δ2H and δ18O used to link flooding to groundwater recharge along the Darling River
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Date
2015-07-09
Journal Title
Journal ISSN
Volume Title
Publisher
University of New South Wales and Australian Nuclear Science and Technology Organisation
Abstract
Understanding where water goes during floods, how much is lost to evaporation, and how river waters exchange with groundwater are key areas underpinning science-based water resource management. The question of whether groundwater recharge, past and present, occurs diffusely via infiltration of rainfall, via river bank leakage or sporadically during flood events is important in evaluating groundwater sustainability. Stable isotopes of water, δ2H and δ180, are valuable tools in answering this question.
Along the Barwon/Darling River, stable water isotope time series from both rainfall and river samples are proving useful in understanding recharge processes. Evaporative enrichment of infiltrating rainwater is expected to lead to groundwater having a lower d-excess than local rainwater, which can be cited as evidence of diffuse recharge. Generally floodwaters, by virtue of their origin in high rainfall events, are characterised by being more depleted in δ2H and δ180 than average flow or average rainfall. However this is highly variable both spatially and between events. Data from various sites along the Barwon/Darling River from Mungindi to Burtundy indicate evaporative enrichment of floodwater with time. At two locations where groundwater recharge has been studied in detail, Glen Villa (Meredith et al, in prep) and Menindee (Brodie et al, in prep), groundwater isotopes have been found to match the isotopic composition of flood waters during a 10 year time series from the Darling River. This relationship between flow rate and isotope composition provides evidence of flooding being the primary recharge mechanism in the lower Darling River.
Description
Keywords
Floods, Ground water, Groundwater recharge, Rivers, New South Wales, Australia
Citation
Hughes, C. E., Meredith K., Brodie R. S., Hollins S. E., Cendón D. I. ((2015). δ2H and δ18O used to link flooding to groundwater recharge along the Darling River. Presentation to the 13th Australasian Environment Isotope Conference (AEIC), Sydney, 8-10th July 2015.