International Association of Hydrogeologists Australia

IAH NSW – April Tech Talk

Sustainable groundwater management – have we really got it right? (Reflections on recharge, groundwater – surface water interactions, isotopes, and GIS)

Presented by Dr. John Bradd – GHD

Produced by: IAH NSW

Date: Tuesday 09 April 2024
Time: 17:30 for an 18:00 start
Where: AECOM Office – 420 George Street, Sydney, Level and room TBH


Throughout Australia and many countries, regulations govern water extraction from groundwater and rivers. An accurate estimation of recharge and baseflow is critical for water managers to make informed decisions about allowable water extraction limits and environmental water requirements for regulatory compliance. Forecasting recharge and baseflow estimates is important for future water security planning given the expectation of altered precipitation patterns from climate change.

Baseflow is intricately linked to groundwater recharge. For example, if long term climatic changes occur where groundwater systems are receiving less recharge from reduced rainfall over time, then baseflow to streams will decrease. Therefore, it is essential to examine groundwater recharge characteristics when estimating or forecasting baseflow in streams.

Are the numbers we use to allocate to the environment and water users realistic? What are they based on? This presentation examines and challenges some of the methods employed in quantifying key hydrogeological parameters that underpin important groundwater management decisions, especially recharge. We explore the intricacies of recharge estimation streamflow partitioning, what do the stable isotope numbers really tell us and explores an alternative approach to spatially representing and quantifying recharge that has potential to provide more defensible numbers for sustainable water management.



John has over 35 years’ experience in hydrogeology and groundwater investigations having directed, managed and conducted groundwater and environmental investigation projects in Australia and South-East Asia. Over the years, John has developed experience in groundwater resource management, land salinisation and catchment management, coal seam gas impacts on groundwater resources, groundwater modelling, contaminant transport, and the application of geochemical and isotope techniques to elucidate groundwater recharge, flow processes and groundwater/surface water interactions. John was responsible for creating the first salinity hazard map for NSW in the 1990’s and the original methodology for NSW groundwater availability and vulnerability maps.

John’s industry experience extends across federal (Ansto) and state regulatory organisation (NSW govt – DLWC/DPIE and its many names), private consulting firms and tertiary education and research institutions. He has been employed for the last 5 years with GHD as Technical Director –Hydrogeology. John graduated in 1988 with an Honours Degree in Geology from UNSW. In 1996, he was awarded a PhD in Hydrogeology at UTS and while currently at GHD, he is an Honorary Professor with the Geoquest Research Centre, Faculty of Science, Medicine and Health, University of Wollongong.



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