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| Titel |
Examining the spatial and temporal variation of groundwater inflows to a valley-to-floodplain river using ²²²Rn, geochemistry and river discharge: the Ovens River, southeast Australia |
| VerfasserIn |
M. C. L. Yu, I. Cartwright, J. L. Braden, S. T. de Bree |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 17, no. 12 ; Nr. 17, no. 12 (2013-12-06), S.4907-4924 |
| Datensatznummer |
250086022
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| Publikation (Nr.) |
 copernicus.org/hess-17-4907-2013.pdf |
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| Zusammenfassung |
| Radon (222Rn) and major ion geochemistry were used to define and
quantify the catchment-scale groundwater-surface water interactions along
the Ovens River in the southeast Murray–Darling Basin, Victoria, Australia,
between September 2009 and October 2011. The Ovens River is characterized by
the transition from a single channel within a mountain valley in the upper
catchment to a multi-channel meandering river on flat alluvial plains in the
lower catchment. Overall, the Ovens River is dominated by gaining reaches,
receiving groundwater from both alluvial and basement aquifers. The
distribution of gaining and losing reaches is governed by catchment
morphology and lithology. In the upper catchment, rapid groundwater recharge
through the permeable aquifers increases the water table. The rising water
table, referred to as hydraulic loading, increases the hydraulic head
gradient toward the river and hence causes high baseflow to the river during
wet (high flow) periods. In the lower catchment, lower rainfall and
finer-gained sediments reduce the magnitude and variability of hydraulic
gradient between the aquifer and the river, producing lower but more
constant groundwater inflows. The water table in the lower reaches has a
shallow gradient, and small changes in river height or groundwater level can
result in fluctuating gaining and losing behaviour. The middle catchment
represents a transition in river-aquifer interactions from the upper to the
lower catchment. High baseflow in some parts of the middle and lower
catchments is caused by groundwater flowing over basement highs. Mass
balance calculations based on 222Rn activities indicate that
groundwater inflows are 2 to 17% of total flow with higher inflows
occurring during high flow periods. In comparison to 222Rn activities,
estimates of groundwater inflows from Cl concentrations are higher by up to
2000% in the upper and middle catchment but lower by 50 to 100% in
the lower catchment. The high baseflow estimates using Cl concentrations may
be due to the lack of sufficient difference between groundwater and surface
water Cl concentrations. Both hydrograph separation and differential flow
gauging yield far higher baseflow fluxes than 222Rn activities and Cl
concentrations, probably indicating the input of other sources to the river
in additional to regional groundwater, such as bank return flows. |
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