<div>The groundwater and surface water systems associated with the Upper Darling River Floodplain (UDF) in arid northwest New South Wales form part of the Murray-Darling Basin drainage system, which hosts 40% of Australia’s agricultural production. Increasing water use demands and a changing regional climate are affecting hydrological systems, and consequently impacting the quality and quantity of water availability to communities, industries and the environment.</div><div>As part of the Australian Government’s Exploring for the Future program, the UDF project is working in collaboration with State partners to collect and integrate new data and information with existing hydrogeological knowledge. The goal is to provide analyses and products that assist water managers to increase water security in the region, with a focus on groundwater resources. </div><div>As part of this project we are assessing the occurrence of, and geological controls on, potable water resources within the Darling Alluvium (DA), which comprises unconsolidated sediments (<140 m thick) associated with the modern and paleo-Darling River. The DA’s relationship to the underlying Eromanga, Surat (Great Artesian Basin) and Murray basins is also important, particularly in the context of potential groundwater sources or sinks, and connection between low and high quality groundwater resources. At least one major fault system is known to influence groundwater flow paths and control groundwater-surface water interaction.</div><div>Data collection across the project area has commenced, with an airborne electromagnetic (AEM) survey already complete, and new geophysical, hydrochemical and hydrodynamic data being acquired. Preliminary interpretation of the new AEM data in conjunction with existing geological and hydrogeological information has already revealed the major paths and geometries of the paleo-Darling River, given important insights into potential fault controls on groundwater flow paths, and shown variation in the thickness, distribution and character of the DA, which has direct implications for groundwater–surface water connectivity.</div><div><br></div>

Long-range, active-source airborne electromagnetic (AEM) systems for near-surface imaging fall into two categories: helicopter borne or fixed-wing aircraft borne. A multitude of factors such as flying height, transmitter loop area and current, source waveforms, aerodynamic stability and data stacking times contribute to the geological resolvability of the subsurface. A comprehensive comparison of the relative merits of each system considering all such factors is difficult, but test flights over known subsurface geology with downhole induction logs are extremely useful for resolution studies. Further, given the non-linear nature of the electromagnetic inverse problem, handling transmitter-receiver geometries in fixed-wing aircraft is especially challenging. As a consequence of this nonlinearity, inspecting the closeness of downhole conductivities to deterministic inversion results is not sufficient for studying resolvability. A more comprehensive picture is provided by examining the width of the depth-wise Bayesian posterior conductivity distributions for each kind of system. For this purpose, probabilistic inversions of data must be carried out -- with acquisition over the same geology, survey noise levels must be measured, and the same prior probabilities on conductivity must be used. With both synthetic models as well as real data from over the Menindee calibration range in New South Wales, Australia, we shed new light on the matter of AEM inverse model resolution. Specifically, we use a novel Bayesian inversion scheme which handles fixed-wing geometry attributes as generic nuisance parameters during Markov chain sampling. Our findings have useful implications in AEM system selection, as well as in the design of better deterministic AEM inversion algorithms. <b>Citation:</b> Anandaroop Ray, Yusen Ley-Cooper, Ross C Brodie, Richard Taylor, Neil Symington, Negin F Moghaddam, An information theoretic Bayesian uncertainty analysis of AEM systems over Menindee Lake, Australia, Geophysical Journal International, Volume 235, Issue 2, November 2023, Pages 1888–1911, <a href="https://doi.org/10.1093/gji/ggad337">https://doi.org/10.1093/gji/ggad337</a>

<div>This package contains Airborne Electromagnetic (AEM) data from the regional survey flown over the Upper Darling Floodplain in New South Wales (NSW), Australia between March-July 2022. Approximately 25,000 line km of transient EM and magnetic data were acquired. Geoscience Australia (GA) commissioned the survey in collaboration with the New South Wales Department of Planning and Environment (NSW DPE) as part of the Australian Government’s Exploring for the Future (EFTF) program (https://www.ga.gov.au/eftf). The NSW DPE were funding contributors to the AEM data collection. GA managed all aspects of the acquisition, quality control and processing of the AEM data.</div>

<div> Airborne electromagnetic (AEM) data has been acquired at 20km line spacing across much of the Australian continent and conductivity models generated by inverting these data are freely available. Despite the wide line spacing these data are suitable for imaging the near surface and better understanding groundwater systems. Twenty-kilometre spaced AEM data acquired over the Cooper Creek floodplain using a fixed-wing towed system were inverted using deterministic and probabilistic methods. The Cooper Creek is an anabranching ephemeral river system in arid eastern central Australia. We integrated conductivity data with a range of surface and subsurface data to characterise the hydrogeology of the region and infer groundwater salinity from the shallow alluvial aquifer across a more than 14,000 km2 Cooper Creek floodplain. The conductivity data also revealed several examples of focused recharge through a river channel forming a freshwater lens within the more regional shallow saline groundwater system.</div><div>&nbsp;</div><div>This work demonstrates that regional AEM conductivity data can be a valuable tool for understanding groundwater processes at various scales with implications for how to responsibly manage water resources. This work is especially important in the Australian context where high quality borehole data is typically sparse, but high-quality geophysical and satellite data are often accessible.</div><div> </div> This presentation was given to the 8th International Airborne Electromagnetics Workshop (AEM2023) (https://www.aseg.org.au/news/aem-2023)

<div>As part of the Exploring for the Future (EFTF) programme, the groundwater team undertook an in-depth investigation into characterising surface water -- groundwater interaction in the Cooper Creek floodplain using airborne electromagnetics (AEM). This work is to be released as part of the Lake Eyre Basin detailed inventory and as an EFTF extended abstract. As part of Geoscience Australia's commitment to transparent science, the scientific workflows that underpinned a large component of this investigation are to be released as a jupyter notebook. This notebook contains python code, figures and explanatory text that the reader can use to understand how the AEM data were processed, visualised, integrated with other data and interpreted.</div>

<div><strong>Yathong, Forbes, Dubbo, and Coonabarabran Airborne Electromagnetic Survey Blocks.</strong></div><div><br></div><div>Geoscience Australia (GA), in collaboration with the Geological Survey of New South Wales (GNSW), conducted an airborne electromagnetic (AEM) survey from April to June 2023. The survey spanned from the north-eastern end of the Yathong-Ivanhoe Trough and extended across the Forbes, Dubbo, and Coonabarabran regions of New South Wales.&nbsp;A total of 15, 090-line kilometres of new AEM and magnetic geophysical data were acquired. This survey was entirely funded by&nbsp;GSNSW and GA managed acquisition, quality control, processing, modelling, and inversion of the AEM data.</div><div><br></div><div>The survey was flown by Xcalibur Aviation (Australia) Pty Ltd using a 6.25 Hz HELITEM® AEM system. The survey blocks were flown at 2500-metre nominal line spacings, with variations down to 100 metres in the Coonabarabran block. It was flown following East-West line directions. Xcalibur also processed the acquired data. This data package includes the acquisition and processing report, the final processed AEM data, and the results of the contractor's conductivity-depth estimates. The data package also contains the results and derived products from a 1D inversion by Geoscience Australia with its own inversion software.</div><div><br></div><div>The survey will be incorporated and become part of the national AusAEM airborne electromagnetic acquisition program, which aims to provide geophysical information to support investigations of the regional geology and groundwater.</div><div><br></div><div><strong>The data release package contains:</strong></div><div><br></div><div>1. A data release package <strong>summary PDF document</strong></div><div>2. The <strong>survey logistics and processing report</strong> and HELITEM® system specification files</div><div>3. <strong>Final processed point located line data</strong> in ASEG-GDF2 format for the five areas</div><div> -final processed dB/dt electromagnetic, magnetic and elevation data</div><div> -final processed B field electromagnetic, magnetic and elevation data</div><div><strong> <em>Conductivity estimates generated by Xcalibur’s inversion&nbsp;</em></strong></div><div> -point located conductivity-depth line data output from the inversion in ASEG-GDF2 format</div><div> -graphical (PDF) multiplot conductivity stacks and section profiles for each flight line</div><div> -graphical (PNG) conductivity sections for each line</div><div> -grids generated from the Xcalibur’s inversion in ER Mapper® format (layer conductivities slices, DTM, X & Z component for each of the 25 channels, time constants, TMI)</div><div>4.<strong> ESRI shape and KML</strong> (Google Earth) files for the flight lines and boundary</div><div>5<strong>. Conductivity estimates generated by Geoscience Australia's inversion&nbsp;</strong></div><div> -point located line data output from the inversion in ASEG-GDF2 format</div><div> -graphical (pdf) multiplot conductivity sections for each line</div><div> -georeferenced (PNG) conductivity sections (suitable for pseudo-3D display in a 2D GIS)</div><div> -GoCAD™ S-Grid 3D objects (suitable for various 3D packages)</div><div> -Curtain image conductivity sections in log & liner colour stretch (suitable 3D display in GA’s EarthSci)</div><div><br></div><div><strong>Directory structure</strong></div><div>├── <strong>01_Report</strong></div><div>├── <strong>02_XCalibur_delivered</strong></div><div>│&nbsp;&nbsp; ├── * survey_block_Name</div><div>│ ├── cdi</div><div>│ │ ├── sections</div><div>│ │ └── stacks</div><div>│ ├── grids</div><div>│ │ ├── cnd</div><div>│ │ ├── dtm</div><div>│ │ ├── emxbf</div><div>│ │ ├── emxdb</div><div>│ │ ├── emxff</div><div>│ │ ├── emxzbf</div><div>│ │ ├── emzdb</div><div>│ │ ├── time_constant</div><div>│ │ └── tmi</div><div>│ ├── located_data</div><div>│ ├── maps</div><div>│ └── waveform</div><div>│&nbsp;&nbsp; </div><div>├── <strong>03_Shape&kml</strong></div><div>└── <strong>04_GA_Layer_Earth_inversion</strong></div><div> ├── * survey_block_Name</div><div> ├── GA_georef_sections</div><div> │ ├── linear-stretch</div><div> │ └── log-stretch</div><div> ├── GA_Inverted_conductivity_models</div><div> ├── GA_multiplots</div><div> └── GA_sgrids</div><div> </div>

<div> A key issue for explorers in Australia is the abundant sedimentary and regolith cover obscuring access to underlying potentially prospective rocks. &nbsp;Multilayered chronostratigraphic interpretation of regional broad line-spaced (~20&nbsp;km) airborne electromagnetic (AEM) conductivity sections have led to breakthroughs in Australia’s near-surface geoscience. &nbsp;A dedicated/systematic workflow has been developed to characterise the thickness of cover and the depth to basement rocks, by delineating contact geometries, and by capturing stratigraphic units, their ages and relationships. &nbsp;Results provide a fundamental geological framework, currently covering 27% of the Australian continent, or approximately 2,085,000&nbsp;km2. &nbsp;Delivery as precompetitive data in various non-proprietary formats and on various platforms ensures that these interpretations represent an enduring and meaningful contribution to academia, government and industry.&nbsp;The outputs support resource exploration, hazard mapping, environmental management, and uncertainty attribution.&nbsp;This work encourages exploration investment, can reduce exploration risks and costs, helps expand search area whilst aiding target identification, and allows users to make well-informed decisions. Presented herein are some key findings from interpretations in potentially prospective, yet in some cases, underexplored regions from around Australia.&nbsp;</div> This abstract was submitted & presented to the 8th International Airborne Electromagnetics Workshop (AEM2023) (https://www.aseg.org.au/news/aem-2023)

As part of the $225 million Exploring for the Future programme, Geoscience Australia have undertaken an investigation into the resource potential of the Officer-Musgrave-Birrindudu region. Part of this project focusses on characterising palaeovalley groundwater resources within the West Musgrave region of Australia. This record presents a three-dimensional palaeovalley model and describes the method used in its generation. Understanding the 3D architecture of palaeovalleys is an important component of conceptualising the shallow groundwater system. In this region groundwater is the only significant water resource, and is critical for supporting local communities, industries and the environment. The data products released alongside this record are a base of gridded Cenozoic surface, a grid of the thickness of the Cenozoic and polygons defining the spatial extent of palaeovalleys. The study area encompasses the upper reaches of several large palaeovalleys. These valleys incised mostly crystalline rocks of the Musgrave Province and sedimentary rocks of the adjoining basin during the late Cretaceous. Subsequently, valleys were filled by Cenozoic-aged sediments, which now form the aquifers and aquitards of the modern-day groundwater system. Palaeovalley architecture has been shaped by a complex interplay of climatic, tectonic, and geological factors over geological time. In some cases, tectonic deformation has caused tilting or disruption of palaeovalleys with implications for groundwater flow. We modelled the base of Cenozoic surface across the project area and used this geological surface to identify palaeovalleys. The modelling process used airborne electromagnetic conductivity models, borehole data and geological outcrop as model inputs. Using these data, we interpreted the base of Cenozoic along AEM flightlines, at borehole locations and at the surface where Pre-Cenozoic geology was cropping out. These data were gridded to generate the base of Cenozoic surface. This surface was then used as the basis for interpreting palaeovalley extents. The resulting model is adequate for its purpose of better understanding the groundwater system. However, the model has considerable uncertainty due to uncertainty in the model inputs and data sparsity. The model performed much better within the centre of the project area within the Musgrave Province compared to the adjoining basins.

<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 airborne electromagnetic (AEM) dataset provides regional scale probabilistic inversion products from 141,000 line km of airborne electromagnetic (AEM) data from the AusAEM program. The two main benefits of a probabilistic inversion over a deterministic one are: - Loss of signal sensitivity at depth does not “fade to blue” by returning to the resistive deterministic reference model. - Ambiguous subsurface features become clearer when examining multiple probability percentiles. Further details are provided in the accompanying technical note. Conductivity products from the following surveys are available: - Frome 2011 - AusAEM 1 NT (2017) - AusAEM 1 QLD (2017) - AusAEM 2 Tranche 1 part (2019) - AusAEM 3 Eastern Resources Corridor (all 3 phases) - AusAEM 3 Western Resources Corridor (Kimberley, Central, Musgraves and South) The 10th, 50th and 90th and mean percentiles of log10 conductivity are provided in a variety of formats: - VTK structured grids - ASCII point clouds - ASEG-GDF2 files - GOCAD S-grids All products have been provided in the coordinate reference system (CRS) the original AEM data were provided in. The VTK unstructured grids are also provided in GDA94 geodetic longitude, latitude coordinates for ease of display in the same CRS.