airborne electromagnetics
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<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> </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)
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<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>
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<div>Abstract to present results so far from Upper Darling floodplain EFTF module at Australasian Groundwater Conference (AGC) in Perth</div> This presentation was given at the 2022 Australasian Groundwater Conference 21-23 November (https://www.aig.org.au/events/australasian-groundwater-conference-2022/)
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<div> The High Quality Geophysical Analysis (HiQGA) package is a framework for geophysical forward modelling, Bayesian inference, and deterministic imaging. A primary focus of the code is production inversion of airborne electromagnetic (AEM) data from a variety of acquisition systems. Adding custom AEM systems is simple using a modern computational idea known as multiple dispatch. For probabilistic spatial inference from geophysical data, only a misfit function needs to be supplied to the inference engine. For deterministic inversion, a linearisation of the forward operator (i.e., Jacobian) is also required. For fixed wing geometry nuisances, probabilistic inversion is carried out using Hierarchical Bayesian inference, and deterministic inversion for these nuisances is done using BFGS optimisation. The code is natively parallel, and inversions from a full day of production AEM acquisition can be inverted on thousands of CPUs within a few hours. This allows for quick assessment of the quality of the acquisition, and provides geological interpreters preliminary subsurface images together with associated uncertainties. These images are then used to create subsurface models for a range of applications from natural resource exploration to its management and conservation.</div><div> </div> This abstract was submitted to/presented at the 8th International Airborne Electromagnetics Workshop (AEM 2023) (https://www.aseg.org.au/news/aem-2023).
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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.
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<div>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 GA Record is a technical report detailing the science undertaken as part of the Musgrave Palaeovalley groundwater project. The project aimed to improve understanding of the region's palaeovalley architecture, groundwater quality, and overall hydrogeology to support responsible water resource management. The most significant work undertaken included three-dimensional modelling of palaeovalley architecture, groundwater characterisation using hydrochemistry, groundwater model conceptualisation and a detailed review of local groundwater around remote communities in the region. This work will underpin responsible groundwater management into the future.</div>
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<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 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>
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This data release includes SPECTREM® AEM data from eleven airborne electromagnetic (AEM) surveys in Western Australia, originally flown for Anglo American Exploration (Australia) Pty Ltd in 2009, 2011 and 2012 and a survey flown in South Australia for Metex Nickel Pty Ltd in 2012. Data for each survey are open-file and were downloaded from the Government of Western Australia, Department of Mines, Industry Regulation and Safety and Government of South Australia, Department of Energy and Mining. AEM data were re-processed and re-inverted to produce conductivity models and a suit of derived datasets using Geoscience Australia Layered-Earth-Inversion as a single standard processing and inversion method to improve continuity and data quality. This data release includes visualisation products including conductivity sections, grids, s-grids, georeferenced sections and earth-sci sections.
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<div>In response to the acquisition of national-scale airborne electromagnetic surveys and the development of a national depth estimates database, a new workflow has been established to interpret airborne electromagnetic conductivity sections. This workflow allows for high quantities of high quality interpretation-specific metadata to be attributed to each interpretation line or point. The conductivity sections are interpreted in 2D space, and are registered in 3D space using code developed at Geoscience Australia. This code also verifies stratigraphic unit information against the national Australian Stratigraphic Units Database, and extracts interpretation geometry and geological data, such as depth estimates compiled in the Estimates of Geological and Geophysical Surfaces database. Interpretations made using this workflow are spatially consistent and contain large amounts of useful stratigraphic unit information. These interpretations are made freely-accessible as 1) text files and 3D objects through an electronic catalogue, 2) as point data through a point database accessible via a data portal, and 3) available for 3D visualisation and interrogation through a 3D data portal. These precompetitive data support the construction of national 3D geological architecture models, including cover and basement surface models, and resource prospectivity models. These models are in turn used to inform academia, industry and governments on decision-making, land use, environmental management, hazard mapping, and resource exploration.</div>
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<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>