Developing (hydro)geological conceptual models to support improved groundwater management. The Upper Darling Floodplain Project, New South Wales

The groundwater and surface water systems associated with the Upper Darling River Floodplain (UDF) in arid northwest New South Wales form part of the Murray-Darling Basin drainage system, which hosts 40% of Australia’s agricultural production. Increasing water use demands and a changing regional climate are affecting hydrological systems, and consequently impacting the quality and quantity of water availability to communities, industries and the environment. As part of the Australian Government’s Exploring for the Future program, the UDF project is working in collaboration with State partners to collect and integrate new data and information with existing hydrogeological knowledge. The goal is to provide analyses and products that assist water managers to increase water security in the region, with a focus on groundwater resources. As part of this project we are assessing the occurrence of, and geological controls on, potable water resources within the Darling Alluvium (DA), which comprises unconsolidated sediments (<140 m thick) associated with the modern and paleo-Darling River. The DA’s relationship to the underlying Eromanga, Surat (Great Artesian Basin) and Murray basins is also important, particularly in the context of potential groundwater sources or sinks, and connection between low and high quality groundwater resources. At least one major fault system is known to influence groundwater flow paths and control groundwater-surface water interaction. Data collection across the project area has commenced, with an airborne electromagnetic (AEM) survey already complete, and new geophysical, hydrochemical and hydrodynamic data being acquired. Preliminary interpretation of the new AEM data in conjunction with existing geological and hydrogeological information has already revealed the major paths and geometries of the paleo-Darling River, given important insights into fault controls on groundwater flow paths, and shown variation in the thickness, distribution and character of the DA, which has direct implications for groundwater–surface water connectivity.