Review of Environmental Impacts of Flow Regulation and Other Water Resource Developments in the River Murray and Lower Darling River System Includes Glossary of Terms Final Report to Murray-Darling Basin Commission by Fluvial Systems Pty Ltd July 2002 Review of Environmental Impacts of Flow Regulation and Other Water Resource Developments in the River Murray and Lower Darling River System Includes Glossary of Terms Final Report to Murray-Darling Basin Commission by Fluvial Systems Pty Ltd Fluvial Systems Pty ltd PO Box 4117 Melbourne University Retail Parkville Vic 3010 ABN 71 085 579 095 Ph 03 93447780 Ph 0411855573 Email: [email protected] Authors Christopher Gippel Dominic Blackham July 2002 This document should be referenced as follows: Gippel, C.J. and Blackham, D. 2002. Review of environmental impacts of flow regulation and other water resource developments in the River Murray and Lower Darling River system. Final Report by Fluvial Systems Pty Ltd, Stockton, to Murray-Darling Basin Commission, Canberra, ACT. Environmental Impacts of Flow Regulation on the River Murray Murray-Darling Basin Commission Contents EXECUTIVE SUMMARY.............................................................................................iv 1 INTRODUCTION ..................................................................................................1 1.1 ENVIRONMENTAL FLOWS AND WATER QUALITY OBJECTIVES FOR THE RIVER MURRAY PROJECT .........................................................................................................1 1.2 OBJECTIVES OF THIS REPORT ...........................................................................1 1.3 STUDY AREA....................................................................................................4 1.4 FLOW REGULATION AND ENVIRONMENTAL FLOWS ..........................................5 1.5 REPORT STRUCTURE ........................................................................................7 1.6 KEY REFERENCES ............................................................................................8 2 RIVER MURRAY FLOW REGULATION BACKGROUND.........................13 2.1 BRIEF HISTORY OF REGULATION ....................................................................13 2.2 HYDROLOGICAL IMPACTS ..............................................................................14 3 GENERAL ECOLOGICAL AND GEOMORPHIC RESPONSES TO FLOW REGULATION ..............................................................................................................19 4 DARTMOUTH DAM TO HUME DAM (MITTA MITTA RIVER)...............27 4.1 SUMMARY OF IMPACTS AND CAUSES .............................................................27 4.2 REGULATION INFLUENCES .............................................................................27 4.3 IDENTIFIED IMPACTS OF REGULATION ON ENVIRONMENTAL VALUES BETWEEN DARTMOUTH DAM AND HUME DAM............................................................................28 5 HUME DAM TO YARRAWONGA ...................................................................32 5.1 SUMMARY OF IMPACTS AND CAUSES .............................................................32 5.2 REGULATION INFLUENCES .............................................................................32 5.3 IDENTIFIED IMPACTS OF REGULATION ON ENVIRONMENTAL VALUES BETWEEN HUME DAM AND YARRAWONGA..................................................................................33 6 YARRAWONGA TO TORRUMBARRY WEIR (INCLUDES EDWARD- WAKOOL SYSTEM)....................................................................................................38 6.1 SUMMARY OF IMPACTS AND CAUSES .............................................................38 6.2 REGULATION INFLUENCES .............................................................................38 6.3 IDENTIFIED IMPACTS OF REGULATION ON ENVIRONMENTAL VALUES FROM YARRAWONGA TO TORRUMBARRY WEIR ....................................................................42 7 TORRUMBARRY WEIR TO LOCK 11 MILDURA.......................................47 7.1 SUMMARY OF IMPACTS AND CAUSES .............................................................47 7.2 REGULATION INFLUENCES .............................................................................47 7.3 IDENTIFIED IMPACTS OF REGULATION ON ENVIRONMENTAL VALUES FROM TORRUMBARRY WEIR TO LOCK 11 MILDURA..............................................................50 8 LOCK 11 MILDURA TO LOCK 3 ....................................................................53 8.1 SUMMARY OF IMPACTS AND CAUSES .............................................................53 8.2 REGULATION INFLUENCES .............................................................................54 8.3 IDENTIFIED IMPACTS OF REGULATION ON ENVIRONMENTAL VALUES FROM LOCK 11 MILDURA TO LOCK 3.....................................................................................56 9 LOCK 3 TO WELLINGTON .............................................................................61 9.1 SUMMARY OF IMPACTS AND CAUSES .............................................................61 9.2 REGULATION INFLUENCES .............................................................................61 9.3 IDENTIFIED IMPACTS OF REGULATION ON ENVIRONMENTAL VALUES FROM LOCK 3 TO WELLINGTON .............................................................................................61 10 WELLINGTON TO THE MOUTH ...................................................................63 10.1 SUMMARY OF IMPACTS AND CAUSES .............................................................63 Fluvial Systems Pty Ltd ii Environmental Impacts of Flow Regulation on the River Murray Murray-Darling Basin Commission 10.2 REGULATION INFLUENCES .............................................................................63 10.3 IDENTIFIED IMPACTS OF REGULATION ON ENVIRONMENTAL VALUES DOWNSTREAM OF WELLINGTON ..................................................................................64 11 LOWER DARLING RIVER AND GREAT ANABRANCH............................68 11.1 SUMMARY OF IMPACTS AND CAUSES .............................................................68 11.2 REGULATION INFLUENCES .............................................................................69 11.3 IDENTIFIED IMPACTS OF REGULATION ON ENVIRONMENTAL VALUES IN THE LOWER DARLING RIVER AND GREAT ANABRANCH .....................................................71 12 SUMMARY OF ENVIRONMENTAL IMPACTS DUE TO REGULATION73 12.1 HYDROLOGY..................................................................................................73 12.2 GEOMORPHOLOGY AND WATER QUALITY ......................................................73 12.3 ECOLOGY.......................................................................................................75 13 IMPLICATIONS FOR ENVIRONMENTAL FLOW OPTIONS ...................76 13.1 PROCESS FOR DEVELOPMENT OF ENVIRONMENTAL FLOW OPTIONS................76 13.2 RELEVANCE OF THIS REPORT TO DEVELOPMENT OF FLOW OPTIONS...............76 14 REFERENCES .....................................................................................................78 APENDIX. GLOSSARY OF TERMS USED IN THE ENVIRONMENTAL FLOWS FIELD..............................................................................................................85 Fluvial Systems Pty Ltd iii Environmental Impacts of Flow Regulation on the River Murray Murray-Darling Basin Commission Executive Summary Introduction Over the past decade, there have been numerous discussions, investigations and decisions made regarding aspects of managing flows in the River Murray to provide environmental benefits. The Murray-Darling Basin Commission (The Commission) has implemented a number of initiatives addressing environmental flow needs of the River. In March 1999 the Environmental Flows and Water Quality Objectives for the River Murray Project (the Project) was established. An important first step in developing environmental flow options for the River Murray is to clearly establish the nature of the flow-related problems. A credible account of the scope and scale of the flow-related environmental problems provides the governments, communities and various interest groups with the basis for developing a common understanding of the issues. If solutions to environmental problems are to be sought through new ways of managing river flows, then the links between environmental condition and river flow should be known with a reasonable level of confidence. The Commission contracted Fluvial Systems Pty Ltd to conduct a review of the environmental impacts of flow regulation and other forms of water resource development along the main stem of the River Murray system. The objective of the review is to collate the key references that document the decline, or otherwise, of the in-channel, riparian and floodplain environments of the River Murray. One major problem faced by researchers of this topic has been the difficulty in isolating changes in the aquatic environment that are due to flow regulation from those that are due to changes in other factors such as catchment land use, fishing pressure, introduced species, riparian vegetation cover, large woody debris distribution, and natural variations in flow regime. Another major problem in determining the environmental impacts of regulation is that regulation of the River Murray occurred progressively over a long period of time, as water resources were developed to meet demands. While availability of data allows the hydrology of the