This report describes the findings of the Great Artesian Basin Water Resource Assessment that have led to advancing the understanding of the GAB. It encapsulates findings that are presented in four region reports and a technical report on conceptualising the GAB that were prepared for the Assessment. Advancing the conceptual understanding of the GAB requires careful evaluation of the geological framework (i.e. the layers of rock), description of how the geology translates into hydrostratigraphy (i.e. the relative ability of specific layers to store and transmit water) and investigation of the groundwater conditions (i.e. watertable, groundwater levels, and inferred movement). It is the geological framework, hydrostratigraphy and groundwater conditions that are the basis for conceptualising water resources in the GAB. The conceptual understanding of the GAB provides the foundation for assessing water availability and providing guidance to water policy and water resource planning.

This document contains metadata for the hydrodynamics products produced by the Great Artesian Basin Water Resource Assessment

This report presents key results from hydrogeological investigations at Alice Springs, completed as part of Exploring for the Future (EFTF)—an eight year, $225 million Australian Government funded geoscience data and information acquisition program focused on better understanding the potential mineral, energy and groundwater resources across Australia. The Southern Stuart Corridor (SSC) project area within the Northern Territory extends in a north–south corridor from Tennant Creek to Alice Springs, encompassing four water control districts and a number of remote communities. Water allocation planning and agricultural expansion in the SSC is currently limited by a paucity of data and information regarding the volume and extent of groundwater resources and groundwater systems more generally. This includes recharge rates, surface water –groundwater connectivity, and the dependency of ecosystems on groundwater. Outside the proposed agricultural areas, the project includes numerous remote communities where there is a need to secure water supplies. Geoscience Australia, in partnership with the Northern Territory Department of Environment and Natural Resources and the Power and Water Corporation, undertook an extensive program of hydrogeological investigations between 2017 and 2019. Data acquisition included helicopter airborne electromagnetic (AEM) and magnetic data, investigative groundwater bore drilling, ground-based and downhole geophysical data (including nuclear magnetic resonance for mapping water content and induction conductivity/gamma for defining geological formations), and hydrochemistry for characterising groundwater systems. This report investigates the hydrogeology across the Alice Springs focus area, which includes the Roe Creek and proposed Rocky Hill borefields, where five hydrostratigraphic units were mapped based on AEM interpretation and borehole geophysical information. The mapping supports the presence of a syncline, with a gentle parabolic fold axis that plunges westward, and demonstrates that the main Siluro-Devonian Mereenie Sandstone and Ordovician Pacoota Sandstone aquifers are continuous from Roe Creek borefield to the Rocky Hill area. Areas with the highest potential for recharge to the Paleozoic strata are where Roe Creek or the Todd River directly overlie shallow subcrop of the aquifer units. Three potential recharge areas are identified: (1) Roe Creek borefield, (2) a 3 km stretch of Roe Creek immediately west of the proposed Rocky Hill borefield, and (3) the viticulture block to the east of Rocky Hill. Analysis of groundwater chemistry and regional hydrology suggests that the rainfall threshold for recharge of the Paleozoic aquifers is ~125 mm/month, and groundwater isotope data indicate that recharge occurs rapidly. The groundwaters have similar major ion chemistry, reflecting similar geology and suggesting that all of the Paleozoic aquifers in the focus area are connected to some degree. Groundwater extraction at Roe Creek borefield since the 1960s has led to the development of a cone of depression and a groundwater divide, which has gradually moved eastward and is now east of the proposed Rocky Hill borefield. The majority of the groundwater within the focus area is of good quality, with <1000 mg/L total dissolved salts (TDS). The brackish water (7000 mg/L TDS) further to the east of the proposed Rocky Hill borefield warrants further investigation to determine the potential risk of it being captured by the cone of depression following the development of this borefield. This study provides new insight to the hydrogeological understanding of the Alice Springs focus area. Specifically, this investigation demonstrates that the Roe Creek and proposed Rocky Hill borefields, and a nearby viticulture area are all extracting from the same aquifer system. This finding will inform the future management and security of the Alice Springs community water supply. New groundwater resource estimates and a water level monitoring scheme can be developed to support the management of this vital groundwater resource.

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

This data set comprises one of three archives of Geoscience Australia work in the project "A Consistent Approach to Groundwater Recharge Determination in Data Poor Areas". The project was carried out by CSIRO and Geoscience Australia and was funded by the National Water Commission Raising National Water Standards program. The data contained included Original data sourced for the project, Final data produced by the project, MXD's of maps created, and tools used within the project. The archives created for this project comprise: 1. Data archive. Data set stored in the GA CDS. Geocat Record number 79804 2. Adminstration and publication archive. Documents stored in TRIM Project P10/67 RECHARGE-DISCHARGE PROJECT 3. References archive. Endnote library located at \\nas\eg\water\References\Recharge_Discharge_Project.enl For more information about the creation of these archives, including the location of files, see TRIM D2014-102808 For more information about the project, see the following references: Leaney F, Crosbie R, O'Grady A, Jolly I, Gow L, Davies P, Wilford J and Kilgour P. 2011. Recharge and discharge estimation in data poor areas: Scientific reference guide. CSIRO: Water for a Healthy Country National Research Flagship. 61 pp (GA Record No. 2011/46 GACat # 71941) Jolly I, Gow L, Davies P, O'Grady A, Leaney F, Crosbie R, Wilford J and Kilgour P. 2011. Recharge and discharge estimation in data poor areas: User guide for the recharge and discharge estimation spreadsheets and MapConnect. CSIRO: Water for a Healthy Country National Research Flagship. 40 pp. (GA Record No. 2011/35 GeoCat # 71940) Pain, C.F., Gow, L.J, Wilford, J.R. and Kilgour, P. 2011. Mapping approaches to recharge and discharge estimation and associated input datasets. A report for CSIRO: Water for a Healthy Country National Research Flagship. (Professional Opinion No. 2011/01 GeoCat # 70392)

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

Poster prepared for International Association of Hydrogeologists Congress 2013 Sonic drilling is a relatively new technology that was used successfully to obtain relatively uncontaminated and undisturbed continuous core samples with excellent (>99%) recovery rates to depths of 206m in unconsolidated fluvio-lacustrine sediments of the Darling River floodplain. However, there are limitations with the standard sonic coring method. Sands, in particular, are disturbed when they are vibrated out of the core barrel into the flexible plastic sampling tube. There can be changes to moisture content, pore fluid chemistry and sediment mineralogy on exposure to the atmosphere, even when the samples are processed and analysed soon after collection. The option exists during sonic drilling to encapsulate the core in rigid polycarbonate lexan tubes. Although this increases costs and reduces drilling rates, atmospheric exposure of the core during drilling is reduced to the ends of the lexan tubes before being capped. In addition, the tubes can be purged with an inert gas such as argon. Lexan coring is best carried out below the watertable as the heat from drilling dry clays can cause the polycarbonate to melt. In the study, 60 sonic holes (4.5 km) and 40 rotary mud holes (2 km) were obtained as part of a program to map and assess potential groundwater resources and managed aquifer recharge (MAR) targets over a large area (7,500 km2) of the Darling River floodplain. Two of the sonic bores were drilled to depths of 60 metres to obtain lexan-encapsulated core samples. These cores were used to obtain less perturbed samples for pore fluid analysis (salinity, major ions, trace metals, stable isotopes), textural analysis, and analysis of mineral phases to help assess aquifer clogging potential (using XRD, XRF, SEM). An additional advantage of the lexan coring was the recovery of encapsulated and intact sediment intervals for determining porosities, effective porosities, hydraulic conductivities, and other geophysical and petrophysical measurements. By painting some tubes black, sand samples were also successfully obtained for optically stimulated luminescence (OSL) dating. Alternatively, opaque black lexan can be made to order by the supplier. Overall, the superior sample integrity obtained from lexan coring enables a greater range of hydrogeological and hydrochemical parameters to be assessed.

Poster prepared for International Association of Hydrogeologists Congress 2013 The Broken Hill Managed Aquifer Recharge (BHMAR) project has successfully mapped a multi-layered sequence of aquitards and aquifers, as well potential groundwater resource and managed aquifer recharge (MAR) targets, in the top 100m of the Darling Floodplain. Near-surface aquitards overlying the Pliocene target aquifers (fluvial Calivil Formation (CFm) and marine Loxton-Parilla Sands (LPS)), were identified initially as variably conductive layers in airborne electromagnetic (AEM) data, and validated by drilling and complementary borehole geophysical, textural, hydrogeological and hydrochemical studies. The stratigraphic unit underlying the Pliocene aquifers is the Miocene upper Renmark Group (uRG). Drilling and AEM data have confirmed this unit is present throughout the study area, deposited predominantly as thick muds. Facies and biofacies analysis suggests these muds were deposited on a low relief sedimentary plain with a high water table and numerous permanent water bodies, with relatively minor sand bodies deposited in narrow anastomosing fixed channel streams. Groundwater in the upper uRG is saline, and muddy sediments form a strongly conductive layer beneath the Pliocene aquifers. This is a much harder geophysical target than the upper confining aquitards, as the target lies at depths of 80-120m, which is near the depth resolution of the AEM system. Furthermore, there is little conductivity contrast between the Pliocene and uRG sediments except in areas where there is fresh groundwater in the former. Hydrochemical and hydrodynamic data shows that there is limited hydrological connection between the uRG and less saline Pliocene aquifers, except where the Pliocene is underlain by uRG channel sands. These channels are much narrower (10s to ~100m) and thinner (1 to 10m) compared with palaeochannels in the overlying CFm. Where the channels are connected, there can be a distinct salinity gradient from the Pliocene into the uRG sands, indicating localised mixing. Given the potential for up-coning of saline groundwater in these instances, a number of sites (e.g. Menindee Common), have been assessed as unsuitable for MAR. Overall, the uRG muds act as a good lower confining aquitard to the Pliocene aquifers over most of the project area, including a number of potential MAR and groundwater resource targets.

This document lists metadata for the hydrogeology products produced by the Great Artesian Basin Water Resource Assessment.

Fresh groundwater resources are a highly valuable commodity, particularly in semi-arid to arid landscapes where annual precipitation is low and surface water is scarce. Water security, often achieved through the development of groundwater resources, is a high priority for rural communities within these water-limited landscapes. However this is often at the expense of the environment when alterations to the groundwater system, often in conjunction with drought conditions, can detrimentally impact floodplain and riparian vegetation structure and function. Remote-sensing methods can be used to detect such changes in vegetation. In this study, a multi-temporal Landsat Normalised Difference Vegetation Index (NDVI) approach was used to detect changes in riparian and floodplain vegetation in the Lower-Darling floodplain, NSW, Australia. When integrated with surface and subsurface data, these changes provided insight into how surface water availability and subsurface geological and hydrogeological characteristics influenced vegetation distribution and behaviour at multiple scales. It was found that while the availability of water resources was the primary driver of changes in vegetation canopy dynamics, this availability was strongly influenced by both tectonic and hydrogeological processes. These findings were of particular importance when considering the suitability of groundwater development options and they have implications for future groundwater assessment studies.