Browsing by Author "Pigois, JP"

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    A 35 ka record of groundwater recharge in south-west Australia using stable water isotopes
    (Elsevier B. V., 2020-05-15) Priestley, SC; Meredith, KT; Treble, PC; Cendón, DI; Griffiths, AD; Hollins, SE; Baker, AA; Pigois, JP
    The isotopic composition of groundwater can be a useful indicator of recharge conditions and may be used as an archive to infer past climate variability. Groundwater from two largely confined aquifers in south-west Australia, recharged at the northernmost extent of the westerly wind belt, can help constrain the palaeoclimate record in this region. We demonstrate that radiocarbon age measurements of dissolved inorganic carbon are appropriate for dating groundwater from the Leederville aquifer and Yarragadee aquifer within the Perth Basin. Variations in groundwater δ18O values with mean residence time were examined using regional and flow line data sets, which were compared. The trends in the regional groundwater data are consistent with the groundwater flow line data supporting the hypothesis that groundwater δ18O is a robust proxy for palaeo-recharge in the Perth Basin. A comparison between modern groundwater and rainfall water isotopes indicates that recharge is biased to months with high volume and/or intense rainfall from the westerly wind circulation and that this has been the case for the last 35 ka. Lower stable water isotope values are interpreted to represent recharge from higher volume and/or more intense rainfall from 35 ka through the Last Glacial Maximum period although potentially modulated by changes in recharge thresholds. The Southern Perth Basin groundwater isotopic record also indicates a trend towards higher volume and/or intense rainfall during the Mid- to Late Holocene. The long-term stable water isotope record provides an understanding of groundwater palaeo-recharge. Knowledge of recharge dynamics over long time scales can be used to improve current water sharing plans and future groundwater model predictions. © Crown Copyright 2019
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    A 35 ka record of groundwater recharge using stable water isotopes for Perth Basin in south-west Australia
    (National Centre for Groundwater Research And Training, & Australian Chapter International Association Of Hydrogeologists, 2019-11-25) Priestley, SC; Meredith, KT; Treble, PC; Cendón, DI; Griffiths, AD; Hollins, SE; Baker, AA; Pigois, JP
    Objectives: As most large groundwater basins can contain ‘old’ groundwater where extraction exceeds groundwater recharge, knowledge of the past conditions and timing under which groundwater was recharged is needed to sustainably manage groundwater resources. Moreover, the isotopic composition of groundwater can be a useful indicator of rainfall isotope compositions and help to determine the drivers and impacts of rainfall and climate change. Applying isotopic tools to groundwater contained in regional aquifer systems can provide low-resolution information on recharge intensity, recharge source and past climatic conditions for the region. Design and Methodology: A dataset containing groundwater ages (14CDIC) and stable isotopes of water (δ18O and δ2H) from two regional groundwater systems within the Perth Basin, the Leederville Formation and Yarragadee Formation, were compiled to create a low-resolution palaeo-archive of groundwater recharge. Original data and results: The trends in stable isotopes of water over time in the regional groundwater data are consistent with groundwater flow line data supporting our hypothesis that groundwater stable isotopes are a proxy for palaeo-recharge. A comparison between modern groundwater and rainfall water isotopes indicates that recharge is biased to months with high volume and/or intense rainfall from the westerly wind circulation and that this has been the case for the last 35 ka. Lower stable water isotope values are interpreted to represent recharge from higher volume and/or more intense rainfall from 35 ka through the Last Glacial Maximum period although potentially modulated by changes in recharge thresholds. Conclusion: The groundwater isotope record is interpreted to be a low-resolution archive of recharge driven by changes in the relative intensity of past rainfall and recharge thresholds. This long-term stable isotopic recharge record provides a greater understanding of groundwater palaeo-recharge, and the connection between recharge and climate in the past. © The Authors
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    Groundwater isotopic signals in the Perth Basin: links to recharge variations and climatic conditions for Western Australia
    (International Association of Hydrogeologists, 2013-09-20) Meredith, KT; Cendón, DI; Hollins, SE; Pigois, JP; Schafer, D; Koomberi, H
    Perth Basin aquifers contain large volumes of groundwater that support ecosystems and an ever increasing demand for irrigation and potable water supply for Western Australia. Applying isotopic tools to groundwaters contained in regional aquifer systems can provide information on recharge intensity, source and past climatic conditions for the region. Large regional aquifer systems, contained within the Perth Basin, were investigated in this study to provide information on climate interaction over the past ~30 ka. The development of regional scale databases containing groundwater age and isotopic records are not common in Australia and are generally more site specific. Therefore, this database from the Perth Basin provides us with a unique opportunity to study and interpret a low-resolution palaeo-archive of groundwater recharge signals for the West of Australia. Groundwater ages (14CDIC) and Stable Water isotope (SWI: δ18/16O and δ2H) data are presented for the Perth Basin. We compare this data with the cyclone impacted recharge areas of the Pilbara region in the far north of Western Australia. We have gathered all known age and SWI data from the Perth Basin and have focused more specifically on the central (near Gingin) and northern (near Geraldton) Perth Basin. Groundwater ages for the Perth Basin span the radiocarbon dating period from 0 to ~35 ka. SWI results plot to the left of the Global and Perth Meteoric Water Lines but when compared with groundwaters from the Pilbara region, are much more enriched indicating different recharge events replenishing the Perth Basin aquifers compared to the north of Western Australia. Cyclic patterns in SWI over the past 35 ka are observed but generally all data plot around -20.0 ± 5.0 % for δ2H (n = >200). Interestingly, the similarity in values over the past 35 ka is not what is observed in other regional aquifers throughout the world such as in Europe and Africa. Groundwater isotopic signatures are compared with higher resolution archives such as rainfall records to interpret the observed groundwater signal. The isotopic signals contained in these extensive groundwater systems may provide information on past climates and more importantly provide understanding on how climate change is likely to influence recharge of these vast groundwater resources.
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    Groundwater δ18O record of paleorecharge and climate for the last 35ka in south-west Western Australia
    (International Union for Quaternary Research (INQUA), 2019-07-30) Priestley, SC; Meredith, KT; Treble, PC; Cendón, DI; Griffiths, AD; Hollins, SE; Baker, AA; Pigois, JP; Schafer, D
    The isotopic composition of groundwater can be a useful indicator of rainfall isotope compositions and help to determine the drivers and impacts of rainfall and climate change. Additionally, as most large groundwater basins can contain ‘old’ groundwater where extraction exceeds groundwater recharge, knowledge of the past conditions and timing under which groundwater was recharged is needed to sustainably manage groundwater resources. Applying isotopic tools to groundwater contained in regional aquifer systems can provide low-resolution information on recharge intensity, recharge source and past climatic conditions for the region. Furthermore, an understanding of how groundwater recharge and climate have been connected in the past can be used to inform climate adaptation strategies for sustaining groundwater resources during climate change. Groundwater from south-west Western Australia located at the northernmost extent of the westerly wind belt can help constrain the drivers and impacts of rainfall and climate change in this region. Large regional groundwater systems contained within the Perth Basin in south-west Western Australia were used in this study to provide information on groundwater recharge and climate over the past 35,000 years. This dataset containing groundwater ages (14CDIC) and stable isotopes of water (δ18O and δ2H) from two regional groundwater systems within the Perth Basin provides a unique opportunity to produce a low-resolution palaeo-archive of groundwater recharge, and hence interpret rainfall and climate change, for south-west Western Australia. The trends in stable isotopes of water over time in the regional groundwater data are consistent with the groundwater flow line data supporting our hypothesis that groundwater stable isotopes are a proxy for palaeo-recharge. The Southern Perth Basin groundwater isotope record is interpreted to be a low resolution archive of recharge driven by changes in the relative intensity of past rainfall, moisture source from changes in the position of the westerlies and recharge thresholds. This long-term stable isotopic recharge record provides a greater understanding of groundwater palaeo-recharge, and the connection between recharge and climate in the past.
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    Using 14C and 3H to delineate a recharge 'window' into the Perth Basin aquifers, North Gnanagara groundwater system, Western Australia
    (Elsevier B. V., 2012-01-01) Meredith, KT; Cendón, DI; Pigois, JP; Hollins, SE; Jacobsen, GE
    The Gnangara Mound and the underlying Perth Basin aquifers are the largest source of groundwater for the southwest of Australia, supplying between 35 and 50% of Perth's potable water (2009–2010). However, declining health of wetlands on the Mound coupled with the reduction in groundwater levels from increased irrigation demands and drier climatic conditions means this resource is experiencing increased pressures. The northern Gnangara is an area where the Yarragadee aquifer occurs at shallow depths (~ 50 m) and is in direct contact with the superficial aquifer, suggesting the possibility of direct recharge into a generally confined aquifer. Environmental isotopes (14C and 3H) and hydrochemical modelling were used to assess the presence of a recharge ‘window’ as well as understand the groundwater residence time within different aquifers. Forty-nine groundwater samples were collected from depths ranging from 11 to 311 m below ground surface. The isotopic variation observed in the superficial aquifer was found to be controlled by the different lithologies present, i.e. quartz-rich Bassendean Sand and carbonate-rich sediments of the Ascot Formation. Rainfall recharge into the Bassendean Sand inherits its dissolved inorganic carbon from the soil CO2. Organic matter throughout the soil profile is degraded by oxidation leading to anoxic/acidic groundwater, which if in contact with the Ascot Formation leads to enhanced dissolution of carbonates. Hydrochemical mass balance modelling showed that carbonate dissolution could contribute 1–2 mmol kg− 1 of carbon to groundwaters recharged through the Ascot Formation. The corrected groundwater residence times of the Yarragadee aquifer in the northern part of the study area ranged from 23 to 35 ka, while waters in the southeastern corner ranged from sub-modern to 2 ka. Groundwater ages increase with distance radiating from the recharge ‘window’. This study delineates a recharge ‘window’ into the commonly presumed confined aquifers of the Perth Basin, highlighting the need for appropriate sustainable management. Crown Copyright © 2011 Published by Elsevier B.V. All rights reserved