Browsing by Author "Wohling, DL"

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    Hydrochemical variations of groundwater and spring discharge of the western Great Artesian Basin
    (National Centre for Groundwater Research And Training, & Australian Chapter International Association Of Hydrogeologists, 2019-11-25) Priestley, SC; Shand, P; Love, AJ; Crossey, LJ; Karlstrom, KE; Keppel, MN; Wohling, DL; Rousseau-Guetin, P
    Objectives: The chemical variations of groundwater provide important clues to the geochemical processes responsible for water quality and evolution across the western GAB. The objective of this study was to examine the hydrochemical variations of groundwater and spring discharge along the entire western GAB expanding on several key results from a 4-year project studying the hydrochemistry of the western GAB presented in Love et al. (2013) and Love et al. (2013). Design and Methodology: The dataset comprises data collected during the Allocating Water and Maintaining Springs in the Great Artesian Basin project funded by the National Water Commission (Love, et al., 2013, Love, et al., 2013), with additional data from a government database, as well as, a number of published government reports and journal articles. Electrical balances and comparison of monitoring and duplicate data was undertaken to ensure the collated data were representative and accurate. Original data and results: The regional hydrochemical trends generally support the modern interpreted flow paths, indicating that these generally represent the long-term flow paths. However, the chemical variations along the flow paths in the western GAB are complex with their composition being a function of several controlling processes, including recharge location, evapotranspiration and water-rock interactions. These processes being spatially variable cause groundwaters to be generally of Na-HCO3 type east of Lake Eyre and Na-Cl-(-SO4) type when originating from the western margin. Springs within the western GAB springs appear to be discharging water predominantly from the main GAB aquifer. However, springs on the Peake and Denison Inlier are either completely or partially fractured rock source and there are several springs discharging water with a component from a source other than the main GAB aquifer. Conclusion: The source, evolution and several key geochemical processes responsible for water quality were identified through this study. However, work is still needed to fully characterise all water-rock interactions and geochemical processes occurring within the main GAB aquifer. © The Authors
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    Use of U-isotopes in exploring groundwater flow and inter-aquifer leakage in the south-western margin of the Great Artesian Basin and Arckaringa Basin, central Australia
    (Elsevier, 2018-11) Priestley, SC; Payne, TE; Harrison, JJ; Post, VEA; Shand, P; Love, AJ; Wohling, DL
    The distribution of uranium isotopes (238U and 234U) in groundwaters of the south-western margin of the Great Artesian Basin (GAB), Australia, and underlying Arckaringa Basin were examined using groundwater samples and a sequential extraction of aquifer sediments. Rock weathering, the geochemical environment and α-recoil of daughter products control the 238U and 234U isotope distributions giving rise to large spatial variations. Generally, the shallowest aquifer (J aquifer) contains groundwater with higher 238U activity concentrations and 234U/238U activity ratios close to secular equilibrium. However, the source input of uranium is spatially variable as intermittent recharge from ephemeral rivers passes through rocks that have already undergone extensive weathering and contain low 238U activity concentrations. Other locations in the J aquifer that receive little or no recharge contain higher 238U activity concentrations because uranium from localised uranium-rich rocks have been leached into solution and the geochemical environment allows the uranium to be kept in solution. The geochemical conditions of the deeper aquifers generally result in lower 238U activity concentrations in the groundwater accompanied by higher 234U/238U activity ratios. The sequential extraction of aquifer sediments showed that α-recoil of 234U from the solid mineral phases into the groundwater, rather than dissolution of, or exchange with the groundwater accessible minerals in the aquifer, caused enrichment of groundwater 234U/238U activity ratios in the Boorthanna Formation. Decay of 238U in uranium-rich coatings on J aquifer sediments caused resistant phase 234U/238U activity ratio enrichment. The groundwater 234U/238U activity ratio is dependent on groundwater residence time or flow rate, depending on the flow path trajectory. Thus, uranium isotope variations confirmed earlier groundwater flow interpretations based on other tracers; however, spatial heterogeneity, and the lack of clear regional correlations, made it difficult to identify recharge and inter-aquifer leakage. Crown Copyright © 2018 Published by Elsevier Ltd