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Title: Catchment-scale groundwater-flow and recharge paradox revealed from base flow analysis during the Australian Millennium Drought (Mt Lofty Ranges, South Australia)
Authors: Anderson, TT
Bestland, EA
Wallis, I
Kretschmer, PJC
Soloninka, L
Banks, EW
Werner, AD
Cendón, DI
Pichler, MM
Guan, H
Keywords: Watersheds
Groundwater recharge
Ground water
Water resources
South Australia
Issue Date: 30-Jan-2021
Publisher: Springer Nature Limited
Citation: Anderson, T. T., Bestland, E. A., Wallis, I., Kretschmer, P. J. C., Soloninka, L., Banks, E. W., Werner, A. D., Cendón, D. I., Pichler, M. M., & Guan, H. (2021). Catchment-scale groundwater-flow and recharge paradox revealed from base flow analysis during the Australian Millennium Drought (Mt Lofty Ranges, South Australia). Hydrogeology Journal, 29(3), 963-983. doi:10.1007/s10040-020-02281-0
Abstract: Catchment-scale recharge and water balance estimates are commonly made for the purposes of water resource management. Few catchments have had these estimates ground-truthed. One confounding aspect is that runoff and soil-water inputs commonly occur throughout the year; however, in climates with strong dry seasons, base flow can be directly sampled. In an experimental catchment in the Mt. Lofty Ranges of South Australia, run-of-stream hydrochemical parameters were monitored. In this Mediterranean climate during the Millennium Drought (2001–2009), the stream was reduced to disconnected groundwater-fed pools. Two groundwater types were identified: (1) high-salinity type from meta-shale bedrock with thick, clayey regolith and (2) low-salinity type from meta-sandstone bedrock with sandy regolith. End-member mixing using silica and chloride concentrations and robust 87Sr/86Sr ratios reveal an apparent groundwater-flow paradox as follows. According to chloride mass balance and spatial distribution of hydrogeological units, the low-salinity groundwater type has seven times more recharge than the high-salinity type. Over the 28-year record, low-salinity groundwater contributed 25% of stream water, whereas high-salinity groundwater contributed 2–5%. During the drought year, however, annual stream flow from the high-salinity groundwater contributed 50%, whereas low-salinity groundwater contributed 18%. High-salinity groundwater dominated dry-season base flow during all years. The paradox can be resolved as follows: The meta-sandstone terrane drains quickly following wet-season recharge and therefore contributes little to dry-season base flow. Conversely, the meta-shale terrane drains slowly and therefore provides stream flow during dry seasons and drought years. © 2021 Springer-Verlag GmbH Germany, part of Springer Nature.
ISSN: 1435-0157
Appears in Collections:Journal Articles

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