustin Brookes - Justin completed his Science degree and Doctor of Philosophy at the University ofAdelaide where he is now affiliate Lecturer at the Department of Environmental Biology. He iscurrently employed as the Reservoir Specialist in the Cooperative Research Centre for Water Qualityand Treatment. Justin’s research interests include cyanobacterial ecology. He has published in thefields of limnology, eutrophication, aquatic toxicology and hydrodynamics.

Doug Fotheringham Doug Fotheringham Doug Fotheringham Doug Fotheringham Doug Fotheringham - Graduating with BA (Hons) Geography from Flinders University in 1976, Dougjoined the Coastal Management Branch in 1982 as a Scientific Officer (geomorphology/ecology).He is currently Senior Scientific Officer in the Office of Coasts and Marine and is primarily involvedwith investigations, monitoring and evaluation. He is also a member of the Sir Richard PeninsulaCommittee and Murray Mouth Advisory Committee.

George Ganf George Ganf George Ganf George Ganf George Ganf - Having worked on lakes, wetlands and rivers in Uganda, Austria, Germany, the USAand England, George is now resident at the Department of Environmental Biology, University ofAdelaide. He has authored or co-authored more than 100 journal publications, supervised PhDstudents and taught aquatic ecology over the past 20 years.

Mike Geddes Mike Geddes Mike Geddes Mike Geddes Mike Geddes – Mike has studied the Coorong and Lake Alexandrina over the past 25 years, lookingmainly at salinity, macroinvertebrates and zooplankton and lately has been working with students onfish. He has run aground on more Coorong sandbars than most.

Michael Hammer - Michael Hammer - Michael Hammer - Michael Hammer - Michael Hammer - Fascinated by a diverse array of habitat types and interesting fish species, Michaelhas spent much time researching the distribution and ecology of fishes found in the lower RiverMurray region, particularly within Lake Alexandrina and streams of the Mount Lofty Ranges. This hasinvolved conservation programs for locally endangered species as well as proactive measures toensure the protection of habitats in the region. He is about to commence a PhD with University ofAdelaide and the Cooperative Research Centre for Freshwater Ecology furthering his research intothe ecology, genetic structure and taxonomy of freshwater fishes.

PPPPPaul Harvey aul Harvey aul Harvey aul Harvey aul Harvey – Paul is the Deputy Director of the Murray-Darling Division in the Department of Water,Land and Biodiversity Conservation. He has had more than 30 years experience in water resourcesand natural resource management across South Australia, and for the past four years has chairedthe Murray Mouth Advisory Committee.

Steve Hemming - Steve Hemming - Steve Hemming - Steve Hemming - Steve Hemming - Currently a lecturer in Australian Studies at Flinders University, Steve previouslyworked as a curator in the South Australian Museum’s Anthropology Division for many years. He hasalso worked for Aboriginal Legal Rights Movement (SA) as an anthropologist researching native titleclaims.

Garry Hera-Singh - Garry Hera-Singh - Garry Hera-Singh - Garry Hera-Singh - Garry Hera-Singh - A third generation fisher with 20 years experience, Garry is the current Presidentof the Southern Fisherman’s Association.

FFFFFreya Higginsreya Higginsreya Higginsreya Higginsreya Higgins-Desbiolles -Desbiolles -Desbiolles -Desbiolles -Desbiolles - A lecturer in Tourism in the School of International Business of theUniversity of South Australia, Freya has interests in the impacts of tourism and sustainability intourism.

Authors

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I M P L I C AI M P L I C AI M P L I C AI M P L I C AI M P L I C A T I O N S O F M U R R AT I O N S O F M U R R AT I O N S O F M U R R AT I O N S O F M U R R AT I O N S O F M U R R A Y M O U T H C LY M O U T H C LY M O U T H C LY M O U T H C LY M O U T H C L O S U R EO S U R EO S U R EO S U R EO S U R E

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Jason Higham - Jason Higham - Jason Higham - Jason Higham - Jason Higham - Jason is a researcher with South Australian Research and Development Institute(SARDI) Aquatic Sciences, and over the past five years has worked in a range of areas. He ispresently investigating the feasibility of fishways at the River Murray barrages.

Glen JonesGlen JonesGlen JonesGlen JonesGlen Jones - Glen is General Manager of the Boating Industry Association of South Australia (BIASA),the peak industry body representing the recreational boating industry in Australia.

David PDavid PDavid PDavid PDavid Paton aton aton aton aton - A Senior Lecturer in the Department of Environmental Biology at the University ofAdelaide, David has broad research interests in the South Australian environment with a specialinterest in the management and conservation of birds and their habitats. He has been studying thebirds, their resources and habitats in the Coorong for the past 20 years.

Matt Rigney - Matt Rigney - Matt Rigney - Matt Rigney - Matt Rigney - Matt Rigney is the chair of the Ngarrindjeri Native Title Management Committee. He isan ATSIC regional councillor for the Putpa Warra Yunti regional council and stood as a Green Partycandidate at the last Federal Election. He was for a number of years the chair of the Putpa WarraYunti ATSIC regional council.

Murray TMurray TMurray TMurray TMurray Townsend ownsend ownsend ownsend ownsend - Currently the Senior Engineer in the Office for Coasts and Marine, National Parksand Wildlife SA, Murray has been with the Department for Environment and Heritage since 1999.Prior to this, he worked as a consultant and academic after completing studies in coastal and oceanengineering. His areas of interest include waves, currents, sea loads on structures, sedimenttransport and field, laboratory and computer based modelling.

TTTTTom Tom Tom Tom Tom Trevorrow - revorrow - revorrow - revorrow - revorrow - Tom Trevorrow is the acting chair of the Ngarrindjeri Heritage Committee and theNgarrindjeri Land and Progress Association. He is the Cultural Program Coordinator at CampCoorong and trained and worked as a National Parks and Wildlife Ranger.

David WDavid WDavid WDavid WDavid Walkeralkeralkeralkeralker - Senior Lecturer in the Department of Civil and Environmental Engineering at the Universityof Adelaide, David has been involved in coastal engineering and coastal research for over 20 years.His main research interests are in long-term modelling of near shore coastal phenomena, environmentalimpacts of human-made changes to coastal features, and physical and chemical processes at thesediment-water interface. He is the author or co-author of over 40 journal or conference papers.

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SummaryWhile a build-up of sand inside the MurrayMouth and reduced tidal flows is not a newphenomenon, the current situation is set apartby the duration and degree of sand build up,which is greater than ever previously reported.The ongoing threat of closure highlights theneed to understand the potential impacts ofthis changed flow regime on the ecologicalhealth of the Coorong and Lower Lakes.

This compilation seeks to explore theseimplications from a range of perspectives, andbring together current knowledge andconcerns to inform and guide futuremanagement decisions.

CCCCCommoommoommoommoommon Gn Gn Gn Gn GrrrrroooooununununundddddWhile each paper reflects a differentperspective and area of interest or expertise,some common views have emerged:ooooo The accumulation of sediment at the

Murray Mouth reflects the vastly alteredhydrology of the River Murray and issymptomatic of the condition of the entireMurray-Darling Basin.

ooooo The implications of closure depend on itsduration, timing and frequency – that is,the period for which the Mouth staysclosed, the time of year when thishappens and the interval betweenclosures.

ooooo Short-term closure, when the Mouth isreopened before water quality is seriouslydegraded, is likely to have minimalimpacts. However, such impacts wouldescalate if closure occurred during thewarmer months.

ooooo Currently, the risk of long-term closure isgreater than ever before due to thecondition of the River Murray– that is,negligible River flows reaching the Mouth,and a major reduction in ‘big flood’events.

ooooo Long-term closure would have seriousdeleterious, and in some casesirreversible, impacts on the ecology of thearea and those who depend on it.

ooooo South Australia has an internationalobligation to protect the ecosystems of theCoorong and Lower Lakes.

ooooo All stakeholders recognise the specialecological value of the area and the needto stop further degradation.

ooooo Any solution needs to be considered in thecontext of the total River Murray system.

PPPPPerererererspspspspspeeeeeccccctttttiiiiivvvvvesesesesesNgarrindjeri CultureNgarrindjeri CultureNgarrindjeri CultureNgarrindjeri CultureNgarrindjeri Culture

The Murray Mouth is an important culturaland spiritual place for the Ngarrindjeri people.The growing environmental degradation ofthe Murray-Darling Basin and the threatened,continuing closure of the Murray Mouth, hasalready, and will continue to place enormouspressure and cultural trauma on theNgarrindjeri community.

The sense of feeling, sense ofbelonging, sense of responsibility forthe River, Lakes and Coorongexperienced by Ngarrindjeri people hassurvived occupation, dispersal andattempted assimilation. It continues toexist irrespective of where Ngarrindjeripeople currently live. The link with theland lies at the heart and soul ofNgarrindjeri culture. A properrelationship and role in managementof the land is a fundamental platformin building and maintainingNgarrindjeri culture and Ngarrindjeriself respect. Ngarrindjeri believe thattheir future involvement in themanagement of the land would bepositive and beneficial to all membersof the community, not just Ngarrindjeri.It would represent a significant step inthe process of reconciliation and co-existence. The strengthening ofNgarrindjeri people and their culturerequires a serious involvement in themanaging of their traditional lands(NRWG 1999).

Fishing IndustryFishing IndustryFishing IndustryFishing IndustryFishing Industry

If the passage for fish between the sea, LowerLakes and estuary is prevented by closure ofthe Murray Mouth, several economicallyimportant fish species will decline.

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Many species depend on movement from theocean into the estuary and freshwater LowerLakes for reproduction and recruitment. Keyspecies are Mulloway (Argyrosomusjaponicus), Goolwa Cockles (Donax deltoides),Black Bream (Acanthopagrus butcheri),Greenback Flounder (Rhombosolea taparina)and Yellow-Eye Mullet (Aldrichetta forsteri).

If Mouth closure occurs over the warmermonths, there is potential for fish kills as aresult of low oxygen levels and algal bloomsassociated with warm, still, high nutrientwater. Long periods (more than two weeks) ofhot weather would increase the probability ofoxygen levels declining below survival levels of1-2ppm. Closure therefore has the potentialto make the existing commercial fisheryuneconomic and reduce recreational fishing.

TTTTTourism and Recreationourism and Recreationourism and Recreationourism and Recreationourism and Recreation

The ecology of the Coorong and Lower Lakesarea is the basis of its tourism and recreationvalue.

The Murray Mouth and the Coorong areunique, iconic sites and serve to differentiateSouth Australia from other touristdestinations. Mouth closure would seriouslyundermine this tourism asset. Mouth closureand its associated impacts would alsoadversely affect a range of recreational uses,particularly fishing, boating and birdwatching.

WWWWWater Qualityater Qualityater Qualityater Qualityater Quality

The major water quality impacts, which mayeventuate from Murray Mouth closure,represent a risk to stakeholders because theydegrade habitat for aquatic organisms orpresent a health risk to recreational users.

The two major factors which will impact waterquality at the Murray Mouth region are thequality of the water arriving from upstream(source water) and density stratification.Closure or restriction of the Murray Mouthwould result in the development ofstratification which is a necessary physicalcondition for many hazards to eventuate,

including blooms of toxic cyanobacteria,anoxia in the deepest water layer(hypolimnion) and nutrient release fromsediment. Mouth closure is also likely toincrease salinity, particularly in the NorthernLagoon, which is strongly influenced by sourcewater from the River Murray.

Fish and InvertebratesFish and InvertebratesFish and InvertebratesFish and InvertebratesFish and Invertebrates

Mouth closure would have multiple effects onthe plants and animals of the Coorong andMurray estuary. Not only would it largelyprevent fish and other organisms frommigrating between the Coorong and the sea(thereby affecting lifecycle processes), but sanddeposited inside the Mouth would alsosmother the productive mudflats in the localarea of the Mouth (affecting food resourcesand water quality for birds and fish).

Further, secondary consequences of Mouthclosure relate to elevated salinities andpossible reduced dissolved oxygenconcentration in the Coorong. There would bereduced food availability and, with lesssuitable habitat for all species, predator-preyinteractions would increase. The most severeeffect would be seen if the Mouth remainsclosed for longer than a year.

Migratory WMigratory WMigratory WMigratory WMigratory Wadersadersadersadersaders

There is sufficient evidence to show that underthe current management regime the estuarinehabitats in the Murray Mouth region aredeclining in area and quality, particularly ashabitat for migratory waders.

Lack of adequate flows through the MurrayMouth leads to a series of changes, all ofwhich erode the quality of the estuarinehabitats for waders. For example, lack offlows allows coarse marine sands to bepushed into the estuary and these caninterfere with the birds’ foraging. Also, lack offlows leads to reductions in the intertidal zonearound the shoreline, limiting suitable habitatwhich is then more likely to become eroded asbirds concentrate and feed in a smaller area.Reductions in the volumes and changes in thefrequency, timing and duration of releases of

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water over the barrages clearly have thepotential to erode habitat quality and feedingefficiency for migratory waders and othershorebirds.Continuing to allow these estuarine habitatsto deteriorate contravenes Australia’sobligations under a series of internationalagreements, including the RamsarConvention, JAMBA and CAMBA. Knowledgeof natural systems remains limited, and thisimpedes management decisions, but there isadequate information to know that completeclosure of the Murray Mouth will exacerbatethe degradation.

Aquatic Plant CommunitiesAquatic Plant CommunitiesAquatic Plant CommunitiesAquatic Plant CommunitiesAquatic Plant Communities

Prior to River regulation, a rich diversity ofplants was distributed across the floodplain,temporary wetlands and main channel.However, with the increase in water turbiditythe aquatic flora is now restricted to the littoralzone. The lack of inundation of the floodplain,coupled with grazing and clearing, has alsoimpacted upon plant biodiversity.A consequence is severely depleted flora,weed invasion and a loss of biodiversity. If theMurray Mouth closed there would be anundesirable impact on plant communitiesallowing depauperate conditions to furtherreduce plant biodiversity.

Coastal ProcessesCoastal ProcessesCoastal ProcessesCoastal ProcessesCoastal Processes

Historically, the Mouth was mobile, movingalong the coast depending on the wave,current and River flow climate. It is likely thatsand accumulated in the Mouth duringperiods of low River flow, but that periodicflooding would have ejected significantquantities of sediment from the Mouth intothe coastal zone.

The Murray Mouth is currently significantlyrestricted and is acting as a sink for sandwhich enters the Mouth from the coastallittoral system. The restriction in the supply ofsand to the downdrift side of the Mouth, theSir Richard Peninsula, is causing the Peninsulato erode and the Mouth to move steadilynorth-west.

If the Mouth became blocked with sand andclosed, it would cease to absorb sand fromthe beach system and the littoral drift wouldcontinue along the beach uninterrupted. Thescour and erosion-induced movement of SirRichard Peninsula would stop, althoughaeolian (wind-blown) movement of sandwould obviously continue, especially given thatthe erosion has exposed large areas ofunvegetated dune to the elements.

What is PWhat is PWhat is PWhat is PWhat is Possible:ossible:ossible:ossible:ossible:Hydrology and MorphologyHydrology and MorphologyHydrology and MorphologyHydrology and MorphologyHydrology and Morphology

Low flows and their effect on the MurrayMouth are not recent phenomena. What haschanged is the frequency at which the lowflow events occur.

Techniques are available to estimate size andposition of the Murray Mouth, and predict thelikely pattern of future restriction.

To determine whether flows from the LowerLakes over the barrages can be manipulatedto optimise Mouth opening, two strategieshave been evaluated:1. an annual concentrated discharge

designed to flush out excess material thathas built up on the flood tidal delta overthe previous 12 months, and

2. additional flows to lift the month by monthreleases in an attempt to prevent the influxof sediment through the Mouth.

Early results indicate that although bothstrategies should be effective, the option thatattempts to maintain some outflowthroughout the whole year appears moreeffective (based on the model developed byWalker to describe Mouth opening). This maybe due to the fact that any flow from the Riverwould tip the balance in the Mouth to a netoutward flow that would assist in preventingsediment entering the inlet during a rising tideand assist in flushing during the ebb flows.

It can therefore be seen that options exist formaintaining flows over the barrages toprevent Mouth closure. The final solution,however, is likely to depend to a large extenton determining a viable pattern of releasesfrom the Lower Lakes taking into account thehealth of the total River system.

Summary

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The Murray Mouth at the River Murray’s endis a significant site to all Australians. Therestriction at the Mouth and threat ofcomplete closure continues with littleunderstanding of the possible impacts.Recognising this, the Murray-Darling BasinCommission and the South AustralianDepartment of Water, Land and BiodiversityConservation commissioned papers from arange of experts and interests to explore theimplications that Murray Mouth closure wouldhave on:

Whilst these topics are not exhaustive, they gosome way toward appreciating the range ofperspectives and complexity of issues involved,and begin to highlight some imperatives andoptions for future management.

TTTTThhhhhe Murre Murre Murre Murre MurraaaaayyyyyThe River Murray terminates atthe Southern Ocean, saving itsmost circuitous route to the veryend of its journey where itpasses through LakesAlexandrina and Albert, theMurray estuary, the Coorong –a hypersaline coastal lagoonand, finally, the Murray Mouth(see page 86). This, in largepart, accounts for both itsunique ecological qualities,recognised internationally1 , andthe challenges it presents tothose involved in managing thearea.

However, current challengeshave been further heightenedby the way the Murray-DarlingBasin has been managed overthe past 100 years. Riverregulation and water diversions

have dramatically reduced River flows andflood frequency, with flows at the Mouth downto 27% of the natural median flow. Since1940, diversions from the River system haveincreased from approximately 3000GL peryear to over 10 000GL per year. Also,barrages constructed at the Mouth toseparate marine and freshwater habitatsdecreased the size of the estuary by 660km2

and further interrupted tidal flows through theMouth.

The accumulation of sediment at the MurrayMouth can therefore be seen as symptomaticof the condition of the entire Murray-DarlingBasin.

TTTTThhhhhe Me Me Me Me MooooouthuthuthuthuthThe Murray Mouth is essentially a tidal inletrestricted by the accumulation of dunematerial on the flanking spits of Sir RichardPeninsula and Younghusband Peninsula(Bourman and Harvey 1983). It is located in ahigh-energy environment and is extremelydynamic.

The location, size and shape of the Mouthand the adjacent estuarine area are dictatedby a combination of River flows, tidal flowsand coastal and ocean processes. The Mouthhas migrated in an east-west direction as aresult of River droughts and floods andcoastal events. Archaeological evidenceindicates that the Mouth has travelled over a6-8km width during the past 3000 years.Since recorded history, the Mouth hasoscillated over a 2km stretch of beach. Therate of change can be dramatic – a singlestorm event in the early 1980s removed800 000m3 of sand from Sir RichardPeninsula.

However, the subtle changes are probablymore important in the long-term. Largevolumes of sand are continually being movedthrough the Mouth by daily tidal flows.Consequently, only a small change in the

Introduction

“Too much water has beendiverted from the river systemand not enough water now

reaches the Lakes andCoorong. The quality of thewater has also fallen. The

water is cloudy, polluted andnot fit for drinking. The

Murray, the Lakes and theCoorong are no longer

environmentally healthy andthis is partly why the

Ngarrindjeri people are nothealthy. The Ngarrindjeriknow that the Coorong,

Lakes and River are dying.”

Ngarrindjeri RamsarWorking Group (1999)

‘Ngarrindjeri perspectives onRamsar Issues’ in Draft

Coorong and LakesAlexandrina and Albert

Ramsar Management Plan,SA Department for

Environment and Heritage.

1 The Coorong Lagoon is listed as a RAMSAR wetland, andis protection under the Japan-Australia and China-AustraliaMigratory Agreements (Edyvane and Carvalho 1995).

o vegetation o water qualityo fish and invertebrates o coastal processeso migratory waders o indigenous cultureo hydrology and morphology o recreation and ecotourismo the commercial fishing industry

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balance of the net amount of sand enteringand remaining inside the Mouth can result ina substantial accumulation of sediment overtime.

The capacity of the tidal flow to transport sandis dependent on two main factors - tidalvelocity and wind and wave action in theimmediate vicinity of the Mouth. Tidal velocityis determined by the tidal range, River flowover the barrages, and the existing water levelin the estuary. Since the capacity of the tidalflow to transport sediment is a power functionof the tidal velocity, even reasonably smallRiver flows counteracting an incoming tidemay result in a significant reduction in thesediment load carried.

There are now more frequent and longerperiods of zero or very low River flows at thebarrages. This flow is insufficient to counteractthe incoming tidal flow, and is a significantfactor in ‘tipping the balance’ towardsincreased deposition inside the Mouth, as hasbeen evident over the past four years.

A MA MA MA MA Modododododesesesesest Ht Ht Ht Ht H iiiiissssstttttooooorrrrryyyyyThe River Murray Mouth has always been adynamic and at times restricted opening intothe Southern Ocean, with severe constrictionsreported in 1914, during the 1920s and in1939. Neither Flinders nor Baudin identifiedthe Mouth when anchored in Encounter Bay inApril 1802, presumably at a time when Riverflow was low. In February 1830, at the end ofhis trip down the River, Captain Charles Sturtcommented that he was disappointed at thesize of the Mouth.

During the years of River transport (1850s to1920s), conditions at the Mouth were oftennot conducive to navigation, with shallowwater, strong currents and large seas makingboat passage difficult and dangerous. Asearly as 1856, Goyder (then Deputy SurveyorGeneral) proposed modifications to improvenavigability of the River Mouth. He recognisedthat the most direct route to the Mouth wouldmaximise the possibility of scouring andsuggested dredging and straighteningMundoo channel.

Towards the end of anexceptionally dry period(1911 to 1914), it isunderstood that theMouth became shallowenough to walk across.Local folklore suggeststhat the Mouth closedand was opened on thenext high-tide by localfishermen using shovels.A similar story is toldabout the Mouth duringthe 1938-1939 drought.In 1981, the MurrayMouth closed for thefirst time in recordedhistory. A rapidaccumulation ofsediment at this timewas attributed tounusually calm sea

The Murray Mouth - 1840The Murray Mouth - 1840The Murray Mouth - 1840The Murray Mouth - 1840The Murray Mouth - 1840

Introduction

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conditions, a period of low high-tides and alack of fluvial action (Bourman and Harvey1983). On 6 May 1981, the Mouth waspartially reopened by a high tide, butcompletely closed again by 14 May 1981. Theadditional flows required to open the Mouthwere greater than the recorded 1956 floodflow levels (1.43m Lake level). The Mouth wasartificially opened on the 15 July 1981 by theexcavation of two channels (Bourman andHarvey 1983). Since this closure, concernsabout restriction and possible closure of theMurray Mouth have been raised on a numberof occasions.

Clearly, if earlier closures did occur, they wereunlike the 1981 event when the sand bar thatevolved across the Mouth was too large toremove with shovels. Differences between therumoured 1914 and 1939 events and theclosure in 1981 are to be expected.

PutPutPutPutPuttttttiiiiinnnnng Cg Cg Cg Cg CurrurrurrurrurreeeeennnnntttttCCCCCooooonnnnnddddditititititioioioioionnnnns is is is is innnnnPPPPPerererererspspspspspeeeeeccccctttttiiiiivvvvveeeeeWhile a build-up of sand inside the MurrayMouth and reduced tidal flows is not a newphenomenon, the current situation is set apartby the duration and degree of sand build up,which is greater than ever previously reported.From analysis of the predicted flow conditionsfor the Mouth, it is evident that periods ofsevere constriction in the River estuary arelikely to persist unless there is some deliberateintervention. Options for intervention arebeing investigated.

The ongoing threat of closure highlights theneed to understand the potential impacts ofthis changed flow regime on the ecologicalhealth of the Coorong. This compilation seeksto explore these implications from a range ofperspectives, and bring together currentknowledge and concerns to inform and guidefuture management decisions.

RRRRReeeeeferferferferfereeeeennnnncccccesesesesesBourman B and Harvey N (1983) The Murray Mouth

Flood Tidal Delta. Australian Geographer15: 403-406.

Edyvane K and Carvalho P (1995) Proceedings of theMurray Mouth Biological ResourceAssessment Workshop. South AustralianResearch and Development Institute (SARDI),Adelaide.

Ngarrindjeri Ramsar Working Group (1999)‘Ngarrindjeri perspectives on Ramsar Issues’ inDraft Coorong and Lakes Alexandrina andAlbert Ramsar Management Plan, Appendix 8.South Australian Department for Environment,Heritage and Aboriginal Affairs, Adelaide.

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TTTTThhhhhe Loe Loe Loe Loe Lowwwwwer Ler Ler Ler Ler Lakes & Cakes & Cakes & Cakes & Cakes & Coooooooooorrrrrooooonnnnnggggg

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“The land and waters must be healthy for the“The land and waters must be healthy for the“The land and waters must be healthy for the“The land and waters must be healthy for the“The land and waters must be healthy for theNgarrindjeri people to be healthyNgarrindjeri people to be healthyNgarrindjeri people to be healthyNgarrindjeri people to be healthyNgarrindjeri people to be healthy.....WWWWWe are hurting for our country…”e are hurting for our country…”e are hurting for our country…”e are hurting for our country…”e are hurting for our country…”

Steve Hemming, Australian Studies, Flinders UniversityTom Trevorrow, Acting Chair, Ngarrindjeri HeritageCommittee and Ngarrindjeri Land and Progress AssociationMatt Rigney, Chair, Ngarrindjeri Native Title ManagementCommittee

“The land and waters must be healthy for the“The land and waters must be healthy for the“The land and waters must be healthy for the“The land and waters must be healthy for the“The land and waters must be healthy for theNgarrindjeri people to be healthyNgarrindjeri people to be healthyNgarrindjeri people to be healthyNgarrindjeri people to be healthyNgarrindjeri people to be healthy.....WWWWWe are hurting for our country…”e are hurting for our country…”e are hurting for our country…”e are hurting for our country…”e are hurting for our country…”

Steve Hemming, Australian Studies, Flinders UniversityTom Trevorrow, Acting Chair, Ngarrindjeri HeritageCommittee and Ngarrindjeri Land and Progress AssociationMatt Rigney, Chair, Ngarrindjeri Native Title ManagementCommittee

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This chapter provides a preliminaryThis chapter provides a preliminaryThis chapter provides a preliminaryThis chapter provides a preliminaryThis chapter provides a preliminaryNgarrindjeri perspective on the effectNgarrindjeri perspective on the effectNgarrindjeri perspective on the effectNgarrindjeri perspective on the effectNgarrindjeri perspective on the effectthat the closure of the Murray Mouththat the closure of the Murray Mouththat the closure of the Murray Mouththat the closure of the Murray Mouththat the closure of the Murray Mouthwill have on the Ngarrindjeri people ofwill have on the Ngarrindjeri people ofwill have on the Ngarrindjeri people ofwill have on the Ngarrindjeri people ofwill have on the Ngarrindjeri people ofthe Lthe Lthe Lthe Lthe Lower Murrayower Murrayower Murrayower Murrayower Murray, Coorong and L, Coorong and L, Coorong and L, Coorong and L, Coorong and LowerowerowerowerowerLakes area of South Australia. It is notLakes area of South Australia. It is notLakes area of South Australia. It is notLakes area of South Australia. It is notLakes area of South Australia. It is nota community perspective, but providesa community perspective, but providesa community perspective, but providesa community perspective, but providesa community perspective, but providesthe views of two senior Ngarrindjerithe views of two senior Ngarrindjerithe views of two senior Ngarrindjerithe views of two senior Ngarrindjerithe views of two senior Ngarrindjerimen and includes relevant materialmen and includes relevant materialmen and includes relevant materialmen and includes relevant materialmen and includes relevant materialthat illustrates broader Ngarrindjerithat illustrates broader Ngarrindjerithat illustrates broader Ngarrindjerithat illustrates broader Ngarrindjerithat illustrates broader Ngarrindjericommunity perspectives. In particularcommunity perspectives. In particularcommunity perspectives. In particularcommunity perspectives. In particularcommunity perspectives. In particular,,,,,it calls for a newit calls for a newit calls for a newit calls for a newit calls for a new, negotiated, negotiated, negotiated, negotiated, negotiatedpartnership to steer the managementpartnership to steer the managementpartnership to steer the managementpartnership to steer the managementpartnership to steer the managementof this invaluable part of Ngarrindjeriof this invaluable part of Ngarrindjeriof this invaluable part of Ngarrindjeriof this invaluable part of Ngarrindjeriof this invaluable part of Ngarrindjericountry into the future and to ensurecountry into the future and to ensurecountry into the future and to ensurecountry into the future and to ensurecountry into the future and to ensureNgarrindjeri survival on their lands.Ngarrindjeri survival on their lands.Ngarrindjeri survival on their lands.Ngarrindjeri survival on their lands.Ngarrindjeri survival on their lands.

NgNgNgNgNgaaaaarrrrrrrrrriiiiinnnnndddddjjjjjerererereri Ci Ci Ci Ci CuuuuultltltltltururururureeeeeSSSSSTEVETEVETEVETEVETEVE H H H H HEMMINGEMMINGEMMINGEMMINGEMMING Australian Studies, Flinders University

TTTTTOMOMOMOMOM T T T T TREVREVREVREVREVORROWORROWORROWORROWORROW Acting Chair, Ngarrindjeri Heritage Committee and Ngarrindjeri Land and Progress Association

MMMMMAAAAATTTTTTTTTT R R R R RIGNEYIGNEYIGNEYIGNEYIGNEY Chair, Ngarrindjeri Native Title Management Committee

IIIIInnnnntrtrtrtrtrodododododuuuuuccccctttttioioioioionnnnnThe Ngarrindjeri authors of this chapterstrongly believe that a formal partnershipshould be established between theNgarrindjeri people and the Murray-DarlingBasin Commission (MDBC). This would be amajor step on the path towards a future inwhich the Murray Mouth area remains healthyand the Lower Murray, Lower Lakes andCoorong continue to sustain and nurture theNgarrindjeri people and their culture. As TomTrevorrow points out at the beginning of thisreport, the closure of the Murray Mouth is anindicator that Ngarrindjeri survival is at stake.

Please note, this is not an exhaustive reportand the reader’s attention is drawn to thefollowing chapter development discussion.

CCCCChhhhhaaaaapppppttttterererererdddddeeeeevvvvveeeee lololololopmpmpmpmpmeeeeennnnntttttdddddiiiiisssss cucucucucussssssssssioioioioionnnnnDue to the restricted time-frame available forthe development of this report, Tom Trevorrowand Matt Rigney, as senior Ngarrindjeripeople and experienced leaders in theircommunity, have made the decision to workwith Steve Hemming (non-Indigenousresearcher) to produce a preliminarydiscussion of the implications of the closure ofthe Murray Mouth for the Ngarrindjeri. Theybelieve that it is vital that a statementintroducing Ngarrindjeri perspectives besubmitted to the next Murray-Darling BasinMinisterial Council meeting. Along with theviews of Tom Trevorrow and Matt Rigney, thischapter also includes some reference toseveral key reports and publications providingNgarrindjeri knowledge and perspectivesrelevant to this issue. In particular, theNgarrindjeri Ramsar Working Group’s

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(NRWG) paper ‘Ngarrindjeri perspective onRamsar Issues’, developed for the Coorong,Lake Alexandrina and Lake Albert RamsarManagement Plan, is considered of centralimportance (NRWG 1999). Importantly, thisextended discussion of issues relevant to theclosure of the Murray Mouth has Ngarrindjericommunity endorsement.

The Ngarrindjeri authors of this reportconsider that their expertise in Ngarrindjericultural and political affairs, combined withthe positions that they presently occupy,provide them with the responsibility to takethis opportunity to identify a set of preliminaryrecommendations for the consideration of theMurray-Darling Basin Ministerial Council. Theydo not wish to discuss in any detail what areoften defined as the ‘cultural heritage’implications (often misunderstood by non-Indigenous people as relating only to the past)for the Ngarrindjeri. For example, this wouldinclude impacts on Dreaming sites andmiddens, or the spiritual significance ofdamage to the land and waters (see forexample: Fergie 1994 and Bell 1998). Such areport would take considerable time andbroad Ngarrindjeri community discussion.After their experiences with the Kumarangk(Hindmarsh Island) issue, the Ngarrindjeriauthors believe that these issues areNgarrindjeri business and should not be thestarting point and basis of a public discussionof the implication of the closure of the MurrayMouth for Ngarrindjeri people.

Of course, Ngarrindjeri people support thesharing of their knowledge with non-Indigenous people, but this must be onIndigenous terms. Camp Coorong’s RaceRelations and Cultural Education Centre, nearMeningie on the shores of Lake Albert, wasestablished in the 1980s by the NgarrindjeriLand and Progress Association (NLPA) to helpperform this function (see Hemming 1993).

The recommendations provided in this reportcontain a request for sufficient resources toenable the Ngarrindjeri to stage appropriate

community meetings to discuss theimplications of the closure of the MurrayMouth and develop a detailed and thoughtfulposition. This is a complex problem for theNgarrindjeri and it has a range of inter-related implications relating to political,economic, cultural and social issues.Ngarrindjeri interests in an area such as theMurray Mouth cannot be reduced to what isoften called ‘heritage’. The importance of theNgarrindjeri relationship to the land andwaters is made very clear by Tom Trevorrow atthe beginning of this chapter.

Finally, as mentioned above, it should berecognised that this is by no means anexhaustive report: it seeks predominantly todraw the attention of the relevant GovernmentMinisters to the urgent need for a new,negotiated, partnership between theNgarrindjeri and the MDBC in thedevelopment of a long-term approach to thesustainable management of the Murray-Darling Basin.

BBBBBaaaaackckckckckgrgrgrgrgroooooununununundddddIt has only been since the 1980s that the viewsand participation of Ngarrindjeri people havebeen considered important by StateGovernment agencies in the planning andmanagement of places such as nationalparks. The passing of the South AustralianAboriginal Heritage Act 1988 was a turningpoint in the involvement of South AustralianIndigenous people in issues associated withdevelopment, natural resource managementand regional planning.

Ngarrindjeri organisations such as the LowerMurray and Ngarrindjeri HeritageAssociations, the Lower Murray Nungas Club,the Raukkan Council and the NgarrindjeriLand and Progress Association have workedwith Government and private interests on abroad range of issues and projects.Unfortunately, the serious conflict over thebuilding of a bridge to Kumarangk

Ngarrindjeri Culture

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(Hindmarsh Island) has in many waysadversely affected the positive relations thatwere built up between the Ngarrindjeri andthe non-Indigenous community. The twoNgarrindjeri authors of this paper opposedthe building of the bridge and continue toadvocate the establishment of a ferry serviceto Kumarangk to provide alternative access tothe Island for Ngarrindjeri people.

The Ngarrindjeri manage their country and its‘natural resources’ in the ways taught to themby their old people. For example, fishing,hunting, the gathering of medicine plants andthe harvesting of sedges for basket makingare all governed by Ngarrindjeri tradition(Hemming et al. 1989, Bell 1998).

Ngarrindjeri people also engage in burningand clearing practices and re-vegetation ofdunes to protect and manage their country.Often families have particular rights andresponsibilities for certain areas. There arealso gender restrictions associated withplaces, practices and knowledge. Prior to the1980s, the Ngarrindjeri managed theircountry without significant Governmentrecognition of their rights to engage in thisprocess.

Since the 1980s, the Ngarrindjeri haveaccepted the challenge of working withGovernment organisations to educate thenon-Indigenous public about their culture andtraditions. The establishment of CampCoorong has provided a major impetus in theteaching of Ngarrindjeri culture and history.One of the key themes that Camp Coorongstaff has focussed on in their teaching hasbeen the degradation of the environment ofthe area and the cultural consequences of thisfor Ngarrindjeri and non-Indigenous people.The new Ngarrindjeri ecotourism venture atWarnung (Hack’s Point), whilst operating asan ecotourism venture, continues to have asits main messages the Ngarrindjeri connectionwith the land and waters and the impact ofthe continuing degradation of the

environment on Ngarrindjeri culture. Aspointed out in the NRWG’s submission(NRWG 1999):

Too much water has been divertedfrom the River system and not enoughwater now reaches the Lakes andCoorong. The quality of the water hasalso fallen. The water is cloudy,polluted and not fit for drinking. TheMurray, the Lakes and the Coorongare no longer environmentally healthyand this is partly why the Ngarrindjeripeople are not healthy. TheNgarrindjeri know that the Coorong,Lakes and River are dying.

It should also be remembered that theNgarrindjeri people’s native title claim, whichincludes the Murray Mouth area, has beenregistered in the Federal Court. This providescertain legal obligations to consult with theNgarrindjeri through their Ngarrindjeri NativeTitle Management Committee. Damage toNgarrindjeri native title rights and interests ispotentially a subject for compensation.

The South Australian Aboriginal Heritage Act1988 is also relevant to the implications ofMurray Mouth closure. An importantNgarrindjeri site is being damaged through acomplex series of actions that continue to leadto increasing environmental degradation. Theauthors of this paper recognise that the onlyreal solution to this problem is through long-term planning. This planning must be done inpartnership with the Ngarrindjeri.

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)

NgNgNgNgNgaaaaarrrrrrrrrriiiiinnnnndddddjjjjjerererereriiiiiPPPPPerererererspspspspspeeeee ccccctttttiiiiivvvvvesesesesesOOOOOn Rn Rn Rn Rn Ramamamamamsssssaaaaar r r r r IIIIIssssssssssuesuesuesuesuesA significant part of the Ngarrindjeri landsand waters is designated as a wetland ofinternational significance under the RamsarAgreement.

The Indigenous owners of these wetlands,which include the Murray Mouth area, have afundamental role to play in their sustainablemanagement. In their submission to theRamsar management plan, the NRWGsupported the principles of ‘wise’ and‘sustainable’ use of the wetlands (NRWG1999). This is what Ngarrindjeri have beendoing since the creation of their land andwaters.

One of the six objectives identified in theRamsar management plan highlights the needfor ‘increased opportunities for participationby the Ngarrindjeri people in the planningand management of the Coorong and LowerLakes Ramsar Wetlands subject to SouthAustralian Government policy relating to theresolution of native title claims’ (Departmentfor Environment, Heritage and AboriginalAffairs 2000a). The Ngarrindjeri people have,in numerous forums, expressed their desirefor a central role in the management of theirland and waters - not the least through thelodgement of their native title claim whichincludes the Murray Mouth area. TheNgarrindjeri authors of this report would liketo see a hand-back of the Coorong NationalPark, with a lease-back agreement and jointmanagement with the agency responsible fornational parks. They believe that theNgarrindjeri native title claim should not be animpediment to the development of formalagreements regarding joint management.

The consultative process developed forNgarrindjeri input into the Ramsarmanagement plan has been identified by

Ngarrindjeri people, and more broadly, as anexample of appropriate consultation (seeThomsen 2001). The Ngarrindjeri authors ofthis report believe that theNRWG’s submission should betreated as a starting point fordiscussions with the Ngarrindjericoncerning the implications ofMurray Mouth closure (NRWG1999).

The following are some of therelevant statements andrecommendations contained inthe submission:ooooo Ngarrindjeri people strongly

support the Ramsar principlesand objectives.

ooooo The production andimplementation of a RamsarPlan provides an opportunityfor reconciliation.

ooooo Ngarrindjeri seek a morevaluable role in the futuremanagement of the naturaland cultural resourcescontained within the Ramsarplanning area. Ngarrindjeribelieve such a role would be beneficial toall members of the community, not justthe Ngarrindjeri.

ooooo Ngarrindjeri support moves aimed atincreasing water flows and water qualityfor environmental purposes.

ooooo More water should be made available toreach the Lower Lakes and Coorong. Thiswater will help to support all life andnourish Ngarrindjeri country, Ngarrindjericulture and Ngarrindjeri people.

ooooo The quality of the water should beimproved.

ooooo The Upper Southeast Drainage Scheme’swaters should be added to the Coorongat Salt Creek. Many Ngarrindjeri Elderscan remember freshwater flows into theCoorong during the late 1950s andbelieve these flows brought new life to thesouthern lagoon.

Ngarrindjeri Culture

The Ngarrindjeri lands- inparticular the River, the

Lakes and the Coorong arecrucial for the survival of theNgarrindjeri people. They

have a spiritual andreligious connection with theland and the living things

associated with it.The fish, birds and other

living things are the Ngartjis(totems) of the Ngarrindjeripeople. Many Ngarrindjeri

people have a strongspiritual connection to theirNgartjis and a responsibility

to protect them. Withouttheir Njartjis they believe

they cannot survive.

(Ngarrindjeri RamsarWorking Group 1999).

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))The waters flowing down the Murray-

Darling system bring life to the River,the Lakes and Coorong. The watersbring life to the Ngarrindjeri too. Thisis both a practical and a spiritualstatement. There are extensiveculturally significant teachingsexplaining how the Ngarrindjeri worldwas created. Ngurunderi and theSeven Sisters are two of manyteachings which describe how the landand water, animals and people cameto be what and who they are.

The threat to Ngarrindjeri Ngartjis connectedwith the closure of the Murray Mouth is ofparticular concern to the Ngarrindjeri. Asstated by the NRWG (1999):

Many Ngarrindjeri people still retain aspecial relationship with specificwildlife species occurring within theplanning area. This totemicrelationship is deeply embedded inNgarrindjeri culture and spirituality.Many Ngarrindjeri people have theirown Ngartji or special friend. Thisassociation with wildlife provides aspecial perspective on Ramsar valuesand the maintenance of habitats.

Importantly for this report, it is often notunderstood that the Ngarrindjeri have fewresources and little infrastructure to respondto the growing pressures on them from a widerange of Government departments andagencies. To properly engage in the process of‘natural resource’ management theNgarrindjeri need substantial resources andinfrastructure. A considerable portion of whatthe Ngarrindjeri do as part of their‘responsibilities’, as a result of heritage andnative title legislation, is still largely voluntary.This creates enormous pressures onindividuals, families and communities andsignificantly adds to community stress andgeneral poor health. The decision to take partin the development of this report has posed

ooooo The manipulation of the barrages and themanipulation of Lake levels to improvenatural environmental processes issupported by Ngarrindjeri, particularly ifthis is in association with increased waterflows and an improvement in waterquality.

It was very disappointing to the Ngarrindjerithat the NRWG submission was not includedin the final report or even its appendices - asinitially expected.

DDDDDiiiiisssss cucucucucussssssssssioioioioionnnnnThe Murray Mouth is an important culturaland spiritual place for the Ngarrindjeri people(see for example: Bell 1998). It is part of anarea that is fundamentally important to thehealth of Ngarrindjeri people. There areDreaming stories such as Thukabi,Ngurunderi and the Seven Sisters associatedwith the Murray Mouth area that informs theNgarrindjeri people’s understanding of itssignificance. The relationship of the Dreamingancestor Ngurunderi to the area has forexample been the subject of publications,museum exhibitions and films (see Hemminget al. 1989, Bell 1998). The Murray Moutharea is also a part of the ‘meeting of thewaters’, a place where the mixing of thewaters is spiritually very important to theNgarrindjeri (Bell 1998: 563).

The NRWG (1999) makes the following pointabout the area’s cultural and spiritualsignificance:

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)

Ngarrindjeri CultureDepartment for Environment, Heritage andAboriginal Affairs 2000a and 2000b, andAlexandrina Council 2001). For example, theHindmarsh Island Management Plan raisesthe need for ‘protocols to involve theAboriginal Community in managementdecisions’ (Alexandrina Council 2001).

The urgent need for government bodies suchas the MDBC to negotiate an appropriateprocess enabling Ngarrindjeri to have acentral role in managing their land andwaters is highlighted in the following passageby the NRWG (1999):

The sense of feeling, sense ofbelonging, sense of responsibility forthe River, Lakes and Coorongexperienced by Ngarrindjeri peoplehas survived occupation, dispersaland attempted assimilation. Itcontinues to exist irrespective of whereNgarrindjeri people currently live. Thelink with the land lies at the heart andsoul of Ngarrindjeri culture. A properrelationship and role in managementof the land is a fundamental platformin building and maintainingNgarrindjeri culture and Ngarrindjeriself respect. Ngarrindjeri believe thattheir future involvement in themanagement of the land would bepositive and beneficial to all membersof the community, not justNgarrindjeri. It would represent asignificant step in the process ofreconciliation and co-existence. Thestrengthening of Ngarrindjeri peopleand their culture requires a seriousinvolvement in the managing of theirtraditional lands.

To begin to address the implications of theclosure of the Murray Mouth for theNgarrindjeri the following recommendationsneed to be seriously considered by the MDBMinisterial Council.

serious difficulties and created considerablestress for its Ngarrindjeri authors. The shorttime-frame and lack of resources has notenabled broad community consultation,placing the authors in the difficult position ofhaving to explain and justify their decisionsand involvement in the report process to thebroader Ngarrindjeri community.

This highlights the urgent need forGovernments to recognise the funding needsof the Ngarrindjeri to further develop relevantexpertise and appropriate infrastructure toassist their effective contribution to the long-term management of their lands and waters.

The growing environmental degradation ofthe Murray-Darling Basin and the threatened,continuing closure of the Murray Mouth, hasalready, and will continue to place enormouspressure on the Ngarrindjeri community.Along with the impact of the loss of lands,waters, Ngartjis and other ‘environmental’features comes an imposed, inappropriateapproach to involving Ngarrindjeri people inthe management of their lands and waters.All of these factors cause considerable culturaltrauma for the Ngarrindjeri.

CCCCCooooonnnnnccccc lululululusssssioioioioionnnnnThe Murray-Darling Basin Sustainability Planstates that ‘natural resources management inthe Basin requires’, along with several otherkey points, the ‘recognition of the rights andaspirations of Indigenous Australians’(Murray-Darling Basin Commission 1999).Along with the broader issues raised by thisreport, this also requires careful considerationof the implications of the Ngarrindjeri nativetitle claim and Ngarrindjeri heritage interestsover the Lower Murray, Lower Lakes andCoorong for the management of the area. Anumber of recently developed plans haverecognised the importance of the Ngarrindjeripeople’s role in the management andplanning process (see for examples:

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KKKKKeeeeey poy poy poy poy poiiiiinnnnntttttsssssοοοοο The Ngarrindjeri are culturally and

spiritually part of the Murray Mouth areaand the Lower Murray, Lakes andCoorong region. The value anduniqueness of Ngarrindjeri knowledge,beliefs and culture must be valued,recognised and respected by the MDBCand the wider community for the well-being and health of the Ngarrindjeripeople and their land and waters to beassured.

οοοοο The value of Ngarrindjeri cultural andspiritual knowledge to the MDB planningand management process must berecognised and where culturallyappropriate, respectfully utilized.

οοοοο Funds are required to enableNgarrrindjeri communities to meet,discuss and develop a long-term strategyfor maintaining the health of their landsand waters - including the Murray Moutharea.

οοοοο A formal agreement and long-termprocess should be developed between theNgarrindjeri and the MDBC to secure ahealthy future for Ngarrindjeri people,their lands and waters.

οοοοο Dredging of the Murray Mouth andsurrounding areas is considered culturallyinappropriate. The Ngarrindjeri authors ofthis report believe any short-term fix willhave dire consequences for the MurrayMouth area. Proper and appropriateplanning must take place. This sentimenthas been expressed widely by Ngarrindjeripeople. Recommendations were madeduring Ramsar consultations that broadNgarrindjeri community negotiations anddiscussions should be undertaken todetermine the issues associated with anydredging in the area. The problem lies notat the Mouth - it exists at many otherplaces throughout the River system.

οοοοο We recommend the NRWG’s submissionto the Coorong, Lake Albert and LakeAlexandrina Ramsar Management Plan(NRWG 1999) as a valuable extendeddiscussion of issues relevant to the impact

of the closure of the Murray Mouth onthe Ngarrindjeri. This submission wasendorsed by the Ngarrindjeri community.

We believe that it is in the best interests of allAustralians to work closely with theNgarrindjeri and other Indigenous groups toplan and secure a healthy future for theMurray-Darling Basin.

RRRRReeeeeferferferferfereeeeennnnncccccesesesesesAlexandrina Council (2001) Hindmarsh Island

Management Plan. Goolwa.Bell D (1998) Ngarrindjeri Wurruwarrin: A world

that is, was, and will be. Spinifex, NorthMelbourne.

Department for Environment, Heritage andAboriginal Affairs (2000a) Coorong and LakesAlexandrina and Albert Ramsar ManagementPlan. Adelaide, South Australia.

Department for Environment, Heritage andAboriginal Affairs (2000b) Coroong NationalPark Tourism and Recreation Plan. Adelaide,South Australia.

Fergie D (1994) To all the mothers that were, to allthe mothers that are, and to all the mothersthat will be: An anthropological assessment ofthe threat of injury and desecration toAboriginal tradition by the proposedHindmarsh Island Bridge construction. AReport to the Aboriginal Legal RightsMovement (SA), Adelaide.

Hemming S (1993) ‘Camp Coorong - CombiningRace Relations and Cultural Education’ SocialAlternatives 12(1):37-40.

Hemming S, Jones P and Clarke P (1989)Ngurunderi: An Aboriginal Dreaming. SouthAustralian Museum, Adelaide.

Murray-Darling Basin Commission (1999) Murray-Darling Basin Commission Sustainability Plan.Canberra.

Ngarrindjeri Ramsar Working Group (1999)‘Ngarrindjeri perspectives on Ramsar Issues’ inDraft Coorong and Lakes Alexandrina andAlbert Ramsar Management Plan, Appendix 8.South Australian Department for Environment,Heritage and Aboriginal Affairs, Adelaide.

Thomsen DA (2001) Care or Control? Ngarrindjeriparticipation in natural resource planning.Honours Thesis, Department of Agronomy andFarming Systems, University of Adelaide.

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“Many fish species depend on movement“Many fish species depend on movement“Many fish species depend on movement“Many fish species depend on movement“Many fish species depend on movementfrom the ocean into the estuary andfrom the ocean into the estuary andfrom the ocean into the estuary andfrom the ocean into the estuary andfrom the ocean into the estuary andfreshwater Lower Lakes for reproduction andfreshwater Lower Lakes for reproduction andfreshwater Lower Lakes for reproduction andfreshwater Lower Lakes for reproduction andfreshwater Lower Lakes for reproduction andrecruitment.”recruitment.”recruitment.”recruitment.”recruitment.”

Garry Hera-Singh, Southern Fisherman’s Association

“Many fish species depend on movement“Many fish species depend on movement“Many fish species depend on movement“Many fish species depend on movement“Many fish species depend on movementfrom the ocean into the estuary andfrom the ocean into the estuary andfrom the ocean into the estuary andfrom the ocean into the estuary andfrom the ocean into the estuary andfreshwater Lower Lakes for reproduction andfreshwater Lower Lakes for reproduction andfreshwater Lower Lakes for reproduction andfreshwater Lower Lakes for reproduction andfreshwater Lower Lakes for reproduction andrecruitment.”recruitment.”recruitment.”recruitment.”recruitment.”

Garry Hera-Singh, Southern Fisherman’s Association

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FFFFFiiiiissssshhhhhiiiiinnnnng Ig Ig Ig Ig InnnnnddddduuuuussssstrtrtrtrtryyyyyGGGGGARRARRARRARRARRYYYYY H H H H HERAERAERAERAERA-----SSSSSINGHINGHINGHINGHINGH Southern Fisherman’s Association

zIIIIInnnnntrtrtrtrtrodododododuuuuuccccctttttioioioioionnnnnClosure of the Murray Mouth would have asignificant impact on the fishing industry in theCoorong. With the construction of thebarrages, altered tidal regime of the Murrayestuary and modified River flow, the threat ofMurray Mouth closure has increased. Manyfish species depend on movement from theocean into the estuary and freshwater LowerLakes for reproduction and recruitment.

Key species are Mulloway, Goolwa Cockles,Black Bream, Greenback Flounder and Yellow-Eye Mullet.

MullowayMullowayMullowayMullowayMulloway(((((Argyrosomus japonicusArgyrosomus japonicusArgyrosomus japonicusArgyrosomus japonicusArgyrosomus japonicus)))))This species breeds at sea. Mulloway one-yearand older are attracted to the Coorong byfreshwater flows leaving the Murray Mouth.They utilize the Coorong as an area to gain

condition in preparation for spawningelsewhere. However, access to the region isnot essential for their survival.

Regardless of Murray Mouth closure,Mulloway breeding and development willcontinue offshore. Hence the Mulloway fisheryis not in danger from a likely Mouth closure.

Part of the harvest of Mulloway is undertakenoff the ocean beaches in the vicinity of theMurray Mouth. Lack of flows through theMouth will not attract these fish inshoresufficiently close for them to be accessible torecreational and commercial fishers. Areduced catch-per-unit-effort in these sectorsdoes not necessarily mean that the stock hasdeclined as previous perceptions have implied,but local commercial fishers will suffersignificant economic loss and recreationalfishers will suffer greatly reducedopportunities.

If the passage for fish between theIf the passage for fish between theIf the passage for fish between theIf the passage for fish between theIf the passage for fish between thesea, Lower Lakes and estuary issea, Lower Lakes and estuary issea, Lower Lakes and estuary issea, Lower Lakes and estuary issea, Lower Lakes and estuary isprevented by closure of the Murrayprevented by closure of the Murrayprevented by closure of the Murrayprevented by closure of the Murrayprevented by closure of the MurrayMouth, several economicallyMouth, several economicallyMouth, several economicallyMouth, several economicallyMouth, several economicallyimportant fish species will decline.important fish species will decline.important fish species will decline.important fish species will decline.important fish species will decline.

This chapter outlines the SouthernThis chapter outlines the SouthernThis chapter outlines the SouthernThis chapter outlines the SouthernThis chapter outlines the SouthernFFFFFishermanishermanishermanishermanisherman’s Associations’ opinion on’s Associations’ opinion on’s Associations’ opinion on’s Associations’ opinion on’s Associations’ opinion onthe expected implications of Mouththe expected implications of Mouththe expected implications of Mouththe expected implications of Mouththe expected implications of Mouthclosure on major commercial andclosure on major commercial andclosure on major commercial andclosure on major commercial andclosure on major commercial andrecreational fish species in therecreational fish species in therecreational fish species in therecreational fish species in therecreational fish species in theCoorong region and marine fisheries.Coorong region and marine fisheries.Coorong region and marine fisheries.Coorong region and marine fisheries.Coorong region and marine fisheries.

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FFFFFiiiiissssshhhhhiiiiinnnnng Ig Ig Ig Ig InnnnnddddduuuuussssstrtrtrtrtryyyyyGoolwa CocklesGoolwa CocklesGoolwa CocklesGoolwa CocklesGoolwa Cockles(((((Donax deltoidesDonax deltoidesDonax deltoidesDonax deltoidesDonax deltoides)))))Cockle stocks are dependent on River Murrayoutflows during spring for strong recruitmentand subsequent growth.

The cockles inhabit the beaches along theCoorong and are harvested in their secondyear of growth. If not harvested, they live foran average of four years.

Adult cockles are not directly impacted byMurray Mouth closure. However, recruitmentis immediately impacted by reducedavailability of nutrients, which in turn wouldlead to an increased rate of juvenile mortality.Worldwide, cockle populations have regularlydeclined following over harvest during certainperiods and the species often fail to rapidlyrebound when more favourable conditionseventuate.

The Goolwa cockle population in the Coorongregion is the largest in the world and isprotected from over harvest by restrictingfishers to manual harvesting methods.

Black Bream (Black Bream (Black Bream (Black Bream (Black Bream (Acanthopagrus butcheriAcanthopagrus butcheriAcanthopagrus butcheriAcanthopagrus butcheriAcanthopagrus butcheri )))))and Greenback Flounder (and Greenback Flounder (and Greenback Flounder (and Greenback Flounder (and Greenback Flounder (RhombosoleaRhombosoleaRhombosoleaRhombosoleaRhombosoleataparinataparinataparinataparinataparina)))))These estuarine species live and reproduce inthe Coorong. Breeding success is dependenton a smooth and consistent flow of freshwaterinto the Coorong.

Currently, stocks of Black Bream andGreenback Flounder are well below optimallevels. This is being mitigated, however,through revised barrage operations (byallowing for the slower release of freshwaterinto the estuary).

Although closure of the Murray Mouth wouldnot have a significant impact on these species,changes in the Coorong habitat and aprolonged no flow regime will directly affectfish recruitment and growth with flow oneffects to commercial and recreational fishers.

YYYYYellowellowellowellowellow-Eye Mullet (-Eye Mullet (-Eye Mullet (-Eye Mullet (-Eye Mullet (Aldrichetta forsteriAldrichetta forsteriAldrichetta forsteriAldrichetta forsteriAldrichetta forsteri)))))This species is extremely abundant in theCoorong. Current Yellow-Eye Mullet stockswould survive through a prolonged MurrayMouth closure.

If the summers are hot and evaporative lossesare higher than average, there is potential forvery large fish kills to occur due to low oxygen.

This would destroy Yellow-Eye Mullet stocks inthe Coorong. (Yellow-Eye Mullet currentlymake up about 50% by weight of the currentcommercial Coorong catch.)

Other SpeciesOther SpeciesOther SpeciesOther SpeciesOther SpeciesCoorong crabs (Mottled Shore Crab Carcinusmaenas), a key bio-indicator of the Coorong,would be reduced should the duration of aMurray Mouth closure extend beyond onesummer.

Fish species, such as the Small-MouthedHardy Head (Atherinosmoa microstoma),would benefit through a reduction inpredators entering the Coorong via theMurray Mouth (for example, Mulloway). Theincrease in these species, however, wouldhave no beneficial impact on the fishingindustry.

Other marine species which occur in theCoorong as vagrants (for example, TommyRuffs Arripis georgianus, Australian SalmonArripis trutta, most species of Shark andGurnards) will be denied access, but these areneither commercially nor recreationallyimportant.

z

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DDDDDiiiiisssss cucucucucussssssssssioioioioionnnnnThe likely period for closure of the MurrayMouth would be following summer. If closureoccurred during the cooler months and onlyextended over the following four to sixmonths, impacts on fish stock survival wouldbe minimal. The abundance of all specieswould be significantly reduced due to lack ofnatural migration between the ocean and theCoorong.

If, however, the closure was prolonged andincluded the following summer, or evenextended for several years, the fishing industrywould experience fish loss, threatening theeconomic viability of the commercial fishery2

and creating an environment in which arecreational fishery cannot be carried.

Habitat impacts related to the fishery are alsoimportant to consider. Closure will likely occurduring autumn. There is potential, however,for low oxygen kills related to algal bloomsassociated with warm, still, high nutrient waterif Murray Mouth closure continued until thefollowing summer. Closure during warmermonths, would trigger fish kills over sand flatsand shallow bays in the early hours of themorning after several hot, still days. If oxygenlevels in nearby channels remain suitable forfish (that is, above 1-2ppm), this will not be ofmajor concern.

Long periods of hot weather (greater than twoweeks) would increase the probability ofoxygen levels declining below survival levels of1-2ppm. This would be a major concern tofish stocks.

The majority of the Northern Lagoon of theCoorong is likely to become hypersaline withan extended Mouth closure. The estuaryregion adjacent to the barrages would be lessaffected due to leakage of freshwater throughthe barrage network and adjoining islands(causeways).

CCCCCooooonnnnnccccc lululululusssssioioioioionnnnnAs can be seen from the above discussion,closure of the Murray Mouth brings with it thepossibility of the existing commercial fisherybecoming uneconomic and recreationalfishing also having to decline.

It is very unclear, if there is a long-term closure(several seasons) and major fish kills, howmany years it would take for the fishingindustry to recover.

2 The commercial fishery involves 37 fishers employingapproximately 110 people with a landed wholesalevalue of approximately $5.5 million per annum

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“The Murray Mouth and the Coorong are unique,“The Murray Mouth and the Coorong are unique,“The Murray Mouth and the Coorong are unique,“The Murray Mouth and the Coorong are unique,“The Murray Mouth and the Coorong are unique,almost iconic sites…”almost iconic sites…”almost iconic sites…”almost iconic sites…”almost iconic sites…”

Freya Higgins-Desbiolles, School of International Business,University of South AustraliaGlen Jones, Boating Industry Association of South Australia

“The Murray Mouth and the Coorong are unique,“The Murray Mouth and the Coorong are unique,“The Murray Mouth and the Coorong are unique,“The Murray Mouth and the Coorong are unique,“The Murray Mouth and the Coorong are unique,almost iconic sites…”almost iconic sites…”almost iconic sites…”almost iconic sites…”almost iconic sites…”

Freya Higgins-Desbiolles, School of International Business,University of South AustraliaGlen Jones, Boating Industry Association of South Australia

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RRRRReeeeecrcrcrcrcreaeaeaeaeatttttioioioioion & Tn & Tn & Tn & Tn & TooooourururururiiiiismsmsmsmsmFFFFFREYREYREYREYREYAAAAA H H H H HIGGINSIGGINSIGGINSIGGINSIGGINS-D-D-D-D-DESBIOLLESESBIOLLESESBIOLLESESBIOLLESESBIOLLES School of International Business, University of South Australia

GGGGGLENLENLENLENLEN J J J J JONESONESONESONESONES Boating Industry Association of South Australia

This chapter assesses the likelyThis chapter assesses the likelyThis chapter assesses the likelyThis chapter assesses the likelyThis chapter assesses the likelyimpacts that the closure of the Murrayimpacts that the closure of the Murrayimpacts that the closure of the Murrayimpacts that the closure of the Murrayimpacts that the closure of the MurrayMouth would have on the tourism andMouth would have on the tourism andMouth would have on the tourism andMouth would have on the tourism andMouth would have on the tourism andrecreation industries of the Coorongrecreation industries of the Coorongrecreation industries of the Coorongrecreation industries of the Coorongrecreation industries of the Coorongand Lower Lakes area of Southand Lower Lakes area of Southand Lower Lakes area of Southand Lower Lakes area of Southand Lower Lakes area of SouthAustralia as well as addressing theAustralia as well as addressing theAustralia as well as addressing theAustralia as well as addressing theAustralia as well as addressing thesignificance of the area from a varietysignificance of the area from a varietysignificance of the area from a varietysignificance of the area from a varietysignificance of the area from a varietyof perspectives.of perspectives.of perspectives.of perspectives.of perspectives.

The importance of the Murray MouthThe importance of the Murray MouthThe importance of the Murray MouthThe importance of the Murray MouthThe importance of the Murray Mouthto the tourism and recreationto the tourism and recreationto the tourism and recreationto the tourism and recreationto the tourism and recreationindustries should not beindustries should not beindustries should not beindustries should not beindustries should not beunderestimated and requiresunderestimated and requiresunderestimated and requiresunderestimated and requiresunderestimated and requiresappropriate management strategies.appropriate management strategies.appropriate management strategies.appropriate management strategies.appropriate management strategies.

IIIIInnnnntrtrtrtrtrodododododuuuuuccccctttttioioioioionnnnnMuch of the Coorong and Lower Lakes areasare designated as a wetland of internationalsignificance under the Ramsar Agreement.Tourism and recreational users are allowedaccess under the principle of ‘wise use’ whichrefers to “… their sustainable utilisation forthe benefit of mankind in a way compatiblewith the maintenance of the natural propertiesof the ecosystem” (Department of Environmentand Heritage 2000).

This area is one of the most important tourismand recreation resources to the people of theAdelaide metropolitan area because of itsunique natural beauty and proximity to thecity (Berggy and Gilliland 1998).

To assess the perceived impacts of MurrayMouth closure on recreational and tourismstakeholders in the area, two meetings wereconvened in which a cross section ofinterested parties were invited to comment onperceptions of the relevant issues underconsideration. Where particular stakeholderscould not attend such meetings, they wereconsulted separately as required. Other

information was gathered from publishedmaterials and is included in the reference listat the end of this chapter.

In considering implications of the closure ofthe Murray Mouth, the two important issuesare the duration of the closure and thefrequency of closures.

In 1981, for the first recorded time sinceEuropean settlement, the Mouth closedcompletely for 17 weeks. However, it appearsthat when discussion is focused on the‘closure of the Mouth’, it is often not wellunderstood that the ‘plug’ that blocks theMouth is not necessarily located right in theMouth itself. For instance, the ‘plug’ thatexisted at the end of 2000, was a large areaof drift sand on the inside of the Mouth whichbarred access from the Goolwa Lock, past theMouth and on into the Coorong and viceversa.

When the Mouth is silted in this way,recreational and commercial boating accessfrom the Goolwa area to the Coorong (andvice versa) must be via the hand operatedTauwitchere Lock.

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RRRRReeeeecrcrcrcrcreaeaeaeaeatttttioioioioion & Tn & Tn & Tn & Tn & TooooourururururiiiiismsmsmsmsmIn 2001/2002, the Mouth silted up early in thespring/summer season. This is raising graveconcerns because this situation may notchange until significant rainfall occursupstream at the top of the catchment. Thissilting will seriously impede recreational andcommercial boating activities in the Goolwa,Murray Mouth and Coorong areas to thedetriment of the regional economy. (See ‘Whatis Possible: Hydrology and Morphology’chapter for further discussion on land formchanges.)

With significant national tourism events3

increasingly staged in the area, theimplications of closure are being more widelyrecognised than at any time in the past.

IIIIImmmmmpopopopoporrrrrtttttaaaaannnnnccccce oe oe oe oe of thf thf thf thf theeeeeeeeeecccccooooololololologggggiiiiicccccal cal cal cal cal chhhhhaaaaarrrrraaaaacccccttttterererererWhile the various stakeholders consulted aspart of this study have particular concerns, themajority of recreational and tourism usersalso have something in common – they areattracted to the area by its ecologicalattributes.

When the Mouth closes for a significantperiod, resulting in a severe decline in waterquality, the attendant problems of smellymudflats and degradation in the visualpanorama will deter visits by ecotourists whoare searching for pristine environments.

Birdwatchers will follow the waders to betterwetlands, and recreational boaters and fisherswho cannot find convenient passage betweenthe Goolwa and Coorong channels are likelyto leave for destinations ‘upriver’.

Closure of the Mouth has been identified asone of the significant threats of concernduring the community consultation process inthe formulation of the Coorong National ParkTourism and Recreation Plan (National Parksand Wildlife SA 1999:25).

RRRRReeeeecrcrcrcrcreaeaeaeaeatttttioioioioionnnnnal ual ual ual ual usersersersersersssssRecreational FishingRecreational FishingRecreational FishingRecreational FishingRecreational FishingRecreational fishing is important to theeconomy of the region. However, the value isdifficult to quantify (pers comm. Hera-Singh).

It is estimated that recreational fishing on theRiver Murray contributes $400 million per yearto the South Australian economy (Murray-Darling Association 2001). The region aroundthe Mouth is important for recreational fishingdue to the variety of fish that feed and breedin the area and the unique scenery to befound there.

Recreational fishers can use four-wheel drivevehicles or watercraft to reach the lessaccessible parts of the area, such as theYounghusband Peninsula, or use beaches andboat ramps at accessible points like SugarsBeach. However, the most popular area forrecreational fishers tends to be that betweenthe Mouth and Pelican Point and the mostpopular catches are Yellow-Eye Mullet andMulloway (Kluske 1996).

Mouth closure has the potential to adverselyaffect recreational fishing in the area. Whenthe Mouth silts up for a significant period, thewater quality is degraded due to restrictedflow of water through the Mouth causing thegradual heating up of shallow trapped waterthat can result in fish deaths and negativeimpacts on breeding patterns.

For more detail on the likely impacts forrecreational fishers, see the ‘Fishing Industry’chapter.

Recreational BoatersRecreational BoatersRecreational BoatersRecreational BoatersRecreational BoatersThe Coorong and Lower Lakes area issignificant for recreational boating, offeringover 800km2 of ‘boating opportunities’. The

3 Such as the celebration in February 2001 whenTammy van Wisse reached the Mouth following herepic swim of the entire length of the River Murray, the“Source to Sea” Bicentennial Boating Event October2001, and the launch of the International Year ofEcotourism 2002.

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types of craft used in the area includepowerboats, sailboats, jet skis and canoes.Some of the activities associated with

recreational boating conducted inthe area include water skiing andfishing.

The peak industry body forrecreational and light commercialboating in South Australia, theBoating Industry Association ofSouth Australia Inc. (BIASA),estimates that the number oftrailerable watercraft in regular usein the area to be not less than6000 (January 2001 Transport SASurvey). Total boat use is estimatedat 120 000 user days per annum.Extrapolating from an estimate byBIASA of $40 per day averagespending on consumables such asfood, drink and fuel, this couldequate to nearly $5 million beinginjected into the local economyannually from the boating industryalone.

Recreational boats operating in thearea that are not trailerable (oftenby virtue of their size), numberapproximately 800 (March 2001BIASA Survey). Average sized boatsprovide accommodation for fourpersons. Extrapolating fromBIASA’s estimate of$40 per day average spending onconsumables referred to above,this could equate to a further(nearly) $3 million annually fromthe boating industry.

Significant boating events are alsoimportant tourism and recreationalattractions to the area, includingthe Goolwa-Meningie Yacht Race(SA), Milang Goolwa FreshwaterClassic and South Australia’sWooden Boat Festival at Goolwa.

Infrastructure development is occurring whichwill encourage further recreational boatinguse of the area, including the continuedexpansion of Hindmarsh Island Marina in2002 and a $4 million Goolwa Wharf Precinctredevelopment project being undertaken byAlexandrina Council in 2002.

The silting up of the Murray Mouth has majorimplications for recreational boaters. Thesilting up of channels can block accessbetween the Goolwa channel and the rest ofthe Coorong making boat passage extremelydifficult.

Safety concerns are also significant. Boatersmay be unaware that a channel previouslyopen has become impassable overnight andcan end up in grave difficulty. Furthermore,when the Mouth closes, the Marine SafetyOfficers, Fisheries Inspectors and otherregulatory personnel cannot patrol theirassigned areas and therefore are unable tocarry out marine safety and associatedregulatory checks on boaters using the area(pers comm. Neville Clifford).

Recreational boaters are drawn to the area toenjoy the opportunities and beauty of theMurray Mouth and the Coorong NationalPark. Recreational stakeholders consultedindicated that many of these people wouldpermanently move ‘upriver’ should a Mouthclosure prevent their free passage through theCoorong waterways. Therefore, other tourismregions such as the Murraylands might benefitat the expense of those ‘down river’.

BirdwatchersBirdwatchersBirdwatchersBirdwatchersBirdwatchersThe wetlands of the Coorong and LowerLakes attract some 85 species of waterbirds,ranking as one of the most significant five orsix waterbird sites in the country (amongst thetop handful in the world). Access to this areais therefore highly valued by birdwatchers(Murray-Darling Association 2001).

Mouth closure and reduced River flows woulddiminish the productivity of the estuarine

Boating StatisticsBoating StatisticsBoating StatisticsBoating StatisticsBoating Statistics

o o o o o Taking into account ‘allboats’ (trailerable and nontrailerable) in terms ofvisitation/recreation daysspent in the Murray/LowerLakes and Coorong systemin South Australia, theAustralian Bureau ofStatistics estimates that12.6% of South Australiansare regularly involved inboating activities (in excessof 130 000 people).

o o o o o Nearly 700 000 leisuredays or ‘holiday days’ areenjoyed, annually, on boardboats which are moored ininland waters (River Murray,Lakes and Coorong)annually. This visitationinvolves fuelling, servicing ofcraft, catering, purchase ofother supplies, gas, ice,fishing tackle, food anddrinks and delivers anenormous economic benefitto the regional communitieslocated en-route to, and on,the waterway. Of these‘holiday days’, 170 000 arevia the house boat industryand another 175 000‘holiday days’ arecontributed by moretraditional types of craft,normally single hulled(including yachts andcruisers etc which aremoored).

o o o o o Trailerable boats alsoprovide live-aboardaccommodation and deliversignificant economic benefitto the communities en-routeto, or on, the waterways.

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waters, reducing their habitat value. Manywaders would be forced to either leave formore amenable wetlands or die out(Department of Environment and Heritage2000: 17).

The decline of migratory waders is of concernto committed environmentalists, birdwatchersand others (see ‘Migratory Waders’ chapter).

From a tourism perspective, research by theSouth Australian Tourism Commission (SATC)identified bird watching as one of the morelucrative tourism markets to pursue (SouthAustralian Tourism Commission 2001). If birdsare forced to leave the Coorong due to theimpacts of Mouth closure, the tourism impactswould be significant.

Bush WBush WBush WBush WBush WalkersalkersalkersalkersalkersMany visitors to the area enjoy the scenicbeauty by using designated walking trails suchas the Murray Mouth walk on the Sir RichardPeninsula.

Mouth closure might serve as an addedattraction to bush walkers because it wouldinvite viewing and areas previouslyinaccessible to walkers could becometemporarily accessible. For example, walkersmay be able to cross from Hindmarsh Island’sSugars Beach to the Mouth and between theSir Richard and Younghusband peninsulas.Additional management may be needed toaddress potential impacts.

FFFFFourourourourour-----Wheel Drive UsersWheel Drive UsersWheel Drive UsersWheel Drive UsersWheel Drive UsersFour-wheel drive enthusiasts are commonvisitors to the areas of the Sir RichardPeninsula and Younghusband Peninsula,which are located on either side of the MurrayMouth. Their vehicles are allowed accessthrough designated tracks and under certainregulations. The representative body, theSouth Australian Association of Four WheelDrive Clubs, does not see the issue of closureof the Mouth as a concern for their membersbecause regulations enforced by the NationalParks and Wildlife Officers in the region will

come in force when the Mouth closes.Namely, four-wheel drive vehicles will beprohibited from using Mouth closure as anopportunity to cross between the Sir Richardand Younghusband peninsulas as an issue ofsafety (pers comm. Don Ransom).

TTTTTooooourururururiiiiismsmsmsmsmTourism to this area is of growing importanceas evidenced by the South Australian TourismCommission’s (SATC) ‘Australian launch’ ofthe International Year of Ecotourism 2002 inthe Coorong National Park. In particular,because of the attractions of the CoorongNational Park, this area is seen as ideal fornature-based and ecotourism promotionwhich is a lucrative niche market that is inhigh demand and provides high yield.

Tourism data specific to the location thatwould be impacted by changes in the MurrayMouth is not available making it difficult toascertain quantitatively how valuable tourismis to the area. Data for the Coorong NationalPark provides some insight. In 2000/2001,106 200 people visited the Park (SATC 2000/2001), the third highest number of visitors(after the Flinders Ranges and Innes-YorkePeninsula national parks) of all of SouthAustralia’s non-metropolitan parks.

Coorong National PCoorong National PCoorong National PCoorong National PCoorong National ParkarkarkarkarkThe South Australian Government hasformulated a Parks Agenda in consultationwith the community to provide a frameworkfor the management of South Australia’snatural resources.

Key elements of the Parks Agenda include:ooooo to create a representative and

professionally managed parks and wildlifesystem

ooooo to encourage an understanding,supportive and active communitycommitted to its parks

ooooo to deliver quality services which activelypromote the conservation ethic, and

ooooo to promote sustainable businessopportunities (The Parks Agenda 1997:4).

RRRRReeeeecrcrcrcrcreaeaeaeaeatttttioioioioion & Tn & Tn & Tn & Tn & Tooooourururururiiiiismsmsmsmsm

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The Parks Agenda also provides a “valuableframework for guiding the planning anddevelopment of visitor services within theCoorong National Park”. Initiatives towardsthis include:ooooo a review of standards for parks visitor

infrastructure and a strategic upgrade offacilities for key parks

ooooo the systematic collection and evaluation ofquantitative and qualitative visitor data toassess trends for visitor numbers andlevels of satisfaction

ooooo a review of standards for the delivery ofinformation and interpretation servicesand monitoring performance againstbenchmarks

ooooo the preparation of a marketing plan inconsultation with the tourism industry

ooooo the adoption of a client-oriented approachto service delivery

ooooo the application of ‘best practice’ in thedelivery of visitor services and themaintenance of quality standards by aregular review in consultation with otheragencies

ooooo the strengthening of our [National Parksand Wildlife SA] relationship with thetourism industry by joining and activelyparticipating in industry groups andRegional Tourism Boards (The ParksAgenda 1997: 14-15).

OOOOOththththther Rer Rer Rer Rer ReeeeegggggioioioioionnnnnsssssThree tourism regions have an interest in thearea:ooooo Fleurieu Peninsula Region, which

encompasses the important tourist centreof Goolwa

ooooo Limestone Coast Region (formerly knownas the South East Region),which recentlyexpanded to include the Coorong in itsmarketing campaigns, and

ooooo Murraylands Region, which views theCoorong National Park as a key asset forattracting visitors.

Alexandrina Council in its recent ManagementPlan for Hindmarsh Island calls for thedevelopment of tourism in the immediate area

of the Murray Mouth, including infrastructureto cater for large tour buses and theirpassengers and an interpretive centre nearSugars Beach on Hindmarsh Island (Day2001).

Also important is the purchase of the Wyngateproperty by the South Australian andCommonwealth governments, which includes1081 hectares of south-eastern HindmarshIsland (opposite the Murray Mouth). Reasonsunderpinning the purchase are diverse,ranging from assisting the Save the Murrayprogram, protecting wetlands andincorporating the Murray Mouth islands intothe Coorong National Park. According to aDepartment for Environment and Heritagepublication, enhancing South Australianecotourism to the Mouth is also a significantmotivation (Department for Environment andHeritage 2001).

Additionally, the Marina Hindmarsh Islanddevelopment has the potential to boosttourism with plans to become the largest suchdevelopment in the southern hemisphere, withover 1000 residential properties, 1100 berths,four-star resort, yacht club, tavern and retailfacilities.

Finally, the South Australian TourismCommission has focused considerable energyon promoting the nature-based attractions ofSouth Australia4 . The Murray Mouth and theCoorong are unique, iconic sites and serve todifferentiate South Australia from itscompetition. As a result, the SATC’s upcomingreview of the State Tourism Plan 2001-2006will have the Coorong as an important focusof promotion (pers comm. Leanne Muffet).

NgNgNgNgNgaaaaarrrrrrrrrriiiiinnnnndddddjjjjjerererereriiiiiTTTTTooooourururururiiiiismsmsmsmsmMany Ngarrindjeri are ambivalent abouttourism’s impacts because of the long historyof being the subject of the tourists’ ‘gaze’ andconflicts such as the Hindmarsh Island bridgecontroversy (see ‘Ngarrindjeri Culture’chapter).4 See SATC brochure “South AustralianNature”, 2002.

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However, the potential for Ngarrindjericontributions to enhance the tourism productof the area is well recognised and is evident inmany documents and plans (see NationalParks and Wildlife 1999 and Day 2001).Current involvement in tourism in the areaincludes two particularly significant ventures:ooooo Camp Coorong’s Race Relations and

Cultural Education Centre, located 10kmsouth of Meningie, teaches about theenvironmental changes the Coorong hasundergone from human impact. It hasbeen featured in several importantnational tourism publications such as ATalent for Tourism (1996), and hasreceived a number of tourism awards.

ooooo Coorong Wilderness Lodge, located atHack’s Peninsula on the Coorong,receives visits from organised touristgroups and individual motorists on theMelbourne to Adelaide circuit.

Both of these ventures rely on the environmentfor the services they provide.

Environmental degradation will jeopardise thebush tucker and bush medicine walks offered,endanger the rushes required for the basket-weaving workshops and diminish the drawingpower of their environmental educationprograms.

Also important to note, the Ngarrindjeri holda registered Native Title claim to this area asof January 2000. This predicates specific legalobligations in any matters such as tourismdevelopment that subsequently effects thisarea.

CCCCCooooonnnnnccccc lululululusssssioioioioionnnnnWhile closure of the Murray Mouth might bean initial attraction, as tourists and visitors aredrawn to see what is still a relatively unusualphenomenon, this impact would be short-livedand yield little immediate or ongoingeconomic value to the economy. There is littledoubt among tourism stakeholders that in thelonger term, the negative impacts would besignificant, particularly for Goolwa, which ispromoted as a gateway to the Coorong andthe Mouth.

Tourism operators who conduct boat tours inthe area will be directly affected by closure ofthe Mouth, but there are also many othersthat will feel the effects including: marinas,accommodation sector, and providers ofservices and amenities (such as food andliquor outlets, petrol stations, retail shops,etc).

There are currently 12 operators whoconsistently take tourists on cruises in thedesignated area. When the Murray Mouthsilts up they must find alternative routes to theGoolwa channel. One alternative for the boatoperators is to launch from the ramp atMundoo Channel, as has been occurringsince December 2001 because of the silting ofthe Mouth. However, this option is less thanideal due to the lack of facilities andinfrastructure for adequate and safe parking,refuelling and handling the removal of‘blackwater’ from the vessels. The otheralternative is to divert the tour on a lengthyjourney past Clayton and through the lock atTauwitchere Barrage to reach the Mouth.However, in addition to the added fuel costs,this option may not be available in latesummer when water levels drop and the lockcan become impassable.

Although this article has focused on the effectsin the immediate area of the Murray Mouth,there is concern that tourism in adjacentregions will be negatively affected in the eventof Mouth closure (pers comm. PeterCampbell).

Some key points raised during consultationswith tourism and recreational stakeholdersinclude:ooooo Stakeholders see the reinstatement of

River water flows as a significant issue.Because interest in this area is based onits ecological attributes and it is widelyrecognised as a Ramsar wetland, theperceived deterioration of water qualitywill significantly undermine the promotionof nature-based tourism and recreationaluse.

RRRRReeeeecrcrcrcrcreaeaeaeaeatttttioioioioion & Tn & Tn & Tn & Tn & Tooooourururururiiiiismsmsmsmsm

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ooooo All stakeholders advocated furtherresearch into the area and a commitmentto adequate action to prevent furtherdegradation.

ooooo Some stakeholders advocate acommitment to keeping Scab Channelopen as a more viable option thandredging the Mouth, as it is a lessexpensive option with more likelihood ofsuccess. This dredging arrangement mayfacilitate navigation but will do little tomitigate the damage to water quality thatwill accompany Mouth closure.

ooooo Some stakeholders advocated researchinto the possibility of placing breakwatersat the Murray Mouth. This, it is argued,could make the passage more easilynavigable for recreational boaters, assistPort Elliot’s search and rescue boat inlaunching through the Mouth andencourage the development of marineindustry in Goolwa and HindmarshIsland. However, this proposal was a pointfor some argument regarding its efficacy.

RRRRReeeeeferferferferfereeeeennnnncccccesesesesesBerrgy J (1998) Coorong and Estuary Issues,

Discussion Paper No. 6, Coorong andLower Lakes Ramsar Management Plan.Department of Environment and NaturalResources, Adelaide.

Berrgy J and Gilliland J (1998) Recreation andTourism Use of the Coorong and LowerLakes Region, Discussion Paper No. 4,Coorong and Lower Lakes RamsarManagement Plan. Department ofEnvironment and Natural Resources,Adelaide.

Day PR (2001) Hindmarsh IslandManagement Plan. November, 2001.Alexandrina Council, Goolwa.

Department of Environment and Heritage(2000) Coorong and Lakes Alexandrinaand Albert Ramsar Management Plan.September, 2000. Adelaide.

Department for Environment and Heritage(2001) Environment State: Murray Mouthland protected by the purchase ofWyngate, November, 2000. Adelaide.

Kluske J (1996) Coorong Park Notes. NationalParks and Wildlife, Adelaide.

Murray-Darling Association (2001) SouthAustralia’s Majestic Murray: A User’sGuide. 2nd edition, July 2001, Adelaide.

National Parks and Wildlife SA (1999)Coorong National Park Tourism andRecreation Plan.

Ngarrindjeri/Ramsar Working Group (1999)Ngarrindjeri Perspectives on RamsarIssues. Submission to Coorong and LowerLakes Ramsar Draft Management Plan,Appendix 8, Vol. 2.

Office of National Tourism (1996) A Talent forTourism.

South Australian Tourism Commission (2001)Nature Tourism and Birdwatching – FlyingTogether. Strategic Edge, Winter/Spring.

South Australian Tourism Commission (2000/2001) ‘Visitation to Major Attractions andEvents 2000/2001’, Tourism Research, at:http://www.tourism.sa.gov.au/publications

PPPPPererererersososososonnnnnalalalalalcccccommunommunommunommunommuniiiiicccccaaaaatttttioioioioionnnnnsssssNeville Clifford, Marine Safety Office,

15/01/02Don Ransom, SA Association of Four Wheel

Drive Clubs, Inc., 15/01/02Garry Hera-Singh, Southern Fisherman’s

Association, 18/01/02Leanne Muffet, SATC, 21/01/02Peter Campbell, Acting CEO, Murraylands

Regional Development Board, 23/01/02

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“The major water quality implications“The major water quality implications“The major water quality implications“The major water quality implications“The major water quality implicationsassociated with Murray Mouth closureassociated with Murray Mouth closureassociated with Murray Mouth closureassociated with Murray Mouth closureassociated with Murray Mouth closureare stratification and salinityare stratification and salinityare stratification and salinityare stratification and salinityare stratification and salinity.”.”.”.”.”

Dr Justin Brookes, CRC for Water Quality andTreatment, Australian Water Quality Centre

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e

WWWWWaaaaattttter Qer Qer Qer Qer Quuuuualitalitalitalitalityyyyy

IIIIInnnnntrtrtrtrtrodododododuuuuuccccctttttioioioioionnnnnThe area of consideration from the LowerLakes downstream can be divided crudely intofour regions which differ in water quality, thequality and type of habitat they offer, anddegree of interest of various stakeholders inthe region. The four regions are:1. the main channel of the lower River

Murray2. the Lower Lakes (Lake Alexandrina and

Lake Albert)3. the Northern Lagoon of the Coorong, and4. the Southern Lagoon of the Coorong.

Although these regions differ in somerespects, the underlying chemical, physicaland biological principles determining waterquality are similar and will be discussedconcurrently. The water quality of the lowerRiver Murray is important in determining thewater quality of the Lower Lakes and so isincluded in this discussion.

The major water quality hazards, which mayeventuate from Murray Mouth closure,represent a risk to stakeholders because theydegrade habitat for aquatic organisms orpresent a potential health risk to recreationalusers.

Two major factors which will impact waterquality at the Murray Mouth region are thequality of the water arriving from upstream(source water) and density stratification(defined below).

Density stratification will lead to a greater riskof several hazards, particularly toxiccyanobacterial blooms, anoxia in thehypolimnion and nutrient release fromsediment. Pathogens and sainity are the othermajor water quality issues in the Coorong.Pathogen hazards are generally associatedwith contamination from external sources withthe greatest risk occuring during periods ofhigh rainfall, and salinity is affected by sea

DDDDDRRRRR J J J J JUSTINUSTINUSTINUSTINUSTIN B B B B BROOKESROOKESROOKESROOKESROOKES CRC for Water Quality and Treatment, Australian Water Quality Centre

As some water quality concerns mayAs some water quality concerns mayAs some water quality concerns mayAs some water quality concerns mayAs some water quality concerns mayeventuate before Murray Moutheventuate before Murray Moutheventuate before Murray Moutheventuate before Murray Moutheventuate before Murray Mouthclosure (as a result of low flows in theclosure (as a result of low flows in theclosure (as a result of low flows in theclosure (as a result of low flows in theclosure (as a result of low flows in thelower River Murray) there are twolower River Murray) there are twolower River Murray) there are twolower River Murray) there are twolower River Murray) there are twoquestions to consider:questions to consider:questions to consider:questions to consider:questions to consider:ooooo What minimum flow is required toWhat minimum flow is required toWhat minimum flow is required toWhat minimum flow is required toWhat minimum flow is required to

maintain a satisfactory watermaintain a satisfactory watermaintain a satisfactory watermaintain a satisfactory watermaintain a satisfactory waterquality within the Lower Lakes andquality within the Lower Lakes andquality within the Lower Lakes andquality within the Lower Lakes andquality within the Lower Lakes andCoorong?Coorong?Coorong?Coorong?Coorong?

ooooo How does Murray Mouth closureHow does Murray Mouth closureHow does Murray Mouth closureHow does Murray Mouth closureHow does Murray Mouth closureaffect water quality?affect water quality?affect water quality?affect water quality?affect water quality?

Specific issues discussed here includeSpecific issues discussed here includeSpecific issues discussed here includeSpecific issues discussed here includeSpecific issues discussed here includequality of source waterquality of source waterquality of source waterquality of source waterquality of source water, stratification,, stratification,, stratification,, stratification,, stratification,phytoplankton, salinity andphytoplankton, salinity andphytoplankton, salinity andphytoplankton, salinity andphytoplankton, salinity andpathogens. In some instances, it waspathogens. In some instances, it waspathogens. In some instances, it waspathogens. In some instances, it waspathogens. In some instances, it wasnecessary to extrapolate fromnecessary to extrapolate fromnecessary to extrapolate fromnecessary to extrapolate fromnecessary to extrapolate fromobservations upstream or from similarobservations upstream or from similarobservations upstream or from similarobservations upstream or from similarobservations upstream or from similar

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water entering the Murray Mouth,evaporation and freshwater inflows.

In this chapter there is a focus on the qualityof the source water from the lower RiverMurray, stratification and hazards eventuatingat the lower estuary site. Except in the case ofsalinity, it is difficult to isolate the impact of lowflow from Murray Mouth closure as low flowleads to stratification which sets the physicalenvironment for hazard generation.

Salinity and cyanobacteria represent thebiggest water quality issues in the lower RiverMurray, and the Lower Lakes and estuary.

The cyanobacterial hazard not only presents atoxic threat to wildlife but is also poorlyconsumed by Australian zooplankton (Boon etal. 1994) and so during cyanobacterialblooms the sustainable biomass of grazers(zooplankton) may be reduced. This hasimplications for the sustainable biomass ofhigher order organisms.

CCCCCooooonnnnnttttteeeeexxxxxtttttThe Murray-Darling River system drains theWestern slopes of the Great Dividing Range insouth-east Australia. The River Murrayoriginates in south-east New South Wales(NSW) and joins the Darling River (atWentworth) which originates in north-eastNew South Wales. The Darling contributesabout 10% of the total average annualdischarge (Walker and Thoms 1992). This isan important feature for consideration asthese different catchments deliver water ofvarying quality to the lower River Murraysystem.

SSSSStrtrtrtrtraaaaatttttiiiiifffffiiiiicccccaaaaatttttioioioioionnnnnDensity stratification is a natural feature ofwater bodies and is characterised by a verticalgradient in density caused by differentialheating of the water surface and/ordifferences in salinity. A major water quality

problem associated with stratification, and therestriction of vertical mixing, is the isolation ofthe hypolimnion from the atmosphere.Bacteria within the sediment and watercolumn can rapidly deplete the oxygen in thehypolimnion and generate reducingconditions at the sediment-water interface andin the hypolimnion. Under low oxygenconditions nutrient and metal contaminants,which are resolubilised from sediment, remainin solution and can compromise water quality.

Although depth-dependent temperature is notrecorded continuously in Lake Alexandrina,several assumptions can still be maderegarding water movement of the Lake. Thedegree of stratification in the Lower Lakes is afunction of stratifying thermal energy(temperature) and destratifying kinetic energy(wind and flow).

Baker (2000) suggested that the influence ofwind in the shallow Lower Lakes (mean depth2.9m) was significant in destabilising thermalstratification. Temperature data presented inGeddes (1988) suggests there is thermalstratification in Lake Alexandrina; however thetime-scale of measurement does not allowinterpretation of whether the water-bodymixed to the bottom overnight or remainedpersistently stratified. The strong afternoonwind speeds, which are measured at Goolwa,would suggest that the Lake is regularly fullymixed.

With a restriction of flow through the LowerLakes and Coorong, these sites would stratify,at least part of the time, and may bepersistently stratified during warm stableperiods with low wind.

Closure or restriction of the Murray Mouthwould assist in the development ofstratification which is a necessary physicalcondition for many hazards to eventuateincluding blooms of toxic cyanobacteria,anoxia in the hypolimnion and nutrientrelease from sediment.

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NNNNNutrutrutrutrutriiiiieeeeennnnntttttsssssThe major nutrient sources are the catchmentand the internal load derived from sedimentand from the atmosphere.

The sources contributing to elevated nitrogenoxide species in the atmosphere (which canthen end up in the River Murray via rainfall)include soil emission, fossil fuel combustion,lightning and biomass burning in forests andsavannah (IPCC 1996). These sources,together with nutrients derived from thecatchment, are difficult for water managers tocontrol.

In a typical phosphorus cycle, phosphorus isremobilised from sediment or decayingorganic matter and entrained into the watercolumn, where it is taken up by algae. Fromthere the phosphorus is either passed on tohigher levels of the food web or lost to thebottom as the algae sediment. In deep lakes,the resolubilisation of phosphorus from thesediment is vertically separated from the algaeand so each phosphorus molecule can onlybe accessed with entrainment from thehypolimnion to the epilimnion (surface water).In strongly stratified, deep lakes this mayhappen only once or twice a year duringsignificant ‘over-turn’ events.

In contrast, shallow lakes, such asthe Lower Lakes and the Coorong, have thezone of phosphorus resolubilisation muchcloser to the zone of greatest productivity anda single molecule may be recycled a numberof times during the growing season (Reynolds1997) and thereby sustain a high algalbiomass for longer. This is why shallow lakesprove so much more difficult to restore thandeep ones (Sas 1989, Reynolds 1992).

Geddes (1984) states that the nutrient levels inLake Alexandrina reflect those in the lowerRiver Murray. For the period 1975 to 1978,nutrient levels were 89mg to 385mg TotalPhosphorus (TP) per m (mean 223mg m-3)and Total Kjeldahl Nitrogen (TKN) 600mg per

m to 2700mg per m (mean 1314mg m-3).Although there is considerable variability innutrient concentrations, the concentrationsobserved by Geddes (1984) are typical for theregion. During the 1975 to 1978 period, thenutrient levels in Lake Alexandrina were in theeutrophic-hypereutrophic range ofVollenweider (1968) and in the eutrophiccategory of Walker and Hillman (1977)(Geddes 1984). This means that the Lake cansupport high algal populations and may beprone to cyanobacterial blooms.

There is a gradient in TP and TKN down theCoorong which correlates with an increase insalinity (Thomas 1999, Figures 1, 2 and 3).The source of the higher nutrients in thesouthern basin is unknown but it could beeither higher algal biomass, or resuspendedsediment. It is unlikely to be from catchmentinputs as the tributaries, which used toprovide freshwater inflows to the southernCoorong, have been diverted. Thomas (1999)classified the TP and TKN concentrations asmoderate according to his water qualityclassification.

Slow flow and deposition of particulateorganic material may increase the nutrientpool which is available for release when thewater body stratifies. When River flow issufficiently high, this particulate materialshould be scoured from the River or estuarybed and flushed from the system.

The major water quality hazard associatedwith nutrients is the toxic phytoplankton. Thesize of the sustainable biomass is often directlycorrelated with nutrient availability.Additionally, an increased nutrient pool mayalso increase bacterial activity which wouldincrease the oxygen demand and increase therate at which anoxia occurs. (See also pg 23‘Fishing Industry’ chapter.)

Murray Mouth closure or restriction may leadto increased nutrients in the region of theestuary as nutrients are released from thesediments as a result of a reducing

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conductivity atconductivity atconductivity atconductivity atconductivity atsites in thesites in thesites in thesites in thesites in the

CoorongCoorongCoorongCoorongCoorong( reproduced( reproduced( reproduced( reproduced( reproduced

from Thomasfrom Thomasfrom Thomasfrom Thomasfrom Thomas1999)1999)1999)1999)1999)

Figure 2:Figure 2:Figure 2:Figure 2:Figure 2:Median TKNMedian TKNMedian TKNMedian TKNMedian TKN

at sites in theat sites in theat sites in theat sites in theat sites in theCoorongCoorongCoorongCoorongCoorong

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phosphorus atphosphorus atphosphorus atphosphorus atphosphorus atsites in thesites in thesites in thesites in thesites in the

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environment during stratification.Deposition of particulate material due to lowturbulence may also have long-term impactson the nutrient climate of the region. Thenutrient concentrations in the region will alsobe highly influenced by the quality of thesource water from the River Murray.

EEEEEl Nl Nl Nl Nl Niiiiino ano ano ano ano annnnnd sod sod sod sod sourururururccccceeeeewwwwwaaaaatttttererererer: I: I: I: I: Innnnntttttererererer-----aaaaannnnnnnnnnuuuuualalalalalvvvvvaaaaarrrrriaiaiaiaiabbbbbilitilitilitilitility iy iy iy iy in fn fn fn fn f lololololowwwwwaaaaannnnnd nd nd nd nd nutrutrutrutrutriiiiieeeeennnnntttttsssssFlow within the Australian context is highlyvariable and plays a significant role in nutrienttransport from catchment to stream and themaintenance of particles in suspension.Consequently, regional weather patternscontribute to the inter-annual variability ofwater quality, quantity and the demand on thewater resource by upstream consumers.

The nutrient concentrations in the region ofthe Murray Mouth display inter-annualvariability which is a function of source (forexample, upper Murray or Darling) and theduration of stratification resulting from lowflow and low wind.

IIIIImmmmmplipliplipliplicccccaaaaatttttioioioioionnnnnsssssooooof a sf a sf a sf a sf a salt walt walt walt walt weeeeedddddggggge oe oe oe oe onnnnnssssstrtrtrtrtraaaaatttttiiiiifffffiiiiicccccaaaaatttttioioioioion an an an an annnnndddddnnnnnutrutrutrutrutriiiiieeeeennnnntttttsssssA natural feature of tidal estuaries is a salineintrusion which is often referred to as a ‘saltwedge’. The intrusion of dense saline waterfrom the sea below the fresher water in theriver can travel a considerable distanceupstream if there are no barriers in place. (Seealso ‘Coastal Processes’ chapter.)

Currently, the barrages at Goolwa stop theintrusion from travelling through the Lower

Lakes and into the main channel of the lowerRiver Murray. The saline intrusion increasesdensity stratification and the lack of mixingbetween the fresh and saline water can leadto anoxic conditions in the intrusion.Consequently, the reducing condition in theintrusion can lead to nutrient release and therelease of other contaminants such ashydrogen sulphide, which has an unpleasantodour.

Because of the extremely windy conditions atthe Lower Lakes, and the expected coolingfrom the high evaporation, there may beconsiderable mixing which would negate thestratifying thermal energy. However, thermalstratification would occur at times and thedegree of stratification would be strengthenedby the salinity gradient.

PPPPPhhhhhyyyyytttttoooooplplplplplaaaaanknknknknktttttooooonnnnnCyanobacteria in the lowerCyanobacteria in the lowerCyanobacteria in the lowerCyanobacteria in the lowerCyanobacteria in the lowerRiver Murray - River Murray - River Murray - River Murray - River Murray - AnabaenaAnabaenaAnabaenaAnabaenaAnabaena and and and and andflowflowflowflowflowFlow is a major factor determining thephytoplankton abundance and speciescomposition in Australian lowland rivers(Burch et al. 1994, Hotzel and Croome 1994,Sherman et al. 1998). Of particular concernare the cyanobacteria as these organismsproduce toxins, tastes and odours whichcompromise the quality of drinking andbathing waters.

In the River Murray at Morgan there is atransition between the dominant diatomspecies Aulacoseira granulata (non-toxic) andAnabaena spp. (possibly toxic) which is highlydependent on flow (Figure 4). Theobservations made at Morgan are similar toother lower Murray sites.

Observations fromObservations fromObservations fromObservations fromObservations fromthe lower River Murraythe lower River Murraythe lower River Murraythe lower River Murraythe lower River MurrayBaker et al. (2000) tracked parcels of water ina reach of the lower River Murray during thesummer of 1994/1995 and calculated growthof the dominant cyanobacteria.

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FLOWFLOWFLOWFLOWFLOW Low4000 MLday-1

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Figure 5: Conceptual model of the physical and environmentalFigure 5: Conceptual model of the physical and environmentalFigure 5: Conceptual model of the physical and environmentalFigure 5: Conceptual model of the physical and environmentalFigure 5: Conceptual model of the physical and environmentalfactors governing cyanobacteria abundance in the lower River Murrayfactors governing cyanobacteria abundance in the lower River Murrayfactors governing cyanobacteria abundance in the lower River Murrayfactors governing cyanobacteria abundance in the lower River Murrayfactors governing cyanobacteria abundance in the lower River Murray

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Figure 4: River flow and the dominance of Figure 4: River flow and the dominance of Figure 4: River flow and the dominance of Figure 4: River flow and the dominance of Figure 4: River flow and the dominance of AulacoseiraAulacoseiraAulacoseiraAulacoseiraAulacoseiraor or or or or AnabaenaAnabaenaAnabaenaAnabaenaAnabaena at Morgan on the lower River Murray at Morgan on the lower River Murray at Morgan on the lower River Murray at Morgan on the lower River Murray at Morgan on the lower River Murray

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strength is low (<1.2m per s). During periodsof low flow, equivalent to summer entitlementflows (4000ML per day), turbulence issufficiently low to allow some degree ofthermal stratification, provided that windstrength is low to moderate (<3m per s).Persistent stratification may result when windspeed is <1.2m per s (and flow is low), whilestratification during the day is more likely atwind speeds between 1.2m per s and 3m pers. Irrespective of flow, high wind speed (>3mper s) will disrupt thermal stratification andresult in a mixed water column.

In the model, the source of water is the otherenvironmental factor affecting algaebehaviour.

If water is sourced from the Darling River, or ifover-bank flooding has occurred during thehigh spring flows originating from the upperRiver Murray, phosphorus concentrations mayincrease. When phosphorus concentrationsare high, nitrogen availability will thendetermine which species dominate.

High soluble inorganic nitrogen availabilityfavours non-nitrogen fixing cyanobacterialgenera, such as Microcystis and Planktothrix,and other phytoplankton. However, if nitrogenavailability is low, nitrogen fixing genera, suchas Anabaena, Aphanizomenon,Anabaenopsis and Cylindrospermopsis obtaina comparative advantage.

If River flow originates from the upper RiverMurray and flow remains within the mainchannel, available phosphorus will be low andconsequently phytoplankton abundance willremain low.

Mean growth rates of Anabaena circinalis andA. flos-aquae were 0.176 and 0.132 per dayrespectively. However, maximum cell densitieswere only 2670 and 4560 cells per mL foreach species, which is low abundance andsuggests that nutrients or grazing werelimiting phytoplankton growth.

During the summer of 1995/1996, nutrientgrowth bioassays and FDA-conversionbioassays (Brookes et al. 2000) revealednitrogen limitation on several occasions in thelower River Murray was limiting phytoplanktongrowth. In contrast, phosphorus limitationwas detected on only one occasion andbetween 8% and 70% of the total phosphoruswas available to organisms for growth (Bakeret al. 2000).

It is likely that although phosphorus mayultimately limit total phytoplankton biomass,low nitrogen concentrations in the RiverMurray favour nitrogen-fixing species, such asAnabaena circinalis and Anabaena flos-aquae, while limiting the growth capacity ofnon-nitrogen fixing species, such asMicrocystis aeruginosa. The particularcombination of physical and chemicalconditions presumably favoured the growth ofAnabaena in preference to non-nitrogen fixingcyanobacteria, albeit at sub-optimumconditions.

Conceptual model ofConceptual model ofConceptual model ofConceptual model ofConceptual model ofcyanobacteria in the lowercyanobacteria in the lowercyanobacteria in the lowercyanobacteria in the lowercyanobacteria in the lowerRiver Murray channelRiver Murray channelRiver Murray channelRiver Murray channelRiver Murray channelA conceptual model has been developed tosummarise the physical and chemical factorsgoverning the abundance of cyanobacteria inthe lower River Murray (Figure 5). Flow isranked as the primary factor affecting thedevelopment of cyanobacterial populations.

High flow (>10 000ML per day) results in highturbulence and species such as the diatom,Aulacoseira granulata are favoured. Whenflow is moderate (ca. 10 000ML per day),stratification during the day occurs if wind

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WWWWWaaaaattttter Qer Qer Qer Qer QuuuuualitalitalitalitalityyyyyRiver management for controlRiver management for controlRiver management for controlRiver management for controlRiver management for controlof cyanobacteria in the mainof cyanobacteria in the mainof cyanobacteria in the mainof cyanobacteria in the mainof cyanobacteria in the mainchannelchannelchannelchannelchannelThe correlation between the occurrence ofAnabaena with low flow suggests that themanipulation of flow may be used to controlcyanobacteria. Bormans and Webster (1997)developed a mixing criterion for turbid riverswhich is applicable to many lowland rivers. Insummary, the degree of stratification in awater column is determined by the relativesupply rates of stratifying thermal energy anddestratifying turbulent kinetic energy. Inregulated rivers, the magnitude and timing ofdischarge can be manipulated to disruptstratification every few days thereby controllingcyanobacterial growth.

Maier et al. (2001) modelled various flowscenarios for the control of stratification. Theyfound that under current entitlement flowthere is little risk of sustained blooms in thelower River Murray at Morgan, which could beextrapolated to include lower reaches of theRiver. Consequently, the best mechanism forcyanobacterial control is not to increase baseflow but to disperse existing blooms with flowderived from reducing weir pool levelsupstream, providing the impacts on aquaticmacrophytes and benthic algae areconsidered. (See ‘Aquatic Plant Communities’chapter.)

PhytoplanktonPhytoplanktonPhytoplanktonPhytoplanktonPhytoplanktonin the Lower Lakesin the Lower Lakesin the Lower Lakesin the Lower Lakesin the Lower LakesThe dominant phytoplankton species in LakeAlexandrina is Planctonema lauterbornei andis generally present during conditions of highturbidity, low light availability and highnutrients (Geddes 1988, Baker 2000).However, the major phytoplankton species ofconcern are Nodularia spumigena andAnabaena circinalis as these species havebeen associated with toxic cyanobacterialblooms in the Lower Lakes (Baker 2000). It iswell established that stratification can lead tothe dominance of the phytoplankton

community by cyanobacteria. However, in theLower Lakes the small increase in base flowmay not disrupt stratification, as it does in thelower River Murray channel and wind wouldplay a greater role at dispersingcyanobacterial blooms. Baker (2000) reportsthat the occurrence of Nodularia in thesummer/autumn of 1990/1991 and 1995was associated with periods of low flow (<10000ML per day), moderate turbidity (less than50NTU), conductivity 400EC to 1100EC(freshwater) and variable nutrientconcentrations. This is similar to observationsin the main channel of the River Murray.

PhytoplanktonPhytoplanktonPhytoplanktonPhytoplanktonPhytoplanktonin coastal lagoonsin coastal lagoonsin coastal lagoonsin coastal lagoonsin coastal lagoonsThe species of concern in coastal lagoons arethe cyanobacteria Nodularia, which has beenobserved in Orielton Lagoon in Tasmania(Jones et al. 1994) and Peel-Harvey estuary(Lukatelich and McComb 1986), and toxicdinoflagellates which produce paralyticshellfish toxins. The dinoflagellate generaAlexandrium, which are known toxinproducers, and Heterosigma, which has beenimplicated in fish kills, have been observed inWest Lakes and the Port River.

The bloom of Nodularia in Orielton Lagoon,Tasmania, occurred during a period ofrelatively low salinity (14g per L). However,later on the bloom salinities increased to 22gper L to 24g per L (Jones et al. 1994).

At the lower salinities, laboratory studiesshowed that akinete (reproductive restingspores) production was low relative to that atthe higher salinities. This suggests thatNodularia prefers the lower salinities andprepares for dormancy as salinities increase.

Salinity was also implicated in akinetegermination, with the extent of germinationinversely related to salinity in the Peel-Harveyestuary (Huber 1985).There are no phytoplankton records for the

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Coorong on the Australian Water QualityCentre database and a current contentssearch for ‘Coorong and Phytoplankton’ yieldsno results. This represents a significant gap inour knowledge. The problematicdinoflagellates (‘red tides’) have, however,been observed in the Coorong estuary (Baker2000).

Dinoflagellates and cyanobacteria aregenerally associated with stratification, whichwould occur during low flow and MurrayMouth closure. Boon (2000) states that in theSouthern Lagoon there may be a limitednumber of phytoplankton includingDunaliella, Amphora, Nitzschia and severaldiatom species. There are no major waterquality issues related to these phytoplankton.

Closure of the Murray Mouth may stimulategreater algal blooms than those currentlyobserved during periods of low flow,particularly in the Northern Lagoon where theduration of stratification may increase.

However, cyanobacteria may becomeproblematic in the main channel of the RiverMurray and in Lake Alexandrina at flows lessthan 10 000ML per day.

The cyanobacteria represent a poor foodsource for zooplankton which will haveimplications for higher order organismsincluding birds and fish.

SSSSSalialialialialinnnnnititititityyyyyPerhaps the most astounding feature of theestuarine region is that it now only operatesover 11% of its original area (Newman 2000).A consequence of this is that the gradualgradient from fresh to saline waters, whichwould have prevailed historically, is not evidentin the present system. Consequently, there islarge variability in salinity, which fluctuates atshort time scales depending upon tidal actionand River flow. (See ‘Fish and Invertebrates’chapter.)

The Southern Lagoon is naturally hypersaline,but Geddes and Hall (1990) argue that theCoorong is more saline now than prior toRiver regulation. Monitoring of salinity duringrecent barrage closure allowed Geddes andHall (1990) to document the impact of MurrayMouth restriction/closure on salinity. Theyreport that between 1980 and 1983 RiverMurray flows were below average and therewere long periods of barrage closure and

Figure 6:Figure 6:Figure 6:Figure 6:Figure 6:PredictedPredictedPredictedPredictedPredictedMouthMouthMouthMouthMouthopening basedopening basedopening basedopening basedopening basedon model ofon model ofon model ofon model ofon model ofWWWWWalker (2000).alker (2000).alker (2000).alker (2000).alker (2000).A level whereA level whereA level whereA level whereA level wheretidal influencetidal influencetidal influencetidal influencetidal influenceis reduced tois reduced tois reduced tois reduced tois reduced toR<0.05 wasR<0.05 wasR<0.05 wasR<0.05 wasR<0.05 wasselected toselected toselected toselected toselected toindicate Mouthindicate Mouthindicate Mouthindicate Mouthindicate Mouthclosure. Theclosure. Theclosure. Theclosure. Theclosure. Thebars indicatebars indicatebars indicatebars indicatebars indicateperiods whereperiods whereperiods whereperiods whereperiods whereconductivity atconductivity atconductivity atconductivity atconductivity atLLLLLong Pong Pong Pong Pong Point inoint inoint inoint inoint inthe Northernthe Northernthe Northernthe Northernthe NorthernLagoonLagoonLagoonLagoonLagoonexceeds theexceeds theexceeds theexceeds theexceeds theconductivity ofconductivity ofconductivity ofconductivity ofconductivity ofseawaterseawaterseawaterseawaterseawater(52 m(52 m(52 m(52 m(52 m-1-1-1-1-1).).).).).

5 Note: The salinity of seawater was subtracted fromthe salinity at Long Point and positive values wereconsidered as periods of high salinity.

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salinities were high throughout the Coorong.

The Southern Lagoon may have somemoderately freshwater inputs in the nearfuture from the Upper South-East DrainageSystem.

Salinity in the Lower Lakes is stronglyinfluenced by the source water from the RiverMurray and so the region which mayexperience the greatest fluctuations in salinityand be most impacted by Murray Mouthclosure is the Northern Lagoon.

Historical salinity at Long Point in the NorthernLagoon was used to determine how MurrayMouth closure has impacted the salinity in theNorthern Lagoon (see Figure 6). The NorthernLagoon is tidal and so salinities equivalent toseawater would be tolerable(52 000µS cm-1).5

These values were plotted with the outputfrom the model of Walker (1999) to determinewhether high salinity in the Northern Lagoonwas associated with Murray Mouth closure.

It is apparent that periods of high salinity donot always correspond to periods of predictedMouth closure (Relative Mouth opening <0.05using the Walker model (1999) – see ‘What isPossible: Hydrology and Morphology’chapter). Therefore, it appears that salinity inthe Northern Lagoon is also affected by thesalinity in the Southern Lagoon. There couldbe considerable mixing of waters between thetwo basins with wind driven surface flows anddeeper return flows. Differential heating andcooling within the two basins could alsogenerate considerable flow and basinexchange.

The encroachment of hyper-saline water intothe Northern Lagoon, from the SouthernLagoon, will restrict the available habitat fororganisms which can only tolerate salinity ashigh as seawater.

AnoAnoAnoAnoAnoxxxxxiaiaiaiaiaThe water quality problems resulting fromanoxia are contaminant resolubilisation fromsediment and a reduction of habitat fororganisms which need oxygen to survive (forexample, fish). The rate of onset of anoxia is afunction of stratification, temperature, organicsubstrate and microbial activity.

As discussed earlier, the strong wind speedsrecorded at Goolwa would suggestreasonably regular, rapid mixing in theshallow lagoons of the Coorong. However,during calm, warm weather anoxia maybecome an issue. Sediment may beresuspended when there is turbulence at thesurface of the sediment due to either windmixing in shallow regions or where there iswave-generated turbulence. Sedimentdisturbance increases the chemical oxygendemand and may induce low oxygenconcentrations.

TTTTTurururururbbbbbiiiiidddddititititityyyyyLight penetration will have a significant impacton plant growth in the Lower Lakes andCoorong. High turbidity currently restrictsplant growth to near shore boundaries whereit is susceptible to wind and wave action (Ganf2000). (See also pg 71 ‘Aquatic PlantCommunities’ chapter.)

The factors influencing turbidity include thesource water (Murray River, Darling River oroceanic), flow and wind induced turbulence,and phytoplankton abundance. Turbidity atMilang and Lake Alexandrina displayedannual inter-annual variability (Baker 2000)with high turbidity in each year correspondingwith high flow. A peak in turbidity andnutrients at Milang in 1991 was attributed toa high proportion of River flow originatingfrom the Darling River (Baker 2000). Windaction and wave-generated turbulence alsocontribute to high turbidity in the Lower Lakes.

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It is anticipated that closure of the MurrayMouth would improve water clarity as particleswould tend to drop out from suspension. Theincreased salinity resulting from evaporationwould tend to flocculate colloidal material andfurther increase the rate of sedimentation.

PPPPPesesesesestttttiiiiiccccciiiiidddddesesesesesaaaaannnnnd hd hd hd hd herererererbbbbbiiiiiccccciiiiidddddesesesesesThe risk of pesticide hazards eventuating inaquatic systems is a complex interactionbetween fate and transport of the organiccompounds. Residue of the monitoredpesticides and herbicides in the CoorongLagoons are mostly below detectable levels(Thomas 1999). The risk associated with themis sufficiently low that Thomas (1999)recommended that they only be monitoredonce yearly. Closure or restriction of theMurray Mouth would not significantly increasethe risk associated with pesticides andherbicides, which are currently considered lowrisk in this system.

lateM lateM lateM lateM lateM)latot( )latot( )latot( )latot( )latot(

21-1snoogalmorfstluseR 21-1snoogalmorfstluseR 21-1snoogalmorfstluseR 21-1snoogalmorfstluseR 21-1snoogalmorfstluseR)yrdgk/gm()egnar( )yrdgk/gm()egnar( )yrdgk/gm()egnar( )yrdgk/gm()egnar( )yrdgk/gm()egnar(

eulavenilediuG eulavenilediuG eulavenilediuG eulavenilediuG eulavenilediuG)yrdgk/gm( )yrdgk/gm( )yrdgk/gm( )yrdgk/gm( )yrdgk/gm(

muinimulA muinimulA muinimulA muinimulA muinimulA 0604-282 0604-282 0604-282 0604-282 0604-282-----

ynomitnA ynomitnA ynomitnA ynomitnA ynomitnA 2.0<llA 2.0<llA 2.0<llA 2.0<llA 2.0<llA22222

cinesrA cinesrA cinesrA cinesrA cinesrA 4.7-8.0 4.7-8.0 4.7-8.0 4.7-8.0 4.7-8.00202020202

muimdaC muimdaC muimdaC muimdaC muimdaC 2.0<llA 2.0<llA 2.0<llA 2.0<llA 2.0<llA5.1 5.1 5.1 5.1 5.1

muimorhC muimorhC muimorhC muimorhC muimorhC 1.51-6.3 1.51-6.3 1.51-6.3 1.51-6.3 1.51-6.30808080808

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muineleS muineleS muineleS muineleS muineleS 100.0<llA 100.0<llA 100.0<llA 100.0<llA 100.0<llA-----

revliS revliS revliS revliS revliS 5.0-2.0< 5.0-2.0< 5.0-2.0< 5.0-2.0< 5.0-2.0<0.1 0.1 0.1 0.1 0.1

cniZ cniZ cniZ cniZ cniZ 561-21 561-21 561-21 561-21 561-21002 002 002 002 002

HHHHHeaeaeaeaeavvvvvy my my my my meeeeetttttalalalalalsssssThomas (1999) reports that the sub-lagoonsof the Coorong have moderate to low levels ofmetals, with the exception of zinc (Zn) andsilver (Ag) which have moderate to highconcentrations (Zn: 0.042-0.174mg per L; Ag:0.0003-0.0017mg per L).

Murray Mouth closure may lead tostratification and reducing conditions whichmay in turn lead to resolubilisation of somemetals. However, the concentrations of metalsin the sediment (Table 1) are below theguideline value (Thomas 1999).

There is low risk from metal contamination,with the exception of zinc, which is present inelevated concentrations in several sub-lagoons.The risk associated with iron and manganeseis usually that these compounds contributedirty water problems as the ions oxidise uponexiting consumers’ taps. Since the water of

TTTTTable 1: Sedimentable 1: Sedimentable 1: Sedimentable 1: Sedimentable 1: Sedimentchemistry data fromchemistry data fromchemistry data fromchemistry data fromchemistry data from

the Coorongthe Coorongthe Coorongthe Coorongthe CoorongLagoons 8 AprilLagoons 8 AprilLagoons 8 AprilLagoons 8 AprilLagoons 8 April

19981998199819981998(Reproduced from(Reproduced from(Reproduced from(Reproduced from(Reproduced from

Thomas 1999).Thomas 1999).Thomas 1999).Thomas 1999).Thomas 1999).

e

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Lake Alexandrina is only used for limitedpotable supply, the risk associated with ironand manganese is considered low.

PPPPPaaaaathththththooooogggggeeeeennnnnsssssThe major water-borne organisms whichimpact on human health in Australia areCryptosporidium, Giardia andCampylobacter. These pathogens causesevere diarrhoea and dehydration and spreadby the excretion of microscopic, spore-likecysts (Giardia) or oocysts (Cryptosporidium).While generally not life-threatening to healthyindividuals, they can cause severe illness inyoung children, the elderly and individualswith an impaired immune system (Walker andStedinger 1999).

The threat associated with pathogens in theLower Lakes and Coorong is largely unknown.There is little draw off for potable supply andinfection would generally be restricted torecreational exposure at sites where there issewage contamination or agricultural runoff.Furthermore, pathogen contamination fromthe catchment occurs during significant rainevents, which typically occur during winter andspring in Mediterranean climates such asours, and so there would be considerabledilution.

Run-off from irrigated pasture may alsopresent a pathogen source. The transfer offresh faecal material into watercourses andthe River is a major problem. A recent localexample of pathogen contamination occurredat Aldgate Creek, South Australia, whereconcentrations of E.coli, Enterococcus spp,Campylobacter and Cryptosporidiumincreased by two orders of magnitudefollowing 10mm to 15mm rain (pers. comm.Phil Adcock AWQC).

Enterohaemorragic Escherichia coli, which isassociated with cattle and irrigation run-off, isalso an emerging issue. This organism has alow infective dose, is potentially lifethreatening and has recently been implicated

with outbreaks of disease related to poorlytreated drinking water (Walkerton outbreak2000). The implications of recreational contacthave not been investigated at this stage.

It is anticipated that restriction of the MurrayMouth and low flow may alter the pathogenthreat as sewage contamination and irrigationrun-off is not diluted.

The risk of pathogens to recreational users ofthe Lower Lakes and Coorong is largelyunknown and warrants investigation.

PuPuPuPuPubbbbblililililic hc hc hc hc healthealthealthealthealthaaaaannnnnd gud gud gud gud guiiiiidddddeeeee lililililinnnnnesesesesesWhile the pathogens are generally a riskfollowing ingestion, the cyanobacteria presenthealth problems from both ingestion and skincontact.

The hepatotoxins produced by Nodulariaspumigena are known to produce chronic liverdamage, whereas the neurotoxins producedby Anabaena circinalis present a low risk ofacute poisoning and have no known sub-acute or chronic effects (Jones et al. 1993).Nodularia spumigena intoxication has beenimplicated in an individual suffering skinrashes and diarrhoea (Jones et al. 1994);hence contact with cyanobacterial scumsshould be avoided. Furthermore, there issome epidemiological evidence whichimplicate cyanobacteria in symptomoccurrence from exposure during recreationalactivities at Goolwa (Pilotto et al. 1997).

The buoyant habit of cyanobacteria meansthey are easily wind blown and accumulate onleeward shores, where they present thegreatest risk. The guideline for recreationalexposure is currently 20 000 cells per mL ofcyanobacteria (WHO 1999). Similar guidelinesexist for pathogens(see www.waterquality.crc.org.au/guide.htmand www.waterquality.crc.org.au/guide.htm).

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Whether Murray Mouth closure is likely toincrease pathogen risk and exceed theguideline is unknown.

HoHoHoHoHow muw muw muw muw muccccchhhhhfffff lololololow iw iw iw iw is es es es es enononononouuuuuggggghhhhh?????Prior to the construction of the weirs, the RiverMurray would have displayed strongerseasonal variability in flow than presentlyobserved as the magnitude of floods and lowflow have been tempered. Low flow was anatural feature of the Murray system. Figure 6in Close and McLeod (2000) shows a photo ofSir Ronald East straddling the River Murraynear Swan Hill in March 1923. Close andMcLeod predict that flow at this site withoutthe upstream water extraction would havebeen 2000ML per day. This flow is below theentitlement flows which presently may lead toclosure or restriction of the Murray Mouth.

It could be concluded that in its natural statethe Murray Mouth may have closed overperiodically. However, it is estimated that 79%of natural median flow is now extracted andconsumed in the Basin. The consequence ofthis is that the River Murray now experiencessevere drought-like flows in over 60% of yearscompared with 5% of years under natural flowcondition (Close and McLeod 2000).

If the aim is solely to keep the Murray Mouthopen, then River flow could be increased toflush the Mouth of sediment. However, it isprudent to note that there are otherenvironmental impacts from elevated flowwhich demand consideration. Walker (2000)developed a model which predicted Mouthrestriction based on flow through thebarrages using relative tide amplitudedifferences between the barrages and VictorHarbour. Mouth closure was predicted for 58months in the 35-year period from 1963 to1998 (13.8% of the time). The model ofWalker (2000) provides a prediction of howmuch additional flow is required to reduce thenumber of months the Murray Mouth is

e

closed. To reduce the number of closures to5% of the time, which is the approximatenumber of drought years under natural flows(Close and McLeod 2000), an additional flowof 840GL, delivered as a monthly supplement,would be required. (See also ‘What is Possible:Hydrology and Morphology’ chapter.)

An alternative strategy may be to expand theregion of the tidal estuary and use oceanicwater in combination with increased flows todestratify, oxygenate and maintain salinity. Ifthe aim is to control salinity increases, thenwater could be released from the moreSouthern barrages to moderate the salinitygradient in the Northern Lagoon.

CCCCCooooonnnnnccccc lululululusssssioioioioionnnnnThe water quality implications of low flow andMurray Mouth restriction/closure arenumerous and compromise the Cooronghabitat and recreational use of the region. Ofequal importance, however, is the quality ofthe source water flowing into South Australiaand the Lower Lakes/Coorong. This water has1.5 million consumers and contributessignificantly to agriculture and horticulture inSouth Australia.

The maintenance of quality source water iseconomically and environmentally importantand plays a fundamental role, along with thequantity of source water, in determining thequality of water and habitat in the lowerMurray, the Lower Lakes and the estuary.

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19781989

1983

1995

1997

1981

In 1981 the Murray Mouth closed forIn 1981 the Murray Mouth closed forIn 1981 the Murray Mouth closed forIn 1981 the Murray Mouth closed forIn 1981 the Murray Mouth closed forthe first time in recorded historythe first time in recorded historythe first time in recorded historythe first time in recorded historythe first time in recorded history. It. It. It. It. It

was closed for 3 months beforewas closed for 3 months beforewas closed for 3 months beforewas closed for 3 months beforewas closed for 3 months beforebeing opened by dredging.being opened by dredging.being opened by dredging.being opened by dredging.being opened by dredging.

SSSSSnnnnnaaaaapppppssssshhhhhototototots is is is is in tn tn tn tn timimimimimeeeee

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1999

2000

2002

2001

1998

currently the Murraycurrently the Murraycurrently the Murraycurrently the Murraycurrently the MurrayMouth is threatenedMouth is threatenedMouth is threatenedMouth is threatenedMouth is threatenedwith closure for thewith closure for thewith closure for thewith closure for thewith closure for the

second time insecond time insecond time insecond time insecond time inrecorded historyrecorded historyrecorded historyrecorded historyrecorded history

Photography supplied by MAPLAND,Environmental and Geographic Information, Department for Environment and Heritage.

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WWWWWaaaaattttter Qer Qer Qer Qer QuuuuualitalitalitalitalityyyyyRRRRReeeeeferferferferfereeeeennnnncccccesesesesesBaker P (1999) The role of akinetes in the

development of cyanobacterial populations inthe lower River Murray. Marine andFreshwater Research 50: 265-279.

Baker P (2000) Phytoplankton in the lower Lakesof the River Murray. In River Murray BarragesEnvironmental Flows, Jensen A, Good M,Tucker P and Long M (eds). Department forEnvironment, Heritage and Aboriginal Affairs.

Baker P, Brookes J, Burch M, Maier H and Ganf G(2000) Advection, growth and nutrient statusof phytoplankton in the lower River Murray,South Australia. Regulated Rivers: Researchand Management 16: 327-344.

Boon PI (2000) Biological impacts of changes towater level and salinity in the Coorong.Report to Upper South-East Dryland Salinityand Flood Management Scheme.

Boon PI, Bunn SE, Green JD and Shiel RJ (1994)Consumption of cyanobacteria by freshwaterzooplankton: implications for the success of‘Top-down’ control of cyanobacterial bloomsin Australia. Australian Journal of Marine andFreshwater Research 45: 875-887.

Bormans M, Maier H, Burch M and Baker P(1997) Temperature stratification in the lowerRiver Murray, Australia: implication forcyanobacterial bloom development. Marineand Freshwater Research 48: 647-654.

Bormans M and Webster IT (1997) A mixingcriterion for turbid rivers. EnvironmentalModelling and Software 12: 329-333.

Brookes JD, Geary SM, Ganf GG and Burch MD(2000) Use of FDA and flow cytometry toassess metabolic activity as an indicator ofnutrient status in phytoplankton. Marine andFreshwater Research 51: 817-823.

Burch MD, Steffenson DA, Bursill DB, Bain DB,Ganf GG and Brookes JD (1994) Criticalflow and blooms of the cyanobacteriumAnabaena circinalis in the Murray Riversystem. In Environmental Flows, Canberra(August 25-26), pp44-51. Australian Waterand Wastewater Association.

Condie SA and Bormans M (1997) The influenceof density stratification on particle settling,dispersion and population growth. Journal ofTheoretical Biology 187: 65-75.

Ganf GG (1974) Diurnal mixing and the verticaldistribution of phytoplankton in a shallowequatorial lake (Lake George, Uganda).Journal of Ecology 62: 611-629.

Ganf GG (2000) Aquatic and RiparianVegetation. In River Murray BarragesEnvironmental Flows, Jensen A, Good M,Tucker P and Long M (eds). Department forEnvironment, Heritage and Aboriginal Affairs.

Geddes MC (1984) Seasonal studies on thezooplankton community of Lake Alexandrina,River Murray, South Australia, and the role ofturbidity in determining zooplanktoncommunity structure. Australian Journal ofMarine and Freshwater Research 35: 417-426.

Geddes MC (1988) The role of turbidity in thelimnology of Lake Alexandrina, River Murray,South Australia: comparison between clearand turbid phases. Australian Journal ofMarine and Freshwater Research 39: 201-209.

Geddes MC and Butler AJ (1984) Physio-chemical and biological studies on theCoorong Lagoons, South Australia, and theeffect of salinity on the distribution of themacrobenthos. Transactions of the RoyalSociety of South Australia 108: 51-62.

Geddes M and Hall D (1990) The Murray Mouthand Coorong. In The Murray, Mackay N andEastburn D (eds), pp 200-213. Murray-Darling Basin Commission. Canberra,Australia.

Hotzel G and Croome R (1994) Long termphytoplankton monitoring of the Darling Riverat Burtundy, New South Wales: incidence andsignificance of cyanobacterial blooms.Australian Journal of Marine and FreshwaterResearch 45: 747-760.

Huber AL (1985) Factors affecting thegermination of akinetes of Nodulariaspumigena (Cyanobacteriacae). Applied andEnvironmental Microbiology 49: 73-78.

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IPCC (1996) Revised 1996 IPCC Guidelines forNational Greenhouse Gas Inventories. Inter-governmental Panel on Climate Exchange,Hadley Centre, UK Meteorological Office,Bracknell, UK 3 vols. http://www.ipcc-nggip.iges.or.jp/public/gl/invs1.htm

Jones GJ, Burch MD, Falconer IG and Craig K(1993) Cyanobacterial Toxicity. In Murray-Darling Basin Commission Algal ManagementStrategy. Technical Advisory Group Report, ch3, pp17-32.

Jones GJ, Blackburn SI and Parker NS (1994) Atoxic bloom of Nodularia spumigena Mertensin Orielton Lagoon, Tasmania. AustralianJournal of Marine and Freshwater Research45: 787-800.

Lukatelich RJ and McComb AJ (1986) Nutrientlevels and the development of diatom andblue-green algal blooms in a shallowAustralian estuary. Journal of PlanktonResearch 8: 597-618.

Maier HR, Burch MD and Bormans M (2001)Flow management strategies to controlblooms of the cyanobacterium Anabaenacircinalis in the lower River Murray atMorgan, South Australia. Regulated Rivers:Research and Management. (in press).

Newman R (2000) Hydrology of the Lower Lakesand Coorong. In Jensen et al. (eds). RiverMurray Barrages Environmental Flows.Department for Environment, Heritage andAboriginal Affairs.

Pilotto L, Douglas RM, Burch MD, Cameron S,Beers M, Robinson P, Kirk M, Cowie CT,Hardiman S, Morre C and Attewell RG(1997) Health effects of exposure tocyanobacteria (blue-green algae) duringrecreational water-related activities.Australian and New Zealand Journal of PublicHealth 21: 562-566.

Reynolds CS (1992) Eutrophication and themanagement of planktonic algae: whatVollenweider couldn’t tell us. InEutrophication: Research and Application toWater Supply. Jones JG and Sutcliffe DW(eds). Freshwater Biological Association.Ambleside, U.K.

Reynolds CS (1997) Vegetation Processes in thePelagic: A model for Ecosystem Theory.Ecology Institute Oldendorf/Luhe Germany.

Sas H (1989) Lake restoration by reduction ofnutrient loading: Expectations, Experiences,Extrapolations. Sankt Augustin: AcademiaVerlag Richarz.

Shafron M, Croome R and Rolls J (1990) WaterQuality. In The Murray, Mackay N andEastburn D (eds). Murray-Darling BasinCommission. Canberra, Australia.

Sherman BS, Webster IT, Jones GJ and Oliver RL(1998) Transitions between Aulacoseira andAnabaena dominance in a turbid river weirpool. Limnology and Oceanography 43:1902-1915.

Thomas PM (1999) Water quality monitoring ofCoorong Lagoons. Australian Water QualityMonitoring. December 1999.

Vollenweider RA (1968) Scientific fundamentals ofthe eutrophication of lakes and flowingwaters, with particular reference to nitrogenand phosphorus as factors in eutrophication.O.E.C.D., Paris DAS/CSI/68:27.

Walker DJ (2000) Recent behaviour of the RiverMurray Mouth. Water 27(4): 43-47.

Walker FR and Stedinger JR (1999) Fate andtransport model of Cryptosporidium. Journalof Environmental Engineering 125: 325-333.

Walker KF and Hillman T J (1977) Limnologicalsurvey of the River Murray in relation toAlbury-Wodonga, 1973-1976. Report onbehalf of Gutteridge, Haskins and Davey tothe Albury-Wodonga DevelopmentCorporation, Albury.

Walker KF and Thoms MC (1992) Environmentaleffects of flow regulation on the lower RiverMurray, Australia. Regulated Rivers: Researchand Management 8: 103-119.

Webster IT, Maier H, Baker P and Burch M (1997)Influence of wind on water levels and lagoonlevels and lagoon-river exchange in the RiverMurray, Australia. Marine and FreshwaterResearch 48: 541-550.

WHO (1999) Toxic cyanobacteria in water.Chorus I. and Bartram J. (eds). Published onbehalf of the World Health Organization by E& FN Spon, London.

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“The flow conditions in the River Murray and“The flow conditions in the River Murray and“The flow conditions in the River Murray and“The flow conditions in the River Murray and“The flow conditions in the River Murray andclosure of the Murray Mouth… have aclosure of the Murray Mouth… have aclosure of the Murray Mouth… have aclosure of the Murray Mouth… have aclosure of the Murray Mouth… have asignificant effect upon the hydrology of thesignificant effect upon the hydrology of thesignificant effect upon the hydrology of thesignificant effect upon the hydrology of thesignificant effect upon the hydrology of theCoorong and consequentlyCoorong and consequentlyCoorong and consequentlyCoorong and consequentlyCoorong and consequently, the biology of, the biology of, the biology of, the biology of, the biology ofregional inhabitants.”regional inhabitants.”regional inhabitants.”regional inhabitants.”regional inhabitants.”

Jason Higham, SARDI Aquatic SciencesMichael Hammer and Associate Professor Michael Geddes,Department of Environmental Biology, University ofAdelaide

“The flow conditions in the River Murray and“The flow conditions in the River Murray and“The flow conditions in the River Murray and“The flow conditions in the River Murray and“The flow conditions in the River Murray andclosure of the Murray Mouth… have aclosure of the Murray Mouth… have aclosure of the Murray Mouth… have aclosure of the Murray Mouth… have aclosure of the Murray Mouth… have asignificant effect upon the hydrology of thesignificant effect upon the hydrology of thesignificant effect upon the hydrology of thesignificant effect upon the hydrology of thesignificant effect upon the hydrology of theCoorong and consequentlyCoorong and consequentlyCoorong and consequentlyCoorong and consequentlyCoorong and consequently, the biology of, the biology of, the biology of, the biology of, the biology ofregional inhabitants.”regional inhabitants.”regional inhabitants.”regional inhabitants.”regional inhabitants.”

Jason Higham, SARDI Aquatic SciencesMichael Hammer and Associate Professor Michael Geddes,Department of Environmental Biology, University ofAdelaide

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IIIIInnnnntrtrtrtrtrodododododuuuuuccccctttttioioioioionnnnnDuring periods of moderate or high RiverMurray flow, the barrage gates are opened tovarying degrees and freshwater flows from theLower Lakes (Lakes Alexandrina and Albert)into the Murray Mouth region. The majority offreshwater flows out to sea via the MurrayMouth, but water is available for mixing intothe Coorong, easily impacting on salinitypatterns in the Northern Lagoon (Geddes andHall 1990).

From the work of Geddes and his coworkers(Geddes 1984, Geddes 1987, Geddes andHall 1990), the Coorong can be divided intothree regions based on different salinitypatterns:1. Murray estuary (extending from Goolwa

Barrage to the southern end ofTauwitchere Barrage at Pelican Point)

2. Northern Lagoon (extending from PelicanPoint to the Narrows), and

3. Southern Lagoon (extending beyond SaltCreek).

There is almost always an increase in salinitysouthwards along the Northern Lagoon.During periods of flow across the barrages,the Northern Lagoon may range from fresh inthe north and estuarine in the south, toseawater in the north and hypermarine(above seawater salinity) in the south duringperiods of ceased flow across the barrages(Geddes and Hall 1990).

Salinity patterns in the Southern Lagoon aremore complex, more variable and moreseasonal due to:

ooooo Interactions of water exchange from theNorthern Lagoon

ooooo High net evaporation in summer, and

ooooo Rainfall, groundwater and possibly surfacewater inflows in winter.

Historically, there have also been occasionalinflows from Salt Creek into the SouthernLagoon.

FFFFFiiiiisssssh & Ih & Ih & Ih & Ih & InnnnnvvvvverererererttttteeeeebbbbbrrrrraaaaatttttesesesesesJJJJJASONASONASONASONASON H H H H HIGHAMIGHAMIGHAMIGHAMIGHAM SARDI Aquatic Sciences

MMMMMICHAELICHAELICHAELICHAELICHAEL H H H H HAMMERAMMERAMMERAMMERAMMER ANDANDANDANDAND A A A A ASSOCIASSOCIASSOCIASSOCIASSOCIATETETETETE P P P P PROFESSORROFESSORROFESSORROFESSORROFESSOR M M M M MICHAELICHAELICHAELICHAELICHAEL G G G G GEDDESEDDESEDDESEDDESEDDES

Department of Environmental Biology, University of Adelaide

During periods of nil or low RiverDuring periods of nil or low RiverDuring periods of nil or low RiverDuring periods of nil or low RiverDuring periods of nil or low RiverMurray flow passing through theMurray flow passing through theMurray flow passing through theMurray flow passing through theMurray flow passing through theMouth, suitable winds, tides and seaMouth, suitable winds, tides and seaMouth, suitable winds, tides and seaMouth, suitable winds, tides and seaMouth, suitable winds, tides and seastate can result in a closure of thestate can result in a closure of thestate can result in a closure of thestate can result in a closure of thestate can result in a closure of theMurray Mouth. The potential impactsMurray Mouth. The potential impactsMurray Mouth. The potential impactsMurray Mouth. The potential impactsMurray Mouth. The potential impactsof a long-term Mouth closure on theof a long-term Mouth closure on theof a long-term Mouth closure on theof a long-term Mouth closure on theof a long-term Mouth closure on thefish and macroinvertebrates of thefish and macroinvertebrates of thefish and macroinvertebrates of thefish and macroinvertebrates of thefish and macroinvertebrates of theCoorong are severe.Coorong are severe.Coorong are severe.Coorong are severe.Coorong are severe.

The following discussion coversThe following discussion coversThe following discussion coversThe following discussion coversThe following discussion coversinvertebrates of the Coorong, fish ofinvertebrates of the Coorong, fish ofinvertebrates of the Coorong, fish ofinvertebrates of the Coorong, fish ofinvertebrates of the Coorong, fish ofthe Lower Lakes and Coorongthe Lower Lakes and Coorongthe Lower Lakes and Coorongthe Lower Lakes and Coorongthe Lower Lakes and Coorong(including life history), implications of(including life history), implications of(including life history), implications of(including life history), implications of(including life history), implications ofMurray Mouth closure and the needMurray Mouth closure and the needMurray Mouth closure and the needMurray Mouth closure and the needMurray Mouth closure and the needfor further research.for further research.for further research.for further research.for further research. q

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q

FFFFFiiiiisssssh & Ih & Ih & Ih & Ih & InnnnnvvvvverererererttttteeeeebbbbbrrrrraaaaatttttesesesesesDuring winter-spring, salinities are lowest andmay be below seawater or up to two or threetimes that of seawater. In summer-autumn,evaporation causes a drop in water levels, anincrease in salinity and the establishment of alongitudinal gradient with salinities as high asthree to five times that of seawater at thesouthern extremity of the Southern Lagoon.

It can therefore be seen that the collectiveCoorong water mass is affected by acombination of tidal exchange with the sea viathe Murray Mouth, freshwater inflow from theRiver Murray through the barrages, as well asrainfall and groundwater inputs. The flowconditions in the River Murray and closure ofthe Murray Mouth therefore would beexpected to have a significant effect upon thehydrology of the Coorong and consequently,the biology of regional inhabitants.

MMMMMaaaaacrcrcrcrcroooooiiiiinnnnnvvvvverererererttttteeeeebbbbbrrrrraaaaatttttesesesesesaaaaannnnnd fd fd fd fd fiiiiissssshhhhhes oes oes oes oes of thf thf thf thf theeeeeMurrMurrMurrMurrMurraaaaay My My My My Mooooouthuthuthuthuth& C& C& C& C& CoooooooooorrrrrooooonnnnngggggInvertebrate faunaInvertebrate faunaInvertebrate faunaInvertebrate faunaInvertebrate faunaAs with much of the aquatic fauna of theCoorong, few studies directly investigatemacroinvertebrates, besides the work ofGeddes and his coworkers.

Geddes and Butler (1984) undertook a 16-month study between December 1981 andMarch 1983 into the aquatic fauna of theCoorong, finding a total of 21macroinvertebrate species dominated bypolychaete worms, gastropods and bivalves. Asimilarity was found between the NorthernLagoon fauna and that of other coastallagoon systems such as Tuggerah Lakes (NewSouth Wales), the Gippsland Lakes (Victoria),and the Peel Harvey system (WesternAustralia). A list of macroinvertebrates (seeTable 1) has been assembled from available

literature including Edyvane et al. (1996) andthe work of Geddes et al. (1984 and 1990).

Fewer species are found in the Coorongcompared to many large estuaries in south-eastern Australia, where on average morethan 100 species can be collected (Geddesand Butler 1984). The low observed diversity isbelieved to reflect the extreme fluctuations insalinity. Those species present are believed torepresent the most euryhaline section (speciesthat are able to tolerate the greatest range ofsalinities) of the macroinvertebrate communitynormally present in estuaries (Geddes andButler 1984). The same authors also state thata similar restricted diversity and speciesassemblage (the group of organisms sharinga common habitat by chance) was observedin the Peel Harvey system where salinitiesfluctuate widely.

Most of the invertebrate fauna listed cantolerate salinities from freshwater up to about55‰6 . At higher salinities the ‘estuarine-lagoonal’ fauna is replaced by ‘salt lake’species such as insect larvae, especially theChironomid (Tanytarsus barbitsaris), the SaltFly (Ephydrella sp.) as well as a fewcrustaceans (Geddes and Hall 1990).

During the period 1981 to 1985, salinities inthe Southern Lagoon were such that nomembers of the estuarine-lagoonalinvertebrate fauna were collected; only ‘saltlake’ associated insect larvae and a fewcrustaceans persisting (Geddes & Hall, 1990).Mounds of tubes from previous populations ofFicopomatus enigmaticus and shells ofNotospisula trigonella gave evidence of anearlier occurrence of ‘estuarine fauna’ in theSouthern Lagoon (Geddes and Butler 1984).The high dispersal power of many of theestuarine-lagoonal macroinvertebrate faunaindicates that they would be expected torecolonise the Southern Lagoon onceconditions were suitable (Geddes and Butler1984). This hypothesis was specifically

6 ‰ = parts per thousand.

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qq

examined through the observation of fish andinvertebrate presence before and after anextended high flow event. Observations byGeddes and Butler (1984) were made duringa low flow or hypermarine phase betweenDecember 1981 and March 1983 that sawsalinities in the Coorong rise as high as100‰.

Following a period of significant freshwaterflow through the barrages during 1983 to1984, Geddes revisited the macroinvertebratefauna patterns of the region (Geddes 1987).Following the flow event of 1983 to 1984, onlytwo further species were collected in theNorthern Lagoon, with no additional faunarecorded for the Southern Lagoon. It isthought that this was due to an insufficientduration of suitable conditions to allow re-colonisation of the Southern Lagoon byNorthern Lagoon populations (Geddes 1987)and highlights the complexities of fauna andtheir vulnerability to changes in regime, suchas Mouth closure.

Fish faunaFish faunaFish faunaFish faunaFish faunaSeveral studies of the Lower Lakes andCoorong fish fauna have been undertakenover the past 30 years, concentrating mostlyon commercial species. Although the relevantliterature lists 78 species of fish recorded fromthe Murray Mouth, Lake Alexandrina and theCoorong lagoons, 34 of these are of marineorigin and are only irregular visitors to theCoorong (see Table 2).

Species distribution appears to be affected bysalinity in a similar pattern for themacroinvertebrate community, withbiodiversity (species diversity) decreasing withincreasing salinity (Geddes and Butler 1984,Geddes 1987, Geddes and Hall 1990,Molsher et al. 1994). When salinities arearound 80‰ or greater in the SouthernLagoon, Small-mouthed Hardyhead(Atherinosmoa microstoma) may be the onlyspecies present, with other species onlyentering the Southern Lagoon when salinities

ssalC ssalC ssalC ssalC ssalC emancifitneicS emancifitneicS emancifitneicS emancifitneicS emancifitneicS

snaecatsurC snaecatsurC snaecatsurC snaecatsurC snaecatsurC .pssisymolartsuA .pssisymolartsuA .pssisymolartsuA .pssisymolartsuA .pssisymolartsuA

atileM atileM atileM atileM atileM acinalyez acinalyez acinalyez acinalyez acinalyez

.ppsmuihporocaraP .ppsmuihporocaraP .ppsmuihporocaraP .ppsmuihporocaraP .ppsmuihporocaraP

.pssupohpmageM .pssupohpmageM .pssupohpmageM .pssupohpmageM .pssupohpmageM

suniramA suniramA suniramA suniramA suniramA sirtsucal sirtsucal sirtsucal sirtsucal sirtsucal

muicnarborcaM muicnarborcaM muicnarborcaM muicnarborcaM muicnarborcaM muidemretni muidemretni muidemretni muidemretni muidemretni

sunicraC sunicraC sunicraC sunicraC sunicraC saneam saneam saneam saneam saneam

suspargaraP suspargaraP suspargaraP suspargaraP suspargaraP iidramiag iidramiag iidramiag iidramiag iidramiag

seteahcyloP seteahcyloP seteahcyloP seteahcyloP seteahcyloP sierenotareC sierenotareC sierenotareC sierenotareC sierenotareC sisnearhtyreoduesp sisnearhtyreoduesp sisnearhtyreoduesp sisnearhtyreoduesp sisnearhtyreoduesp

styhpeN styhpeN styhpeN styhpeN styhpeN sisneilartsua sisneilartsua sisneilartsua sisneilartsua sisneilartsua

sierenolartsuA sierenolartsuA sierenolartsuA sierenolartsuA sierenolartsuA isrelha isrelha isrelha isrelha isrelha

sutamopociF sutamopociF sutamopociF sutamopociF sutamopociF sucitamgine sucitamgine sucitamgine sucitamgine sucitamgine

aidraccoB aidraccoB aidraccoB aidraccoB aidraccoB sisnelihc sisnelihc sisnelihc sisnelihc sisnelihc

alletipaC alletipaC alletipaC alletipaC alletipaC atatipac atatipac atatipac atatipac atatipac

.pssedilletipaC .pssedilletipaC .pssedilletipaC .pssedilletipaC .pssedilletipaC

eaniicirbaF eaniicirbaF eaniicirbaF eaniicirbaF eaniicirbaF

oipsonoirP oipsonoirP oipsonoirP oipsonoirP oipsonoirP *arefirric *arefirric *arefirric *arefirric *arefirric

*eaditseuQ *eaditseuQ *eaditseuQ *eaditseuQ *eaditseuQ

sdoportsaG sdoportsaG sdoportsaG sdoportsaG sdoportsaG aibordyH aibordyH aibordyH aibordyH aibordyH sedioniccub sedioniccub sedioniccub sedioniccub sedioniccub

rotanilaS rotanilaS rotanilaS rotanilaS rotanilaS siligarf siligarf siligarf siligarf siligarf

aetaT aetaT aetaT aetaT aetaT *sirbalifur *sirbalifur *sirbalifur *sirbalifur *sirbalifur

sevlaviB sevlaviB sevlaviB sevlaviB sevlaviB alusipsotoN alusipsotoN alusipsotoN alusipsotoN alusipsotoN allenogirt allenogirt allenogirt allenogirt allenogirt

acitirhtrA acitirhtrA acitirhtrA acitirhtrA acitirhtrA nemes nemes nemes nemes nemes

anilleT anilleT anilleT anilleT anilleT eairam eairam eairam eairam eairam

anilleteloS anilleteloS anilleteloS anilleteloS anilleteloS sedioicanod sedioicanod sedioicanod sedioicanod sedioicanod

stcesnI stcesnI stcesnI stcesnI stcesnI susratynaT susratynaT susratynaT susratynaT susratynaT susratibrab susratibrab susratibrab susratibrab susratibrab

.psallerdyhpE .psallerdyhpE .psallerdyhpE .psallerdyhpE .psallerdyhpE

TTTTTable 1: Macroinvertebrates and fish ofable 1: Macroinvertebrates and fish ofable 1: Macroinvertebrates and fish ofable 1: Macroinvertebrates and fish ofable 1: Macroinvertebrates and fish ofthe Murray Mouth and Coorongthe Murray Mouth and Coorongthe Murray Mouth and Coorongthe Murray Mouth and Coorongthe Murray Mouth and Coorong

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FFFFFiiiiisssssh & Ih & Ih & Ih & Ih & Innnnnvvvvverererererttttteeeeebbbbbrrrrraaaaatttttesesesesesfall to within their tolerance range (Geddesand Hall 1990).

There is commercial interest in the largerfishes of the Lower Lakes and Coorong (see‘Fishing Industry’ chapter); their capture inareas can vary around salinity. Between 1984and 1988, Black Bream (Acanthopagrusbutcheri) were captured in commercialquantities in the Southern Lagoon only inAugust -December of 1985-1986 whenSouthern Lagoon salinities were below 70‰.Yellow-Eye Mullet (Aldrichetta forsteri) werecaptured each year between July andDecember when salinities generally fell below85‰ in the Southern Lagoon. Mulloway andFlounder were not caught during this period,possibly indicating their lack of tolerance tohigh salinities (Geddes and Hall 1990).

The major component of fish production inthe Coorong is limited to a small number ofspecies. All are estuarine dependent for atleast part of their lifecycle (Geddes and Hall1990). The commercially and recreationallyimportant Mulloway (Argrosyomushololepidotus), Yellow-Eye Mullet (Aldrichettaforsteri), Greenback Flounder (Rhombosoleataparina), and Black Bream (Acanthopagrusbutcheri) are all presently believed to beestuarine-dependent species (although somedebate surrounds the dependence ofMulloway on the Coorong). Other commonestuarine species include River Garfish(Hyporamphus regularis), Congolli(Pseudophritis urvilii), Tamar Gobie(Favonigobius tamarensis), Blue Spot Gobie(Pseudogobius sp.) and Bridled Gobie(Arenigobius bifrenatus) as well as the FlatHeaded Gudgeon (Philypnodon grandiceps).

Most of the freshwater fish of LakeAlexandrina have also been recorded in theCoorong. While certain species can inhabitboth regions, it is believed that the majority ofthese fish are ‘flushed’ past the barrages fromLake Alexandrina during periods of freshwateroutflow. Currently, most lakes fish are not able

to return to freshwater due to physicallimitations imposed by the lack of suitable fishpassage across the barrages. This is beingaddressed in partnership with the SouthAustralian Department of Water, Land andBiodiversity Conservation, SA Water, SARDIAquatic Sciences and the Murray-DarlingBasin Commission.

Although some species may be able tomigrate back to freshwater (particularlydiadromous species – those that migratebetween freshwater and the sea as part oftheir life history), this is likely to be acomparatively small proportion of the fish‘flushed’ over the barrages. Besideseuryhaline species, those fish unable to returnto the Lakes eventually die due to high salinityor predation by other fish and birds.

LLLLLiiiiife hfe hfe hfe hfe hiiiiissssstttttooooorrrrryyyyypppppaaaaattttttttttererererernnnnns os os os os of thf thf thf thf theeeeefffffiiiiissssshhhhhes oes oes oes oes of thf thf thf thf the Ce Ce Ce Ce CoooooooooorrrrrooooonnnnngggggIn studies of South African estuaries, fishspecies were categorised by their life historypatterns to determine their estuary association(Whitfield 1999). Whitfield proposes eightcategories of fish utilization in estuaries:1.1.1.1.1. Marine MigrantMarine MigrantMarine MigrantMarine MigrantMarine Migrant - marine species that

make extensive use of estuaries duringjuvenile and/or adult life stages

2.2.2.2.2. Marine StragglerMarine StragglerMarine StragglerMarine StragglerMarine Straggler - marine specieswhere only a small proportion of theoverall population make use of estuaries

3.3.3.3.3. Estuarine Resident Estuarine Resident Estuarine Resident Estuarine Resident Estuarine Resident - species of marineorigin that reside in estuaries and cancomplete their entire lifecycle within thesesystems

4.4.4.4.4. Estuarine MigrantEstuarine MigrantEstuarine MigrantEstuarine MigrantEstuarine Migrant - species of marineorigin that usually reside in estuaries asjuveniles and adults but often have amarine larval phase

5.5.5.5.5. Freshwater MigrantFreshwater MigrantFreshwater MigrantFreshwater MigrantFreshwater Migrant - freshwater fishspecies that are often recorded inestuaries retreating into catchment riverswhen conditions become unfavourable

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q6.6.6.6.6. Freshwater StragglerFreshwater StragglerFreshwater StragglerFreshwater StragglerFreshwater Straggler - freshwater fishspecies that sometimes enter estuarieswhen conditions are favourable

7.7.7.7.7. CatadromousCatadromousCatadromousCatadromousCatadromous - species that spawn atsea but use freshwater catchment areasduring the juvenile and sub-adult lifestages, and

8.8.8.8.8. AnadromousAnadromousAnadromousAnadromousAnadromous - species that spawn infreshwater environments but use estuariesand/or the sea for larval, juvenile and/oradult phases of their life cycle.

Using the above categorisation system, thefish species from the Murray Mouth, LowerLakes and Coorong can be classified intothese eight groups (see Table 2). This allowsclear determination of the relative importanceof free access to estuarine habitats withregard to species life history, reflecting thosefishes most affected by closure of the Mouth.

Among the eight groups, Marine Migrants,Marine Stragglers, Estuarine Migrants,Catadromous and Anadromous species arethose that will be directly affected by Mouthclosure through impacts on population size orparticular lifecycle stages.

As the Marine Stragglers do not rely upon theestuary to complete their lifecycle, they willpersist locally with the Mouth closed andhence will not be affected in the long-term byMouth closure. The prevention of migrationinto the estuary for these species will result ina short-term reduction of biodiversity in theCoorong, but it is expected that this wouldreturn to present levels following the openingof the Mouth to the sea, re-establishment ofsuitable water quality and the presence ofsuitable food/prey.

From Table 2, it can be seen that the followingspecies will be directly affected by Mouthclosure due to an interrupted lifecycle:

Climbing Galaxias (Galaxias brevipinnis)Common Galaxias (Galaxias maculatus)Pouched Lamprey (Geotria australis)Short-Headed Lamprey (Mordacia mordax)Shortfin Eel (Anguilla autralis)Estuary Perch (Macquaria colonorum)Congolli or Tupong (Pseudophritis urvilli)Jumping Mullet (Liza argentea)Yellow-Eye Mullet (Aldrichetta forsteri)Southern Sea Garfish (Hyporhamphusregularis)Mulloway or Dew Fish (Argyrosomushololepidotus)Sea Mullet (Mugil cephalus).

This list includes many of the speciesharvested by commercial and recreationalfishers in the Coorong and a sizeablecontribution to the diversity and abundance ofLower Lakes fauna.

The Goolwa Cockle (Donax deltoides),although not residing inside the Coorong,lives in populations on the surf beaches justoutside the Mouth and its recruitment isbelieved to be strongly related to River Murrayflow (Murray-Jones et al. 2002). With theclosure of the Mouth, the recruitment ofGoolwa Cockles onto the beach from adultpopulations may be depressed in the nextseason due to a reduction in food availability(see pg 22 ‘Fishing Industry’ chapter). Fromrecent studies during periods of near-continual River flow (2001 to 2002), it wasfound that there was always a proportion ofthe local Cockle population able to spawn.When flow is released, food availabilityincreases, triggering the ‘ripe’ animals tospawn. Length frequency distribution data forCockles on Goowa Beach shows severalseparate recruitment events (Murray-Jones etal. 2002).

Any interruption in successful recruitment orspawning for larger species will undoubtedlyaffect the economic viability of the commercialand recreational fishing industry, as well asthe tourism industry of the area.

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FFFFFiiiiisssssh & Ih & Ih & Ih & Ih & Innnnnvvvvverererererttttteeeeebbbbbrrrrraaaaatttttesesesesesvery important ecologically as a major preyspecies for many birds and predatory fishesincluding Mulloway (Molsher et al. 1994, Hall1986). If the Coorong population wasdepleted (for example, fish kills arising fromlow oxygen levels), the effect could bedisastrous for the ecology of the region. (See‘Migratory Waders’ chapter.) Because themacroinvertebrates that inhabit the Coorongcomplete their entire lifecycle within theestuary/lagoons, they will be affected similarlyto the estuarine resident fish species.

q

As most Cockles are two or more years of agebefore reaching minimum legal length, theeffects of lifecycle interruption will initially bemasked. Over time, the effect will be reflectedas a decrease in catch per unit of fishing effortin the commercial returns supplied to SARDIby commercial fishers.

The Catadromous and Anadromousfreshwater species together with the EstuarineResident species will probably not be affectedby Mouth closure in the short term, exceptthrough secondary impacts such as:

ooooo Salinity increases

ooooo Reduced food availability

ooooo Increased frequency of predator-preyinteractions (due to the ‘concentration’ ofresidents)

ooooo Increased risk of algal blooms (toxicityand/or eutrophication), and

ooooo Reduced dissolved oxygen levels.

For the above mentioned species and to alesser extent Catadromous and Anadromousspecies, fish passage across the barragesbetween the estuary and the Lower Lakes/Lower Murray is of more relevance withregard to inhibition of lifecycle stages.

Species that will be indirectly affected byMouth closure due to degraded water qualityand salinity impacts include:

Black Bream (Acanthopagrus butcheri)Bridled Goby (Arenogobius bifrenatus)Small-Mouthed Hardyhead (Atherinosomamicrostoma)Tamar Goby (Favonigobius tamarensis)Swan River Goby (Pseudogobius olorum)Greenback Flounder (Rhombosolea tapirina)Lagoon Goby (Tasmanogobius lasti)Flathead Gudgeon (Philypnodon grandiceps).

Two of these species are commercial orsought after as a game fish. The Small-Mouthed Hardyhead (Atherinosomamicrostoma), a non-commercial species, is

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emaNcifitneicS emaNcifitneicS emaNcifitneicS emaNcifitneicS emaNcifitneicS emaNnommoC emaNnommoC emaNnommoC emaNnommoC emaNnommoCdleiftihW dleiftihW dleiftihW dleiftihW dleiftihW

noitacifissalC noitacifissalC noitacifissalC noitacifissalC noitacifissalCsaixalaG sinnipiverb saixalaggnibmilc suomordanA

saixalaG sutalucam saixalagnommoC *suomordanA

airtoeG silartsua yerpmaldehcuop suomordanA

aicadroM xadrom yerpmaldedaeh-trohS suomordanA

alliugnA silartsua leEniftrohS suomordataC

airauqcaM muronoloc hcrePyrautsE suomordataC

sitirhpaduesP iillivru illognoCenirautsE/suomordataC

tnediseR

aziL aetnegra tellumgnipmuj tnargiMenirautsE

attehcirdlA iretsrof tellumeye-wolleY tnediseR/tnargiMenirautsE

suhpmahropyH siraluger hsifragreviR tnediseR/tnargiMenirautsE

surgapohtnacA irehctub maerbkcalB tnediseRenirautsE

suiboginerA sutanerfib ybogdeldirB tnediseRenirautsE

amosonirehtA amotsorcim daehydrahhtuomllamS tnediseRenirautsE

suiboginovaF sisneramat ybogramaT tnediseRenirautsE

suibogoduesP murolo yboGreviRnawSrotopseulB tnediseRenirautsE

aelosobmohR aniripat rednuolfkcabneerG tnediseRenirautsE

suibogonamsaT itsal ybognoogaL tnediseRenirautsE

nodonpylihP specidnarg noegdugdaehtalF tnargiMretawhserF

.ppssirtoelespyH xelpmocnoegdugpraC relggartSretawhserF

.psnodonpylihP noegdugdaehtalffrawD relggartSretawhserF

sunaydiB sunaydiB hcreprevliS relggartSretawhserF

suissaraC #sutarua hsifdloG relggartSretawhserF

sulahpecoretarC sulitaivulf daehydrahyarruM relggartSretawhserF

sulahpecoretarC muracsumsucretssuvluf daehydrahdekcepsylF relggartSretawhserF

sunirpyrC #oiprac praC relggartSretawhserF

sispodaG sutaromrom hsifkcalbreviR relggartSretawhserF

saixalaG sudilo saixalagniatnuoM relggartSretawhserF

aisubmaG #ikoorbloh aisubmaGnretsaE relggartSretawhserF

noparehtopoieL rolocinu hcrepdelgnapS relggartSretawhserF

allehcolluccaM ileep doCyarruM relggartSretawhserF

airauqcaM augibma hcrePnedloG relggartSretawhserF

aineatonaleM silitaivulf hsifwobniardettopsnosmirC relggartSretawhserF

adnugroM ^asrepsda noegdugdettopselpruP relggartSretawhserF

acreponnaN silartsua hcrepymgyPnrehtuoS relggartSretawhserF

asolotameN ibere maerbynoB relggartSretawhserF

suhcnyhrocnO #ssikym tuortwobniaR relggartSretawhserF

acreP #silitaivulf nifdeR relggartSretawhserF

* If landlocked,G.maculatus canreproduce entirely infreshwater

# denotes exotic taxa

^ denotes locally extincttaxa

Primary Impactslong term implicationsshort term implications

Secondary Impacts

Unaffected

TTTTTable 2: Impacts ofable 2: Impacts ofable 2: Impacts ofable 2: Impacts ofable 2: Impacts of

Mouth closure onMouth closure onMouth closure onMouth closure onMouth closure on

recordedrecordedrecordedrecordedrecorded

ichthyofauna ofichthyofauna ofichthyofauna ofichthyofauna ofichthyofauna of

Coorong, MurrayCoorong, MurrayCoorong, MurrayCoorong, MurrayCoorong, Murray

Mouth and LowerMouth and LowerMouth and LowerMouth and LowerMouth and Lower

LakesLakesLakesLakesLakes

(Some life history

patterns of these species

are inferred due to lack

of data on those species

within the Coorong

itself.)

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FFFFFiiiiisssssh & Ih & Ih & Ih & Ih & InnnnnvvvvverererererttttteeeeebbbbbrrrrraaaaatttttesesesesesanniporteR inomes tlemsnailartsuA relggartSretawhserF

omlaS #atturt tuortnworB relggartSretawhserF

sunadnaT sunadnaT hsiftacdeliat-leeretawhserF relggartSretawhserF

acniT #acnit hcneT relggartSretawhserF

sumosorygrA sutodipeloloh yawolluM tnargiMeniraM

ligum sulahpec tellumaeS tnargiMeniraM

sudoreohcA iidluog repuorgeulB relggartSeniraM

anacarA atanro hsifwocetanrO relggartSeniraM

sipirrA sunaigroeg gnirrehnailartsuA relggartSeniraM

sipirrA suecatturt nomlasnailartsuA relggartSeniraM

syhthcinodilehC umuk dranruGdeR relggartSeniraM

susutnoC suduaciverb hsifdaotylkcirP relggartSeniraM

sulataparC suiranera hsifdnaS relggartSeniraM

specitsirC silartsua hsifdeewdetsercnrehtuoS relggartSeniraM

siluargnE silartsua yvohcnanrehtuoS relggartSeniraM

susolponE sutamra efiwdlO relggartSeniraM

syhthcilabuE iinnug tekcajrehtaels'nnuG relggartSeniraM

setsipanmyG sutaromram relbboCnailartsuAhtuoS relggartSeniraM

sunelocoileH sediocrep hcrePdranruGdeR relggartSeniraM

setoleH sutaenilixes hcrepdepirtS relggartSeniraM

sunilcoreteH sitsirt hsifdeewesongnoL relggartSeniraM

supmocoppiH silanimodba esrohaesdeilleb-giB relggartSeniraM

suhpolrepyH sutattiv tarpsydnaS relggartSeniraM

suhpmahropyH rihconalem hsifragaeSnrehtuoS relggartSeniraM

sehpabmaleM arbez hsifarbeZ relggartSeniraM

ainehcsueM itenicyerf tekcajrehtaeldenips-xiS relggartSeniraM

anirukustiM inotswo krahsnilboG relggartSeniraM

setsabesoeN sutatcnuporgin hcrepdranrugdettopSkcalB relggartSeniraM

setsabesoeN sedioneaprocs hcrepdranrugnommoC relggartSeniraM

surgaP sutarua reppanS relggartSeniraM

akiraP rebacs tekcajrehtaeltevlev relggartSeniraM

xyretpollyhP sutaloineat nogardaeSnommoC relggartSeniraM

surohpoitsirP sinnipidun krahswasnrehtuoS relggartSeniraM

xnaracoduesP xetned yllaverT relggartSeniraM

syhthcinibocS sutalunarg tekcajrehtaelhguoR relggartSeniraM

sedonigalliS sutatcnup gnitihwegroeGgniK relggartSeniraM

sediolletarpS sutsubor tarpseulB relggartSeniraM

suhtangnyS sirtsoritruc hsifepipdetuons-trohS relggartSeniraM

sonetcarteT rebalg hsifdaothtoomS relggartSeniraM

sonetcarteT inotlimah hsifdaots'nosdrahciR relggartSeniraM

TTTTTahle 2 cont.ahle 2 cont.ahle 2 cont.ahle 2 cont.ahle 2 cont.

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q

IIIIImmmmmplipliplipliplicccccaaaaatttttioioioioionnnnns os os os os offfffMMMMMooooouth cuth cuth cuth cuth closloslosloslosururururure oe oe oe oe onnnnnmamamamamacrcrcrcrcroooooiiiiinnnnnvvvvverererererttttteeeeebbbbbrrrrraaaaattttteseseseses& f& f& f& f& fiiiiissssshhhhhes oes oes oes oes of thf thf thf thf the Ce Ce Ce Ce CoooooooooorrrrrooooonnnnngggggDiminished flow of freshwater into estuaries isa worldwide phenomenon resulting fromheavy and competing demands for irrigationand domestic usage (Geddes and Hall 1990).One problem that results from reduced or lowflows reaching the Coorong is a lessenedvolume of water available to maintain thegeomorphologic character of the MurrayMouth channel (see ‘What is Possible:Hydrology and Morphology’ chapter).

During periods of reduced or low flow andlow rainfall, the Murray Mouth is of centralimportance because sea water becomes themajor source of water to ‘freshen’ theCoorong and to maintain water quality in theMurray estuary and Coorong (Geddes andHall 1990).

If turbulence is low, processes like littoral driftcause complex sand bars to develop acrossthe Mouth, greatly impeding water exchangeand effectively isolating the estuary and theCoorong from the sea (Harvey 2001). This‘closure’ has multiple effects on the plants andanimals of the Coorong and Murray estuary.Not only would Mouth closure largely preventfish and other organisms from migratingbetween the Coorong and the sea, therebyaffecting lifecycle processes, but sanddeposited inside the Mouth will also smotherthe productive mudflats in the local area ofthe Mouth, affecting food resources and waterquality for birds and fish.

Further, secondary consequences of Mouthclosure relate to elevated salinities andpossible reduced dissolved oxygenconcentration in the Coorong, as well as theeffect of reduced food availability andincreased predator-prey interactions due tothe impact of increased salinity reducingsuitable habitat for all species.

Short-term closures may have a comparativelysmall effect on fish populations if:

ooooo Closure occurs outside times when salinityand water quality rapidly degrade, or

ooooo Closure occurs outside periods ofmigration out of the Coorong by sub-adults or into the estuary by larvae andjuveniles of Marine Migrant species oradults of Catadromous species.

Present knowledge of migration patterns formany of the relevant species is deficient for theCoorong, and so it is very difficult todetermine what are the most detrimentaltimes for Mouth closure are therebyrepresenting an urgent area for investigation.Hall (1984) states that closures during theperiod of November to April are most likely toaffect migration, whilst water quality andsalinity are most likely to rapidly changeduring the summer period if the Mouth isclosed.

Complete closures of the Murray Mouth havehappened many times in the past, but havenot been paralleled by a River Murray asrestricted in flow or the pressure placed onaquatic ecosystems from a variety of sourcesas witnessed today. Previous recent andhistoric closures have fortunately been short induration, with the Mouth being re-opened byflow or a combination of flow and humanintervention (excavation) before significantdegradation in water quality occurred. Therisk now with reduced Murray median flowsand diminished flooding frequency andduration, is that closure may persist for thelong-term.

It is possible that during periods of prolongedlow flow and Mouth closure that salinities mayrise beyond the tolerance levels of some of thebiota of the Coorong in the Southern Lagoonand even in the Northern Lagoon (Geddesand Hall 1990), thereby limiting distribution tothe estuary and part of the Northern Lagoon.Although to date salinity in the southern endof the Northern Lagoon has not beenobserved by Geddes or others to rise above

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q

80‰, this salinity level is believed to beoutside the range of many of the fishes listedas residing in the Murray estuary.

If closure persisted for an extended periodwith little or no input of water to ‘freshen’ theCoorong, low summer oxygen concentrationpotentially exacerbated by algal blooms mayproduce fish kills in these areas. If the areasuitable for fish and invertebrates issubstantially reduced because of rising salinity,the effects outlined above will be exacerbatedby the relatively high density of fish in the areanear the Murray estuary.

CCCCCooooonnnnnccccc lululululusssssioioioioionnnnnWhile closure of the Murray Mouth is just onereflection of the vastly altered hydrology of theRiver Murray, it has the potential to severelyaffect the local fish community.

The most severe effect would be witnessed ifthe Mouth remains closed for longer than ayear. A ‘short-term’ closure is expected toresult in a catch reduction of many of therecreational and commercial speciesharvested in and around the Coorong in theshort term only.

Any closure of the Murray Mouth has theability to impact on local biodiversity byrestricting the migratory requirements of anumber of non-commercial species andexceeding their physiochemical tolerances.Only if a closure was sufficiently short, andnot during the hottest months, would salinityand water quality be expected to remainwithin tolerable limits over much of the Murrayestuary and Northern Lagoon, allowing thepersistence of the estuarine fish populationsthat presently reside within the Coorong.

By providing for fish passage across thebarrages and into the Lower Lakes, theuseable habitat in times of Mouth closure orlow flow periods for estuarine species andsome marine migrants will be significantly

increased. This could possibly then improvenot only the overall fishery during periods offlow, but also improve the ‘elasticity’ of thesystem to recover following Mouth closuresthrough re-colonisation of the Cooronglagoons and the Murray estuary under morefavourable conditions by populations retainedin the lakes.

More information regarding migratoryrequirements of the resident fish species isrequired together with the impact of salinityon the productivity of the system, especiallyimpacts of salinity on reproduction andgrowth in macroinvertebrates and residentfish species.

Information regarding the effect of salinityupon life-history for many of the fish andinvertebrate species that utilize the Coorong islacking. This knowledge would greatly assistmanagers and custodians in the sustainablemanagement of the industries reliant uponthe fish and macroinvertebrates of theCoorong. Research into fish passage andLower Lakes habitat use is also recommendedto better assess this as a method of mitigatingMouth closure effects on species utilizing theestuary.

FFFFFiiiiisssssh & Ih & Ih & Ih & Ih & Innnnnvvvvverererererttttteeeeebbbbbrrrrraaaaattttteseseseses

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RRRRReeeeeferferferferfereeeeennnnncccccesesesesesEckert J and Robinson RD (1990) The fishes of

the Coorong. South AustralianNaturalist 65(1): 4-30.

Edyvane K, Carvalho P, Evans K, FotheringhamD, Kinloch M and McGlennon D(1996) Biological resourcesassessment of the Murray Mouthestuary. May 1996. Report preparedby the South Australian Research andDevelopment Institute (AquaticSciences) and the CoastalManagement Branch (Department ofEnvironment and Natural Resources),for the Department of Environmentand Natural Resources and theAustralian Nature ConservationAgency. South Australian Researchand Development Institute (AquaticSciences), Adelaide.

Geddes MC (1987) Changes in salinity and inthe distribution of macrophytes,macrobenthos and fish in theCoorong Lagoons, South Australia,following a period of River Murrayflow. Transactions of the Royal Societyof South Australia 111(4): 173-181.

Geddes MC and Butler AJ (1984)Physicochemical and biological studieson the Coorong Lagoons, SouthAustralia, and the effect of salinity onthe distribution of the macrobenthos.Transactions of the Royal Society ofSouth Australia 108(1): 51-62.

Geddes MC and Hall D (1990) The MurrayMouth and Coorong. In The Murray,MacKay, N and Eastman, D (eds),pp201-213. Murray-Darling BasinCommission, Canberra.

Hale HM (1927) Paragrapsus. In Crustaceansof South Australia, pp179-180.Government Printer, Adelaide.

Hall D (1984) The Coorong: Biology of themajor fish species and fluctuations incatch rates 1976-1983. SAFIC 8(1): 3-17.

Harris JA (1968) Age structure, growth rateand spawning cycle of a population ofyellow-eye mullet Aldrichetta forsteri(Cuv. And Val.) from the CoorongLagoon, South Australia. Transactionsof the Royal Society of South Australia92: 37-50.

Kangas MI and Geddes MC (1984) The effectsof salinity on the distribution ofamphipods in the Coorong, SouthAustralia, in relation to their salinitytolerance. Transactions of the RoyalSociety of South Australia 108(3): 139-145.

Molsher RL, Geddes MC and Paton DC (1994)Population and reproductive ecologyof the small mouthed hardyheadAtherinosoma microstoma (Gunther)(Pisces: Atherninidae) along a salinitygradient in the Coorong, SouthAustralia. Transactions of the RoyalSociety of South Australia 118(4): 207-216.

Murray-Jones S, Johnson JE and Ye Q (2002)Goolwa Cockle Stock Assessment(Draft) 2002. South AustralianResearch and Development Institute,Adelaide, South Australia pp 48.

Sim T, Potts L, Hammer M and Doube J (2000)Fishes. In Natural History ofStrathalbyn & Goolwa Districts, pp 97-107. Strathalbyn Naturalists Club Inc(compiler), Adelaide.

Whitfield AK (1999) Ichthyofaunalassemblages in estuaries: A SouthAfrican case study. Reviews in FishBiology and Fisheries 9: 151-186.

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“Lack of adequate flows through the“Lack of adequate flows through the“Lack of adequate flows through the“Lack of adequate flows through the“Lack of adequate flows through theMurray Mouth leads to a series ofMurray Mouth leads to a series ofMurray Mouth leads to a series ofMurray Mouth leads to a series ofMurray Mouth leads to a series ofchanges, all of which erode the qualitychanges, all of which erode the qualitychanges, all of which erode the qualitychanges, all of which erode the qualitychanges, all of which erode the qualityof the estuarine habitats for waders.”of the estuarine habitats for waders.”of the estuarine habitats for waders.”of the estuarine habitats for waders.”of the estuarine habitats for waders.”

Dr David Paton, Department of EnvironmentalBiology, University of Adelaide

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IIIIInnnnntrtrtrtrtrodododododuuuuuccccctttttioioioioionnnnnFor the purposes of this chapter the estuarinearea is defined as the waterways between thebarrages and the Murray Mouth. This areastretches from Pelican Point on the NarrungPeninsula in the south to the Goolwa Barragein the north.

These estuarine regions, along with samphirecommunities, were listed as the twoenvironmental assets that were currentlyunder extreme risk of ongoing degradationunder the current management regime(ID & A 2001). In particular, the estuarineareas have experienced and are likely toexperience further ongoing, significantecological change as the Mouth becomesincreasingly constricted. Furthermore, unlessprompt action is taken, internationalobligations under the Ramsar Convention willnot be met and key living and economicassets will become increasingly run down (ID& A 2001).

Walker (2001) has recently modelled howchanges in flow over the barrages haveinfluenced the extent of constriction to theMurray Mouth. He argues that if flowscontinue to be greatly reduced in volume andtiming then the Mouth will remain significantlymore restricted than under natural flows.

In conclusion, Walker (2001) explains that ifthe Murray Mouth closed then the immediateconsequences are the risks of: flooding oftowns, shack sites and agricultural landaround Lakes Alexandrina and Albert;damage to the local tourism industry; publicconcern; and significant cost to re-open andclear the congested Mouth area. The extent ofdamage would depend on the duration ofMurray Mouth closure and the intervalsbetween closures.

In the longer term there would be issues ofmaintaining water quality in the Coorong,ecological damage to the Coorong, damageto the fishing industry in the Coorong andreductions in the conservation significance ofthe Mouth area and the Coorong.

MMMMMiiiiigrgrgrgrgraaaaatttttooooorrrrry Wy Wy Wy Wy WaaaaadddddererererersssssDDDDDRRRRR D D D D DAAAAAVIDVIDVIDVIDVID P P P P PAAAAATTTTTONONONONON Department of Environmental Biology, University of Adelaide

There have been significant reductionsThere have been significant reductionsThere have been significant reductionsThere have been significant reductionsThere have been significant reductionsin the numbers of waders that use thein the numbers of waders that use thein the numbers of waders that use thein the numbers of waders that use thein the numbers of waders that use theestuarine regions associated with theestuarine regions associated with theestuarine regions associated with theestuarine regions associated with theestuarine regions associated with theMurray Mouth since the late 1960s.Murray Mouth since the late 1960s.Murray Mouth since the late 1960s.Murray Mouth since the late 1960s.Murray Mouth since the late 1960s.Lack of River flows has also led toLack of River flows has also led toLack of River flows has also led toLack of River flows has also led toLack of River flows has also led toreductions in the quality and quantityreductions in the quality and quantityreductions in the quality and quantityreductions in the quality and quantityreductions in the quality and quantityof the estuarine habitat available toof the estuarine habitat available toof the estuarine habitat available toof the estuarine habitat available toof the estuarine habitat available toshorebirds (waders).shorebirds (waders).shorebirds (waders).shorebirds (waders).shorebirds (waders).

This chapter assesses the likely effectThis chapter assesses the likely effectThis chapter assesses the likely effectThis chapter assesses the likely effectThis chapter assesses the likely effectthat changes in flow over thethat changes in flow over thethat changes in flow over thethat changes in flow over thethat changes in flow over thebarrages will have on estuarinebarrages will have on estuarinebarrages will have on estuarinebarrages will have on estuarinebarrages will have on estuarinehabitats in the Murray Mouth regionhabitats in the Murray Mouth regionhabitats in the Murray Mouth regionhabitats in the Murray Mouth regionhabitats in the Murray Mouth regionand in turn on small migratoryand in turn on small migratoryand in turn on small migratoryand in turn on small migratoryand in turn on small migratorywaders.waders.waders.waders.waders. k

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MMMMMiiiiigrgrgrgrgraaaaatttttooooorrrrry Wy Wy Wy Wy WaaaaadddddererererersssssRRRRReeeeeddddduuuuuccccctttttioioioioionnnnns is is is is in wn wn wn wn waaaaadddddererererernnnnnuuuuummmmmberberberberbers us us us us usssssiiiiinnnnng thg thg thg thg theeeeeesesesesestttttuuuuuaaaaarrrrriiiiinnnnne re re re re reeeeegggggioioioioion on on on on offfffthththththe Murre Murre Murre Murre Murraaaaay My My My My MooooouthuthuthuthuthOver the last 30 or so years there has been adramatic decline in the numbers of wadersreported using the estuarine regionsassociated with the Murray Mouth.

In the 1960s in excess of 250 000 smallmigratory waders were recorded in onesection of the estuarine region alone (Paton1982). Subsequently, the numbers of smallmigratory waders counted in the region havedropped. In the 1980s there were 20 000 to35 000 small migratory waders present in theestuarine region as a whole, while in the1990s and 2000s there were only3000 to 13 000 (see Table 1).

The declines have been particularly dramaticfor Red-necked Stints (Calidris ruficollis) inrecent years with counts for that speciesdropping from 14 000 to 24 000 in the 1980sto 6600 in 1994 to between 1541 and 5455in the late 1990s and early 2000s (see Table1).

Declines for the other species since the 1980shave not been as dramatic (see Table 1)(Wilson 2001).

The declines since the 1960s have beensubstantial and the cause(s) of the declinesare not understood.

The magnitude of the declines, exceeding 50%for Red-necked Stints since the 1980s, issufficient for that species to be listed within theregion as Endangered under IUCN (2000)criterion A2. The causes of the declines maynot be reversible, and are likely to be ongoing.

Activities and actions taking place anywherewithin the range of the species (for example,along their migratory routes, at breedinggrounds or in the non-breeding areas used in

southern Australia), however, may beresponsible for the declines.

Simply dismissing the declines as being due tofactors outside Australia and/or outside theCoorong (for example, Wilson 2001),although providing a convenient scapegoat torelinquish responsibility, does not diminishAustralia’s responsibilities under internationalagreements (for example, the RamsarConvention, the Japan-Australia MigratoryBirds Agreement for the protection ofMigratory Birds and Birds in Danger ofExtinction and their Environment (JAMBA) andthe Agreement between Australia and Chinafor the Protection of Migratory Birds and theirEnvironment (CAMBA)) to protect andenhance the habitats used by these migratoryspecies.

In any case, the declines in Red-necked Stintscannot be easily attributed to environmentalchanges outside the Coorong. For example, iffactors along the migratory routes used by thebirds or at their breeding grounds werelargely responsible, then the declines shouldbe sustained across the whole of southernAustralia. This, however, is not the case. Red-necked Stints, which tend to show high fidelityto their non-breeding ‘wintering’ sites (perscomm. J. R. Wilson), do not show suchdeclines in at least one other area (note: fewareas are regularly counted). Annual countsof Red-necked Stints in Westernport Bay,Victoria from 1980 to 2000 show no obviousdecline in numbers over 20 years (Wilson2001). Given this result, the dramatic changesin abundances of Red-necked Stints in theregion of the Murray Mouth are more likely tobe related to changes in local conditions.

Reductions in flows of freshwater into theestuarine area are likely to lead to reductionsin the quantity and quality of estuarinehabitats in the vicinity of the Murray Mouthand this ongoing loss of habitat and habitatquality could contribute to the decline of thesebirds. k

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TTTTTable 1: Numbers of migratory and non-migratory waders counted in the estuarine regions between theable 1: Numbers of migratory and non-migratory waders counted in the estuarine regions between theable 1: Numbers of migratory and non-migratory waders counted in the estuarine regions between theable 1: Numbers of migratory and non-migratory waders counted in the estuarine regions between theable 1: Numbers of migratory and non-migratory waders counted in the estuarine regions between the

Barrages and Murray Mouth during the 1980s, 1990s and 2000sBarrages and Murray Mouth during the 1980s, 1990s and 2000sBarrages and Murray Mouth during the 1980s, 1990s and 2000sBarrages and Murray Mouth during the 1980s, 1990s and 2000sBarrages and Murray Mouth during the 1980s, 1990s and 2000s

seicepS seicepS seicepS seicepS seicepS 2891 2891 2891 2891 2891)beF( )beF( )beF( )beF( )beF( 11111

7891 7891 7891 7891 7891)beF( )beF( )beF( )beF( )beF( 22222

4991 4991 4991 4991 4991)beF( )beF( )beF( )beF( )beF( 33333

9991 9991 9991 9991 9991)beF( )beF( )beF( )beF( )beF( 44444

9991 9991 9991 9991 9991)beF( )beF( )beF( )beF( )beF( 55555

0002 0002 0002 0002 0002)naJ( )naJ( )naJ( )naJ( )naJ( 66666

0002 0002 0002 0002 0002)beF( )beF( )beF( )beF( )beF( 77777

1002 1002 1002 1002 1002)naJ( )naJ( )naJ( )naJ( )naJ( 88888

1002 1002 1002 1002 1002)beF( )beF( )beF( )beF( )beF( 99999

1002 1002 1002 1002 1002)beF( )beF( )beF( )beF( )beF( 0101010101

sredaWyrotargiMllamS sredaWyrotargiMllamS sredaWyrotargiMllamS sredaWyrotargiMllamS sredaWyrotargiMllamS

tnitSdekcen-deR tnitSdekcen-deR tnitSdekcen-deR tnitSdekcen-deR tnitSdekcen-deR 85341 36342 5666 1451 9852 2025 4284 8633 7245 5545

repipdnaSwelruC repipdnaSwelruC repipdnaSwelruC repipdnaSwelruC repipdnaSwelruC 6303 4216 0003 7341 354 9541 9824 391 0141 0202

repipdnaSdeliat-prahS repipdnaSdeliat-prahS repipdnaSdeliat-prahS repipdnaSdeliat-prahS repipdnaSdeliat-prahS 8294 9115 8802 6721 841 3645 8933 2711 4681 6841

gnilrednaS gnilrednaS gnilrednaS gnilrednaS gnilrednaS 921 803 041 215 35

repipdnaSkereT repipdnaSkereT repipdnaSkereT repipdnaSkereT repipdnaSkereT 5 3

repipdnaSnommoC repipdnaSnommoC repipdnaSnommoC repipdnaSnommoC repipdnaSnommoC 1 2 2 3 2

enotsnruTydduR enotsnruTydduR enotsnruTydduR enotsnruTydduR enotsnruTydduR 1

sredawllamsdeifitnedinu sredawllamsdeifitnedinu sredawllamsdeifitnedinu sredawllamsdeifitnedinu sredawllamsdeifitnedinu 043

sredawyrotargimllamslatoT sredawyrotargimllamslatoT sredawyrotargimllamslatoT sredawyrotargimllamslatoT sredawyrotargimllamslatoT 15422 51953 69811 5954 8913 62121 32031 3374 4578 4698

sredawyrotargimregraL sredawyrotargimregraL sredawyrotargimregraL sredawyrotargimregraL sredawyrotargimregraL

knahsneerG knahsneerG knahsneerG knahsneerG knahsneerG 063 732 061 743 673 333 352 231 881 942

repipdnaShsraM repipdnaShsraM repipdnaShsraM repipdnaShsraM repipdnaShsraM 1 2 4

tonKdeR tonKdeR tonKdeR tonKdeR tonKdeR 08

tonKtaerG tonKtaerG tonKtaerG tonKtaerG tonKtaerG 1

revolPnedloGcificaP revolPnedloGcificaP revolPnedloGcificaP revolPnedloGcificaP revolPnedloGcificaP 412 021 13 97 602 31 54 91 86 601

revolPyerG revolPyerG revolPyerG revolPyerG revolPyerG 9

tiwdoGdeliat-kcalB tiwdoGdeliat-kcalB tiwdoGdeliat-kcalB tiwdoGdeliat-kcalB tiwdoGdeliat-kcalB 581 501 62 041 012 511 1

tiwdoGdeliat-raB tiwdoGdeliat-raB tiwdoGdeliat-raB tiwdoGdeliat-raB tiwdoGdeliat-raB 2 1 2 1 8

lerbmihW lerbmihW lerbmihW lerbmihW lerbmihW 3 1

welruCnretsaE welruCnretsaE welruCnretsaE welruCnretsaE welruCnretsaE 51 3 7 31 51 1 51 8

epinSesenapaJ epinSesenapaJ epinSesenapaJ epinSesenapaJ epinSesenapaJ 1

revolPdednab-elbuoD revolPdednab-elbuoD revolPdednab-elbuoD revolPdednab-elbuoD revolPdednab-elbuoD 7

sredawyrotargimregrallatoT sredawyrotargimregrallatoT sredawyrotargimregrallatoT sredawyrotargimregrallatoT sredawyrotargimregrallatoT 477 864 722 444 906 884 126 151 173 563

sredawcimednE sredawcimednE sredawcimednE sredawcimednE sredawcimednE

revolPdeppac-deR revolPdeppac-deR revolPdeppac-deR revolPdeppac-deR revolPdeppac-deR 242 97 881 653 152 081 67 42 582 662

revolPdedooH revolPdedooH revolPdedooH revolPdedooH revolPdedooH 1

tlitSdegniw-kcalB tlitSdegniw-kcalB tlitSdegniw-kcalB tlitSdegniw-kcalB tlitSdegniw-kcalB 913 95 33 052 071 521 441 651

tlitSdednaB tlitSdednaB tlitSdednaB tlitSdednaB tlitSdednaB 49 005 5 74 61 831

tecovAdekcen-deR tecovAdekcen-deR tecovAdekcen-deR tecovAdekcen-deR tecovAdekcen-deR 444 12 051 71 44 94 42

gniwpaLdeksaM gniwpaLdeksaM gniwpaLdeksaM gniwpaLdeksaM gniwpaLdeksaM 282 511 051 681 443 301 16 802 802 541

rehctacretsyOdeiP rehctacretsyOdeiP rehctacretsyOdeiP rehctacretsyOdeiP rehctacretsyOdeiP 071 52 56 43 52 13 93 65 7 29

rehctacretsyOytooS rehctacretsyOytooS rehctacretsyOytooS rehctacretsyOytooS rehctacretsyOytooS 1 001 12 82 1

sredawcimednelatoT sredawcimednelatoT sredawcimednelatoT sredawcimednelatoT sredawcimednelatoT 1551 003 6811 185 856 295 643 405 907 328

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CCCCChhhhhaaaaannnnnggggges ies ies ies ies in thn thn thn thn theeeeeaaaaarrrrrea oea oea oea oea of esf esf esf esf estttttuuuuuaaaaarrrrriiiiinnnnneeeeehhhhhaaaaabbbbbitititititaaaaattttts is is is is in thn thn thn thn theeeeerrrrreeeeegggggioioioioion on on on on of thf thf thf thf theeeeeMurrMurrMurrMurrMurraaaaay My My My My MooooouthuthuthuthuthThe area of estuarine habitat in the LowerLakes and Murray Mouth region changedsubstantially following the construction of thebarrages in the late 1930s. Estimates suggestthat the estuarine areas are now around 12%of the area that they once were (Pierce 1995).Furthermore, they now lack the gradualtransition between fresh and marine water. Asa consequence the remnant estuary is likely toexperience more abrupt changes in salinity. Inaddition, following extended periods with nofreshwater flows over the barrages, estuarinesalinities (that is, those salinities between freshand marine) may be absent entirely from theregion. Prior to barrage construction theestuarine conditions would have simply shiftedfurther upstream when there were no flowsand so would not have been temporarilyeliminated.

Unfortunately, there are no estimates of thenumbers of birds using the region before theconstruction of the barrages and so no way ofassessing the likely impact on waderpopulations of losing substantial areas ofestuarine habitat.

Since the estuarine regions have stayed moreor less the same in area since the constructionof the barrages, this suggests that area per seis not involved in recent declines. However, thisfails to take into account changes in theaccessibility of estuarine shorelines to thewaders. As illustrated below, the actual areaof estuarine habitat accessible to waders isreduced when the Murray Mouth isconstricted.

MMMMMiiiiigrgrgrgrgraaaaatttttooooorrrrry Wy Wy Wy Wy WaaaaadddddererererersssssCCCCChhhhhaaaaannnnnggggges ies ies ies ies in thn thn thn thn theeeeeqqqqquuuuualitalitalitalitality oy oy oy oy of esf esf esf esf estttttuuuuuaaaaarrrrriiiiinnnnneeeeehhhhhaaaaabbbbbitititititaaaaattttts is is is is in thn thn thn thn theeeeerrrrreeeeegggggioioioioion on on on on of thf thf thf thf theeeeeMurrMurrMurrMurrMurraaaaay My My My My MooooouthuthuthuthuthLack of adequate flows through the MurrayMouth leads to a series of changes, all ofwhich erode the quality of the estuarinehabitats for waders.

First, the lack of flows allows coarse marinesands to be pushed into the estuary. Thesecoarse sands are likely to change the natureof the sediments. For example, coarsesediments or sediments with high sandcontent are known to reduce the growth rates,survival and abundance of invertebrates inother estuaries (for example, Quammen1982, Wanink and Zwarts 1993).Furthermore, Quammen (1982) reported thatheavy siltation of an intertidal lagoon due toflooding resulted in much finer sediments, a2.4-fold increase in prey availability and a 20-fold increase in numbers of shorebirds usingthe lagoon compared with previous years.

Coarse sediments may also interfere with thebirds’ foraging, making prey capture moredifficult because the birds can no longer easilydistinguish between the size of the prey andthe size of the larger sand grains (Quammen1982).

In another study, sediment types alsoinfluenced feeding densities of waders (Nehlsand Tiedemann 1993). Thus, reductions in thevolumes and changes in the frequency, timingand duration of releases of water over thebarrages clearly have the potential to erodehabitat quality and feeding efficiency formigratory waders and other shorebirds.Consistent with this, Paton et al. (2000)reported lower abundances of benthicinvertebrates in sediments with a highproportion of coarse sand compared to thenumbers found in fine sediments whereinvertebrate densities were as much as fourtimes higher.

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kFinally, the lack of flows leads to a reduction inthe width of the Murray Mouth and tocongestion of the channels inside the estuarydue to incursions of marine sands (Walker2001). This, in turn, leads to substantialreductions in the tidal flux and hencereductions in the intertidal zone around theshoreline.

A reduction in the intertidal zone reduces theavailability of habitat to waders. Most smallwaders are limited in where they can forageby the length of their legs. For species likeRed-necked Stints with short legs, foraging islimited to shores and mudflats covered by nomore than about 3cm of water.

According to models produced by Walker(2001) when the Mouth and channels are notrestricted, the amplitude of regular tidalchanges in water level are typically of theorder of 0.5m or more within the estuarineregions. However, under the current flowconditions the Mouth is restricted and the tidalflux greatly reduced to the point where itvaries by 0.2m or less over tidal cycles (that is,is dampened by at least 60%).

For waders feeding around the shoreline,normal tidal changes in water levels shift theforaging of the birds over a relatively wideband of intertidal shoreline with the birdssimply shifting their foraging up and down theintertidal zone with changes in water level.This spreads the foraging effort of the birdsmore broadly over the mudflats of the estuary.However, when there is limited tidal flux thebirds are restricted to a narrower band of themudflats. In other words, the availability ofaccessible habitat is reduced to about 40% ofwhat could be available to the birds if theMouth was not as constricted. Thus, thepotential of the current estuarine area tosupport populations of waders that foragearound the shoreline is reduced.

Furthermore, when the foraging of the birds isconcentrated on a smaller area of habitat forlonger each day there is far greater potentialfor the birds to reduce their food supply. Thus,not only is the area of habitat suitable forforaging reduced for the waders, but thewaders are more likely to erode the quality ofthat habitat.

Ironically, total closure of the Mouth mightlead to a slight elevation in water levelfluctuations above those that currently existdue to wind-induced water level changes.These changes, however, would not operateon the same time scales as the regular twice-daily changes associated with tides. At most,the level of wind-induced water level changeswill be 0.3m (based on measurements takenin the southern Coorong) when the Mouth isfully closed, and probably much lowerdepending on how much the constrictedchannels dampen water movements withinthe enclosed estuary. Furthermore, waterlevels might not change for extended periodsof time (several days) if there is little wind orlittle change in the direction and strength ofthe wind.

When the Mouth is open, changes in waterlevel generated by changes in the directionand intensity of winds will be maskedsubstantially by the tidal changes.

Finally, when the Mouth and associatedchannels are constricted, releases offreshwater over the barrages are more likelyto lead to water levels rising substantiallywithin the estuary. When this happens, mostof the shallow mudflats will be covered by toomuch water that will effectively preventshorebirds from having access to thesediments, particularly those with short legs.

During late December and early January2000-2001, an attempt was made to flush theMurray Mouth by releasing a substantialvolume of water over the barrages. Thisresulted in all of the tidally exposed mudflats

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within the estuary being totally flooded,forcing almost all the waders to vacate thearea (pers comm. R. Owen). The low numbersof waders counted in the estuarine regions on13 January 2001 (see Table 1) may in parthave been due to the earlier flooding of thebirds’ habitat, even though the barrages hadbeen closed for ten days before these countswere made.

CCCCCooooonnnnnccccc lululululusssssioioioioionnnnnThere is sufficient evidence to show that underthe current management regime the estuarinehabitats are declining in area and quality,particularly as habitat for migratory waders.

The lack of adequate flows of water to theMouth of the River Murray will continue toerode the estuarine habitats of the region.Coincident with this, the abundances ofmigratory waders have declined substantiallyover the last 30 to 40 years. Based onchanges in abundances of one species, theRed-necked Stint, the magnitude of thechanges in the last 20 years alone is sufficientfor the species to be classified as Endangeredfor the region under IUCN (2000) criteria.

Continuing to allow these estuarine habitatsto deteriorate contravenes Australia’sobligations under a series of internationalagreements, including the RamsarConvention, JAMBA and CAMBA. Ourknowledge of natural systems remainsseverely limited, and this impedesmanagement decisions, but we do know thatcomplete closure of the Murray Mouth willexacerbate the degradation.

MMMMMiiiiigrgrgrgrgraaaaatttttooooorrrrry Wy Wy Wy Wy Waaaaadddddererererersssss

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RRRRReeeeeferferferferfereeeeennnnncccccesesesesesID&A (2001) Lower Murray Environmental

Scoping Study. Final report MDBC projectR10017.

IUCN (2000) IUCN Red List Categories.IUCN, Switzerland.

Jaensch RP and Barter MA (1988) Waders inthe Coorong South Australia in February1987. RAOU Report No 39. RAOU,Melbourne.

Nehls G and Tiedemann R (1993) Whatdetermines the densities of feeding birdson tidal flats? a case study of dunlinCalidris alpina in the Wadden Sea.Netherlands Journal of Sea Research 31:374-384.

Paton DC, Ziembicki M, Owen P, Hill B, andBailey C (2000) Distribution andabundance of migratory waders and theirfood in the estuarine areas of the MurrayMouth and patterns in the composition ofsediments. Final report for the NationalWetlands Program, EnvironmentAustralia.

Paton DC, Bailey C, Hill B, Lewis T andZiembicki M (2001) Study of the linkbetween migratory bird numbers in theCoorong region, the composition of theirmudflat habitat and the available foodsupply. Final report. MDBC projectR10016.

Paton PA (1982) Biota of the Coorong. A studyfor the Cardwell Buckingham Committee.SADEP 55. Department of Environmentand Planning, Adelaide.

Pedler LP (1994) Waterbirds of the MurrayMouth region, February 1994. Unpubl.report. Department of Environment andPlanning, Adelaide.

Pierce BE (1995) Coorong and Murray Mouthfish and fisheries. In Proceedings of theMurray Mouth Biological ResourceAssessment Workshop, K Edyvane and PCarvalho (eds), pp 43-49. South AustraliaResearch and Development Institute(Aquatic Sciences), West Beach.

Quammen ML (1982) Influence of subtlesubstrate differences on feeding byshorebirds on intertidal mudflats. MarineBiology 71:339-343.

Walker DJ (2001) The behaviour and future ofthe River Murray Mouth. Report for theDepartment for Water Resources,Adelaide.

Wanink JH and Zwarts L (1993) Environmentaleffects on the growth rate of intertidalinvertebrates and some implications forforaging waders. Netherlands Journal ofSea Research 31: 401-418.

Wilson JR (2000) South Australian WaderSurveys January and February 2000. Ajoint project between the AustralasianWader Studies group and the SouthAustralian Ornithological Association. JRWilson, Kingston, Canberra.

Wilson JR (2001) Wader surveys in theCoorong. January and February 2001. JRWilson, Kingston, Canberra.

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“““““A consequence [of River regulation]A consequence [of River regulation]A consequence [of River regulation]A consequence [of River regulation]A consequence [of River regulation]is a depauperate flora, weed invasionis a depauperate flora, weed invasionis a depauperate flora, weed invasionis a depauperate flora, weed invasionis a depauperate flora, weed invasionand a loss of biodiversity… Tand a loss of biodiversity… Tand a loss of biodiversity… Tand a loss of biodiversity… Tand a loss of biodiversity… To doo doo doo doo donothing and allow the Murray Mouthnothing and allow the Murray Mouthnothing and allow the Murray Mouthnothing and allow the Murray Mouthnothing and allow the Murray Mouthto close would… further reduce plantto close would… further reduce plantto close would… further reduce plantto close would… further reduce plantto close would… further reduce plantbiodivers i tybiodivers i tybiodivers i tybiodivers i tybiodivers i ty.”.”.”.”.”

Associate Professor George Ganf, Departmentof Environmental Biology, University of Adelaide

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AAAAAqqqqquuuuuaaaaatttttiiiiic Pc Pc Pc Pc PlllllaaaaannnnntttttCCCCCommunommunommunommunommunitititititiiiiieseseseses

0IIIIInnnnntrtrtrtrtrodododododuuuuuccccctttttioioioioionnnnnAlthough there are no precise descriptions ofthe flora prior to the construction of thebarrages, there is sufficient ecologicalknowledge to infer the likely status of theMurray estuary.

The historical environment of the Lower Lakesand the Murray estuary would have beendynamic allowing a succession of plantspecies to come and go. These species wouldhave provided a diverse range of habitat, foodsource, nesting and hiding places, as well ascontributing to the primary production of theecosystem.

PPPPPlllllaaaaannnnnt st st st st suuuuuccccccccccesesesesessssssioioioioionnnnn:::::A rA rA rA rA respoespoespoespoesponnnnnsesesesesettttto no no no no naaaaatttttururururural fal fal fal fal f lololololowwwwwsssss?????Historically, the Murray estuary was subjectedto a fluctuating environment (Newman 2000).Average spring flows of 1400GL to 1600GLper month from the Murray produced afreshwater environment from August toNovember (Walker 2001, 2002). These flowswere ideal for the germination and growth ofmany freshwater aquatic plants (van der Valk1981).

As flow decreased in December, these plantswould have experienced increasing salinitystress which would have promoted flowering

AAAAASSOCIASSOCIASSOCIASSOCIASSOCIATETETETETE P P P P PROFESSORROFESSORROFESSORROFESSORROFESSOR G G G G GEORGEEORGEEORGEEORGEEORGE G G G G GANFANFANFANFANF Department of Environmental Biology, University of Adelaide

Jensen et al. (2000) reviewed theJensen et al. (2000) reviewed theJensen et al. (2000) reviewed theJensen et al. (2000) reviewed theJensen et al. (2000) reviewed theRiver Murray barrages and theRiver Murray barrages and theRiver Murray barrages and theRiver Murray barrages and theRiver Murray barrages and theenvironmental flow requirement ofenvironmental flow requirement ofenvironmental flow requirement ofenvironmental flow requirement ofenvironmental flow requirement ofthe Lower Lakes and Coorong. Sincethe Lower Lakes and Coorong. Sincethe Lower Lakes and Coorong. Sincethe Lower Lakes and Coorong. Sincethe Lower Lakes and Coorong. Sincethen, Wthen, Wthen, Wthen, Wthen, Walker (2001) has modelled thealker (2001) has modelled thealker (2001) has modelled thealker (2001) has modelled thealker (2001) has modelled theinfluence of freshwater flows on theinfluence of freshwater flows on theinfluence of freshwater flows on theinfluence of freshwater flows on theinfluence of freshwater flows on theopening of the Murray Mouth.opening of the Murray Mouth.opening of the Murray Mouth.opening of the Murray Mouth.opening of the Murray Mouth.

These two publications provide theThese two publications provide theThese two publications provide theThese two publications provide theThese two publications provide thebackground for this discussion on thebackground for this discussion on thebackground for this discussion on thebackground for this discussion on thebackground for this discussion on theimplications to aquatic plantimplications to aquatic plantimplications to aquatic plantimplications to aquatic plantimplications to aquatic plantcommunities of Murray Mouthcommunities of Murray Mouthcommunities of Murray Mouthcommunities of Murray Mouthcommunities of Murray Mouthclosure. This discussion is dividedclosure. This discussion is dividedclosure. This discussion is dividedclosure. This discussion is dividedclosure. This discussion is dividedinto sections dealing with: plantinto sections dealing with: plantinto sections dealing with: plantinto sections dealing with: plantinto sections dealing with: plantsuccession; fresh, brackish and saltsuccession; fresh, brackish and saltsuccession; fresh, brackish and saltsuccession; fresh, brackish and saltsuccession; fresh, brackish and saltwater flora; plant biodiversity;water flora; plant biodiversity;water flora; plant biodiversity;water flora; plant biodiversity;water flora; plant biodiversity;hydrology; and the ecologicalhydrology; and the ecologicalhydrology; and the ecologicalhydrology; and the ecologicalhydrology; and the ecologicalconsequences of additional annualconsequences of additional annualconsequences of additional annualconsequences of additional annualconsequences of additional annualf lowsflowsflowsflowsflows

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and seed set (Payne 1998), thereby ensuring areplenishment of the seed bank and/or theformation of asexual propagules (for example,modified underground stems such asrhizomes from which new shoots arise, orturions above ground that are starch filledreproductive structures found in TasselsRuppia spp). Mud flats would also have beenopened up to support a succession of mudflat dependent species (Rea and Ganf 1994,Payne 1998, Siebentritt et al. 2002). Low flowswere of sufficient duration for species to growand flower before the River flows began toincrease again in April and May.

Historically, salinity tolerant plant communities(Ruppia spp – Clubrush Isolepsis spp, BeadedSamphire Sarcocornia quinqueflora – EmuGrass Distichlis distichophylla, SamphireHalosarcia spp – Distichlis distichophylla)would have dominated the saline mud flatsduring times of minimal flow from February toApril.

The Murray Mouth provided habitat formarine angiosperms such as Eelgrass Zosteramuelleri and Seagrass Heterozosteratasmanica and macroalgal communities(Paton 1982, Edyvane et al. 1996).

The transition zone between fresh and salinewater provided an ideal habitat for floodplainand littoral species such as Sea Club RushBolboschoenus caldwelli, Marsh Club-rushB. medianus, Brass Buttons Cotulacoronopifolia, Pale Rush Juncus pallidus, SeaRush Juncus kraussi, Creeping Monkey FlowerMimulus repens, Water Finger-grassPaspalum distichum, Coastal clubrushSchoenoplectus littoralis, and on the higherground by two species of Thatching GrassGahnia (G. filum and G. trifida).

Submerged species in the zone of fluctuatingsalinity would have included species nowpresent in the Coorong such as Tuberoustassel Ruppia tuberosa, Many-fruit tassel R.polycarpa and Large-fruit tassel R. megacarpaas well as Long-fruit Water-mat Lepilaena

cylindrocarpa and the more salt tolerantspecies of Pond Weed Potamogeton (forexample, Potamogeton pectinatus).

The Stoneworts Chara spp, Nitella spp andLamprothanium spp would have flourished inbrackish water.

The freshwater areas would have includedemergent vegetation such as Cumbungi/Bullrush Typha domingensis, Common reedPhragmites australis and possibly members ofthe genus Baumea (Rushes) and othermembers of the Cyperaceae (for example,Spiny Flat Sedge Cyperus gymnocaulus,Spikerush Eleocharis spp and Sharp LeafSedge Schoenoplectus pungens).

The submerged and semi-emergentvegetation would have included species suchas Water Ribbons Triglochin procerum,Lax-marshflower Villarsia reniformis, RibbonWeed Vallisneria americana and MilfoilMyriophyllum spp, as well as speciesbelonging to the genus Potamogeton.

FFFFFrrrrresesesesesh v bh v bh v bh v bh v brrrrraaaaackckckckckiiiiisssssh vh vh vh vh vsssssaltaltaltaltaltwwwwwaaaaattttter fer fer fer fer f lololololorrrrraaaaaA comparison of the flora associated with thenorthern (freshwater) and southern (saltwater) shores and inundated areas ofHindmarsh Island (Renfrey et al. 1989,Edyvane et al. 1996, Ganf 2000)demonstrates how increasing salinityinfluences the floristic composition. Thus, themore saline and permanent waters of theCoorong and Murray estuary are dominatedby three species of Ruppia, Lepilaena andFoxtail Stonewort Lamprothamniumpapulosum. In addition, the saline but lesspermanently inundated soils of the coastalregion are dominated by Sarcocorniaquinqueflora, Halosarcia spp, SaltmarshWilsonia spp, Austral seablite Suadeaaustralis and Swamp Reed Selliera radicans,as well as the more terrestrial members of theChenopodiaceae (for example, Ruby SaltbushEnchylaena tomentosa).

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0Typha spp, Phragmites australis andBolboschoenus medianus, B. caldwellidominate the emergent vegetation on thenorthern, freshwater side of the barrages.These often form dense monospecific (singlespecies) stands that obscure the smallerspecies that add to the biodiversity of thearea. For example, Bladderwort Utriculariaspp., Duckweeds: Wolfia spp., Lemna spp.,and Spirodella spp and many of the shadeloving Stoneworts (Nitella spp and Charaspp), as well as herbland species such asStreaked Arrowgrass Triglochin striatum whichoccur beneath the canopy of these extensivestands.

Submerged plants frequent the freshwaters tothe north of Hindmarsh Island and Rat Island(for example, Vallisneria americana, HornwortCeratophyllum demersum and Potamogetontricarinatus).

The subtidal salt water habitat is characterisedby opportunistic macroalgal species, such asEnteromorpha and Rhizoclonium, but thecomplete absence of sea grasses.

PPPPPlllllaaaaannnnnt bt bt bt bt biodiodiodiodiodiiiiivvvvvererererersssssititititityyyyyPrior to River regulation, a rich diversity ofplants were distributed across the floodplain,temporary wetlands and main channel.However, with the increase in turbidity theaquatic flora is now restricted to the littoralzone and the lack of inundation of thefloodplain, coupled with grazing and clearing,has impacted upon plant biodiversity.

The submerged vegetation in the Lower Lakesis now restricted to inshore areas, whereasanecdotal evidence suggests that thesespecies were once more widely distributedthroughout the Lake basin.

The explorer Sturt commented on the extremevariability of the water clarity that ranged fromtransparent to so turbid that it was impossibleto see objects (Blanch 1997). In 1962,following exceptionally stable water levels and

low turbidities (< 25NTU), Harris (1963)described a rich aquatic flora 20km upstreamof Blanchetown which extended out into themain channel 20 or 30 feet (8-10m). Whetherthis water clarity was apparent in the LowerLakes and the Mouth is unknown.

Due to a lack of ecological foresight, theconstruction of the barrages and the over useof water has not only increased theprobability of the closure of the River MurrayMouth but also dramatically reduced plantbiodiversity.

The plant successional sequences thatoccurred as the River discharges ebbed andflowed have been replaced by a static systempunctuated by sudden and often ill-timedwater releases of insufficient duration to allowcompletion of the life cycle. Partial completionof the life cycle does not permit a species toreplace itself via seed set or asexualreproductive strategies.

A consequence is a depauperate flora, weedinvasion and a loss of biodiversity. The 1995biological survey of the Murray Mouthconcluded that although estuaries aretraditionally areas of low biodiversity, theMurray Mouth had a particularly low diversitythat was attributable to poor water qualityand flow manipulation (Edyvane et al. 1996).

HydHydHydHydHydrrrrrooooololololologggggyyyyyThe River Murray, the Lower Lakes andwetlands as well as the Northern andSouthern lagoons of the Coorong have beensubjected to intense manipulation. Thediversion of the Snowy River, the constructionof the deflation basin lakes in New SouthWales, dam construction (Hume, Dartmouth)and the drainage system in south-east SouthAustralia are a few examples. These havedramatically altered the hydrology. (For amore detailed discussion on hydrology, see‘What is Possible: Hydrology andMorphology’ chapter.)

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AAAAAqqqqquuuuuaaaaatttttiiiiic Pc Pc Pc Pc Plllllaaaaannnnnt Ct Ct Ct Ct CommunommunommunommunommunitititititiiiiiesesesesesMitsch and Gosselink (1993) state that thehydrology is the most important variable inwetland design and it is not surprising thatmajor ecological changes have occurred.Furthermore, the hydrology is currentlysubject to further manipulation via the inputof brackish water into the Southern Lagoon ofthe Coorong from the drainage system in theupper south-east of South Australia.

The most recent assessment of the behaviourof the River Murray Mouth (Walker 2001) wasdone in isolation from the effects that theUpper South-East Drainage System will haveupon the Southern Lagoon of the Coorong.Walker notes, however, that within livingmemory the Mouth and its environs havebeen subject to extended periods offreshwater to estuarine conditions with widefluctuations in salinity.

However, the construction of the barrages hasled to freshwater conditions in LakeAlexandrina and the periodic freshening ofthe Coorong in the vicinity of the MurrayMouth as freshwater is released from thebarrages.

More recently, the Murray Mouth has closedor partially closed as a result of reduced flowsin the River Murray and the location of thebarrages. This has caused the entrapment ofmillions of cubic metres of sand inside theMouth.

A comparison between the unregulated Riverand the current regulated conditiondemonstrates that the regulated River Mouthis more likely to close under the currentregulation than under a natural flow regime.

Furthermore, Walker (2001) explores thestatus of the Murray Mouth with additionalflows of 0GL to 1200GL per either an annualpulse in September, an evenly spaced monthlyrelease or a flow pattern that mimics moreclosely the historical flows. He concludes thatto do nothing would cause the Mouth to close

frequently and sand to accumulate in theMundoo Channel making boat passagedifficult if not impossible (see pg 27‘Recreation and Tourism’ chapter). Theoutcomes of the other options woulddecrease the probability of the closure of theMouth.

Another option briefly considered by Walker(2001) was the removal of the barrages. Heconcludes (pers com) that even though thisoption would increase the tidal prism, it isdoubtful whether this option would preventthe accumulation of sediment behind theMouth without the benefit of additionalenvironmental flows. The reduced watervelocity in the Coorong would allowsedimentation of sand brought in on theincoming tide due to rough coastal conditionsstirring up the sand.

EEEEEcccccooooo lolololologggggiiiiicccccalalalalalooooonnnnnseseseseseqqqqqueueueueuennnnncccccesesesesesooooof af af af af adddddddddditititititioioioioionnnnnalalalalalaaaaannnnnnnnnnuuuuual fal fal fal fal f lololololowwwwwsssssTo ‘do nothing’ is undesirable for a numberof reasons (see Walker 2001 and ‘MigratoryBirds’ chapter). It is also undesirable for plantcommunities.

The sudden spatial transition from fresh tosaline water provides little habitat forintermediate species and the duration of thefreshwater flows is inconsistent with plantgrowth and reproduction. The accumulationand continually shifting sand in the estuaryduring low or non-existent freshwater flowsprovides an unstable substrate that preventsthe establishment of plant communities.Consequently, the biodiversity of themacrophyte (macroscopic submerged,floating or emergent plants), marineangiosperm (flowering plants) andmacroalgae (seaweeds) communities,particularly south of the barrages, is low. Theoccurrence of the opportunistic macroalgal

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species, such as Enteromorpha andRhizoclonium, and filamentous algae, such asCladophora spp and Oscillatoria spp,indicate a eutrophic (nutrient rich)environment. A similar situation occurred inthe Peel-Harvey estuary in West Australia(State of the Environment Advisory Council1996) which required major expenditure tosolve. Furthermore, there are manyinternational examples (Scheffer et al. 2001)of how shallow lakes have undergone acatastrophic shift from one stable state toanother. Higher water residence times as afunction of the lack of flushing have beenimplicated in the switch from macrophytedominated states to algal dominated statesand the appearance of turbid as opposed toclear water. This shift may proceedexponentially and is often difficult to reverse(Harris 2001). Closure of the Murray Mouthand the associated lack of flushing, sedimentand nutrient accumulation are likely toincrease the probability of this type ofcatsatrophic shift towards a cyanobacterialdominated system (Australian State of theEnvironment 2001).

The two additional options considered byWalker (2001 and pg 94 ‘What is Possible:Hydrology and Morphology’ chapter) appearto achieve the objective of reducing thenumber of months the Mouth would close.However, both options have ecologicalconsequences.

An annual flush concentrated in a singlemonth is not recommended since it would beinconsistent with plant growth requirements(for example, rising water levels, sudden shiftin salinity, insufficient duration).

Evenly spaced monthly releases or a releasepattern that mimics natural flow are morelikely to promote the growth of aquatic plantsand have the additional benefit of flushingproblematic algal blooms out to the ocean. Itwould be interesting to explore what the effectwould be on the Murray Mouth if the annual

supplements suggested by Walker weredistributed differentially across the barrages(Goolwa, Mundoo, Boundary Creek, EweIsland, and Tauwitchere). This will be thesubject of consideration in the near future.

Nevertheless, additional annual flows of500GL to 600GL represent a significantfraction of the average (6000GL per year),median (4047GL per year) or entitlement(1850GL per year) flow to South Australia(Newman 2000). Irrigation (30%, 573GL),metropolitan Adelaide and other towns (10%,180GL) require 40% of South Australia’sannual entitlement (1850GL). The remaining60% of the entitlement covers the evaporativelosses from the Lower Lakes and thetransmission (passage) along the Riverchannel (Newman 2000). In addition, at least35 000ML are required each day to floodupstream wetlands and floodplain. Whetherthe flows required to maintain an open RiverMouth are justifiable when balanced againstthe upstream requirements has not beendebated but needs to be if the ecologicalproblems of the River Mouth are not to betransferred upstream. The additional brackishwater entering the Southern Lagoon of theCoorong (Boon 2000) further complicates theecological state of the region. It does seeminappropriate to consider the Murray Mouth,the Lower Lakes, the Coorong and theupstream environment in isolation from oneanother.

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AAAAAqqqqquuuuuaaaaatttttiiiiic Pc Pc Pc Pc Plllllaaaaannnnnt Ct Ct Ct Ct CommunommunommunommunommunitititititiiiiiesesesesesCCCCCooooonnnnnccccclululululusssssioioioioionnnnnPrior to River regulation, a rich diversity ofplants was distributed across the floodplain,temporary wetlands and main channel.However, with the increase in turbidity theaquatic flora is now restricted to the littoralzone and the lack of inundation of thefloodplain, coupled with grazing and clearing,has impacted upon plant biodiversity.Furthermore, an increased water residencetime with the closure of the Murray Mouth(>60 days) would greatly increase theprobability of a single celled algae (forexample, toxic cyanobacteria ordinoflagellates, (State of the Environment1996)) dominated ecosystem replacing amacrophyte dominated system.

As mentioned above, the 1995 biologicalsurvey of the Murray Mouth concluded thatalthough estuaries are traditionally areas oflow biodiversity the Murray Mouth had aparticularly low diversity that was attributableto poor water quality and flow manipulation(Edyvane et al, 1996).

To do nothing and allow the Murray Mouth toclose would be undesirable for plantcommunities, allowing depauperateconditions to further reduce plant biodiversity.

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RRRRReeeeeferferferferfereeeeennnnncccccesesesesesAustralian State of the Environment (2001)

Independent Report to the CommonwealthMinister for the Environment and Heritage,CSIRO Publishing on behalf of theDepartment of Environment and Heritage,Canberra.

Blanch SJ (1997) Influence of water regime onthe growth and resource allocation in aquaticmacrophytes of the lower Murray River,Australia. PhD thesis, University of Adelaide,pp480.

Boon PI (2000) Biological impacts of changes towater level and salinity in the Coorong.Prepared for the Upper South-East DrylandSalinity and Flood Management Scheme.Final Report, pp 107.

Edyvane K, Carvalho P, Evans K, Fotheringham D,Kinloch M, and McGlennon D (1996)Biological resource assessment of the MurrayMouth Estuary. Report prepared by the SouthAustralian Research and DevelopmentInstitute and the Coastal Management Branchfor the Department of Environment andNatural Resources and the Australian NatureConservation Agency.

Ganf GG (2000) Aquatic and riparianvegetation. In River Murray BarragesEnvironmental Flows an evaluation of theenvironmental flow needs in the Lower Lakesand Coorong. Department for Environment,Heritage and Aboriginal Affairs, SouthAustralia. A report for the Murray-DarlingBasin Commission.

Harris GP (2001) The biogeochemistry ofnitrogen and phosphorus in Australiancatchment, rivers and estuaries. Effects ofland use and flow regulation and comparisonwith global patterns. Journal of Marine andFreshwater Research 52: 139-149.

Harris WK (1963) Observations of water plants inthe River Murray. South Australian Naturalist37: 43-44.

Jensen A, Good M, Tucker P and Long (eds)(2000) River Murray Barrages EnvironmentalFlows an evaluation of the environmentalflow needs in the Lower Lakes and Coorong.Department for Environment, Heritage andAboriginal Affairs, South Australia. A reportfor the Murray-Darling Basin Commission.

Mitsch WJ and Gosselink JG (1993) Wetlands 2ed. Publ. Van Nostrand Reinhold.

Newman B (2000) Hydrology of the Lower Lakesand Coorong. In River Murray BarragesEnvironmental Flows an evaluation of theenvironmental flow needs in the Lower Lakesand Coorong. Jensen A, Good M, Tucker Pand Long M (eds). A report for the Murray-Darling Basin Commission, pp118.

Paton, PA (1982) Biota of the Coorong. A studyfor the Cardwell Buckingham Committee.SADEP 55. Department of Environment andPlanning, Adelaide.

Payne HF (1998) Wildlife habitat management ofwetlands, Krieger and Malabar, Florida.

Rea N and Ganf GG (1994) The role of sexualreproduction and water regime in shapingthe distribution patterns of clonal emergentaquatic plants. Australian Journal of Marineand Freshwater Research 45: 1469-79.

Renfrey APC, Rea N and Ganf GG (1989) Theaquatic flora of Hindmarsh Island, SouthAustralia. Report prepared for theDepartment of Environment and Planning,South Australia.

Scheffer M, Carpenter S, Foley JA, Folke C andWalker B (2001) Catastrophic shifts inecosystems. Nature 413:591-596.

Sienbentritt, MA, Ganf GG and Walker KF(submitted) Effect of an artificially enhancedflood on riparian vegetation. RegulatedRivers: Research and Management 2002.

State of the Environment Advisory Council (1996)Australia: State of the Environment, Chapter7 - Inland Waters. CSIRO Publishing,Melbourne.

Van der Valk AG (1981) Succession in wetlands:a Gleasonian approach Ecology 62:688-696.

Walker DJ (2001) The behaviour and future ofthe River Murray Mouth. Report for theDepartment for Water Resources, Adelaide.

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“Should the Mouth close…, [it] would“Should the Mouth close…, [it] would“Should the Mouth close…, [it] would“Should the Mouth close…, [it] would“Should the Mouth close…, [it] wouldcease to act as a sediment sink and thecease to act as a sediment sink and thecease to act as a sediment sink and thecease to act as a sediment sink and thecease to act as a sediment sink and thesand would bypass the closedsand would bypass the closedsand would bypass the closedsand would bypass the closedsand would bypass the closedentrance.”entrance.”entrance.”entrance.”entrance.”

Murray Townsend and Doug FotheringhamOffice for Coast and Marine, National Parks andWildlife SA, Department for Environment andHeritage

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CCCCCoooooaaaaassssstttttal Pral Pral Pral Pral Procococococesesesesessessessessesses

IIIIInnnnntrtrtrtrtrodododododuuuuuccccctttttioioioioionnnnnThe current severe restriction of the MurrayMouth is acting as a mechanism for furtherrestriction.

The Mouth absorbs large amounts of sandfrom the coastal zone which would otherwisecontinue along the coast.

Should the Mouth close, the mechanism bywhich the Mouth absorbs sand would nolonger operate as there would be no tidalintrusion through the Mouth. The Mouthwould cease to act as a sediment sink and thesand would bypass the closed entrance.

FFFFF lololololow cw cw cw cw cooooonnnnnddddditititititioioioioionnnnnsssssThe influence of the barrages is to restrict thevolume of seawater flowing through theMouth each tidal cycle. The barrages preventtidal movements from raising and loweringthe water levels in the Coorong and LakesAlexandrina and Albert. If there were no inputof fresh water from the River system, the flowsthrough the Mouth would consist only of theoscillatory tidal currents. As it is, there iscurrently a severely limited amount of freshwater from the River and this allows only asmall flow of water through the Mouth to sea.

LLLLLititititittttttooooorrrrral cal cal cal cal cooooonnnnnddddditititititioioioioionnnnnsssssThe coast on the seaward sides of theCoorong and Younghusband and Sir Richardpeninsulas is high-energy beach upon whichbreaks a persistent south-westerly swell (Short2000). This swell and the locally-generatedwind waves break on the beach, suspendingsand which is moved along the coast from the

MMMMMURRAURRAURRAURRAURRAYYYYY T T T T TOWNSENDOWNSENDOWNSENDOWNSENDOWNSEND ANDANDANDANDAND D D D D DOUGOUGOUGOUGOUG F F F F FOOOOOTHERINGHAMTHERINGHAMTHERINGHAMTHERINGHAMTHERINGHAM Office for Coasts and MarineNational Parks and Wildlife SA, Department for Environment and Heritage

The Murray Mouth has beenThe Murray Mouth has beenThe Murray Mouth has beenThe Murray Mouth has beenThe Murray Mouth has beenrestricted for many years now andrestricted for many years now andrestricted for many years now andrestricted for many years now andrestricted for many years now andthe effects of this are clearly evident.the effects of this are clearly evident.the effects of this are clearly evident.the effects of this are clearly evident.the effects of this are clearly evident.The effects of closure on coastalThe effects of closure on coastalThe effects of closure on coastalThe effects of closure on coastalThe effects of closure on coastalprocesses, howeverprocesses, howeverprocesses, howeverprocesses, howeverprocesses, however, are somewhat, are somewhat, are somewhat, are somewhat, are somewhatdifferent from those of restriction.different from those of restriction.different from those of restriction.different from those of restriction.different from those of restriction.

The following discussion explores theThe following discussion explores theThe following discussion explores theThe following discussion explores theThe following discussion explores thelikely effects that restriction orlikely effects that restriction orlikely effects that restriction orlikely effects that restriction orlikely effects that restriction orclosure of the Murray Mouth willclosure of the Murray Mouth willclosure of the Murray Mouth willclosure of the Murray Mouth willclosure of the Murray Mouth willhave on coastal processes along thehave on coastal processes along thehave on coastal processes along thehave on coastal processes along thehave on coastal processes along theocean shorelines of theocean shorelines of theocean shorelines of theocean shorelines of theocean shorelines of theYYYYYounghusband and Sir Richardounghusband and Sir Richardounghusband and Sir Richardounghusband and Sir Richardounghusband and Sir Richardpeninsulas.peninsulas.peninsulas.peninsulas.peninsulas.

6

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6CCCCCoooooaaaaassssstttttal Pral Pral Pral Pral Procococococesesesesessessessessessessouth-east to north-west by the ocean current(a process know as littoral transport). This isevident from the steady movement of theMurray Mouth in a north-westerly direction inrecent years. This means that the stability ofSir Richard Peninsula is at least partlydependent on sediment moving along thecoast from the Coorong, along theYounghusband Peninsula and across theMurray Mouth.

Regular surveys inside the Murray Mouth since1999 have provided information that givessome indication of the rate of sand movementalong the coast. Between December 1999 andJune 2000 the sand deposit inside the Mouthincreased in volume by 88 000m3. Assumingthat the Mouth did not trap all of the sedimentwithin the littoral transport system, the rate atwhich sand is moved (the net littoral transportrate) must exceed 176 000m3 a year.

Reissen and Chappell (1993) used thesediment transport models developed by theUS Coastal Engineering Research Center(CERC 1984) to determine littoral drift ratesadjacent to the Murray Mouth. Theycalculated that the average net littoral driftrate between 1940 and 1990 was 260 000m3

a year.

TTTTThhhhhe ie ie ie ie innnnnfffff luelueluelueluennnnnccccce oe oe oe oe of thf thf thf thf theeeeeMurrMurrMurrMurrMurraaaaay My My My My MooooouthuthuthuthuthThe flows in and out of the Murray Mouthhave a significant role to play in transportingsediment through and across the Mouth.

The tidal flows alone do not result in a netflow in or out of the Mouth. Sand suspendedby wave action on the coast is transportedinto the Mouth by flood tides. Once inside theMouth, there is less energy available tomaintain the sediment in suspension as thewaves do not extend far into the Mouth.Without the water being stirred up by thewaves, the sand drops out of suspension andis deposited inside the Mouth.

Ebb tide flows alone are not sufficient to thentransport all of this sediment out of the Mouthand back into the littoral system, especiallywith the reduced tidal prism.

The deposits in the Mouth initially form a floodtide shoal, which can then build up into sandbars and islands. The restriction caused by theflood tide delta, sand bars and islands furtherreduces the tidal prism. The limited River flowsare not a sufficient addition to the tidal flowsto clear the accumulated sediment from thearea inside the Mouth.

Historically, the Mouth was mobile, andwandering along the coast depending on thewave, current and River flow climate (perscomm. EJ Barnett 2002, see also‘Introduction’). It is likely that sandaccumulated in the Mouth during periods oflow River flow, but that periodic floodingwould have ejected significant quantities ofsediment from the Mouth into the coastalzone. These flood events are restricted by thecontrol of the River flows. The peninsulasthemselves have not been breached by floodflows to create a new Mouth since the sealevel stabilised to its current level,approximately 6600 years ago (Barnett 1993).

The sand that is trapped within the Mouth isnot available down drift of the Mouth on theSir Richard Peninsula and beyond as a supplyof sediment for littoral processes. The erosionof the Sir Richard Peninsula, andcorresponding accretion of the YounghusbandPeninsula, is clearly evident as the Mouthprogresses north-west. The restriction andredirection of the flows in the Mouth becauseof the sand accumulation have furthercontributed to the erosion of the Sir RichardPeninsula in recent years.

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CCCCCooooonnnnnccccc lululululusssssioioioioionnnnnsssssThe Murray Mouth is currently significantlyrestricted and is acting as a sink for sandwhich enters the Mouth from the coastallittoral system. The sand entering the Mouthacts to further constrict the flow whichexacerbates the situation. The restriction in thesupply of sand to the downdrift side of theMouth, the Sir Richard Peninsula, is allowingthe Peninsula to erode and the Mouth to movesteadily north-west.

If the Mouth became blocked with sand andclosed, it would cease to absorb sand fromthe beach system and the littoral drift wouldcontinue along the beach uninterrupted. Thescour and erosion-induced movement of theSir Richard Peninsula would stop, althoughaeolian (wind-blown) movement of sandwould obviously continue, especially given thatthe erosion has exposed large areas ofunvegetated dune to the elements.

RRRRReeeeeferferferferfereeeeennnnncccccesesesesesBarnett EJ (1993) Recent sedimentary history

of Lake Alexandrina and the MurrayEstuary, PhD Thesis, School of EarthSciences, Flinders University of SouthAustralia.

Coastal Engineering Research Centre (1984)Shore Protection Manual, 4th Edition.

Reissen A and Chappell JF (1993) MurrayMouth littoral drift study, Proceedings ofthe 11th Australasian Conference ofCoastal and Ocean Engineering, Vol. 2,pp. 651-654, Townsville, Queensland.

Short AD (2000) Beaches of the SouthAustralian Coast and Kangaroo Island: Aguide to their nature, characteristics , surfand safety. ISBN 0-9586504-2-X

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The final solution, howeverThe final solution, howeverThe final solution, howeverThe final solution, howeverThe final solution, however, is likely to depend, is likely to depend, is likely to depend, is likely to depend, is likely to dependto a large extent on determining a viableto a large extent on determining a viableto a large extent on determining a viableto a large extent on determining a viableto a large extent on determining a viablepattern of releases from the Lower Lakespattern of releases from the Lower Lakespattern of releases from the Lower Lakespattern of releases from the Lower Lakespattern of releases from the Lower Lakestaking into account the health of the totaltaking into account the health of the totaltaking into account the health of the totaltaking into account the health of the totaltaking into account the health of the totalRiver system.River system.River system.River system.River system.

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WWWWWhhhhhaaaaat it it it it is poss poss poss poss possssssiiiiibbbbbllllleeeee:::::HydHydHydHydHydrrrrrooooololololologggggy & My & My & My & My & Mooooorrrrrphphphphphooooololololologggggyyyyy

DDDDDRRRRR D D D D DAVIDAVIDAVIDAVIDAVID W W W W WALKERALKERALKERALKERALKER Department of Civil and Environmental Engineering, University of Adelaide

IIIIInnnnntrtrtrtrtrodododododuuuuuccccctttttioioioioionnnnnFor much of 1999, the Mouth was observedto move steadily towards total closure as largequantities of sediment were deposited on theflood tidal delta, restricting flows, waterexchange and navigation. The situation at theMouth in early 2000 is shown in Figure 1. Thephotograph shows a severely restricted Mouthwith a series of well-defined channels crossingan extensive flood tidal delta.

Figure 1: River Murray Mouth, 29 February 2000Figure 1: River Murray Mouth, 29 February 2000Figure 1: River Murray Mouth, 29 February 2000Figure 1: River Murray Mouth, 29 February 2000Figure 1: River Murray Mouth, 29 February 2000

Current understanding of tidal inlets indicatesthat the state of tidal mouths depends on twofactors: river flows and the coastal climate.The tendency for inlets of this type to closeperiodically has been observed in manyseasonally open inlets both in Australia andaround the world (Australian ParliamentSenate Standing Committee 1981, Bally 1987,Ranasinghe and Pattiaratchi 1999). In thisrespect, the situation at the Murray Mouth isnot unexpected, although closure would be aradical departure from historical behaviour.

HHHHH iiiiissssstttttooooorrrrriiiiicccccal cal cal cal cal cooooonnnnnttttteeeeexxxxxtttttThe size of the Mouth has varied from beingseveral hundred metres wide during heavyflood flows to a situation where it closedcompletely at low tides in April 1981. TheMouth, at the time of the closure in 1981, isshown in Figure 2. It is evident that theblockage involved not just a plug of sand inthe Mouth, but an extensive flood tidal deltathat had built up over the preceeding monthsadjacent to Bird Island.

Recent concerns about the state of theRecent concerns about the state of theRecent concerns about the state of theRecent concerns about the state of theRecent concerns about the state of theRiver Murray Mouth have renewedRiver Murray Mouth have renewedRiver Murray Mouth have renewedRiver Murray Mouth have renewedRiver Murray Mouth have renewedinterest in its behaviourinterest in its behaviourinterest in its behaviourinterest in its behaviourinterest in its behaviour, and in, and in, and in, and in, and inparticular what measures might beparticular what measures might beparticular what measures might beparticular what measures might beparticular what measures might betaken to maintain an effectivetaken to maintain an effectivetaken to maintain an effectivetaken to maintain an effectivetaken to maintain an effectiveopening.opening.opening.opening.opening.

The following discussion outlines workThe following discussion outlines workThe following discussion outlines workThe following discussion outlines workThe following discussion outlines workundertaken to quantify the Mouthundertaken to quantify the Mouthundertaken to quantify the Mouthundertaken to quantify the Mouthundertaken to quantify the Mouth’s’s’s’s’sopening and to determine if it isopening and to determine if it isopening and to determine if it isopening and to determine if it isopening and to determine if it ispossible to manipulate flows so as topossible to manipulate flows so as topossible to manipulate flows so as topossible to manipulate flows so as topossible to manipulate flows so as tooptimise the Mouthoptimise the Mouthoptimise the Mouthoptimise the Mouthoptimise the Mouth’s opening’s opening’s opening’s opening’s opening

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Figure 2: River Murray Mouth in April 1981,Figure 2: River Murray Mouth in April 1981,Figure 2: River Murray Mouth in April 1981,Figure 2: River Murray Mouth in April 1981,Figure 2: River Murray Mouth in April 1981,

showing full blockage at the Mouth andshowing full blockage at the Mouth andshowing full blockage at the Mouth andshowing full blockage at the Mouth andshowing full blockage at the Mouth and

restriction of water exchange between therestriction of water exchange between therestriction of water exchange between therestriction of water exchange between therestriction of water exchange between the

Goolwa (left) and TGoolwa (left) and TGoolwa (left) and TGoolwa (left) and TGoolwa (left) and Tauwitchere (right) channels.auwitchere (right) channels.auwitchere (right) channels.auwitchere (right) channels.auwitchere (right) channels.

Low flows and their effects, however, are not arecent phenomenon. What has changed is thefrequency at which the low flow events occur.

According to Cullen (1999), over 80% of themedian flow at the Mouth of the Murray isnow removed for irrigation and other uses,and drought conditions occur one year in tworather than one year in twenty under naturalconditions. Thomson (1994) found that at theMouth low flows (less than 5000GL/year)occurred 7% of the time under naturalconditions but 66% of the time underregulated conditions. Also at the Mouth, highflows (greater than 25 000GL/year) occurred5% of the time under natural conditions and2% of the time under regulated conditions.Thomson also points out that it is not just theflow that has been removed but the fact thatthe annual spring high-flow events are eithermuch lower or fail to occur at all.

Following closure in 1981, the Mouth wasopened artificially and then kept open bywinter and spring River flows. Based onobservations at the time, it was suggested that

flows of 25 000ML/day to 30 000ML/daywere required to expand and maintain theartificial opening. Currently, much effort isgoing into attempting to determine how to

use River flows most efficiently to maintainan opening.

To illustrate the change in flows, Figure 3shows the predicted flows at the MurrayMouth under natural and regulatedconditions for a 10-year period. The flowpredictions, supplied by the Murray-Darling Basin Commission, were basedon a computer simulation that usesknown River flows at an upstream lockand takes account of known waterextractions, predicted losses due toseepage and evaporation, and the effectsof barrage operation and Lower Lakelevels. The predictions are necessary

because the actual flow over the barrages isnot measured. In Figure 3, the generalreduction in flow is evident, as is the reductionin the peaks that would normally haveoccurred on an annual basis.

The change in the annual cycle of flows is bestillustrated in Figure 4, re-drawn fromThomson (1994), which shows the medianflow at the Murray Mouth under natural andregulated conditions. The spring peak in flowsis seen to occur earlier with a significantlyreduced flow rate.

EEEEEssssstttttimaimaimaimaimatttttiiiiinnnnngggggMMMMMooooouth Outh Outh Outh Outh OpppppeeeeennnnniiiiinnnnngggggThe River Murray Mouth, its position and size,has been the subject of investigation andstudy since the days of European colonisationin the 1830s. However, proper study of its sizehas been hampered by a lack of quantitativedata. While there have been a number ofsurveys of the Mouth region, the area doesnot lend itself to easy measurement althoughmodern methods are making the task easier.

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Figure 3: Predicted monthly flows at the Murray Mouth for 1990 to 2000Figure 3: Predicted monthly flows at the Murray Mouth for 1990 to 2000Figure 3: Predicted monthly flows at the Murray Mouth for 1990 to 2000Figure 3: Predicted monthly flows at the Murray Mouth for 1990 to 2000Figure 3: Predicted monthly flows at the Murray Mouth for 1990 to 2000

River Murray Flow at Mouth

Tides at Victor Harbor and Goolwa Jan 1982

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(Note: The tidal signals have been displaced toassist in viewing the data.)

Figure 5: Tides recorded at Victor Harbour and Goolwa barrage during January 1982Figure 5: Tides recorded at Victor Harbour and Goolwa barrage during January 1982Figure 5: Tides recorded at Victor Harbour and Goolwa barrage during January 1982Figure 5: Tides recorded at Victor Harbour and Goolwa barrage during January 1982Figure 5: Tides recorded at Victor Harbour and Goolwa barrage during January 1982

Figure 4: River Murray median monthly natural and current flowsFigure 4: River Murray median monthly natural and current flowsFigure 4: River Murray median monthly natural and current flowsFigure 4: River Murray median monthly natural and current flowsFigure 4: River Murray median monthly natural and current flows

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Figure 6: Tides recorded at Victor Harbour and Goolwa barrage during January 1981Figure 6: Tides recorded at Victor Harbour and Goolwa barrage during January 1981Figure 6: Tides recorded at Victor Harbour and Goolwa barrage during January 1981Figure 6: Tides recorded at Victor Harbour and Goolwa barrage during January 1981Figure 6: Tides recorded at Victor Harbour and Goolwa barrage during January 1981

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FFFFFigure 8: Tidal energy at Tigure 8: Tidal energy at Tigure 8: Tidal energy at Tigure 8: Tidal energy at Tigure 8: Tidal energy at Tauwitchere Barrage compared to the tidal energy at Victor Harbourauwitchere Barrage compared to the tidal energy at Victor Harbourauwitchere Barrage compared to the tidal energy at Victor Harbourauwitchere Barrage compared to the tidal energy at Victor Harbourauwitchere Barrage compared to the tidal energy at Victor Harbour

Figure 7: Tidal energy at Goolwa Barrage compared to the tidal energy at Victor HarbourFigure 7: Tidal energy at Goolwa Barrage compared to the tidal energy at Victor HarbourFigure 7: Tidal energy at Goolwa Barrage compared to the tidal energy at Victor HarbourFigure 7: Tidal energy at Goolwa Barrage compared to the tidal energy at Victor HarbourFigure 7: Tidal energy at Goolwa Barrage compared to the tidal energy at Victor Harbour

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To overcome this lack of detail, Walker andJessup (1992) used the tide data collectedfrom Victor Harbour (outside the Mouth) andthe Goolwa Barrage (inside the Mouth) todetermine a measure of Mouth opening. Thereasoning behind the method was thatsediment building up in the Mouth would actto restrict the free flow of tidal waters from theocean into the channels leading to thebarrages. Any restriction would reduce tidaltransmission and be reflected in reduced tidalamplitude at the barrages.An example of an open Mouth, with goodtidal transmission is shown in Figure 5. At thistime in 1982 the Mouth had been cleared byhigh River flows and the tidal signal at GoolwaBarrage was almost identical to that at VictorHarbour.

An example of a restricted Mouth is shown inFigure 6 taken in 1981, just prior to closure.In this Figure the signal at Goolwa shows littleresemblance to that at Victor Harbourindicating that the Mouth has effectivelyblocked tidal transmission.

The relative tidal energy (R) was defined:

R =R =R =R =R = EEEEE i n s i d ei n s i d ei n s i d ei n s i d ei n s i d e

EEEEE o u t s i d eo u t s i d eo u t s i d eo u t s i d eo u t s i d e

where E = tidal energy in 12 hourcomponents at locations inside and outsidethe Mouth. Based on this, R should varybetween 0 (complete closure leading to notides inside Mouth) to 1 (complete openingleading to full transmission of tides tobarrages). Data from the tide gauges on theGoolwa and Tauwitchere barrages are shownin figures 7 and 8.

From these figures a number of features canbe highlighted. In Figure 7 the variation inMouth restriction is shown to have some long-term patterns and the closure of 1981 andnear closure in 1983 are clearly visible. Recentrestrictions in 1998, 1999 and 2000 are alsoevident although missing data leave someuncertainty in the fine detail.

In Figure 8 the size of the tide at TauwitchereBarrage is much less than that at Goolwa.This can be explained by the long and narrowchannel that leads to the Coorong andrestricts the free flow of the tide. The tidaltransmission at Tauwitchere shows someperiodicity but, significantly, also appears tobe reducing in the long-term.

MMMMModododododeeeee lllll lililililinnnnngggggMMMMMooooouth Outh Outh Outh Outh OpppppeeeeennnnniiiiinnnnngggggUsing a technique known as ‘Time seriesanalysis’, Walker and Jessup (1992) were ableto describe mathematically the variation inrelative Mouth restriction at Goolwa Barragein terms of River flow. The expression hasrecently been updated taking into accountextra data and can be written:

RRRRRt t t t t = 0.8 R= 0.8 R= 0.8 R= 0.8 R= 0.8 Rt-1 t-1 t-1 t-1 t-1 + 0.0002 F+ 0.0002 F+ 0.0002 F+ 0.0002 F+ 0.0002 Ft-2t-2t-2t-2t-2

where Rt is the relative tidal energy in month t,and Ft is the estimated flow over the barrages(GL/month) in month t. (Ft-2 is therefore theestimated flow two months previously).The relationship indicates that at anyparticular time the relative Mouth openingdepends on the opening in the previousmonth and the flow two months previously.Under zero flow conditions, the openingwould reduce to 80% of the previous month’sopening. If zero flows continued, the Mouthwould continue to close to 64%, 51%, 41%and so on. The model predictions are shownin Figure 9.

Although the agreement between predictedand measured relative Mouth openings is notperfect, the model is shown to be able toreproduce, reasonably well, the variousfluctuations that have occurred over the last30 years. It should be noted that the onlyinput data used to produce the predictionsplotted in Figure 9 are the estimated Riverflows at the Mouth. The predicted flow overthe barrages for the same period is shown inFigure 10.

(Note: the tidal signals have been displaced to assist inviewing the data.)

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WWWWWhhhhhaaaaat it it it it is poss poss poss poss possssssiiiiibbbbbllllleeeee

0

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Figure 9: Predicting Mouth closure using ‘Times series analysis’ model, 1972 - 2002Figure 9: Predicting Mouth closure using ‘Times series analysis’ model, 1972 - 2002Figure 9: Predicting Mouth closure using ‘Times series analysis’ model, 1972 - 2002Figure 9: Predicting Mouth closure using ‘Times series analysis’ model, 1972 - 2002Figure 9: Predicting Mouth closure using ‘Times series analysis’ model, 1972 - 2002

Figure 11: Predicted effect of additional flows either as an annual flush (Strategy option 1) or a monthlyFigure 11: Predicted effect of additional flows either as an annual flush (Strategy option 1) or a monthlyFigure 11: Predicted effect of additional flows either as an annual flush (Strategy option 1) or a monthlyFigure 11: Predicted effect of additional flows either as an annual flush (Strategy option 1) or a monthlyFigure 11: Predicted effect of additional flows either as an annual flush (Strategy option 1) or a monthly

supplement (Strategy option 2).supplement (Strategy option 2).supplement (Strategy option 2).supplement (Strategy option 2).supplement (Strategy option 2).

Figure 10: Predicted flow over the barrages, 1972 – 2002Figure 10: Predicted flow over the barrages, 1972 – 2002Figure 10: Predicted flow over the barrages, 1972 – 2002Figure 10: Predicted flow over the barrages, 1972 – 2002Figure 10: Predicted flow over the barrages, 1972 – 2002

Predicted Flow Over Barrages

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The model also predicts the periods when theMouth became severely restricted. Although,since it ignores the coastal processes, it isunlikely to be able to predict total closuresaccurately.

In addition to low flows, Culver (quoted inAustralian Parliament Senate StandingCommittee 1981) has observed that calmseas and reduced tides appear necessary fora complete closure. Work in Western Australiaby Ranasinghe and Pattiaratchi (1999) hasalso highlighted the importance of coastalprocesses on the final closure of a restrictedinlet.

OOOOOppppptttttimimimimimiiiiisssssiiiiinnnnngggggBBBBBaaaaarrrrrrrrrraaaaaggggge Re Re Re Re Reeeee llllleaeaeaeaeasessessessessesThe next phase in the study of the MurrayMouth is to determine if it is possible tomanipulate the release of flows from theLower Lakes over the barrages to optimise theMouth opening.Two basic strategies are being evaluated:1. an annual concentrated discharge

designed to flush out excess material thathas built up on the flood tidal delta overthe previous 12 months, and

2. additional flows to lift the month by monthreleases in an attempt to prevent the influxof sediment through the Mouth.

Early results indicate that both strategiesshould be effective, although an option thatattempts to maintain some outflowthroughout the whole year appears moreeffective based on the model developed todescribe Mouth opening.

The options are compared in Figure 11 wherea range of additional flows are assumed to beavailable to supplement what had beenavailable historically over the last 35 years.It is evident from the Figure that attempting tomaintain even a low flow each month over thebarrages and out the Mouth appears to

provide a better result in terms of Mouthopening. This may be due to the fact that anyflow from the River would tip the balance inthe Mouth to a net outward flow that wouldassist in preventing sediment entering the inletduring a rising tide and assist in flushingduring the ebb flows.

CCCCCooooonnnnnccccc lululululusssssioioioioionnnnnIn conclusion, it can be seen that options existfor the maintenance of flows over thebarrages to prevent Mouth closure.

The final solution, however, is likely to dependto a large extent on determining a viablepattern of releases from the Lower Lakestaking into account the health of the totalRiver system.

G

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G

RRRRReeeeeferferferferfereeeeennnnncccccesesesesesAustralian Parliament Senate Standing

Committee (1981) Progress Report on theContinuing Scrutiny of Pollution - TheRiver Murray. Implications of Low Flowand the Mouth Closure. AustralianGovernment Publishing Service,Canberra.

Bally R (1987) Conservation Problems andManagement Options in Estuaries: TheBot River Estuary, South Africa, as a Case-History for Management of ClosedEstuaries. Environmental Conservation14: 45-51.

Barnett E (1995) Distinguishing Natural andAnthropogenic Influences: A Case Studyof Lake Alexandrina. South AustralianGeographical Journal 94: 36-49.

Bourman RP and Barnett EJ (1995) Impacts ofRiver Regulation on the Terminal Lakesand Mouth of the River Murray, SouthAustralia. Australian GeographicalStudies 33: 101-115.

Bourman B, and Harvey N, (1983) The MurrayMouth Flood Tidal Delta. AustralianGeographer 15: 403-406.

Cullen P (1999) Water and the EmergingPolitical Imperatives. Water ResearchFoundation of Australia, Research Report.

Department of Environment, Heritage andAboriginal Affairs (1999) South Australia.In A Century of Water ResourcesDevelopment in Australia (ed. W.Boughton), pp 110-141. Institution ofEngineers Australia.

Harvey N (1988) Coastal Management Issuesfor the Mouth of the River Murray, SouthAustralia. Coastal Management 16: 139-149.

Harvey N (1996) The Significance of CoastalProcesses for Management of the RiverMurray Estuary. Australian GeographicalStudies 34: 45-57.

Murray Mouth Advisory Committee (1983)Investigations into the Behaviour of theMouth of the River Murray. ProgressReport No. 1, Government of SouthAustralia.

Murray Mouth Advisory Committee (1987)Investigations into the Behaviour of theMouth of the River Murray. ProgressReport No. 2, Government of SouthAustralia.

Ranasinghe R and Pattiaratchi C (1999) TheSeasonal Closure of Tidal Inlets: WilsonInlet – A Case Study. Coastal Engineering37: 37-56.

Thomson C (1994) The Impact of RiverRegulation on the Natural Flows of theMurray-Darling Basin. Murray-DarlingBasin Commission Technical Report 92/5.3.

Thomson RM (1975) The Geomorphology ofthe Murray Valley in South Australia.Thesis for M.A., University of Adelaide.

Walker DJ and Jessup A (1992) Analysis of theDynamic Aspects of the River MurrayMouth, South Australia. Journal ofCoastal Research 8: 71-76.

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aeolianaeolianaeolianaeolianaeolian erosion and deposition of sediments by wind-blown movement

akineteakineteakineteakineteakinete reproductive resting spores of plants

angiospermangiospermangiospermangiospermangiosperm a flowering plant

anoxiaanoxiaanoxiaanoxiaanoxia absence or deficiency of oxygen

benthic algaebenthic algaebenthic algaebenthic algaebenthic algae a collection of plant species that thrive at the bottom of a water body,such as a lake. Many algae are primitive unicellular organisms.

bioassaysbioassaysbioassaysbioassaysbioassays biological test

blackwaterblackwaterblackwaterblackwaterblackwater polluted water (sewage or grey water) from boats

catchmentcatchmentcatchmentcatchmentcatchment the area of land drained by a river and its tributaries

collodialcollodialcollodialcollodialcollodial particles suspended within a liquid - not dissolved

cyanobacteriacyanobacteriacyanobacteriacyanobacteriacyanobacteria aquatic bacteria that can photosynthesize

crustaceanscrustaceanscrustaceanscrustaceanscrustaceans belonging to the Crustacea, a phylum of (chiefly aquatic)arthropod animals, including the lobsters, prawns, crabs, barnacles,slaters, etc., commonly having the body covered with a hard exoskeletonor carapace.

density stratificationdensity stratificationdensity stratificationdensity stratificationdensity stratification formation of layers within water of different densities or weight.

destratifyingdestratifyingdestratifyingdestratifyingdestratifying a natural feature of water bodies characterised by a vertical gradient indensity caused by differential heating of the water surface and/ordifferences in salinity

dinoflagellatesdinoflagellatesdinoflagellatesdinoflagellatesdinoflagellates microscopic, (usually) unicellular, flagellated, often photosynthetic protists,commonly regarded as “algae”

ebb tideebb tideebb tideebb tideebb tide receding tide

entitlement flowentitlement flowentitlement flowentitlement flowentitlement flow 1850GL River flow per year guaranteed to South Australia each yearunder the Murray-Darling Agreement

epilimnionepilimnionepilimnionepilimnionepilimnion a layer of water on the surface of some lakes

euryhalineeuryhalineeuryhalineeuryhalineeuryhaline exhibiting or tolerating a wide range of salinity

eutrophiceutrophiceutrophiceutrophiceutrophic having water high in nutrients

flocculateflocculateflocculateflocculateflocculate collect into lumps or tufts

gigalitregigalitregigalitregigalitregigalitre one thousand million litres

hypereutrophichypereutrophichypereutrophichypereutrophichypereutrophic extremely high nutrients

GGGGGlosloslosloslossssssaaaaarrrrryyyyy

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hypermarinehypermarinehypermarinehypermarinehypermarine ocean water with very high salinity

hypersalinehypersalinehypersalinehypersalinehypersaline water with very high salinityhypolimnionhypolimnionhypolimnionhypolimnionhypolimnion the cold, lower layers of a body of water

ichthyofaunaichthyofaunaichthyofaunaichthyofaunaichthyofauna the indigenous fish of a region

invertebrateinvertebrateinvertebrateinvertebrateinvertebrate any organism that does not have a vertebral column and well developedbrain or an animal lacking a backbone and internal skeleton

littoral zonelittoral zonelittoral zonelittoral zonelittoral zone the area between the highest and lowest tide marks on the seashore

macroalgaemacroalgaemacroalgaemacroalgaemacroalgae seaweed

macroinvertebratemacroinvertebratemacroinvertebratemacroinvertebratemacroinvertebrate see ‘invertebrate’

macrophytesmacrophytesmacrophytesmacrophytesmacrophytes water plant that is not algae, and may be either floating or rooted

median flowmedian flowmedian flowmedian flowmedian flow the flow that occurs in the most number of years

megalitremegalitremegalitremegalitremegalitre one million litres

nutrientsnutrientsnutrientsnutrientsnutrients any substance which has nutritious qualities – that is, which nourishes orpromotes growth

pathogenpathogenpathogenpathogenpathogen disease producing organism

propagulespropagulespropagulespropagulespropagules any vegetative portions of a plant, such as a bud or other offshoot, thataid in dispersal of the species and from which a new individual maydevelop

saline intrusionsaline intrusionsaline intrusionsaline intrusionsaline intrusion often referred to as a ‘salt wedge’, it is the intrusion of dense saline waterfrom the sea below the fresher water in the river

shoalshoalshoalshoalshoal a sandy elevation on the bottom of a body of water, a sandbank orsandbar.

stratifyingstratifyingstratifyingstratifyingstratifying formation of layers

tidal prismtidal prismtidal prismtidal prismtidal prism the volume of water that passes in and out of an inlet during a tidal cycle.

total Kjeldahl Nitrogentotal Kjeldahl Nitrogentotal Kjeldahl Nitrogentotal Kjeldahl Nitrogentotal Kjeldahl Nitrogen inorganic nitrogen

total phosphoroustotal phosphoroustotal phosphoroustotal phosphoroustotal phosphorous inorganic and organic phosphorus

turbidityturbidityturbidityturbidityturbidity the murkiness of water caused by suspended sediment

turbulenceturbulenceturbulenceturbulenceturbulence haphazard motion within water due to eddies

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AAAAATSICTSICTSICTSICTSIC Aboriginal and Torres Strait Islander Commission

AWQCAWQCAWQCAWQCAWQC Australia Water Quality Centre

CAMBACAMBACAMBACAMBACAMBA China and Australia Migratory Bird Agreement

CERCCERCCERCCERCCERC Coastal Engineering Research Centre

cmcmcmcmcm centimetres

ECECECECEC electroconductivity

ggggg grams

GLGLGLGLGL gigalitres

IPCCIPCCIPCCIPCCIPCC Intergovernmental Panel on Climate Change

IUCNIUCNIUCNIUCNIUCN World Conservation Union

JAMBAJAMBAJAMBAJAMBAJAMBA Japan and Australia Migratory Bird Agreement

LLLLL litres

mmmmm metres

MDBCMDBCMDBCMDBCMDBC Murray-Darling Basin Commission

MLMLMLMLML megalitres

mLmLmLmLmL millilitre

NTUNTUNTUNTUNTU Nephelometric Turbidity Unit

ppmppmppmppmppm parts per million

sssss seconds

SARDISARDISARDISARDISARDI South Australian Research and Development Institute

SASASASASATTTTTCCCCC South Australian Tourism Commission

TKNTKNTKNTKNTKN Total Kjeldahl Nitrogen

TPTPTPTPTP Total Phosphorus

u Su Su Su Su S microsiemens

WHOWHOWHOWHOWHO World Health Organisation

AAAAAbbbbbbbbbbrrrrreeeeeviaviaviaviaviatttttioioioioionnnnnsssss

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