Browsing by Author "Schafer, D"

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    Characterisation of the Yarragadee aquifer - Northern Perth Basin, Western Australia
    (International Association of Hydrogeologists, 2013-09-19) Schafer, D; Kern, A; Meredith, KT
    The Yarragadee aquifer in the Northern Perth Basin near Geraldton in Western Australia has been characterised using a variety of groundwater investigation techniques to enable better aquifer management for town water supply, industrial and agricultural usages. New structural contour surfaces and sand percentage maps for aquifer layers have been generated using borehole gamma and lithology data from over 200 bores (including 27 new bores). 3-D salinity distribution maps have been developed using correlations with borehole resistivity, airborne transient electromagnetic (TEM) data and borehole salinity measurements. Groundwater chemistry, stable isotopes (δ18/16O and δ2H0) and radiocarbon (14CDIC) data collected from 45 bores was used to characterise localised shallow and sub-regional groundwater-flow systems. Detailed hydrographs were prepared using data-loggers that recorded water level at hourly intervals to understand groundwater recharge dynamics. Localised shallow groundwater in the study area was found to be fresh (<1000 mg/L TDS) and relatively young (~1.5 to 7.0 ka) and in contrast, the deeper sub-regional groundwater was more saline (~ 2000 to 7000 mg/L TDS) and older (>9 ka). Recharge rates for the localised shallow groundwater were found to be much higher than sub-regional groundwater. The influence of faults on groundwater flow is demonstrated by conductivity contrasts observed across faults along TEM flight lines. Stable isotope data indicates that all groundwater is meteoric in origin and Na-Cl type waters dominate the area. Water level rises of around 10 m have been observed in upland areas since a major period of land clearing took place in the 1960s and 1970s. Post-clearing recharge rates have been estimated to be approximately double those of pre-clearing recharge rates. Significant salt input has been inferred to be incorporated during recharge of the sub-regional groundwater which occurs further inland and higher in the landscape. The localised shallow groundwater is fresher, likely because higher recharge and groundwater-ow rates dilute the salt input from rainfall. The improve understanding of recharge, groundwater flow and the source of groundwater salinity will enable the reassessment of available groundwater in the Yarragadee aquifer near Geraldton to be undertaken.
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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.