Sources and mean transit times of stream water in an intermittent river system: the upper Wimmera River, southeast Australia

[摘要] Determining the mean transit times (MTTs) and water sources in catchments atdifferent flow conditions helps better understand river functioning, andmanage river health and water resources. Despite being common in a range ofenvironments, the MTTs and water sources in intermittent streams are muchless well understood compared to perennial streams. Major ion geochemistry,stable isotopes, 14 C, and 3 H were used in this study to identifywater sources and MTTs of the periodically intermittent upper Wimmera Riverfrom southeast Australia at different flow conditions, including zero-flowperiods. The disconnected pool waters during the zero-flow period in thesummer months of 2019 had 3 H activities of 0.64 to 3.29 TU. These andthe variations in total dissolved solids and stable isotopes imply thatthese pools contained a mixture of older groundwater and younger streamwater impacted by evaporation. 3 H activities during the high-flowperiod in July 2019 were 1.85 to 3.00 TU, yielding MTTs of up to 17 years.The 3 H activities at moderate and low-flow conditions in September andNovember 2019 ranged from 2.26 to 2.88 TU, implying MTTs of 1.6 to 7.8 years. Regional groundwater near the Wimmera River had 3 H activities of  0.02 to 0.45 TU and 14 C activities of 57 to 103 pMC, and was not recharged by the river at high flows. The Wimmera River and other intermittent streams in southeast Australia are sustained by youngercatchment waters from relatively small near-river stores than comparableperennial streams, which have older deeper regional groundwater inputs. Thisresults in these intermittent streams being more susceptible to short-termchanges in climate and necessitates the protection of near-river corridorsto maintain the health of the riverine systems.

[学科分类] 妇产科学