Climate Change Scenarios and Managing the Scarce Water Resources of the Macquarie River

Climate Change Scenarios and Managing the Scarce Water Resources of the Macquarie River FINAL REPORT Prepared for Environment Australia [Climate Change Impacts and Adaptation Grants Program] Prepared by HASSALL & ASSOCIATES PTY LTD and the NSW DEPARTMENT OF LAND AND WATER CONSERVATION, NSW NATIONAL PARKS AND WILDLIFE SERVICE, and CSIRO DIVISION OF ATMOSPHERIC RESEARCH c/- HASSALL & ASSOCIATES PTY LTD 9/60 Pitt Street, GPO Box 4625 SYDNEY NSW 2001 Telephone: (02) 9241.5655 Facsimile: (02) 9241.5684 Email: [email protected] MARCH 1998 AUS-671 Climate Change Scenarios & Managing the Scarce Water Resources - Macquarie River Environment Australia TABLE OF CONTENTS PROJECT SUMMARY: CLIMATE CHANGE SCENARIOS AND MANAGING THE SCARCE WATER RESOURCES OF THE MACQUARIE RIVER ..................................6 CONFERENCE OPENING .....................................................................................................9 1 INTRODUCTION................................................................................................................13 1.1 THE MACQUARIE VALLEY ...............................................................................................14 Figure 1.1 Macquarie River Valley Catchment ............................................................15 1.2 IRRIGATION DEVELOPMENT ..............................................................................................16 1.3 THE MACQUARIE MARSHES .............................................................................................16 1.4 REPLENISHMENT FLOWS AND UNREGULATED FLOW SHARING...........................................17 REFERENCES ..........................................................................................................................17 2. CLIMATE CHANGE METHODOLOGY AND RESULTS.........................................18 2.1 CLIMATE MODELLING......................................................................................................18 2.2 PREPARATION OF THE SCENARIOS.....................................................................................19 2.2.1 Regional climate model results ................................................................................19 2.2.2 Scaling the DARLAM results for 2030....................................................................19 2.3 THE SCENARIOS................................................................................................................20 2.4 WHAT OTHER SCENARIOS ARE POSSIBLE?.........................................................................21 2.5 WHERE TO FROM HERE? ..................................................................................................21 REFERENCES ..........................................................................................................................22 Figure 2.1: Global warming scenarios 1990-2100. ....................................................23 Figure 2.2: High and low scenarios for seasonal mean temperature change in 2030.24 Figure 2.3: As Figure 2.2, but for percent change in potential evaporation...............25 Figure 2.4: As Figure 2.2, but for percent change in precipitation.............................26 3. RIVER FLOW MODELLING ..........................................................................................27 3.1 INTRODUCTION.................................................................................................................27 3.2 METHODOLOGY FOR PREDICTING THE EFFECT OF CLIMATE CHANGE SCENARIOS...............27 3.2.1 Sacramento rainfall-runoff model ............................................................................27 Figure 3.1 Schematic Representation of Sacramento Model........................................28 3.2.2 Application of Sacramento model to the Macquarie Valley....................................29 3.2.3 IQQM river basin simulation model ........................................................................29 3.2.4 Application of IQQM to the Macquarie River Valley .............................................29 3.3 CLIMATE CHANGE SCENARIOS ..........................................................................................30 Figure 3.2 Grid Squares used for Climate Change Factors Macquarie River Valley Catchment .....................................................................................................................31 3.4 RESULTS FOR CHANGES IN RUNOFF (FROM SACRAMENTO MODEL) ...................................32 3.4.1 Burrendong Dam inflows.........................................................................................32 Figure 3.3 Daily Inflows into Burrendong Dam (Base vs Low Case) ..........................33 Figure 3.4 Daily Inflows into Burrendong Dam (Base vs High Case) ........................34 Figure 3.5 Annual Inflows into Burrendong Dam .......................................................35 Figure 3.6 Monthly Average Burrendong Inflows for 1890-1991 Period ...................36 3.5 RESULTS FOR CHANGES IN CROP DEMANDS (FROM MACQUARIE IQQM)..........................37 Hassall & Associates Pty Ltd Page : 2 Climate Change Scenarios & Managing the Scarce Water Resources - Macquarie River Environment Australia 3.5.1 Regulated Macquarie system allocation reliability ..................................................37 Figure 3.7 Allocation Reliability on 1st January..........................................................38 3.5.2 Irrigation plantings and river diversions ..................................................................39 Figure 3.8 Exceedance Curve for Annual Sustainable Areas.......................................40 3.6 RESULTS FOR CHANGES IN MACQUARIE MARSHES INFLOWS............................................41 Figure 3.9 Annual Inflows into Macquarie Marshes....................................................42 Figure 3.10 Monthly Average Macquarie Marshes Inflows for 1890-1991 Period .....43 3.7 WHERE TO FROM HERE? ...................................................................................................44 REFERENCES ..........................................................................................................................45 4. CONSEQUENCES FOR THE AGRICULTURAL ECONOMY ..................................46 4.1 BACKGROUND AND METHODOLOGY ................................................................................46 Figure 4.1 Contribution of Agriculture to the regional economy of the Macquarie Valley ............................................................................................................................47 4.2 ADJUSTMENT FOR THE BENEFICIAL EFFECTS OF ENHANCED CARBON DIOXIDE ON PLANT GROWTH.................................................................................................................................47 4.3 IMPACT ON LIVESTOCK INDUSTRIES .................................................................................48 Figure 4.2 Pasture Growth Indices for selected sites in the Macquarie Valley 2030 ..50 4.4 IMPACT ON DRYLAND CROPPING ....................................................................................52 4.5 IMPACT ON IRRIGATED CROPPING ....................................................................................54 4.6 AGGREGATE ANNUAL IMPACT .........................................................................................55 Figure 4.3 Aggregate annual impact of climate change on the Macquarie Valley Economy........................................................................................................................56 4.7 PRACTICAL IMPLICATIONS OF THIS RESEARCH..................................................................56 4.8 WHERE TO FROM HERE? ...................................................................................................57 REFERENCES ..........................................................................................................................57 APPENDIX I: STATISTICAL LOCAL AREAS INCLUDED IN THE STUDY AREA ..............................59 APPENDIX II: SIZE AND VALUE OF EACH ENTERPRISE IN THE STUDY AREA.............................60 5. CONSEQUENCES FOR THE MACQUARIE MARSHES ...........................................61 5.1 THE MACQUARIE MARSHES .............................................................................................61 5.2 CONSERVATION IMPORTANCE ..........................................................................................62 5.2.1 Vegetation ................................................................................................................62 5.2.2 Waterbirds................................................................................................................62 5.3 INDICATORS OF WETLAND HEALTH..................................................................................62 5.3.1 Vegetation ................................................................................................................62 5.3.2 Colonially Nesting Waterbirds.................................................................................63 5.4 EFFECT OF CLIMATE CHANGE SCENARIOS........................................................................63 5.4.1 Vegetation ................................................................................................................63 5.4.2 Breeding of Colonially Nesting Waterbirds.............................................................64 5.4.3 Other fauna...............................................................................................................65

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