We collected 38 groundwater and two surface water samples in the semi-arid Lake Woods region of the Northern Territory to better understand the hydrogeochemistry of this system, which straddles the Wiso, Tennant Creek and Georgina geological regions. Lake Woods is presently a losing waterbody feeding the underlying groundwater system. The main aquifers comprise mainly carbonate (limestone and dolostone), siliciclastic (sandstone and siltstone) and evaporitic units. The water composition was determined in terms of bulk properties (pH, electrical conductivity, temperature, dissolved oxygen, redox potential), 40 major, minor and trace elements as well as six isotopes (δ18Owater, δ2Hwater, δ13CDIC, δ34SSO4=, δ18OSO4=, 87Sr/86Sr). The groundwater is recharged through infiltration in the catchment from monsoonal rainfall (annual average rainfall ~600 mm) and runoff. It evolves geochemically mainly through evapotranspiration and water–mineral interaction (dissolution of carbonates, silicates, and to a lesser extent sulfates). The two surface waters (one from the main creek feeding the lake, the other from the lake itself) are extraordinarily enriched in 18O and 2H isotopes (δ18O of +10.9 and +16.4 ‰ VSMOW, and δ2H of +41 and +93 ‰ VSMOW, respectively), which is interpreted to reflect evaporation during the dry season (annual average evaporation ~3000 mm) under low humidity conditions (annual average relative humidity ~40 %). This interpretation is supported by modelling results. The potassium (K) relative enrichment (K/Cl mass ratio over 50 times that of sea water) is similar to that observed in salt-lake systems worldwide that are prospective for potash resources. Potassium enrichment is believed to derive partly from dust during atmospheric transport/deposition, but mostly from weathering of K-silicates in the aquifer materials (and possibly underlying formations). Further studies of Australian salt-lake systems are required to reach evidence-based conclusions on their mineral potential for potash, lithium, boron and other low-temperature mineral system commodities such as uranium. <b>Citation:</b> P. de Caritat, E. N. Bastrakov, S. Jaireth, P. M. English, J. D. A. Clarke, T. P. Mernagh, A. S. Wygralak, H. E. Dulfer & J. Trafford (2019) Groundwater geochemistry, hydrogeology and potash mineral potential of the Lake Woods region, Northern Territory, Australia, <i>Australian Journal of Earth Sciences</i>, 66:3, 411-430, DOI: 10.1080/08120099.2018.1543208

This report documents the conceptual Managed Aquifer Recharge (MAR) and groundwater resource targets identified from initial analysis of airborne electromagnetics (AEM) data acquired during Phase 2 of the Broken Hill Managed Aquifer Recharge (BHMAR) Project (Lawrie, 2009; Lawrie et al., 2008a, 2009a, b; Figure 1). The BHMAR Phase 2 study builds on an earlier scoping study (Lewis et al., 2008) and Phase 1 technical risk assessment (Lawrie et al, 2009a, b), and is part of the Australian Government's plan to secure Broken Hill's water supply and allow for significant amounts of water currently stored at Menindee Lakes to be returned to the environment. The Australian Government has committed up to $400 million to the project, which is managed through the Australian Government Department of the Environment, Water, Heritage and the Arts (DEWHA).

Under the Community Stream Sampling and Salinity Mapping Project, the Australian Government through the Department of Agriculture, Fisheries and Forestry and the Department of Environment and Heritage, acting through Bureau of Rural Sciences, funded an airborne electromagnetic (AEM) survey to provide information in relation to land use questions in selected areas along the River Murray Corridor (RMC). The proposed study areas and major land use issues were identified by the RMC Reference Group at its inception meeting on 26th July, 2006. This report has been prepared to facilitate recommendations on the Lindsay-Wallpolla study area. The work was developed in consultation with the RMC Technical Working Group (TWG) to provide a basis for the RMC Reference Group and other stake holders to understand the value and application of AEM data to the study area. This understanding, combined with the Reference Group's assessment of the final results and taking in account policy and land management issues, will enable the Reference Group to make recommendations to the Australian Government.

Under the Community Stream Sampling and Salinity Mapping Project, the Australian Government through the Department of Agriculture, Fisheries and Forestry and the Department of Environment and Heritage, acting through Bureau of Rural Sciences, funded an airborne electromagnetic (AEM) survey to provide information in relation to land use questions in selected areas along the River Murray Corridor (RMC). The proposed study areas and major land use issues were identified by the RMC Reference Group at its inception meeting on 26th July, 2006. This report has been prepared to facilitate recommendations on the Nangiloc - Colignan study area. The work was developed in consultation with the RMC Technical Working Group (TWG) to provide a basis for the RMC Reference Group and other stake holders to understand the value and application of AEM data to the study area. This understanding, combined with the Reference Group's assessment of the final results and taking in account policy and land management issues, will enable the Reference Group to make recommendations to the Australian Government.

The Broken Hill Managed Aquifer Recharge (BHMAR) project is part of a larger strategic effort aimed at securing Broken Hill's water supply and identifying significant water-saving measures for the Darling River system. Hydrogeological investigations to rapidly identify and assess potential MAR targets and groundwater resources over a large area (>7,500 km2), included acquisition of an airborne electromagnetics (AEM) survey, a 7.5 km drilling program (100 sonic and rotary mud holes), and complementary field and laboratory hydrogeochemical investigations. In this study, AEM mapping validated by drilling has identified significant groundwater resources and potential MAR targets within shallow unconsolidated Pliocene sediments at relatively shallow depths (25-100m). Pliocene sand aquifers comprise the fluvial Calivil Formation, with the shallow marine Loxton-Parilla Sands restricted to the southernmost part of the area. The Calivil Formation is widely distributed, and has high storage capacity and very high transmissivities (up to 50 l/s), with particularly good aquifers developed in palaeochannels at the confluence of palaeo-river systems. The hydraulic properties make the Calivil Formation aquifer potentially suitable for groundwater extraction and/or MAR injection, with excellent recovery efficiencies predicted. The aquifer is sandwiched between variably thick clay aquitards, and can be characterised as varying from a confined to a 'leaky confined' system. Post-depositional warping, tilting and discrete offsets associated with neotoectonics are also recognised. Entry-level risk assessments were carried out for a number of potential MAR targets, with a pre-commissioning semi-quantitative residual risk assessment carried out for a priority site. Assessment of 12 hazard types included hydrogeological modelling, laboratory column clogging studies and geochemical assessment to assess source water treatment requirements.

Technical report on operational activities, including data, analysis and interpretation, for the Murchison demonstration study site conducted for the Palaeovalley Groundwater Project. This work was funded by the National Water Commission and managed by Geoscience Australia.

Multiple new geophysical (airborne electromagnetics, borehole gamma and NMR), geospatial (LiDAR), sonic drilling and geochronological datasets have been used to map and resolve the nature of Quaternary fluvial deposition in the Lower Darling Valley (LDV), NSW. The LDV Cenozoic sequence contains Paleogene and Neogene shallow marine, fluvial and shoreline sediments overlain by Quaternary lacustrine, aeolian and fluvial units. In the LDV Quaternary fluvial sequence, multiple scroll-plain tracts are incised into higher, older more featureless floodplains. Prior to this study, these were respectively correlated to the Coonambidgal and Shepparton Formations of the Riverine Plain in the eastern Murray Basin and associated with the subsequently discarded Prior Stream/Ancestral River chronosequence of different climatically controlled depositional styles. In contrast to that proposition, we ascribe all LDV Quaternary fluvial deposition to lateral-migration depositional phases of one style, though with more variable stream discharges and channel and meander-scroll dimensions. Successively higher overbank-mud deposition through time obscures scroll traces and provides the main ongoing morphologic difference. A new morphostratigraphic unit, the Menindee Formation, refers to the mostly older and higher floodplain sediments, where scroll traces are obscured by overbank mud which continues to be deposited by the highest modern floods. Younger inset scroll-plain tracts, with visible scroll-plain traces, are still referred to the Coonambidgal Formation. Another new stratigraphic unit, the Willotia beds, refers to even older fluvial sediments, now above modern floodplain levels and mostly covered by aeolian sediments. This work provides important insights into hydrogeological processes and the nature of Australian Quaternary fluvial deposition.

The Sustainable Management of Coastal Groundwater Resources Project was co-funded by the Raising National Water Standards Program, which supports the implementation of the National Water Initiative Program. The project was led by GHD Hassall, in consultation with Kempsey Shire Council, Geoscience Australia, NSW Department of Environment, Climate Change and Water, and Ecoseal Developments Pty. Ltd. The project aimed to improve the management of groundwater in coastal dune aquifers, undertaking a case study of the Hat Head National Park region on the Mid North Coast of New South Wales. Due to increasing pressures on groundwater resources from expanding urbanisation and tourism in this region, the sustainable management of the existing groundwater resources is of vital importance. There are many potential risks associated with extraction of groundwater resources including acidification of soils, seawater intrusion and increased salinity levels, and detrimental impacts on groundwater dependent ecosystems (GDEs). This final report documents all of the work undertaken by Geoscience Australia relating to Groundwater Dependent Ecosystems, or more specifically groundwater dependent terrestrial vegetation. Groundwater dependent ecosystems (GDEs) are naturally occurring ecosystems that require access to groundwater to meet all or some of their water requirements so as to maintain their communities of plants and animals, ecological processes and ecosystems services. Often the natural water regime of GDEs will comprise one or more of groundwater, surface water and soil moisture.

The success of Aquifer Storage and Recovery (ASR) schemes rely on defining appropriate design and operational parameters in order to maintain high injection rates over the long term. The objective of this study was to develop a methodology to define the water quality criteria and hence minimum pre-treatment requirements to allow recharge at an acceptable scale. Laboratory column studies using four types of treated source water were performed at constant temperature (19°C) with light excluded, to determine the potential for near-well clogging for a proposed ASR scheme. The source water was turbid raw water from the Darling River and three treated waters including bank filtration, coagulation, and coagulation and granular activated carbon (GAC). Over the 37 days of the experiment, declines in hydraulic conductivity occurred in the columns packed with representative aquifer fluvial sands. The GAC treated town water gave an 8% decline in hydraulic conductivity, which was significantly different from the other three source waters with mean declines of 26-29%. Over the first 3 cm of column length, where most clogging occurred in each column, the mean hydraulic conductivity declined by 10% for GAC treated water compared with 40 to 50% for the other source waters. Evidence from polysaccharide concentrations and bacterial numbers in columns when they were dissected and analysed at the end of the experiment confirmed that biological growth was the dominant form of clogging in the treated waters. Further chemical clogging through precipitation of minerals was found not to occur within the laboratory columns, and dispersion of clay was also found to be negligible.

This report summarises the result of a study into seawater intrusion into coastal aquifers in the Northern territory coastal plain using AEM data, down hole geophysics, and bore hole geology carried out by Geoscience Australia on behalf of the National Water Commission and in partnership with NRETAS. The study showed that ground-validated AEM is able to map areas of saline aquifers in the area and differentiate them from bedrock conductors.