Exploring for the Future — Geological and hydrogeological investigations in the Western Davenport region: Northern Territory

This report presents key results from the Western Davenport study conducted as part of Exploring for the Future (EFTF), an Australian Government-funded geoscience data and information acquisition program. The Western Davenport (WD) investigation used existing geological and hydrogeological data and new AEM data to develop a 3D hydrostratigraphic model of the central part of the study area. This was augmented by existing and newly acquired hydrogeological and hydrochemistry data to improve the understanding of groundwater in the area. The collection and interpretation of these datasets have enabled a correlation between hydrostratigraphic units in the Wiso and Georgina basins in the WD area. The hydrochemistry data shows that the central zone of the WD is characterised by good-quality groundwater (<1000 mg/L total dissolved solids), with the newly drilled bores identifying areas of low-salinity groundwater. These initial hydrochemistry results suggest groundwater in the WD could support irrigated agriculture. The hydrochemistry data has identified three zones of potentially higher recharge. The groundwater stable isotope dataset suggests that there is minimal evaporation of water prior to recharge and that groundwater recharge only occurs following heavy rainfall events. This preliminary information suggests recharge to groundwater is dominated by episodic recharge from floodouts and creeks rather than direct infiltration across the WD area from large rainfall events. However, more data are needed to better define the role of floodouts in recharge to the groundwater system and to determine the contribution of creek beds versus floodouts to recharge. Given the aridity of the area and the variable nature of recharge events, managed aquifer recharge could increase the security of groundwater resources in the area. The regolith mapping presented can assist in better understanding the surface and near-surface environments, and their influence on hydrogeological processes. This provides a tool with which to begin identifying potential areas for enhancing natural recharge processes to supplement existing groundwater resources. This mapping was possible because of the increasing availability of higher resolution digital elevation, airborne radiometric and Landsat satellite remotely sensed data. The improved understanding of geology and hydrogeology, coupled with managed aquifer recharge mapping undertaken as part of the EFTF program, provides new information to support groundwater management in the WD area.