<div>As part of the EFTF Program, Geoscience has completed a 4-year multi-disciplinary study to investigate the energy resource potential of selected onshore basins within central Australia under the Australia’s Future Energy Resources (AFER) Project. A key component of the AFER Project has been a qualitative and quantitative play-based assessment of hydrocarbon resources and geological storage of CO2 (GSC) potential within the Pedirka and western Eromanga basins (Bradshaw et al., 2024a). This study has provided a regional interpretive data set which includes regional seismic and well log interpretations (Bradshaw et al.&nbsp;2024b, 2024c); depth-structure and isochore maps for 14 play intervals (Iwanec et al., 2024); gross-depositional environment maps for 14 play intervals (Bradshaw et al., 2024c); and petrophysical analysis of wireline log data from 23 wells (Spicer et al., 2024). This report provides a high-level summary of the hydrogeology of Pedirka and western Eromanga basins as background information for the other assessments and some findings from the 3D models that may inform future understanding of the hydrogeology of these basins. </div><div><br></div><div>The assessment area extends over ~210,000 km2 across the Northern Territory, South Australia and Queensland (Figure 1). Much of the assessment area underlies national parks in South Australia and Queensland. No petroleum exploration access is allowed in the Munga Thirri Simpson Desert Conservation Park or the Witjira National Park (Dalhousie Springs area) in South Australia or Munga Thirri National Park in Queensland (Figure 1).</div><div><br></div><div>The AFER assessment area is situated within the Kati Thanda-Lake Eyre surface water catchment. The catchment’s arid climate and ephemeral river flow regime (Evans et al., 2024) makes groundwater a critical source of water for the environment, industry and communities, especially during dry periods. Groundwater dependent features in the region include water supplies for communities, industry and pastoral stations, as well as springs and other groundwater dependent ecosystems. Groundwater resources are managed by state and territory jurisdictions (see: NT Government, 2013; Queensland Government, 2017, SA Government, 2021). Across the three jurisdictions, the most important groundwater resources are those of the western Eromanga Basin (a part of Great Artesian Basin or GAB). In collaboration with state jurisdictions the Commonwealth provides a cross-jurisdictional policy framework for the GAB as well as the Lake Eyre surface water basin (DCCEEW, 2024). Key management goals include maintaining artesian pressures, water quality and viability of GAB dependent ecosystems, including springs.&nbsp;</div><div><br></div><div><br></div><div><br></div>

Integrating surface water and groundwater sampling with pore fluid analysis of cored sediments, combined with fuzzy-k means (FCM) cluster analysis, provides a novel, relatively simple but powerful tool to interpret groundwater processes. This methodology has been applied to a study of shallow (<120m) alluvial aquifers in the Darling River floodplain, Pore fluids were extracted from sediments from 100 sonic-cored bores, and together with surface and groundwater samples, provided a hydrochemical dataset with over 1600 samples and 25 analytes. The FCM cluster analysis used analytes that were present in at least 60% of samples and resulted in samples being classified into eight classes (or hydrochemical facies). Pore fluids and groundwaters with the greatest affinity to the surface water samples were easily identified. In this way, sites with significant active recharge, principally by river leakage, were mapped. Downhole plots of the pore fluid FCM classes provided additional insights into groundwater processes. Comparing the FCM classification of pore fluids within the target (semi)confined aquifer with those from the overlying clay aquitard and shallow aquifer allowed the assessment of vertical inter-aquifer leakage. The FCM cluster analysis also assigns indices to each sample as indicators of how well it relates to each of the eight classes. A simple recharge index was calculated from these FCM indices. This novel approach has provided invaluable new insights into groundwater processes and has assisted greatly with assessing groundwater resources and managed aquifer recharge options.

Legacy product - no abstract available

Water resource assessment for the Great Artesian Basin. Synthesis of a report to the Australian Government from the CSIRO Great Artesian Basin Water Resource Assessment

Progress report for Milestone 8 of Palaeovalley Groundwater project. Report prepared by Geoscience Australia for delivery to National Water Commission.

Legacy product - no abstract available

Geomorphic landscape features and associated surface materials are fundamental to groundwater recharge processes as they form the first layer through which surface water passes before it becomes groundwater. Different surface materials exhibit different water-holding capacity and hence permeability characteristics. In the Broken Hill Managed Aquifer Recharge project, surface-materials mapping in conjunction with geomorphic mapping, has assisted hydrogeological investigations, including recharge predictions, salinity hazard and the identification of potential infiltration basins. Prior to landform identification, LiDAR DEM data was levelled using trend surfaces to eliminate regional slope (~20m). As a consequence of this, an ArcGIS interactive contour tool could be used to identify specific breaks in elevation associated with landform features. Multivariate image analysis of elevation, high resolution SPOT and Landsat-derived wetness further enhanced the contrast between geomorphic elements to confirm mapping boundaries. While specific landforms can be characterised by particular surface materials, these sediments can vary within a single geomorphic feature. Consequently, SPOT multispectral satellite imagery was used to identify surface materials using principal component analysis and unsupervised classification. This approach generated 20 classes; each assigned a preliminary cover/landform attribute using SPOT imagery. Field data (surface and borehole sample, and observations at shallow pits) were used to refine the classification approach. Interactive mapping using a de-trended DEM provided a rapid, effective and accurate alternative to time consuming manual landform digitisation. The combination of these two new products - surface-materials and geomorphic maps - has assisted in the identification of potential recharge sites and naturally occurring infiltration sites.

Report on operational activities with data, analysis and interpretation for the Gawler - Eucla demonstration study site in South Australia

Phase 1 report (Exposure/Impact Analysis) for Assessment of Groundwater Vulnerability to Climate Change in the Pacific Islands Project.

An integrated multi-scale approach has been used to map and assess shallow (<100m) aquitards in unconsolidated alluvial sediments beneath the Darling River floodplain. The study integrated a regional-scale (7,500km2) airborne electromagnetics (AEM) survey with targeted ground electrical surveys, downhole lithological and geophysical (induction, gamma and nuclear magnetic resonance (NMR)) logging, hydraulic testing and hydrogeochemistry obtained from a 100 borehole (7.5km) sonic and rotary drilling program. Electrical conductivity mapping confirmed a relatively continuous lacustrine Blanchetown Clay aquitard, mostly below the water table. The Blanchetown Clay is typically 5-10m thick with a maximum thickness of 18m but, importantly, can also be absent. Variations (up to 60m) in the elevation of the aquitard top surface are attributed partly to neotectonics, including warping, discrete fault offsets, and regional tilting. Hydrograph responses in overlying and underlying aquifers, laboratory permeameter measurements on cores, and hydrogeochemical data demonstrate where the Blanchetown Clay acts as an effective aquitard. In these areas, the AEM and induction logs can show an electrical conductivity (EC) decrease towards the centre of the clay rich aquitard, contrary to the typical response of saturated clays. Even though the aquitard centre is below the watertable, core moisture data and NMR total water logs indicate very low water content, explaining the relatively low EC response. The NMR logs also indicate that the clay aquitard is partially saturated both from the top and the bottom. This suggests very low hydraulic conductivities for the aquitard resulting in negligible vertical leakage in these areas. This is supported by core permeameter measurements of less than 10-12 m/s.