ORCID Profile
0000-0002-0804-7781
Current Organisation
Deakin University
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Publisher: Copernicus GmbH
Date: 09-09-2022
DOI: 10.5194/HESS-26-4497-2022
Abstract: Abstract. Determining the mean transit times (MTTs) and water sources in catchments at different flow conditions helps better understand river functioning, and manage river health and water resources. Despite being common in a range of environments, the MTTs and water sources in intermittent streams are much less well understood compared to perennial streams. Major ion geochemistry, stable isotopes, 14C, and 3H were used in this study to identify water sources and MTTs of the periodically intermittent upper Wimmera River from southeast Australia at different flow conditions, including zero-flow periods. The disconnected pool waters during the zero-flow period in the summer months of 2019 had 3H activities of 0.64 to 3.29 TU. These and the variations in total dissolved solids and stable isotopes imply that these pools contained a mixture of older groundwater and younger stream water impacted by evaporation. 3H activities during the high-flow period in July 2019 were 1.85 to 3.00 TU, yielding MTTs of up to 17 years. The 3H activities at moderate and low-flow conditions in September and November 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 3H activities of 0.02 to 0.45 TU and 14C 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 younger catchment waters from relatively small near-river stores than comparable perennial streams, which have older deeper regional groundwater inputs. This results in these intermittent streams being more susceptible to short-term changes in climate and necessitates the protection of near-river corridors to maintain the health of the riverine systems.
Publisher: Copernicus GmbH
Date: 31-01-2022
DOI: 10.5194/HESS-2022-18
Abstract: Abstract. Determining the mean transit times (MTTs) and water sources in catchments at different flow conditions helps better understand river functioning, manage riverine system health and water resources, and discern the responses to climate change and global water stress. Despite being common in a range of environments, understanding of MTTs and variable water sources in intermittent streams remain incomplete compared to perennial streams. Major ion geochemistry, stable isotopes, 14C, 3H and were used in this study to identify water sources and MTTs of a periodically-intermittent river from southeast Australia at different flow conditions, including zero-flow periods. The disconnected pool waters during the zero-flow period in the summer months of 2019 had 3H activities of 0.64 to 3.29 TU. These and the variations in total dissolved solids and stable isotopes imply that these pools contained a mixture of groundwater and younger evaporated stream water. 3H activities during the high-flow period in July 2019 were 1.85 to 3.00 TU, yielding MTTs of up to 17 years. The 3H activities at moderate and low-flow conditions in September and November 2019 ranged from 2.26 to 2.88 TU, implying MTTs of 1.6 to 7.8 years. Regional groundwater near the Wimmera River has 3H activities of 0.02 to 0.45 TU and 14C activities of 57 to 103 pMC and is not recharged by the river at high flows. The Wimmera River and other intermittent streams in southeast Australia are sustained by smaller volumes of younger catchment waters than comparable perennials streams, indicating that near-river stores have significant impacts on maintaining streamflow during low-flow periods than older deeper regional groundwater. These smaller reservoirs result in the intermittent streams being more susceptible to changes of climate and streamflow and necessitate protection of near-river corridors to maintain the health of the riverine systems.
Publisher: Copernicus GmbH
Date: 27-03-2022
DOI: 10.5194/EGUSPHERE-EGU22-3350
Abstract: & & Streams may be connected to a large store of water, such as regional groundwater, and/or sustained by smaller near-river stores (such as riparian groundwater). Documenting the sources of water in streams is important for understanding catchment water balances, protecting riverine environments from pollution, and predicting the efforts of near-river pumping. Additionally, streams connected to large water stores will be buffered against the impacts of short-term climate variability (such as droughts that last a few years). Many techniques that document groundwater-stream water interaction allow the location and fluxes of baseflow to be determined but do not constrain from where in the catchment the baseflow is derived. The mean transit time (MTT) represents the time taken for water to migrate from where it is recharged in the catchment to where it discharges into the stream. Estimating the MTTs of stream water allows the volume (V) of the water store that sustains streamflow (Q) to be estimated (V=Q& #215 MTT). This study compares the water stores sustaining streamflow in contrasting rivers in southeast Australia based on tritium MTTs calculated using lumped parameter models. Perennial streams (Oven, Yarra, Latrobe, and Gellibrand Catchments) have long MTTs (4 to 179 years) that are higher at low streamflows. By contrast, the MTTs of similar size intermittent streams (Deep Creek, Wimmera, and Gatum Catchments) range from & to 35 years (and are mostly less than 20 years). The estimated volumes of the catchment contributing to streamflow are 3 to 5 orders of magnitude smaller than those in comparable perennial streams. These differences reflect the limited connection between the intermittent streams and the deeper regional groundwater system compared with the perennial streams, especially at low flows. Rather, intermittent streams may be sustained mainly by smaller younger reservoirs in the riparian zone. These intermittent streams will be more susceptible to short-term climate variabilities and changes to flow regimes may have significant impacts on water supplies and the health of the riverine system. Intermittent streams are globally distributed in a range of environments, especially in semi-arid areas. Climate change and water stress have resulted in many perennial streams gradually becoming intermittent and this trend is expected to increase. In southeast Australia, around 30% of catchments have not recovered following multiple drought years between 1996 and 2010 (the Millennium Drought), and streamflow has kept declining. The increased intermittence fundamentally changes the catchment water balance, specifically making regional groundwater less important, and increases the reliance of these streams on more vulnerable small young water stores.& &
Publisher: Copernicus GmbH
Date: 31-01-2022
No related grants have been discovered for Zibo Zhou.