MDBC barrages flowcover 27/8/01 2:40 PM Page 2 River Murray Barrages Environmental Flows An evaluation of environmental flow needs in the Lower Lakes and Coorong A report for the Murray – Darling Basin Commission — June 2000 Edited by Anne Jensen, Michael Good, Prudence Tucker and Martine Long Murray Barrages flow edit 28/8/01 11:14 AM Page i RIVER MURRAY BARRAGES ENVIRONMENTAL FLOWS An evaluation of environmental flow needs in the Lower Lakes and Coorong A report for the Murray–Darling Basin Commission June 2000 Edited by Anne Jensen, Michael Good, Paul Harvey, Prudence Tucker and Martine Long Project funded by the Murray–Darling Basin Commission Wetlands Management Program Department for Water Resources GPO Box 1047 Adelaide South Australia 5001 River Murray Barrages Environmental Flows i Murray Barrages flow edit 28/8/01 11:14 AM Page ii ACKNOWLEDGEMENTS Scott Nichols for initial coordination of scientific panel Murray-Darling Basin Commision workshops and field trips. 15 Moore Street Canberra City, Daphne Matthews for organisational assistance in Australian Capital Territory arrangements for workshops and field trips. Postal address: GPO Box 409; Gary Tong for providing a presentation on his work on modelling of the Coorong estuary. Canberra ACT 2601 Jane Doolan of DNRE in Victoria for attending the first Telephone: (02) 6279 0100; workshop to provide links with the upstream scientific international 612 6279 0100 panel. Facsimile: (02) 6248 8053; Andy Close of MDBC Canberra for attending two international 612 6248 8053 workshops to provide system hydrology information and links with the upstream scientific panel approach. Website: http://www.mdbc.gov.au River Murray Environmental Flows Scientific Panel for access to their draft report to ensure consistent linkages. This work is copyright. Except for the MDBC logo, Jim Marsh for giving time to meet the scientific panel in the field and share knowledge on operation of the graphical and textual information in this publication barrages. may be reproduced in whole or in part provided that it is not sold or put to commercial use and its source John Eckert for giving time to meet the scientific panel in the field and share knowledge on managing saltmarsh (“River Murray Barrages Environmental Flows”) is habitat for waders at Tolderol. acknowledged. Such reproduction includes fair dealing for the purpose of private study, research criticism or Gary Hera Singh for giving time to meet the scientific panel in the field and share knowledge on issues for review as permitted under the Copyright Act 1968. professional fishers. Reproduction for other purposes is prohibited without Graham Camac for giving time to meet the scientific the written permission of the Murray-Darling Basin panel in the field and share knowledge on the problem of Commission. lake shore erosion. John Gilliland for giving time to meet the scientific panel in the field and share knowledge on issues raised in the The contents of this publication do not purport to community in relation to wise use of the Ramsar wetland. represent the position of the Murray-Darling Basin. They are presented solely to stimulate discussion for Editing, layout and production: Lynne Griffiths Cover design: Phoenix Design improved management of the Basin’s natural resources. Wetlands Management Program Department for Water Resources ISBN 0 7308 5831 6 GPO Box 1047 Adelaide South Australia 5001 © Copyright Murray-Darling Basin Commission 2000 ii River Murray Barrages Environmental Flows Murray Barrages flow edit 28/8/01 11:14 AM Page iii CONTENTS ACKNOWLEDGEMENTS ii EXECUTIVE SUMMARY viii PART 1: Introduction and Methodology 1 INTRODUCTION 2 Project brief 2 Membership of the panel and steering committee 2 METHODOLOGY 5 Definition of study area 5 Process of evaluation 5 Background and current status of Lower Lakes and Coorong 8 Context of management issues and constraints 10 Summary of upstream panel findings and recommendations 11 Management framework for future operation of barrages 11 PART 2: CURRENT STATUS, KEY ISSUES AND ECOLOGICAL NEEDS 13 HYDROLOGY OF THE LOWER LAKES AND COORONG 14 R Newman, Water Resource Manager Murray SA, DENR, Murraylands Region Current status 14 Hydrology of the Murray–Darling Basin 14 Construction of the barrages 14 Lower Lakes and Coorong 15 River regulation and development 1900 to 1980 18 Key issues 19 Controlling diversions from the Murray–Darling system 19 Major changes in flow regimes 19 Estuary–Murray Mouth zone 19 The Lower Lakes 20 The Coorong 20 Opportunities for improved barrage operation 20 The challenge 21 GEOMORPHOLOGY OF THE LOWER MURRAY LAKES AND COORONG 23 R P Bourman, Faculty of Engineering and the Environment, University of South Australia Background and current status 23 Key issues 24 Natural changes 24 Geomorphic impacts of river and lake regulation 25 Reduction of River Murray estuary 27 Ecological needs 28 Opportunities for improvement 28 AQUATIC AND RIPARIAN VEGETATION 30 G G Ganf, Botany Department, University of Adelaide Background and current status 30 Key issues 31 Salinity 31 River Murray Barrages Environmental Flows iii Murray Barrages flow edit 28/8/01 11:14 AM Page iv Turbidity 31 Water regime 32 Wave action and wind 32 Supplementary issues 32 ECOLOGICAL NEEDS 33 Opportunities for improved environmental conditions 33 BIRD ECOLOGY IN THE COORONG AND LAKES REGION 35 D C Paton, Department of Zoology, University of Adelaide BACKGROUND AND CURRENT STATUS 35 KEY ISSUES 37 Lakeshore erosion 37 Turbidity 39 Increasing sedimentation 39 European carp 39 Rapid changes in water level 39 Impacts of human activity 40 ECOLOGICAL NEEDS 40 OPPORTUNITIES FOR IMPROVEMENT 40 FISH AND INVERTEBRATES 43 M Geddes, Zoology Department, University of Adelaide BACKGROUND AND CURRENT STATUS 43 KEY ISSUES 45 Reduced estuarine area 46 Changed water regime 47 ECOLOGICAL NEEDS 47 OPPORTUNITIES FOR IMPROVED ENVIRONMENTAL CONDITIONS 49 PHYTOPLANKTON IN THE LOWER LAKES OF THE RIVER MURRAY 51 P Baker, Australian Water Quality Centre, Salisbury SA BACKGROUND AND CURRENT STATUS 51 KEY ISSUES 54 ECOLOGICAL NEEDS 54 OPPORTUNITIES FOR IMPROVED ENVIRONMENTAL CONDITIONS 55 PART 3: OPPORTUNITIES FOR IMPROVED ENVIRONMENTAL CONDITIONS 57 ECOLOGICAL NEEDS AND OPPORTUNITIES FOR IMPROVED HYDROLOGICAL MANAGEMENT 58 Universal outcomes 58 Short-term opportunities 58 Medium-term opportunities 67 Long-term opportunities 71 Effectiveness of management options 74 Complementary management opportunities 74 iv River Murray Barrages Environmental Flows Murray Barrages flow edit 28/8/01 11:14 AM Page v Shoreline erosion 76 Riparian buffer zones 76 Carp 76 Dryland salinity 76 CONCLUSIONS 77 KEY ISSUES 77 Reduced estuarine area 77 Changed water regimes of the lakes and river 78 Freshening of brackish and saline habitats 78 Reduced habitat for aquatic plants 78 Increased algal blooms 78 Dryland salinity 78 CURRENT STATUS AND FUTURE PROGNOSIS FOR THE LOWER LAKES AND COORONG 79 RECOMMENDATIONS OF THE SCIENTIFIC PANEL 79 Short-term 79 Medium-term 79 Long-term 80 General recommendations 80 IMPLEMENTATION 80 GUIDELINES 80 Barrage operation 80 Coorong water levels 80 Flushing of lakes 81 Enlarge estuary 81 Fish passage 81 Lake levels 81 Vegetation 81 Sedimentation 81 Erosion control 81 OPERATING CRITERIA 82 FURTHER INVESTIGATIONS 83 Sedimentation 83 Bird ecology 83 Fish and invertebrates 83 Hydrological management 83 Phytoplankton 83 SALINITY 84 LINKS TO OTHER ACTIVITIES 84 IMPLICATIONS FOR MANAGEMENT AGENCIES 84 IMPLICATIONS FOR UPSTREAM WATER MANAGEMENT 84 CONSULTATION 85 REFERENCES 86 APPENDICES 91 River Murray Barrages Environmental Flows v Murray Barrages flow edit 28/8/01 11:14 AM Page vi I Process for Evaluating Environmental Flow Requirements for the River Murray Barrages 92 II Assessment Process for Environmental Flow Requirements for River Murray and Lower Darling 103 III Issues Raised in Ramsar Planning Process for the Lower Lakes and Coorong 105 IV Constraints and Current Operation Strategies for the Barrages and Lower Lakes 106 V Constraints and Operating Strategies for the River Murray System 110 VI Impacts of the Barrages on Sedimentation Interactions Between the Lower Lakes and the Coorong 111 VII Issues in Fish Management and Proposals for Changed Management of the Barrages 115 VIII Interactions with Coorong Reserve Management Issues 117 IX On Site Talk to Expert Panel 118 ILLUSTRATIONS PLATES 1 River Murray Barrages Environmental Flows Scientific Panel on Tauwitchere Barrage 1 2 Murray Mouth – aerial view 8 3 Goolwa Barrage 13 4 Pelicans, Ewe Island 37 5 Expert panel at Lake Albert 57 FIGURES 1.1 Lower Murray and lakes study area 4 1.2 Methodology flow chart for the River Murray Barrages Environmental Flows Scientific Panel 5 1.3 Five ecological areas: eroding lakeshores, prograding lakeshores, Coorong Northern Lagoon (from Pelican Point to Hells Gate), Coorong Southern Lagoon and estuary 7 1.4 The locality of the five barrages inside the Murray Mouth 9 2.1 Annual flow patterns at the barrages 15 2.2 Operational history of barrage openings at Goolwa, 1982–96 16 2.3 Growth of diversions in the Murray–Darling Basin 17 2.4 SA diversions as a proportion of ‘entitlement flow’ 18 2.5 Pelican Point salinity – boundary conditions for long-term model 22 2.6 Development of the Murray Mouth flood tidal delta 23 2.7 Coorong and Lower Lakes Ramsar Wetland area – key to critical bird habitats 38 2.8 Longitudinal and vertical salinity patterns in the Coorong at irregular intervals between 1975 and 1985 43 2.9 Total commercial catches of mulloway