This report presents palynological data compiled and analysed as part of Geoscience Australia’s ‘Assessing the Status of Groundwater in the Great Artesian Basin’ project, commissioned by the Australian Government through the National Water Infrastructure Fund – Expansion. Diverse historic nomenclature within the Great Artesian Basin (GAB) Jurassic‒Cretaceous succession in different parts of the GAB makes it difficult to map consistently GAB resources across borders, at a basin-wide scale, in order to provide a geological and hydrogeological framework to underpin effective long-term management of GAB water resources. The study undertaken by MGPalaeo, in collaboration with Geoscience Australia, examined 706 wells across the GAB and compiled 407 wells, having Jurassic‒Cretaceous succession, with reviewed palynology data (down to total depth). This initial palynology data review allowed identification of new data samples from 20 wells (within the 407 wells) in Queensland and South Australia to fill data and knowledge gaps within the Jurassic‒Cretaceous GAB succession. This study resulted in: 1) a summary compilation of existing palynology data on 407 wells selected to create a regional framework between the Surat, eastern Eromanga and western Eromanga basins, to help regional correlations across the GAB, 2) a review of several different palynology zonation schemes and adaptation to a single consistent scheme, applying the scheme of Price (1997) for the spore pollen zonation and Partridge (2006) for the marine zonation, 3) updated stratigraphic charts across the Surat, Eromanga and Carpentaria basins, 4) identification of data and knowledge gaps, and 5) sampling of new palynology data to help fill some data and knowledge gaps identified in 13 key wells in the Surat Basin and 10 key wells in the Eromanga Basin. In the Surat Basin the new sampling program has targeted units within: the Evergreen Formation, Hutton Sandstone, Springbok Sandstone, Gubberamunda Sandstone, Orallo Formation, Mooga Sandstone, Bungil Formation. In the Eromanga Basin the sampling program targeted units within: the Poolowanna Formation, Hutton Sandstone, Adori Sandstone, Algebuckina Sandstone, Namur Sandstone and Hooray Sandstone. The study undertaken by MGPalaeo, in collaboration with Geoscience Australia, provides updated biostratigraphic information compiled in a standardised chronostratigraphic framework across the Surat, Eromanga and Carpentaria basins that mostly comprise the GAB. This work allows comparison of various geological, lithological, hydrogeological schemes. It provides links between various lithostratigraphic units, with different nomenclature, across jurisdictions. It also links these units to some key regional chronostratigraphic markers that can be used to generate consistent surfaces that correlate to aquifer and aquitard boundaries. The compilation of legacy and newly sampled and analysed palynology data allows refinement of a regional chronostratigraphic framework that can be used to map a common Mesozoic play interval scheme across all the resource types, for basin-scale assessments of groundwater, hydrocarbons, carbon capture and storage, and mineral potential. From this correlation of time equivalent geological units deposited in different environments, it is then possible to map internal lithological variations in stratigraphic facies within sequences that influence hydraulic properties and connectivity within and between aquifers across the GAB. The updated geometry and variability mapping within and between aquifers will help refine the conceptual hydrogeological model, to assess how aquifers and aquitards are connected within the GAB. The revised conceptual hydrogeological model can facilitate an improved understanding of potential impacts from exploitation of sub-surface resources in the basin, providing a basis for more robust water balance estimates.

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.

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.

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).

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).

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).

<b>This data package is superseded by a second iteration presenting updates on 3D geological and hydrogeological surfaces across eastern Australia that can be accessed through </b><a href="https://dx.doi.org/10.26186/148552">https://dx.doi.org/10.26186/148552</a> The Australian Government, through the National Water Infrastructure Fund – Expansion, commissioned Geoscience Australia to undertake the project ‘Assessing the Status of Groundwater in the Great Artesian Basin’ (GAB). The project commenced in July 2019 and will finish in June 2022, with an aim to develop and evaluate new tools and techniques to assess the status of GAB groundwater systems in support of responsible management of basin water resources. While our hydrogeological conceptual understanding of the GAB continues to grow, in many places we are still reliant on legacy data and knowledge from the 1970s. Additional information provided by recent studies in various parts of the GAB highlights the level of complexity and spatial variability in hydrostratigraphic units across the basin. We now recognise the need to link these regional studies to map such geological complexity in a consistent, basin-wide hydrostratigraphic framework that can support effective long-term management of GAB water resources. Geological unit markers have been compiled and geological surfaces associated with lithostratigraphic units have been correlated across the GAB to update and refine the associated hydrogeological surfaces. Recent studies in the Surat Basin in Queensland and the Eromanga Basin in South Australia are integrated with investigations from other regions within the GAB. These bodies of work present an opportunity to link regional studies and develop a revised, internally consistent geological framework to map geological complexity across the GAB. Legacy borehole data from various sources, seismic and airborne electromagnetic (AEM) data were compiled, then combined and analysed in a common 3D domain. Correlation of interpreted geological units and stratigraphic markers from these various data sets are classified using a consistent nomenclature. This nomenclature uses geological unit subdivisions applied in the Surat Cumulative Management Area (OGIA (Office of Groundwater Impact Assessment), 2019) to correlate time equivalent regional hydrogeological units. Herein we provide an update of the surface extents and thicknesses for key hydrogeological units, reconciling geology across borders and providing the basis for a consistent hydrogeological framework at a basin-wide scale. The new surfaces can be used for facilitating an integrated basin systems assessment to improve our understanding of potential impacts from exploitation of sub-surface resources (e.g., extractive industries, agriculture and injection of large volumes of CO2 into the sub-surface) in the GAB and providing a basis for more robust water balance estimates. This report is associated with a data package including (Appendix A – Supplementary material): • Nineteen geological and hydrogeological surfaces from the Base Permo-Carboniferous, Top Permian, Base Jurassic, Base Cenozoic to the surface (Table 2.1), • Twenty-one geological and hydrogeological unit thickness maps from the top crystalline basement to the surface (Figure 3.7 to Figure 3.27), • The formation picks and constraining data points (i.e., from boreholes, seismic, AEM and outcrops) compiled and used for gridding each surface (Table 3.8).

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.

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.