ORCID Profile
0000-0002-9483-6321
Current Organisations
College of Physicians and Surgeons Pakistan
,
CSIRO
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Publisher: Society of Exploration Geophysicists
Date: 09-2021
Abstract: A hydrogeologic conceptualization is critical to understand, manage, protect, and sustain groundwater resources, particularly in regions where data are sparse and accessibility is difficult. We used airborne electromagnetics (AEM), shallow seismic reflection and refraction, and downhole nuclear magnetic resonance (NMR) logs to improve our understanding of an arid groundwater system influenced by palaeovalleys. We found that there is a limited connection between the palaeovalley and fractured bedrock aquifers because they are separated by a spatially variable layer of saprolite, which is the layer of chemically altered rock on top of the fractured bedrock. The AEM data provided an estimate of the top of the saprolite but failed to effectively image the bottom. In contrast, the seismic data provided an estimate of the bottom of the saprolite but failed to image the top. This geophysical combination of electrical and seismic data allowed us to map saprolite thickness in detail along a 1.7 km long transect that runs perpendicular the main trunk of a well-defined palaeovalley. These data indicate that the palaeovalley is lined with a heterogeneous layer of saprolite (approximately 3–120 m thick) that is thickest near its edges. Despite the observed variability, only a small percentage of the fractured bedrock aquifer (8%–17%) appears to be in contact with the palaeovalley aquifer. Furthermore, the lack of an elastic boundary at the top of saprolite suggests that the porosity of the saprolite is similar to the palaeovalley sediments — an observation that is supported by the downhole NMR-derived water contents. The electrical change at the top of saprolite is caused by a combination of a decrease in total dissolved solids of the groundwater in the saprolite and a change in pore structure associated weathering in situ versus transported weathered materials. The presence of saprolite, which commonly behaves as an aquitard, may limit the groundwater exchange between the palaeovalley and bedrock aquifers, with implications for the regional groundwater resource potential.
Publisher: Elsevier BV
Date: 2021
Publisher: Elsevier BV
Date: 04-2021
Publisher: Informa UK Limited
Date: 2018
Publisher: Informa UK Limited
Date: 12-2015
Publisher: Informa UK Limited
Date: 12-2015
Publisher: CSIRO
Date: 2018
Publisher: Society of Exploration Geophysicists
Date: 12-2014
Abstract: The Aboriginal population of the Aṉangu Pitjantjatjara Yankunytjatjara (APY) lands in South Australia is dependent on groundwater for nearly all water needs. In that region, placement of wells in productive aquifers of appropriate water quality is challenging because of lack of hydrologic data and variable aquifer properties. It is desirable to have an improved ability to identify and evaluate groundwater resources in this remote region with cost-effective methods that make minimal impact on the environment. A project supported by the Society of Exploration Geophysicists program Geoscientists Without Borders tested a combined geophysical approach with airborne and ground-based data sets to locate a potential aquifer, confirm water content, and estimate the subsurface extent of the water-bearing zone. This hydrogeophysical approach was an effective means for exploration and evaluation of groundwater resources in APY lands generally, and it characterized a specific aquifer as a case study.
Publisher: CSIRO
Date: 2020
DOI: 10.25919/TG90-3X77
Publisher: CSIRO
Date: 2013
Publisher: CSIRO
Date: 2012
Publisher: CSIRO Water for a Healthy Country Flagship
Date: 2013
Publisher: CSIRO
Date: 2011
Publisher: CSIRO
Date: 2018
Location: Australia
Location: United Kingdom of Great Britain and Northern Ireland
Location: Pakistan
No related grants have been discovered for Kevin Cahill.