Identification of neotectonic features in Australia's interior is challenging with a lack of outcrop, and a subtlety in surface expression that is only recently being detected using high resolution surface elevation mapping methods. Many more geologically-recent tectonic features are completely buried with no present-day surface expression. In this study, airborne electromagnetics (AEM) and high resolution LiDAR datasets were acquired as part of 3D mapping of the hydrogeology in the Darling Floodplain. Neotectonic faulting and uplift has previously been described in the Broken Hill area, and along the north-western margin of the Murray Basin, along the Darling Lineament. The AEM data (acquired over an area of 7,500 sq km), validated by 100 new boreholes, reveal that an important Pleistocene aquitard (Blanchetown Clay) confining the main aquifer of interest (Calivil Formation), has an undulating surface, which is locally sharply offset. Gridding of the interpreted top surface suggests that it has been affected by local warping and faulting, as well as regional tilting due to basin subsidence or margin uplift. Some of the up-warped areas are associated with local landscape highs, suggesting relatively recent movement. Overall, the top surface of the Blanchetown Clay varies in elevation by 60m, with important implications for groundwater flow and recharge dynamics. This study also illustrates that the zone of tectonic activity can be extended southeast from the Broken Hill area to the Darling Floodplain, and that the area of seismic hazard associated with the Darling Lineament may be broader than previously anticipated.

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.

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 Robinvale - Boundary Bend 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 Groups 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.

One of the primary requirements of managing water resources sustainably is an understanding of the water balance. Groundwater recharge is a key input of any water balance model but is seldom measured, with single point measurements often applied to a catchment or region. Other times, recharge is assumed to be a percentage of annual rainfall. In the absence of sufficient direct measurements, indirect approaches for estimating recharge in data poor areas using surrogate measures have been developed. These approaches commonly use rainfall data for recharge estimation This approach may be a valuable tool in some landscapes, however in some floodplain landscape, particularly in losing reaches of river systems, it is not able to take into account understanding of local surface-groundwater interaction associated with river or lake leakage or flood-related recharge. Using these indirect approaches, estimates of recharge to the Darling Floodplain region is very low (0.1 - 7.3mm/yr; mean 1.8mm/yr), suggesting that groundwater and surface water are effectively disconnected. In contrast, measurements from a recently established bore network (40 bores over 7,500km2) recorded a 0.5 - 3.4m response to the 2010/11 floods in the shallow aquifer and a 0.2-4m response in the deeper semi-confined aquifer. This indicates a high degree of connectivity between surface water and groundwater across the floodplain during major flood events. In summary, caution needs to be exercised in using indirect estimates of recharge in floodplain environments, and holistic, long term field-based data is essential where the value of the water resource dictates.

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 GA Record report is one of a series of 4 reports undertaken by the GA Groundwater Group under the National Collaboration Framework Project Agreement with the Office of Water Science (in the Department of the Environment). The report was originally submitted to the OWS in July 2013, and subsequently reviewed by Queensland government. The Maryborough Basin in Queensland is a priority coal-bearing sedimentary basin that is not currently slated for Bioregional Assessment.

This GA Record report is one of a series of 4 reports undertaken by the GA Groundwater Group under the National Collaboration Framework Project Agreement with the Office of Water Science (in the Department of the Environment). The report was originally submitted to the OWS in July 2013, and subsequently reviewed by the SA government. The St Vincent Basin in South Australia is a priority coal-bearing sedimentary basin that is not currently slated for initial Bioregional Assessment.

The objectives of hydrogeologically mapping the Murray basin were to generate a set of maps at 1:250 000 scale to: - show the influence of groundwater on land salinisation and surface water salinity - delineate useable groundwater resources - highlight present and potential salinity hazard and - enhance community awareness and understanding of groundwater systems and processes and provide a groundwater data-base for the Murray Basin to facilitate land and water resource management decisions. The production of the Murray Basin Hydrogeological Map Series was a major coordinated Government action in the management of groundwater to combat degradation through salinisation and enable sustainable land and water use in the Murray Basin. The Hydrogeological Map Series was a collaborative effort between the various water authorities of South Australia, Victoria and New South Wales. Explaining this product in detail is an article by Evans, W.R. 1992, "The Murray Basin Hydrogeological Map Series", Water pp. 20-23.

In 2008, the Ord Irrigation Cooperative commissioned an airborne electromagnetics (AEM) survey of the ORIA Stage 1 and 2 areas to identify, quantify and understand any potential salinity risks in the current Ord irrigation area and the parts of the catchment that have been identified as potential future irrigation sites or potentially impacted by future irrigation. The project has been funded by the Australian and Western Australian governments through the National Action Plan for Salinity and Water Quality. Geoscience Australia and CSIRO were contracted to carry out the analysis and interpretation of the AEM dataset, and produce customised interpretation products. Some of the more specific questions it was hoped to address included: - Are we at risk of salinity in the Ord Catchment? - If so what areas are at the greatest risk? - Where can we target management to reduce this risk? - How can we plan future development to minimise salinity risk and maximise longevity of projects? The areas surveyed include the current Stage 1 Ord Irrigation Area, Stage 2 Irrigation Area (including Weaber and Knox Plains and Carlton Hill - Parry's Lagoon Conservation Area. The inclusion of undeveloped land in this survey is because the technology provides the opportunity to ensure any future irrigation development is guided by the best available information on soil type, aquifer quality and location and salinity risk. The information generated by this project will be publicly available and can be used for such things as: - Identifying leaky areas in the landscape that may require more concentrated management or can be designated for more suitable land use; - Where salt is stored in the landscape and at what depth, and where in the landscape it may influence plant growth; - Provide new constraints on the connectivity of aquifer systems in 3D across the ORIA and enable the construction of more realistic hydrogeological models to improve surface and groundwater management.

In 2008, the Ord Irrigation Cooperative commissioned an airborne electromagnetics (AEM) survey of the ORIA Stage 1 and 2 areas to identify, quantify and understand any potential salinity risks in the current Ord irrigation area and the parts of the catchment that have been identified as potential future irrigation sites or potentially impacted by future irrigation. The project has been funded by the Australian and Western Australian governments through the National Action Plan for Salinity and Water Quality. Geoscience Australia and CSIRO were contracted to carry out the analysis and interpretation of the AEM dataset, and produce customised interpretation products. Some of the more specific questions it was hoped to address included: - Are we at risk of salinity in the Ord Catchment? - If so what areas are at the greatest risk? - Where can we target management to reduce this risk? - How can we plan future development to minimise salinity risk and maximise longevity of projects? The areas surveyed include the current Stage 1 Ord Irrigation Area, Stage 2 Irrigation Area (including Weaber and Knox Plains and Carlton Hill - Parry's Lagoon Conservation Area. The inclusion of undeveloped land in this survey is because the technology provides the opportunity to ensure any future irrigation development is guided by the best available information on soil type, aquifer quality and location and salinity risk. The information generated by this project will be publicly available and can be used for such things as: - Identifying leaky areas in the landscape that may require more concentrated management or can be designated for more suitable land use; - Where salt is stored in the landscape and at what depth, and where in the landscape it may influence plant growth; - Provide new constraints on the connectivity of aquifer systems in 3D across the ORIA and enable the construction of more realistic hydrogeological models to improve surface and groundwater management.