Climatic Influence on Shallow Fractured Rock Groundwater Systems in the Murray-Darling Basin
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Climatic influence on shallow fractured-rock groundwater systems in the Murray–Darling Basin, NSW Acknowledgments The Murray–Darling Basin Salinity Audit project acknowledges the assistance of the Wagga Wagga Resource Centre staff, past and present (Peter Barker, Sandy Grant, Frank Harvey, Darryl Lindner, Sarah McGeoch, Michelle Miller, Lisa Pike and Gregory Summerell); other former DNR employees (Dugald Black, Andrew Davidson, Tahir Hameed, Stuart Lucas, Callan Pearson, Darice Pepper, John Scown, Haridharan Seevaratnaram, Marina Sivkova, Michael Williams) and scientists (John Cooper, David Read, Wasyl Drosdowsky, Roger Jones, Rex Wagner and Kathryn Wells). Prepared by: Aleksandra Rančić 1,2, Gabriel Salas 3, Amrit Kathuria 4, Ian Acworth 2, William Johnston 3, Ann Smithson 3 and Geoffrey Beale 3 1 Department of Environment and Climate Change NSW (DECC) 2 School of Civil and Environmental Engineering, University of New South Wales 3 Former Department of Infrastructure Planning and Natural Resources (DIPNR) and Department of Natural Resources (DNR) 4 NSW Department of Primary Industries Published by: Department of Environment and Climate Change NSW 59–61 Goulburn Street PO Box A290 Sydney South 1232 Phone: (02) 9995 5000 (switchboard) Phone: 131 555 (environment information and publications requests) Phone: 1300 361 967 (national parks information and publications requests) Fax: (02) 9995 5999 TTY: (02) 9211 4723 Email: [email protected] Website: www.environment.nsw.gov.au In April 2007 the Department of Natural Resources NSW became part of the Department of Environment and Climate Change NSW. This material may be reproduced in whole or in part, provided the meaning is unchanged and the source is acknowledged. ISBN 978 1 74122 871 7 DECC 2009/108 February 2009 While every reasonable effort has been made to ensure that this document is correct at the time of printing, the State of New South Wales, its agents and employees disclaim any and all liability to any person in respect of anything or the consequences of anything done or omitted to be done in reliance upon the whole or any part of this document. ii Contents Abstract ...................................................................................................................................vii 1 Introduction ...................................................................................................................1 1.1 Background........................................................................................................1 1.2 Groundwater monitoring and analysis of groundwater trends in NSW ..............2 2 Study area.....................................................................................................................5 2.1 Topography........................................................................................................6 2.2 Climate...............................................................................................................7 2.3 Surface water resources ..................................................................................11 2.4 Geology............................................................................................................12 2.5 Hydrogeology...................................................................................................14 2.6 Clearing and land use within the study area ....................................................15 3 Methods ......................................................................................................................18 3.1 Rainfall data .....................................................................................................18 3.2 Bore data..........................................................................................................19 3.3 Data analysis....................................................................................................23 4 Results ........................................................................................................................34 4.1 Rainfall .............................................................................................................34 4.2 Bore data..........................................................................................................40 4.3 Relationships between rainfall and standing water level..................................42 5 Discussion...................................................................................................................50 5.1 Rainfall analysis ...............................................................................................51 5.2 Standing water level analysis and the relationship with rainfall .......................52 5.3 Interpretation of the observed lags...................................................................57 5.4 Implications for dryland salinity ........................................................................59 5.5 Conclusions......................................................................................................60 5.6 Recommendations ...........................................................................................63 6 References..................................................................................................................67 7 Glossary ......................................................................................................................73 Appendix ................................................................................................................................75 iii Figures Figure 1: Residual mass curve of SWL and rainfall presented by Salas and Smithson (2002) ....................................................................................................................3 Figure 2: Study area .............................................................................................................5 Figure 3: Topography............................................................................................................6 Figure 4: Average annual rainfall in the study area ..............................................................8 Figure 5: Annual cycle of the mean latitude of the subtropical ridge along the east coast of Australia ...................................................................................................9 Figure 6: Geology of eastern NSW .....................................................................................13 Figure 7: The two-point (ΔSWL) method of detecting change in standing water level (Salas and Smithson 2002) vs single-point method adopted in this study...........20 Figure 8: Example of residual mass curve (in blue) with extremes (red triangles) which show the timing of two major changes in rainfall regimes .........................25 Figure 9: Curves illustrating the filtering effect of applying (left to right, top row) 5- year, 7-year, (bottom row) 11-year, and 21-year moving averages (red trace) to annual rainfall data (—•—) for Forbes; green horizontal line indicates the long-term average rainfall of 687 mm.............................................26 Figure 10: Example of radar graph, showing change in monthly rainfall (mm) associated with the change in rainfall regime in 1947 (analysis based on recorded monthly rainfall data only, and does not include estimates before 1898)....................................................................................................................27 Figure 11: Clear rainfall shift in the summer rainfall zone: residual mass curve (left) and time-series graph (right) with two degrees of filtering (7- and 21-year moving averages) for the 54003 Barraba Post Office rainfall station...................34 Figure 12: Clear rainfall shift observed across entire uniform rainfall zone ..........................35 Figure 13: Unclear signal observed in some stations in summer rainfall zone, such as 54004 Bingara Post Office (Gwydir) ....................................................................35 Figure 14: Unclear rainfall shift observed across the winter rainfall zone, such as at 74008 Grong Grong (Berembed) rainfall station in Murrumbidgee West.............36 Figure 15: Reasonably clear rainfall shift observed at a very small number of stations in the winter rainfall zone, such as Adelong (Gundagai), (Murrumbidgee West, west of Snowy Mountains).........................................................................36 Figure 16: Residual mass curves of rainfall, and radar graphs showing pre-1947 and post-1947 average monthly rainfalls at Barraba PO, Forbes and Tumbarumba .......................................................................................................39 Figure 17: Example of the procedures used in analysing relationships between rainfall and SWL, using data for the Peel section............................................................44 Figure 18: Lachlan catchment sections and topography ......................................................50 Figure 19: Predicted (solid pink line) and measured (grey line) SWL data, together with 95% confidence intervals (dashed pink line); Prediction made using a linear or quadratic trend function. (In the case of the Gwydir the relationship was not statistically significant.)...........................................................................55 iv Figure 20: Predicted (solid pink line) and measured (grey line) SWL data, together with 95% confidence intervals (dashed pink