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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
Author(s) -
Peyrard D.,
Sauvage S.,
Vervier P.,
SanchezPerez J. M.,
Quintard M.
Publication year - 2008
Publication title -
hydrological processes
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.222
H-Index - 161
eISSN - 1099-1085
pISSN - 0885-6087
DOI - 10.1002/hyp.7035
Subject(s) - piezometer , aquifer , floodplain , hydrology (agriculture) , geology , meander (mathematics) , alluvium , groundwater , flood myth , groundwater flow , hydraulics , aquifer properties , environmental science , geomorphology , geotechnical engineering , groundwater recharge , ecology , philosophy , geometry , mathematics , theology , biology , engineering , aerospace engineering
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 km 2 ) 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 km 2 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. Copyright © 2008 John Wiley & Sons, Ltd.