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- Title
On the contribution of groundwater to streamflow in laterite catchments of the Darling Range, south‐western Australia.
- Authors
Grigg, Andrew Haden; Kinal, Joe
- Abstract
In deeply weathered laterite catchments of the Darling Range in south‐western Australia, the direct contribution (i.e., discharge) of permanent groundwater to streamflow has long been considered as minor. Instead, downslope shallow throughflow was thought to dominate, generating more than 90% of streamflow. We used a chemical hydrograph separation approach to estimate annual groundwater discharge for three catchments over periods of up to 39 years, and found that direct groundwater contributions to streamflow were far more variable across catchments and through time than has previously been acknowledged. The estimated proportion of annual streamflow sourced directly from groundwater ranged from 0 to 93% and was related linearly to the size of the groundwater discharge area in the catchment valley floor. In contrast, contributions from shallow sources including shallow throughflow varied primarily and linearly with annual rainfall. However, the response to rainfall was "amplified" in a predictable way by the size of the groundwater discharge area, consistent with the variable source area concept. We derived a functional relationship between catchment annual rainfall‐runoff ratio and groundwater discharge area and successfully applied this to a further four catchments, inferring that the results were broadly applicable across the Darling Range. The implications for an improved understanding of streamflow generating processes in the study region, and for laterite catchments generally, are discussed.
- Subjects
AUSTRALIA; STREAMFLOW; LATERITE; GROUNDWATER; STREAM salinity; WATERSHEDS
- Publication
Hydrological Processes, 2020, Vol 34, Issue 25, p5070
- ISSN
0885-6087
- Publication type
Article
- DOI
10.1002/hyp.13928