Salinity predictions for NSW rivers within the Murray-Darling Basin G.T.H. Beale R. Beecham K. Harris D. O'Neill H. Schroo N.K. Tuteja R.M. Williams Acknowledgements The following have contributed to this report, as authors and/or by providing analytical and mapping inputs: G. Beale, R. Beecham, S. Bish, J. Bradd, R. Cooke, R. Crawford, J. Dwyer, S. Grant, K. Harris, F. Harvey, S. Keane, D. O’Neill, S. Rish, E. Roberts, H. Schroo, G. Summerell, B. Turner, N. Tuteja, M. Williams and D. Woolley. Published by: Centre for Natural Resources NSW Department of Land and Water Conservation 10 Valentine Av, Parramatta NSW 2150 January 2000 © NSW Government ISBN 0 7347 51117 CNR99.048 ii TABLE OF CONTENTS Summary................................................................................................................................................. I 1 INTRODUCTION........................................................................................................................................1 1.1 BACKGROUND ............................................................................................................................................1 1.2 PROJECT OUTLINE ......................................................................................................................................3 2 DATA AVAILABILITY ..............................................................................................................................6 2.1 HYDROGEOLOGY DATA ..............................................................................................................................6 2.2 SURFACE HYDROLOGY DATA .....................................................................................................................7 2.3 GIS SPATIAL DATA.....................................................................................................................................8 3 METHODOLOGY.......................................................................................................................................9 3.1 GROUNDWATER DERIVED SALT BALANCE .................................................................................................9 3.1.1 Determination of groundwater level trends and salinity.................................................................10 3.1.2 Predicted areas with groundwater levels at less than 2 m..............................................................10 3.1.3 Calculation of the potential salt loads delivered from the groundwater system to the soil.............12 3.1.4 Summary of assumptions made in estimating the groundwater derived potential salt loads..........13 3.2 ESTIMATION OF ACTUAL DELIVERED IN-STREAM SALT LOADS FROM RUNOFF GENERATION AND SALT WASH OFF MECHANISMS ..........................................................................................................................13 3.2.1 Choice of scale for the ‘current’ salt balance analysis...................................................................14 3.2.2 Estimation of daily salt loads from third order catchments ............................................................14 3.3 ‘CURRENT’ IN-STREAM SALT BALANCES AT END OF SYSTEM FOR EACH SECOND ORDER CATCHMENT .............................................................................................................................................19 3.4 ESTIMATION OF SALT EXPORT FROM SECOND ORDER CATCHMENTS UNDER LIKELY FUTURE CONDITIONS..............................................................................................................................................20 4 POTENTIAL SALT LOADS DELIVERED FROM THE GROUNDWATER SYSTEM UNDER ‘CURRENT’ AND LIKELY FUTURE CONDITIONS AT 2020, 2050 AND 2100 ......................................25 4.1 GROUNDWATER SALINITIES AND GROUNDWATER LEVEL TRENDS ...........................................................27 4.2 POTENTIALLY SALINISED AREAS AS INDICATED BY WATERTABLE DEPTH LESS THAN 2 M.......................28 4.3 PREDICTED POTENTIAL SALT LOADS ........................................................................................................28 4.4 AREAS EXCLUDED FROM THE ANALYSIS ..................................................................................................35 5 IN-STREAM SALT BALANCES FOR SECOND ORDER CATCHMENTS UNDER ‘CURRENT’ CONDITIONS.....................................................................................................................................................37 5.1 SALT BALANCE FOR THE BORDER RIVERS ................................................................................................38 5.2 SALT BALANCE FOR GWYDIR....................................................................................................................50 5.3 SALT BALANCE FOR NAMOI......................................................................................................................59 5.4 SALT BALANCE FOR CASTLEREAGH ..........................................................................................................70 iii 5.5 SALT BALANCE FOR MACQUARIE–BOGAN................................................................................................70 5.6 SALT BALANCE FOR LACHLAN..................................................................................................................80 5.7 SALT BALANCE FOR MURRUMBIDGEE ......................................................................................................87 6 FUTURE PREDICTED IN-STREAM SALT LOADS EXPORTED FROM SECOND ORDER CATCHMENTS..................................................................................................................................................95 6.1 SCALING FACTORS....................................................................................................................................96 6.1.1 Determining factors for the Gwydir Catchment..............................................................................97 6.2 BORDER RIVERS (MACINTYRE RIVER)—FUTURE SALT EXPORTS ............................................................99 6.3 GWYDIR RIVERFUTURE SALT EXPORTS..............................................................................................102 6.4 NAMOI RIVERFUTURE SALT EXPORTS ................................................................................................105 6.5 CASTLEREAGH RIVERFUTURE SALT EXPORTS ....................................................................................108 6.6 MACQUARIE BASINFUTURE SALT EXPORTS........................................................................................110 6.6.1 Macquarie Riverfuture salt exports...........................................................................................111 6.6.2 Bogan Riverfuture salt exports..................................................................................................114 6.7 LACHLAN RIVERFUTURE SALT EXPORTS ............................................................................................116 6.8 MURRUMBIDGEE RIVERFUTURE SALT EXPORTS.................................................................................118 6.9 MURRAY RIVERFUTURE SALT EXPORTS.............................................................................................121 7 CATCHMENT SCALE SALT BALANCE STUDY (CATSALT).......................................................124 8 POTENTIAL ENVIRONMENTAL CONSEQUENCES OF INCREASING DRYLAND SALINITY IN STREAMS AND WETLANDS...................................................................................................................133 8.1 INTRODUCTION .......................................................................................................................................133 8.2 SENSITIVITY OF AQUATIC BIOTA.............................................................................................................135 8.2.1 Fish ...............................................................................................................................................135 8.2.2 Aquatic plants ...............................................................................................................................135 8.2.3 Riparian vegetation.......................................................................................................................136 8.2.4 Waterbirds.....................................................................................................................................136 8.2.5 Frogs.............................................................................................................................................137 8.2.6 Invertebrates .................................................................................................................................137 8.2.7 Other species.................................................................................................................................138 8.2.8 Implications...................................................................................................................................138 8.3 WATER QUALITY IMPLICATIONS.............................................................................................................138 8.4 IMPACTS ON END OF SYSTEM WETLANDS...............................................................................................139 8.4.1 Wetland impacts of increased salinity levels.................................................................................139