This report presents key results of the Ti Tree Basin study 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. As part of EFTF, Geoscience Australia undertook an assessment of available and new hydrochemical data collected in the Ti Tree Basin, Northern Territory. The basin is one of the four water control districts within the Southern Stuart Corridor Project area. Communities, irrigation farms and pastoral stations in the basin rely on groundwater, and extensive groundwater sampling and hydrochemical investigations have been undertaken over the past 50 years. An opportunity was recognised to collate and interpret the existing data, supplemented by new EFTF data, not only to add value to the understanding of groundwater processes in the basin itself but also to provide a useful knowledge base for other groundwater resources in the region that are poorly understood. This study largely relied on the available groundwater analysis data from the Northern Territory Department of Environment and Natural Resources database, supplemented by publicly available analyses from other sampling campaigns, including the EFTF, totaling 1913 groundwater samples across the district. The key findings of the study are: • The hydrochemistry data, particularly on salinity (total dissolved solids (TDS)), ion ratios (e.g. HCO3/Cl, Cl/(Cl+HCO3), Cl/(Cl+HCO3+SO4), Na/Cl) and radiocarbon (14C) could be used to map the three major recharge areas for the basin—the floodout of the Woodforde River to the west, the floodout of Allungra Creek in the basin centre, and the eastern basin margin. This is consistent with the current accepted interpretation that recharge is dominated by episodic run-on and infiltration in drainage floodout areas, driven by intense rainfall events that generate runoff in upland basement headwaters and ephemeral flows in basin creeks. There are no hydrochemical indicators of recharge in the vicinity of the channelised reaches of the basin creeks (i.e. both Woodforde River and Allungra Creek), located upstream of the floodouts. • From a groundwater resource perspective, the Allungra Creek floodout has broadly the best combination of low-salinity groundwater (median TDS = 740 mg/L) and bore yield statistics (median = 10 L/s). The Woodforde River floodout also has areas with high-yielding bores (>10 L/s) of fresh groundwater (<1000 mg/L), with the borehole distribution suggesting that the fresh groundwater resource is significantly more extensive to the west of the river than that previously mapped. The eastern basin margin generally has low-salinity groundwater (median TDS = 775 mg/L) but lower bore yields (median = 4.4 L/s). • There are differences in the recharge characteristics of the three floodout areas, due to differences in drainage catchments and floodout hydrogeology. The Woodforde River floodout has the most depleted stable isotopes, interpreted to be due to a higher rainfall/runoff threshold for recharge (>150 mm/month). It also has the largest isotopic range and the best δ18O-δ2H linear regression, suggesting the most influence of evaporation, such as a longer period of surface water ponding. In comparison, the stable isotope signature for Allungra Creek groundwaters suggests a lower rainfall/runoff threshold for recharge (>100 mm/month) and low evaporative influence, hence relatively rapid infiltration. This is also inferred to be the case for the low-salinity eastern basin margin groundwaters. For both Woodforde River and Allungra Creek, modern recharge is indicated by groundwaters with high radiocarbon activity (14C percent modern carbon (pMC) >70). For the eastern basin margin, radiocarbon activity is low to moderate (14C pMC 20–50). This is interpreted to reflect a longer travel time in the unsaturated zone. • In the floodout areas, the dominant hydrogeochemical process relating to the fresh groundwater is water–rock interactions. Groundwater tends to be the least evolved Ca(Mg)-HCO3 or transitional Na(K)-HCO3 water type, according to Chadha plots. Zones of prevalence of carbonate-gypsum dissolution or Na-silicate weathering could be mapped using indicators such as cation chloride ratio. Ion exchange is also a likely process in these fresh groundwaters, as inferred from chloro-alkaline indices. • Groundwater salinity is higher away from the floodout areas. This increased salinity is due to evapotranspirative concentration in addition to water–rock interactions, as inferred from ion ratios, including Cl/Br. Stable isotopes indicate that transpiration of groundwater by vegetation accessing the watertable, rather than direct evaporation, is the dominant process in these areas. This process is particularly evident in the Wilora Palaeochannel, the northern extension of the basin, which generally has the highest groundwater salinities (median TDS = 1575 mg/L), the lowest bore yields (median = 1.9 L/s) and the greatest prevalence of shallow watertables (<15 m). With higher salinities, groundwaters tend to be the evolved Ca(Mg)-Cl(SO4) and Na(K)-Cl(SO4) water types and potentially influenced by reverse ion exchange processes. • Mountain-front recharge has previously been proposed as an additional recharge mechanism, notably near the southern basin margin. Although sampling is limited in this area, hydrochemical indicators such as low HCO3/Cl, high Na/Cl and evolved Na(K)-Cl(SO4) water type suggests that active recharge is not significant. The watertable is deep along the southern basin margin (>50 m), so groundwater chemistry can be strongly influenced by processes during downward infiltration through a thick unsaturated zone. • Limited sampling of deeper bores (>80 m), potentially in the Hale Formation, generally have the characteristics of being more saline and lower yielding compared to bores in the shallow groundwater resource (particularly from 40 m to 80 m). However, there are deep bores with good yields of fresh groundwater; of 57 bores in the basin with interval depths exceeding 80 m, eight (14%) have the combination of yield >5 L/s and salinity <1000 mg/L. The deeper groundwaters are typically Ca(Mg)-Cl(SO4) and Na(K)-Cl(SO4) water types, with the latter, more evolved, water type dominating at depths >120 m. There are very few stable isotope analyses for the deeper groundwaters, but these are within the isotopic range for the shallow groundwaters in the same area, suggesting similarity in recharge processes and a degree of aquifer connectivity. Likewise, there are very few radiocarbon analyses for deeper groundwaters (depth >60 m), but these consistently show low 14C activity (pMC <40). The higher salinities, evolved water types and low 14C activity reflect longer residence times in the deeper groundwater system. The study highlighted that floodout recharge, involving episodic flow of basin creeks from headwater catchments, is the most dominant mechanism, rather than direct infiltration from large rainfall events. The study also identified that recharge characteristics, particularly the rainfall threshold for effective recharge and the role of evaporation, are not consistent across the floodout zones in the basin. This likely reflects differences in upland catchment size and geology, as well as floodout landform and hydrogeology. The study also highlighted the importance of groundwater-dependent vegetation in the basin, with dominance of transpiration of groundwater rather than direct evaporation. The groundwater hydrochemistry datasets and interpretation maps can support informed water management decisions within the basin. For example, improved understanding of the spatial and temporal distribution of recharge is not only needed for defining groundwater extraction limits but also used in strategies such as managed aquifer recharge. The EFTF work adds to the knowledge base and datasets that have developed over decades for the Ti Tree Basin, which are also valuable assets for broader understanding of groundwater resources in central Australia.

We present a multifaceted hydrogeological investigation of the McBride and Nulla basalt provinces in the Upper Burdekin region, north Queensland. The project aims to better understand their key groundwater system processes to inform future development and water management decisions. This work, carried out as part of the Exploring for the Future Upper Burdekin Groundwater Project, has shown that basalt aquifers in each province are typically unconfined where monitored. Groundwater recharge is widespread but highly variable, largely occurring within the boundaries of the basalt provinces. Groundwater salinity based on electrical conductivity is <1000 μS/cm in the McBride Basalt Province (MBP) and up to 2000 μS/cm in the Nulla Basalt Province (NBP). Groundwater levels have been declining since 2011 (following major flooding in Queensland), showing that the study period covers a small fraction of a longer-functioning dynamic groundwater system. The basalt provinces contain distinct lava flows, and the degree of hydraulic connectivity between them is unclear. Despite similarities in their rock properties, the geometry of lava emplacement leads to different groundwater flow regimes within the two basalt provinces. Radial flow away from the central high elevations towards the edges is characteristic of the MBP, while regional flow from west to east dominates the NBP. Basalt aquifers in both provinces support a range of groundwater-dependent ecosystems, such as springs, some of which sustain flow in tributaries of the Burdekin River. Where streams intersect basalt aquifers, this also results in direct groundwater discharge. Springs and perennial tributaries, particularly emanating from the MBP, provide important inflows to the Burdekin River, especially in the dry season. This work has highlighted that management of MBP and NBP groundwater sources is crucial for maintaining a range of environmental assets in the region and for ensuring access for existing and future users. <b>Citation:</b> Ransley, T.R., Dixon-Jain, P., Cook, S.B., Lai, E.C.S., Kilgour, P., Wallace, L., Dunn, B., Hansen, J.W.L. and Herbert, G., 2020. Hydrogeology of the McBride and Nulla basalt provinces in the Upper Burdekin region, north Queensland. In: Czarnota, K., Roach, I., Abbott, S., Haynes, M., Kositcin, N., Ray, A. and Slatter, E. (eds.) Exploring for the Future: Extended Abstracts, Geoscience Australia, Canberra, 1–4.

This report presents key results from hydrogeological investigations in the Tennant Creek region, 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 EFTF Southern Stuart Corridor (SSC) Project area is located in the Northern Territory and 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 limited by a paucity of data and information regarding the volume and extent of groundwater resources and groundwater systems more generally. Geoscience Australia, in partnership with the Northern Territory Department of Environment and Natural Resources and Power and Water Corporation, undertook an extensive program of hydrogeological investigations in the SSC Project area between 2017 and 2019. Data acquisition included; helicopter airborne electromagnetic (AEM) and magnetic data; water bore drilling; ground-based and downhole geophysical data for mapping water content and defining geological formations; hydrochemistry for characterising groundwater systems; and landscape assessment to identify potential managed aquifer recharge (MAR) targets. This report focuses on the Tennant Creek region—part of the Barkly region of the Northern Territory. Investigations in this region utilised existing geological and geophysical data and information, which were applied in the interpretation and integration of AEM and ground-based geophysical data, as well as existing and newly acquired groundwater hydrochemical and isotope data. The AEM and borehole lithological data reveal the highly weathered (decomposed) nature of the geology, which is reflected in the hydrochemistry. These data offer revised parameters, such as lower bulk electrical conductivity values and increased potential aquifer volumes, for improved modelling of local groundwater systems. In many instances the groundwater is shown to be young and of relatively good quality (salinity generally <1000 mg/L total dissolved solids), with evidence that parts of the system are rapidly recharged by large rainfall events. The exception to this is in the Wiso Basin to the west of Tennant Creek. Here lower quality groundwater occurs extensively in the upper 100 m below ground level, but this may sit above potentially potable groundwater and that possibility should be investigated further. Faults are demonstrated to have significantly influenced the occurrence and distribution of weathered rocks and of groundwater, with implications for groundwater storage and movement. Previously unrecognised faults in the existing borefield areas should be investigated for their potential role in compartmentalising groundwater. Additionally a previously unrecognised sub-basin proximal to Tennant Creek may have potential as a groundwater resource or a target for MAR. This study has improved understanding of the quantity and character of existing groundwater resources in the region and identified a managed aquifer recharge target and potential new groundwater resources. The outcomes of the study support informed water management decisions and improved water security for communities; providing a basis for future economic investment and protection of environmental and cultural values in the Tennant Creek and broader Barkly region. Data and information related to the project are summarised in the conclusions of this report and are accessible via the EFTF portal (https://portal.ga.gov.au/).

This report presents a summary of the groundwater hydrochemistry data release from the Western Davenport project conducted as part of Exploring for the Future (EFTF). This data release records the groundwater sample collection methods and hydrochemistry and isotope data from monitoring bores in the Western Davenport project area, Northern Territory (NT). The Western Davenport project is a collaborative study between Geoscience Australia and the NT Government. Hydrochemistry and isotope data were collected from existing and newly drilled bores in the Western Davenport area.

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).

Hydrochemistry analysis of GAB bores and springs for various aquifers within the Great Artesian Basin, and some from the overlying Karumba Basin, for the period 1974-1996.

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

Recent national and state assessments have concluded that sedimentary formations that underlie or are within the Great Artesian Basin (GAB) may be suitable for the storage of greenhouse gases. These same formations contain methane and naturally generated carbon dioxide that has been trapped for millions of years. The Queensland government has released exploration permits for Greenhouse Gas Storage in the Bowen and Surat basins. An important consideration in assessing the potential economic, environmental, health and safety risks of such projects is the potential impact CO2 migrating out of storage reservoirs could have on overlying groundwater resources. The risk and impact of CO2 migrating from a greenhouse gas storage reservoir into groundwater cannot be objectively assessed without knowledge of the natural baseline characteristics of the groundwater within these systems. Due to the phase behaviour of CO2, geological storage of carbon dioxide in the supercritical state requires depths greater than 800m, but there are no hydrochemical studies of such deeper aquifers in the prospective storage areas. Geoscience Australia (GA) and the Geological Survey of Queensland (GSQ), Queensland Department of Mines and Energy, worked collaboratively under the National Geoscience Agreement (NGA) to characterise the regional hydrochemistry of the Denison Trough and Surat Basin and trialled different groundwater monitoring strategies. The output from this Project constitutes part of a regional baseline reference set for future site-specific and semi-regional monitoring and verification programmes conducted by geological storage proponents. The dataset provides a reference of hydrochemistry for future competing resource users.

<div>This report brings together data and information relevant to understanding the regional geology, hydrogeology, and groundwater systems of the South Nicholson – Georgina (SNG) region in the Northern Territory and Queensland. This integrated, basin-scale hydrogeological assessment is part of Geoscience Australia’s National Groundwater Systems project in the Exploring for the Future program. While the northern Georgina Basin has been at the centre of recent investigations as part of studies into the underlying Beetaloo Sub-basin, no regional groundwater assessments have focused on central and southern parts of the Georgina Basin since the 1970s. Similarly, there has been no regional-scale hydrogeological investigation of the deeper South Nicholson Basin, although the paucity of groundwater data limited detailed assessment of the hydrogeology of this basin. This comprehensive desktop study has integrated numerous geoscience and hydrogeological datasets to develop a new whole-of-basin conceptualisation of groundwater flow systems and recharge and discharge processes within the regional unconfined aquifers of the Georgina Basin.</div><div><br></div><div>Key outputs arising from this study include: (1) the development of a hydrostratigraphic framework for the region, incorporating improved aquifer attribution for over 5,000 bores; and (2) publicly available basin-scale groundwater GIS data layers and maps, including a regional watertable map for the whole Georgina Basin. This regional assessment provides new insights into the hydrogeological characteristics and groundwater flow dynamics within the Georgina Basin, which can aid in the sustainable management of groundwater for current and future users reliant on this critical water resource.</div><div><br></div><div><br></div>

This report presents a summary of the groundwater hydrochemistry data release from the Ti Tree project conducted 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. This data release records the groundwater sample collection methods and hydrochemistry and isotope data from monitoring bores in the Alice Springs project area, Northern Territory (NT). The Ti Tree project is a collaborative study between Geoscience Australia and the NT Government. Hydrochemistry and isotope data were collected from existing and newly drilled bores in the Ti Tree area