This web service provides access to geological, hydrogeological and hydrochemical digital datasets that have been published by Geoscience Australia for the Great Artesian Basin (GAB).

The Australian Government, through the National Water Infrastructure Development Fund, commissioned Geoscience Australia to undertake a 3-year project ‘Assessing the Status of Groundwater in the Great Artesian Basin’. The overall aim of the project was to analyse existing and new geoscientific data acquired by the project to improve understanding of the hydrogeological system and water balance in the GAB. In conjunction, the project assessed satellite based technologies for monitoring groundwater storage and level change. This talk will discuss some of the key results of the project. These include: an updated hydrogeological framework for the GAB, mapping aquifer and aquitard properties, geometry and extent; revised groundwater recharge rate estimates in the eastern GAB groundwater intake beds; new groundwater system conceptual models of groundwater recharge processes and groundwater flow; an assessment of the Gravity Recovery and Climate Experiment (GRACE) satellite derived groundwater storage change estimates for the GAB; and Interferometric Synthetic Aperture Radar (InSAR) satellite data, for detecting changes in groundwater levels.

As part of the Great Artesian Basin (GAB) Project a pilot study was conducted in the northern Surat Basin, Queensland, to test the ability of existing and new geoscientific data and technologies to further improve our understanding of hydrogeological systems within the GAB, in order to support responsible management of basin water resources. This report presents selected examples from the preliminary interpretation of modelled airborne electromagnetic (AEM) data acquired as part of this pilot study. The examples are selected to highlight key observations from the AEM with potential relevance to groundwater recharge and connectivity. Previous investigations in the northern Surat Basin have suggested that diffuse groundwater recharge rates are generally low (in the order of only a few millimetres per year) across large areas of the GAB intake beds—outcropping geological units which represent a pathway for rainfall to enter the aquifers—and that, within key aquifer units, recharge rates and volumes can be heterogeneous. Spatial variability in AEM conductivity responses is identified across different parts of the northern Surat Basin, including within the key Hutton Sandstone aquifer. Consistent with findings from other studies, this variability is interpreted as potential lithological heterogeneity, which may contribute to reduced volumes of groundwater entering the deeper aquifer. The influence of geological structure on aquifer geometry is also examined. Larger structural zones are seen to influence both pre- and post-depositional architecture, including the presence, thickness and dip of hydrogeological units (or parts thereof). Folds and faults within the Surat Basin sequences are, in places, seen as potential groundwater divides which may contribute to compartmentalisation of aquifers. Discrete faults have the potential to influence inter-aquifer connectivity. The examples presented here demonstrate the utility of AEM models, in conjunction with other appropriate geophysical and geological data, for characterising potential recharge areas and pathways within the main GAB aquifer units, by helping to better define aquifer geometry, lithological heterogeneity and possible structural controls. Such assessments have the potential to further improve our understanding of groundwater recharge and flow path variability at local to regional scales. Acquisition of broader AEM data coverage across groundwater recharge areas, along with complementary geophysical, geological and hydrogeological data, would further assist in quantifying recharge variability, facilitating revised water balance estimates for the basin and thereby supporting GAB water resource management and policy decision-making.

This report presents the results of an assessment of geoscience data and tools applied in the eastern Eromanga Basin to improve the hydrogeological conceptualisations. The assessment is one component of the Australian Government funded project ‘Assessing the Status of Groundwater in the Great Artesian Basin’. The results demonstrate that the application of existing and new geoscientific data and technologies has the potential to further improve our understanding of the Great Artesian Basin (GAB) hydrogeological system thus supporting the responsible management of basin water resources. Hydrogeological synthesis using airborne electromagnetic data, in conjunction with hydro- and chrono-stratigraphic data and well geological information, are effective at mapping the three dimensional distribution of the aquifers and aquitards. The results lead to an improved understanding of groundwater intake bed geometry, potential connectivity between aquifers, possible structural controls on groundwater flow paths, and plausible source of groundwater discharging as springs. In the southern part of the study area, the dominantly shale-rich Evergreen Formation is electrically conductive, but is locally resistive in places due to sand-rich facies. These areas allow hydraulic connectivity between the overlying and underlying Hutton and Precipice sandstone aquifers. Anticlinal folds and juxtaposed strata are observed on AEM traverses along the strike of the aquifer units, and includes the Hutton, Adori and Cadna-owie – Hooray sandstones. Abrupt folding and juxtaposed strata were interpreted as fault zones. Both structural features have the potential of controlling groundwater flow directions or groundwater storage compartmentalisation. The northern limits of Precipice Sandstone and Evergreen Formation are at Blackall and south of Barcaldine towns respectively. This zone also coincides with the southern edge of the east-west trending sub-surface Barcaldine Ridge where the basal Jurassic sequence abut against. On and north of the Barcaldine Ridge, the Cadna-owie – Hooray, Adori and Hutton sandstones are present. Mapping using AEM conductivity sections affirm that the Hutton Sandstone is the major aquifer in the northern part of the study area. The Poolowanna Formation, an age equivalent to the Evergreen Formation and Precipice Sandstone, is laterally extensive towards the northern part of the study area. This formation crops-out west of Lake Buchanan in the Great Dividing Range, but forms sub-crops elsewhere along the groundwater recharge areas. Numerous groundwater springs and spring clusters are present along the east and west of the outcropping sandstone hills in the Great Dividing Range. In the northern parts of the study area, source of groundwater for the springs are mainly derived from the Hutton Sandstone aquifers through either gravity-feed or lateral groundwater flow process. Polygonal faults mainly occur on conductive and fined-grained sedimentary units of the Rolling Downs Group. There is lack of observable evidence from AEM conductivity sections on the presence of polygonal faults to suggest preferential groundwater flows along these potential hydraulic conduits. Further investigation using ground based methods are needed to establish the presence of the faults and their hydraulic properties.

This web service provides access to geological, hydrogeological and hydrochemical digital datasets that have been published by Geoscience Australia for the Great Artesian Basin (GAB).

The GAB covers parts of New South Wales, Northern Territory, Queensland and South Australia, each with their own water management regimes. Regular assessment of the groundwater resources of the GAB at a whole-of-basin scale is important for reviewing the effectiveness and interaction of the different management approaches. However, historically this type of assessment has been undertaken on an ad hoc basis, by different agencies, for different reporting units, using different methodologies and input datasets, meaning it is difficult to compare assessments. The water balance presented here has been undertaken to test incorporating and communicating uncertainty estimates as part of a whole-of-GAB water balance. The water balance incorporates new work, where available, from the jurisdictions and from this project (specifically groundwater recharge estimates). This project has produced quantified uncertainty for a single component of the water balance - groundwater recharge, the largest input component of the water balance. The water balance, as presented in this report, is not intended to represent a comprehensive critical appraisal of the techniques used by previous workers to estimate each element of the water balance, nor was it intended to develop new techniques for the estimation of the water balance elements other than groundwater recharge. The incorporation of a component of the uncertainty in the water balance of the GAB is new. The uncertainty in the water balance has always been there, in all past iterations, though it has not been quantified. This estimation of uncertainty is important in the communication of the water balance, as it highlights several key issues: • using current information, a whole-of-basin water balance for the GAB is not sufficiently detailed to be of use to water managers • local monitoring of groundwater levels and pressures remains the primary management tool for monitoring groundwater resources in the GAB. The Project produced a point-in-time assessment of the water balance of the GAB, comparing inflows (including long-term average groundwater recharge) and outflows to the main regional aquifers, for the year 2019 (The year 2019 was the latest year for which data was available at the start of the Project). Most components of the water balance cannot be directly measured and in some cases reported values are long-term averages (e.g. groundwater recharge) and estimated values for the reporting time period. As such, the water balance relies on indirect measurements, long term averages and approximations, which have a level of inherent uncertainty resulting from the underlying assumptions used in their estimation. To calculate a whole-of GAB water balance, the project divided all the formations in the GAB into four different ‘aquifer groups’: Rolling Downs Aquifer Group; Cadna-owie Aquifer Group; Hutton – Injune Creek Aquifer Group; and Precipice Aquifer Group. This approach was developed by KCB (KCB 2016b,c,d) in Queensland and has been adopted for this Project, as it ensures all inflows and outflows from the GAB were included in the water balance. The whole-of-GAB water balance has been calculated, based on water balances estimates calculated for each constituent sub-basin – the Eromanga, Carpentaria and Surat basins. This was done to provide a picture of variations in the water balance across different parts of the GAB. The whole-of-GAB water balance, calculated using the 5th, 50th and 95th percentiles of modelled long term average groundwater recharge rates, estimates a range of storage change volumes of -859 GL, -29 GL and +1,212 GL respectively, in 2019. The large variation in estimated storage volumes, ranging from a negative to positive groundwater storage change, highlights the large uncertainty associated with the water balance. Using 50th percentile modelled groundwater recharge rates, sub-basin water balances shows an increase in groundwater storage for the Eromanga Basin (-229 GL 5th percentile; 51 GL 50th percentile and 424 GL 95th percentile) and a decrease in groundwater storage of the Carpentaria Basin (-413 GL 5th percentile; -72 GL 50th percentile and 511 GL 95th percentile) and Surat Basin (-217 GL 5th percentile; -9 GL 50th percentile and 277GL 95th percentile). Using 50th percentile modelled groundwater recharge rates for major aquifer groups across the basin, water balance estimates for the Cadna-owie Aquifer Group and Precipice Aquifer Group suggest a decrease in storage volumes, while water balance estimates for the Hutton - Injune Creek Aquifer Group and the Rolling Downs Aquifer Group suggest an increase in storage volumes. While the whole-of-GAB, sub-basin and major aquifer water balances provide basin-wide perspectives of the groundwater resource components, they also highlight the high uncertainties associated with estimating groundwater recharge at a regional scale. The large range in groundwater storage values calculated for the water balance presented here, are too great to confidently provide a whole-of-GAB scale assessment of groundwater resources. The techniques used to estimate some water balance components have improved, for example Queensland has developed a repeatable methodology for estimating unmetered groundwater extraction. This project shows that our ability to confidently model groundwater recharge to the GAB is still evolving, and will continue to improve as further investigations are undertaken. Limited hydrograph analysis showed that areas where formerly free-flowing artesian bores have been rehabilitated, through the Great Artesian Basin Sustainability Initiative and predecessor programs, are seeing stabilisation or even recovery of water levels. Monitoring bores and hydrograph analysis continue to be important elements of any water resource assessment. Undertaking the water balance for the GAB and sub-basins has been useful for highlighting components of the water balance that should be considered carefully by groundwater resource managers and where necessary, targeted for future research eg. groundwater recharge, consistent GAB wide bore discharge estimates and evapotranspiration.

The Great Artesian Basin Research Priorities Workshop, organised by Geoscience Australia (GA), was held in Canberra on 27 and 28 April 2016. Workshop attendees represented a spectrum of stakeholders including government, policy, management, scientific and technical representatives interested in GAB-related water management. This workshop was aimed at identifying and documenting key science issues and strategies to fill hydrogeological knowledge gaps that will assist federal and state/territory governments in addressing groundwater management issues within the GAB, such as influencing the development of the next Strategic Management Plan for the GAB. This report summarises the findings out of the workshop.

Geoscience Australia’s regional assessments and basin inventories are investigating Australia’s groundwater systems to improve knowledge of the nation’s groundwater potential under the Exploring for the Future (EFTF) Program and Geoscience Australia’s Strategy 2028. Where applicable, integrated basin analysis workflows are being used to build geological architecture advancing our understanding of hydrostratigraphic units and tie them to a nationally consistent chronostratigraphic framework. Here we focus on the Great Artesian Basin (GAB) and overlying Lake Eyre Basin (LEB), where groundwater is vital for pastoral, agricultural and extractive industries, community water supplies, as well as supporting indigenous cultural values and sustaining a range of groundwater dependent ecosystems such as springs and vegetation communities. Geoscience Australia continued to revise the chronostratigraphic framework and hydrostratigraphy for the GAB infilling key data and knowledge gaps from previous compilations. In collaboration with Commonwealth and State government agencies, we compiled and standardised thousands of boreholes, stratigraphic picks, 2D seismic and airborne electromagnetic data across the GAB. We undertook a detailed stratigraphic review on hundreds of key boreholes with geophysical logs to construct consistent regional transects across the GAB and LEB, using geological time constraints from hundreds of boreholes with existing and newly interpreted biostratigraphic data. We infilled the stratigraphic correlations along key transects across Queensland, New South Wales, South Australia and Northern Territory borders to refine nomenclature and stratigraphic relationships between the Surat, Eromanga and Carpentaria basins, improving chronostratigraphic understanding within the Jurassic to Cretaceous units. We extended the GAB geological framework to the overlying LEB to better resolve the Cenozoic stratigraphy and potential hydrogeological connectivity. New data and information fill gaps and refine the previous 3D hydrogeological model of the entire GAB and LEB. The new 3D geological and hydrostratigraphic model provides a framework to integrate additional hydrogeological and rock property data. It assists in refining hydraulic relationships between aquifers within the GAB and provides a basis for developing more detailed hydrogeological system conceptualisations. This is a step towards the future goal of quantifying hydraulic linkages with underlying basins, and overlying Cenozoic aquifers to underpin more robust understanding of the hydrogeological systems within the GAB. This approach can be extended to other regional hydrogeological systems. This Abstract was submitted/presented at the 2023 Australasian Exploration Geoscience Conference (AEGC) 13-18 March (https://2023.aegc.com.au/)

This report presents palynological data compiled and analysed as part of the National Groundwater Systems (NGS) Project. NGS is 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. This study builds on previous work (Hannaford et al., 2022) undertaken as part of the ‘Assessing the Status of Groundwater in the Great Artesian Basin’ project, commissioned by the Australian Government through the National Water Infrastructure Fund – Expansion. The study undertaken by MGPalaeo, in collaboration with Geoscience Australia, examined an additional 688 boreholes across the GAB and compiled 149 new palynological summary sheets having Jurassic‒Cretaceous succession, with reviewed palynology data (down to total depth). The combined borehole palynological data examined from this study and the previous GAB work (Hannaford et al., 2022) is compiled in Appendix B4. The combined dataset totals 1,394 boreholes examined and 652 with palynology in the stratigraphic interval of interest, 102 of these boreholes contained Cenozoic palynology relevant to the Lake Eyre Basin. This information has been used to revise stratigraphic correlations across the GAB (Norton & Rollet, 2022 and 2023). Initial review of the stratigraphy in the Lake Eyre Basin (LEB) compiled existing palynology from outcrop, mineral and petroleum boreholes. An additional 28 boreholes in the Upper Darling Floodplain region were examined, 16 of which contained relevant palynology. The main palynological data infill in the GAB and LEB region during this follow-up study focused on: 1. Collecting, processing and analysing new biostratigraphic data on 149 key boreholes particularly across the Eromanga and Surat basins boundary. The study focussed on integrating data in New South Wales from the southern Surat Basin and central Eromanga Basin. 2. Further palynological data infill and palynological analysis on 15 samples from 7 boreholes in the western Eromanga Basin to assess difficulties in correlating the stratigraphy across the Algebuckina Sandstone. 3. Compiling existing analyses and update any historical palynological data in the Lake Eyre Basin to reflect the latest zonation scheme developed in this study. The new palynological data combined with new zircon data from other studies in the Carpentaria and Surat basins (Foley et al., 2020, 2021, 2022; La Croix et al., 2022, respectively) provides information on the tie to the geological timescale and help refine the chronostratigraphic chart that summarises stratigraphic correlations across the Carpentaria, Surat and Eromanga basins of Hannaford et al. (2022). All boreholes were examined outside of the Cooper and Bowen basins boundaries with selected boreholes around transects defined for stratigraphic correlation review through the Cooper and Bowen basin outlines (Norton & Rollet, 2022 and 2023). As a result, most of the remaining unreviewed palynological data lies within the Cooper and Bowen basins. The results of the palynology data infill in the western Eromanga Basin, in South Australia and Northern Territory, show that the Algebuckina Sandstone section is dominated by clean sandstone and so the cuttings samples were also dominated by sand. Although attempts were made to concentrate the shale from the cuttings in the thicker shale mid formation, this did not yield results, due to the amount of caved Cretaceous material. An initial assessment of the Lake Eyre Basin palynological data and zonation scheme was undertaken using information derived from water, mineral and petroleum boreholes. This provides an initial state of knowledge for the Lake Eyre Basin that can be built on in the future. Recommendations are provided for further studies to build a better understanding of the stratigraphy in the Great Artesian and Lake Eyre basins.

This report presents a stratigraphic review of some key boreholes across the Jurassic-Cretaceous Eromanga, Surat and Carpentaria basins that form the groundwater Great Artesian Basin (GAB), as well as across the overlying Cenozoic Lake Eyre Basin (LEB), completed during the National Groundwater Systems (NGS) Project. The NGS Project is 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 study presented here builds on previous work (Norton & Rollet, 2022a) undertaken as part of the ‘Assessing the Status of Groundwater in the Great Artesian Basin’ Project, commissioned by the Australian Government through the National Water Infrastructure Fund – Expansion. Although not intended to be a major re-interpretation of existing data, this stratigraphy review updates stratigraphic picks where necessary to obtain a consistent interpretation across the study area, based on the refined geological and hydrostratigraphical framework developed through this project. Problems and inconsistencies in the input data or current interpretations have been highlighted to suggest where further studies or investigations may be useful. This study includes Phase 2 of the National Groundwater Systems Project, which was undertaken by Catherine Jane Norton in collaboration with Geoscience Australia; and compiled, processed and correlated a variety of borehole log data to review the stratigraphy and improve the understanding of distribution and characteristics of Jurassic and Cretaceous sediments across the Eromanga and Surat basins and overlying LEB. To complement the previous 322 key boreholes compiled in Phase 1 (Norton & Rollet, 2022) additional stratigraphic correlations have been made between geological units of similar age (constrained using palynological data) from 706 key boreholes along 35 regional transects across the GAB and from 406 key boreholes along 20 regional transects across the central LEB. Also included in this study is Phase 3 in-fill work of four additional transects, extending the study further south in New South Wales, to tie in to the Cenozoic of the Murray Basin. This later phase 3 of the project also included a review and quality control of approximately 2,572 central LEB boreholes, and the addition of 278 boreholes in the GAB in southern Queensland and New South Wales. Phase 3 also expanded on the results used for mapping regional sand/shale ratios that began in the previous phase (Evans et al., 2020; Norton & Rollet, 2022a). Normalised Gamma Ray (GR) calculations have now been made for 1,778 LEB boreholes and 676 GAB boreholes spanning the entire sequence from the surface, through the Cenozoic and down to the base Jurassic unconformity. The previous phase, mentioned above, concentrated on either just the LEB or the GAB intervals from Cadna-owie Formation to base Jurassic. An additional 17 transects in the LEB and 27 transects in the GAB were created to visualise the lithological variation. The distribution of generalised sand/shale ratios are used to estimate the thickness of sand and shale in different formations, with implications for formation porosity and the hydraulic properties of aquifers and aquitards. This study fills data gaps identified in the previous study (Norton & Rollet, 2022) and refines the regional distribution of lithological heterogeneity in each hydrogeological unit, contributing to an improved understanding of connectivity within and between aquifers. The datasets compiled and examined in this study are in Appendix A. Attempts were made to standardise lithostratigraphic units, which are currently described using varying nomenclature, to produce a single chronostratigraphic chart across the entirety of the GAB and LEB basins. The main stratigraphic correlation infill in the GAB and LEB regions focused on: • The transition between the Eromanga and Surat basins in New South Wales and the tie-in to existing transects in Queensland and South Australia, • The Eromanga Basin in South Australia and Queensland and the tie-in to Phase 1 transects, • The central Eromanga Basin and Frome Embayment areas, extending the GAB units to the overlying Lake Eyre Basin stratigraphy to better assess potential connectivity between these basins, • The transition between the Lake Eyre and Murray Basins in the Upper Darling Floodplain (UDF) area in New South Wales and the tie-in to Phase 1 transects in New South Wales. This report and associated data package provide a data compilation on 706 and 278 key boreholes in the Surat and Eromanga basins respectively, to assist in updating the geological framework for the GAB and LEB. Recommendations are provided for further studies to continue refining the understanding of the stratigraphy in the Great Artesian and Lake Eyre basins.