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Assessment of the quantitative and qualitative buffer function of an alluvial wetland: hydrological modelling of a large floodplain (Garonne River, France)

Weng, P. and Sanchez-Pérez, José-Miguel and Sauvage, Sabine and Vervier, Philippe and Giraud, F. Assessment of the quantitative and qualitative buffer function of an alluvial wetland: hydrological modelling of a large floodplain (Garonne River, France). (2003) Hydrological Processes, vol. 1 (n° 12). pp.2375-2392. ISSN 0885-6087

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Official URL: http://dx.doi.org/10.1002/hyp.1248

Abstract

For 2 years, water flow-patterns in the Garonne floodplain of south-western France were studied in the field and through hydrodynamic modelling (MARTHE Hydrodynamic Software developed by BRGM). Water flow-paths and the transport of dissolved elements between river and aquifer have been investigated and modelled. In order to quantify the buffer function of the alluvial floodplain, we focused our work on the effect of a major flood on the water flowdirection, and on nitrate transport. Thus, we showed that the effect of a large flood in the river was rapidly lost with increasing distance from the river. During the observation period, a hydrologically active strip only 300 m wide on either side of the riverbed played a buffering role in absorbing the flood crest. It was also found that meanders favour the exchange between river and alluvial aquifer, shown by the creation of bypasses between the upstream and downstream parts of meanders. This, in turn, contributes to a dilution of nitrates in the phreatic aquifer, which here has higher nitrate content than the surface water; such dilution may result in an overestimation of the denitrification process in the wooded riverbanks. The coupling of chemical measurements—especially of chlorides and nitrate—with modelling of the dissolved-element transport allows us to establish the water balance for the riparian wetland, and to separate the effect of dilution and denitrification on nitrate concentration. This indicated the existence of areas in the riparian wetlands where denitrification is particularly strong, leading to reductions in nitrate concentrations of 10 to 30 mg/l NO3 during the flood.

Item Type:Article
Additional Information:Thanks to John Wiley & Sons, Ltd editor. The definitive version is available at http://www3.interscience.wiley.com/journal/104551814/issue. The original PDF of the article can be found at Wiley InterScience website: http://www3.interscience.wiley.com/cgi-bin/fulltext/104551815/PDFSTART
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:French research institutions > Centre National de la Recherche Scientifique - CNRS
Université de Toulouse > Université Paul Sabatier-Toulouse III - UPS
French research institutions > Bureau de recherches géologiques et minières - BRGM
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Deposited By: Florence Amor
Deposited On:02 Jun 2010 09:50

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