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A coupled vertically integrated model to describe lateral exchanges between surface and subsurface in large alluvial floodplains with a fully penetrating river

Peyrard, Dimitri and Sauvage, Sabine and Vervier, Philippe and Sanchez-Pérez, José-Miguel and Quintard, Michel A coupled vertically integrated model to describe lateral exchanges between surface and subsurface in large alluvial floodplains with a fully penetrating river. (2008) Hydrological Processes, vol. 22 (n° 21). pp. 4257-4273. ISSN 0885-6087

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Official URL: http://dx.doi.org/10.1002/hyp.7035

Abstract

This paper presents a vertically averaged model for studying water and solute exchanges between a large river and its adjacent alluvial aquifer. The hydraulic model couples horizontal 2D Saint Venant equations for river flow and a 2D Dupuit equation for aquifer flow. The dynamic coupling between river and aquifer is provided by continuity of fluxes and water level elevation between the two domains. Equations are solved simultaneously by linking the two hydrological system matrices in a single global matrix in order to ensure the continuity conditions between river and aquifer and to accurately model two-way coupling between these two domains. The model is applied to a large reach (about 36 km2) of the Garonne River (south-western France) and its floodplain, including an instrumented site in a meander. Simulated hydraulic heads are compared with experimental measurements on the Garonne River and aquifer in the floodplain. Model verification includes comparisons for one point sampling date (27 piezometers, 30 March 2000) and for hydraulic heads variations measured continuously over 5 months (5 piezometers, 1 January to 1 June 2000). The model accurately reproduces the strong hydraulic connections between the Garonne River and its aquifer, which are confirmed by the simultaneous variation of the water level in the river and in piezometers located near the river bank. The simulations also confirmed that the model is able to reproduce groundwater flow dynamics during flood events. Given these results, the hydraulic model was coupled with a solute-transport component, based on advection-dispersion equations, to investigate the theoretical dynamics of a conservative tracer over 5 years throughout the 36 km2 reach studied. Meanders were shown to favour exchanges between river and aquifer, and although the tracer was diluted in the river, the contamination moved downstream from the injection plots and affected both river banks.

Item Type:Article
Additional Information:Thanks to Wiley editor. The definitive version is available at http://dx.doi.org/10.1002/hyp.7035
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:French research institutions > Centre National de la Recherche Scientifique - CNRS
Université de Toulouse > Institut National Polytechnique de Toulouse - INPT
Université de Toulouse > Université Paul Sabatier-Toulouse III - UPS
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Deposited By: Nadia Kelmouss
Deposited On:24 May 2012 11:44

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