Estimating groundwater-river connectivity factor for quantifying changes in irrigation return flows in the Murray–Darling Basin

ABSTRACT

Concerns have been raised that the use of infrastructure and water efficiency projects to recover water entitlements for the environment in the Murray–Darling Basin (MDB) could be undermined by a reduction in return flows to rivers. Water use efficiency changes prior to 2009 had already reduced surface return flows. A dimensionless and normalised variable, connectivity factor (CF), has been used to analyse the cumulative impact on river flow from actions that alter groundwater recharge or extraction. CF is objectively estimated from existing modelling outputs for three large alluvial groundwater systems in south-eastern MDB relevant to a major water use efficiency program. Lower values of CF (0.05–0.45) imply lower reductions of return flows, less impacts on recovered water entitlements, with impacts more likely to be managed adaptively within current water management plans. The study should help allay concerns by explaining why previous estimates had been overly high.

KEYWORDS:

• Irrigation efficiency
• groundwater modelling
• river flow
• connectivity

Acknowledgments

The authors would like to thank the Murray–Darling Basin Authority for their support of the work and provision of Figure 2; and with CSIRO for the public release of various modelling reports. The authors would like to thank the anonymous reviewers for their many constructive comments.

Additional information

Funding

This work was supported by the Murray–Darling Basin Authority [TP707166].

Notes on contributors

Glen Walker

Glen R. Walker is a groundwater hydrologist, who worked with CSIRO in Adelaide for over 30 years before setting up his own consultancy, Grounded in Water. He specializes in salinity and groundwater sustainability. He has won the WE Woods Award for Salinity research and was the National Centre Groundwater Research for Training Distinguished Lecturer for 2017, speaking on ‘Climate Change and Australian Groundwater’. He was a member of the Independent Scientific Expert Committee on Coal Seam and Large Gas Developments and is a member of the MDBA Independent Audit Group for Salinity.

Quan J. Wang

QJWangis a Professor of Hydrological Forecasting at the University of Melbourne, where he conducts research on ensemble forecasting of floods, short-term and seasonal streamflow, and ensemble forecasting of weather, climate and drought. He is interested in analysis of climate and hydrological data, post-processing of forecasts from weather and climate models, catchment water balance and river routing modelling, hydrological model prediction updating and uncertainty quantification, and verification of ensemble forecasts. Prior to joining University of Melbourne in 2017, he was Chief Executive Science Leader and Senior Principal Research Scientist at CSIRO Land and Water and before joining CSIRO in 2007, he was Principal Scientist at the Victorian Department of Primary Industries, where he led irrigation research. QJ served on the Queensland Government Chief Scientist’s Science, Engineering and Technology Expert Panel following the devastating 2010-11 Queensland Floods. He was awarded the 2014 GN Alexander Medal by the Institution of Engineers, Australia, and the 2016 CSIRO Medal for Impact from Science. Dr Wang is a co-chair of HEPEX, the peak international community for research and practice of ensemble hydrological forecasting (http://www.hepex.org).

Avril C. Horne

Dr Avril Horne is an ARC Discovery Early Career Researcher at the University of Melbourne. She is a water policy specialist, with a combination of experience across economics, hydrology and policy. With fifteen years’ experience across a range of interdisciplinary projects, she has spent time in consulting, government and academia. She is currently working on projects developing tools and systems to assist efficient and adaptive environmental water management; allocation mechanisms and institutional arrangements for environmental water; and reallocation policies between water sectors. She is the lead editor for “Water for the Environment: from policy and science to implementation and management”, a book that includes contributions from over 50 leading scientists and practitioners internationally. Research interests- environmental water management and allocation- water resource management and policy- water allocation- tradeoff decisions in water resource management- water markets and trade. Prior to joining University of Melbourne in 2014, she was Assistant Director in the water group at the Australian Competition and Consumer Commission, where she assisted with the development of the water trading rules for the Murray Darling Basin Plan.

Rick Evans

Dr Richard Evans is Principal Hydrogeologist with Jacobs. Rick has 40 years of experience in all aspects of hydrogeology, groundwater resource management and groundwater engineering. He has worked on numerous water resource projects throughout Australia and Asia. He has specialised in groundwater management, surface water groundwater interaction, unconventional gas, assessing the impacts of groundwater developments and integrating science with policy. His strong interest is on the potential for conjunctive water management and managed aquifer recharge to secure both urban and irrigation development throughout Australia.

Stuart Richardson

Stuart Richardson is Managing Director of CDM Smith Australia. As a Principal Hydrogeologist, Stuart has more than 30 years of experience in groundwater investigations, aquifer-scale impact assessments and regulatory liaison. Stuart's background in the development of water planning strategies for industry and government has allowed him to work on projects that include aquifer-scale assessment of sustainable yield, water allocation planning and bringing together technical studies and policy development. He has been heavily involved in studies related to the interaction of rivers and aquifers in the Murray-Darling Basin over the past 15 years.