A 35 ka record of groundwater recharge in south-west Australia using stable water isotopes

Stacey C Priestley; Karina T Meredith; Pauline C Treble; Dioni I Cendón; Alan D Griffiths; Suzanne E Hollins; Andy Baker; Jon-Philippe Pigois

doi:10.1016/j.scitotenv.2019.135105

A 35 ka record of groundwater recharge in south-west Australia using stable water isotopes

Sci Total Environ. 2020 May 15:717:135105. doi: 10.1016/j.scitotenv.2019.135105. Epub 2019 Nov 21.

Authors

Stacey C Priestley¹, Karina T Meredith², Pauline C Treble², Dioni I Cendón², Alan D Griffiths³, Suzanne E Hollins³, Andy Baker⁴, Jon-Philippe Pigois⁵

Affiliations

¹ ANSTO, Lucas Heights NSW, Australia. Electronic address: stacey.priestley@ansto.gov.au.
² ANSTO, Lucas Heights NSW, Australia; Connected Waters Initiative Research Centre, UNSW Sydney, Kensington NSW, Australia.
³ ANSTO, Lucas Heights NSW, Australia.
⁴ Connected Waters Initiative Research Centre, UNSW Sydney, Kensington NSW, Australia.
⁵ Department of Water, Perth WA, Australia.

PMID: 31839292
DOI: 10.1016/j.scitotenv.2019.135105

Abstract

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.

Keywords: Groundwater dating; Isotopes; Palaeo-recharge; Palaeoclimate; South-west Australia.