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| Titel |
Exchange between a river and groundwater, assessed with hydrochemical data |
| VerfasserIn |
E. Hoehn, A. Scholtis |
| 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 ; 15, no. 3 ; Nr. 15, no. 3 (2011-03-21), S.983-988 |
| Datensatznummer |
250012694
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| Publikation (Nr.) |
 copernicus.org/hess-15-983-2011.pdf |
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| Zusammenfassung |
| We describe the chemical composition of groundwater from an alluvial
granular aquifer in a valley fill flood plain (River Thur Valley). The river
flows along this valley and is mostly downwelling on its way, indirectly
through an unsaturated zone in the upstream part, and directly through the
water-saturated bed in the downstream part. River Thur has been channelized
with barriers for more than a century. In 1992, the authorities started to
restore a section of River Thur with riverbed enlargements. The land use in
the flood plain and the seasonal and climatic conditions (e.g., hot dry
summer 2003) result in alterations of the natural geochemical composition of
the river water. This groundwater is partly to mainly recharged by bank
filtration. Several wells exist near the river that draw groundwater for
drinking. In some of these wells, the groundwater has a very short residence
time in the subsurface of days to weeks. Bed enlargements and other
operations for an enhancement of the exchange of water between the river and
groundwater increase the contamination risk of the nearby wells. During bank
filtration, the groundwater changes gradually its composition, with
increasing distance from the river and with depth in the aquifer. From
today's changes of the water quality during riverbank filtration, we tried
to extrapolate to the groundwater quality that may arise from future river
restorations. Today the groundwater body consists of a mixture of
groundwater from the seepage of precipitation and from riverbank filtration.
The main difference between river water and groundwater results from the
microbial activity in riverbed and bank materials. This activity leads to a
consumption of O2 and to a higher partial pressure of CO2 in the
groundwater. Criteria for the distinction of different groundwater
compositions are the distance of a well from the river and the subsurface
residence time of the groundwater to reach this well. |
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