|Title:||Improved simulation of river water and groundwater exchange in an alluvial plain using the SWAT model |
|Authors:||Sun, X., L. Bernard-Jannin, C. Garneau, M. Volk, J.G. Arnold, R. Srinivasan, S. Sauvage and J.M. Sánchez-Pérez |
|Journal:||Hydrological Processes |
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|Broad Application Category:||hydrologic only |
|Primary Application Category:||groundwater and/or soil water impacts |
|Secondary Application Category:||hydrologic assessment |
|Watershed Description:||13,370 km^2 Garonne River, which is located in southwest France and is the third longest river in France.
Additional information: The Garonne River hydrology is influenced by Mediterranean climate and melting snow from the mountainous areas. The typical alluvial plain starts from the middle section of the Garonne River. It contains between 4 and 7 m coarse deposits (quaternary sand and gravel) eroded from the Pyrenees Mountains during the past glacial periods that overlie the impermeable layer of molassic substratum (Lancaster, 2005). The Verdun gauging station is located at about 4 km upstream of the study site-Monbéqui. It is the nearest gauging station to the study site at the Garonne River. At the Verdun gauging station, the Garonne has a watershed size of 13 730 km² and an annual average flow of about 200 m³·s-1. The monthly average flow ranges from about 75 m³·s-1 in August to about 340 m³·s-1 in May (Banque Hydro, http://www.hydro.eaufrance.fr/). The greatest discharges occur twice a year, in the spring as a result of snow melt and in late autumn following intense rainfalls (Sánchez-Pérez et al., 2003c). Previous studies in the Garonne river basin have shown that the river/groundwater interface play an important role at the reach scale, both in the retention of nitrogen and phosphorous (Vervier et al., 2009) and in controlling aquifer water quality (Iribar et al., 2008). The study area is characterised by high nitrate pollution caused by agriculture (Jégo et al., 2008, 2012).
The study site is located in a meander of the alluvial plain of the Garonne River (Monbéqui) and the width of the floodplain in the area is about 4 km. The mean annual precipitation is about 690 mm in this area. The alluvium thickness ranges from 2.5 to 7.5 m, with an arithmetic mean of 5.7m (Sánchez-Pérez et al., 2003c). The groundwater table varies from 2 to 5 m in low water periods and rise rapidly up to soil profile during floods (Weng et al., 2003). The first 50 - 200 m of the riverbank is covered by riparian forest and poplar plantations, surrounded by agricultural land. Several terraces exist in this area, generated by sediment deposition and washing out by flooding events. Artificial dykes have been constructed in the region to protect the agricultural land. |
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|Keywords:||SWAT model, Landscape Unit, water exchange, floodplain, Garonne River |