In Australia’s semi-arid and arid interior, groundwater resources provide water supply security for agriculture and community consumptive use and are critical for underpinning economic development. . The Southern Stuart Corridor Project in central Australia, is an inter-disciplinary study which aims to better characterise regional groundwater systems and identify the location, quantity and quality of new groundwater resources. The main aims of the project are(1) to de-risk investment in development of a potential agricultural precinct in the Western Davenport Basin, and expansion of horticulture in Ti-Tree Basin, (2) to identify future water supplies for Alice Springs and Tennant Creek, and (3) for regional water supplies for mineral resource development.The project is funded by Geoscience Australia (GA) as part of the Exploring for the Future (EFTF) Programme. The project integrates airborne electromagnetic (AEM), ground geophysics (ground magnetic resonance (GMR) and borehole geophysics (Induction, gamma and nuclear Magnetic Resonance (NMR)) with drilling and pump testing; hydrochemistry and geochronology; and geomorphic, geological, hydrogeological and structural mapping and modelling. Advancements in temporal remote sensing technologies for surface hydrology, vegetation and landscape mapping are also used to facilitate the identification of recharge and discharge zones and groundwater-dependent vegetation.This paper reports on initial AEM inversion results for the Alice Springs, Ti-Tree Basin, Western Davenport and Tennant Creek areas and the use of a machine learning approach for rapid geological and hydrogeological interpretation of the AEM data. These machine learning approaches have the potential to significantly reduce interpretation time and facilitate the rapid delivery of project results.
The presence of Neogene fault systems can have a significant impact on hydraulic connectivity of aquifers, juxtaposing otherwise disconnected aquifers, enhancing recharge and/or discharge or acting as barriers to flow and consequently compartmentalising groundwater resources. Previously, regional airborne electromagnetics (AEM) transects allied with groundwater investigations have pointed to the potential for localised compartmentalisation of the Daly River Basin groundwater systems. However, existing data is sparse, and equivocal.In this context, the main aim of the Daly River Basin Project is to determine if compartmentalisation of the aquifers is a significant factor and thus should be explicitly considered in groundwater modelling and water allocation planning. The objectives of the project main goals of the project are to: (1) map Neogene faults through the use of airborne electromagnetic (AEM) and morphotectonic mapping, and (2) assess the permeability and transmissivity of mapped fault zones and their role in potential groundwater system compartmentalisation. Data acquisition includes 3325 line-kilometres of new AEM and airborne magnetics, ground (ground magnetic resonance (GMR)), and borehole geophysics, drilling, groundwater sampling and hydrochemical analysis, geomorphic and morphotectonics mapping. Hydrogeophysical, geomorphic and hydrogeological data will also be used to better understand groundwater-surface water connectivity and the potential for managed aquifer recharge schemes to replenish extracted groundwater resources. The outcomes of this project will inform decisions on water allocations and underpin effective and efficient groundwater use. This paper specifically reports on the ability of AEM and morphotectonics mapping to identify Neogene fault systems in the Daly River Basin.
In the Howards East Aquifer (HEA) in Darwin’s Rural District, groundwater resources in a dolomitic and karstic aquifer system provide important water security for Darwin and a large horticultural industry. Previously (2011), a widely-spaced (550m) regional airborne electromagnetics (AEM) survey in this area mapped conductivity anomalies that were interpreted as potential zones of seawater intrusion (SWI) coincident with major fault zones. Subsequent drilling confirmed elevated groundwater salinities in some bores marginal to the main aquifer. It was recommended that more detailed investigations be undertaken to better define the SWI risk.The Howards East Project is an inter-disciplinary study which focussed on delineating and characterising the present SWI interface and potential future hazards from sea water intrusion. The Project is funded by Geoscience Australia (GA) as part of the Exploring for the Future (EFTF) Programme. New data acquisition includes 2,096 line-kilometres of 100 m line-spaced AEM and airborne magnetics data, ground magnetic resonance (GMR), and borehole nuclear magnetic resonance (NMR) data, drilling and pump testing; and hydrochemistry. The main aims of this study are to: (1) delineate potential SWI zones; (2) quantify the porosity, permeability and transmissivity of the Koolpinyah-Coomalie Dolomite aquifer along potential fault zones (coincident with magnetic anomalies) and (3) identify other structural and/or sedimentological preferential flow paths or barriers to ingress.This paper reports on: (1) initial AEM inversion results and spatio-temporal changes in groundwater quality arising since acquisition of previous AEM in 2011, and (2) the interplay between the sea water intrusion interface and structural/sedimentological flow paths/barriers.
Neogene fault systems are increasingly recognised as an important control on hydraulic connectivity in some of Australia’s energy rich basins. However, accurate delineation of these faults systems is challenging and expensive. In this context, the main objective of the Exploring for the Future (EFTF) Surat-Galilee Basin (Phase 1) Project is to test novel methods for more cost-effective mapping of Neogene fault systems in the Coal Seam Gas (CSG) basins of eastern Australia. Methods assessed in this project include morphotectonic mapping using temporal remote sensing data and high-resolution terrain mapping techniques, airborne electromagnetics (AEM), and the use of earthquake databases to inform active tectonic and geomechanical analysis.The project is funded by Geoscience Australia (GA) as part of its EFTF Programme, and is focussed on exemplar areas in the Surat and Galilee Basins where Neogene fault activity has been interpreted on high-resolution 2D and 3D seismic reflection surveys. This paper reports on the use of airborne electromagnetics (AEM) for detecting near-surface (<50-150m) Neogene faults in both basins. Approximately 4,500 line km of AEM data were acquired in a number of smaller acquisition blocks where Neogene faults had previously been identified. The AEM inversion results are compared with interpretation of seismic reflection data, morphotectonic mapping, and other hydrogeological and tectonic/geomechanical data. The utility of AEM to map the broader hydrogeological system in these basins, including groundwater-surface water connectivity (springs and rivers), is also assessed.
The Australian Government has recently provided Aus$100.5M to Geoscience Australia over 4 years (2016-2020) to manage the Exploring for the Future (EFTF) programme designed to increase investment in minerals, energy and groundwater resources, primarily in Northern Australia. The programme includes Aus$30.8M for groundwater-specific investigations, recognizing that there are major gaps in our knowledge of Northern Australia’s groundwater systems and resources. The groundwater component of the EFTF programme is focused on addressing these knowledge gaps, with the aim of underpinning future opportunities for irrigated agriculture, mineral and energy development, and community water supply. The groundwater programme will include identification and assessment of potential groundwater resources and water banking options in priority regional areas, while also analyzing the salinity risk (including seawater intrusion).To rapidly map, characterise and assess regional groundwater systems and resources in the data-poor ‘frontier’ areas of Northern Australia, a multi-physics, inter-disciplinary approach has been developed. The programme involves the initial use of temporal remote sensing ‘data cube’ technologies for surface hydrology and landscape mapping, and acquisition of airborne electromagnetic (AEM) and Ground Magnetic Resonance (GMR) datasets. This provides a framework for targeted investigations including passive seismic, microgravity and GPR; borehole geophysics (Induction, gamma and Nuclear Magnetic Resonance (NMR)); drilling and pump testing; hydrochemistry and geochronology (water, landscapes and geology); as well as soils, regolith and basin/bedrock geological, hydrogeological and structural mapping and modelling.This methodology has enabled rapid identification and assessment of potential groundwater resources, salinity and seawater intrusion hazards, and groundwater dependent ecosystems in several priority regions.
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