Improved simulation of river water and groundwater exchange in an alluvial plain using the SWAT model |
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| Authors: | X Sun L Bernard‐Jannin C Garneau M Volk J G Arnold R Srinivasan S Sauvage J M Sánchez‐Pérez |
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| Institution: | 1. INPT, UPS;2. Laboratoire Ecologie Fonctionnelle et Environnement (EcoLab), University of Toulouse, Castanet Tolosan, Cedex, France;3. EcoLab, CNRS, Castanet Tolosan, Cedex, France;4. Department of Computational Landscape Ecology, UFZ Helmholtz Centre for Environmental Research, Leipzig, Germany;5. Grassland, Soil & Water Research Laboratory, USDA‐ARS, Temple, TX, USA;6. Spatial Science Laboratory in the Department of Ecosystem Science and Management, Texas A&M University, College Station, TX, USA |
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| Abstract: | Hydrological interaction between surface and subsurface water systems has a significant impact on water quality, ecosystems and biogeochemistry cycling of both systems. Distributed models have been developed to simulate this function, but they require detailed spatial inputs and extensive computation time. The soil and water assessment tool (SWAT) model is a semi‐distributed model that has been successfully applied around the world. However, it has not been able to simulate the two‐way exchanges between surface water and groundwater. In this study, the SWAT‐landscape unit (LU) model – based on a catena method that routes flow across three LUs (the divide, the hillslope and the valley) – was modified and applied in the floodplain of the Garonne River. The modified model was called SWAT‐LUD. Darcy's equation was applied to simulate groundwater flow. The algorithm for surface water‐level simulation during flooding periods was modified, and the influence of flooding on groundwater levels was added to the model. Chloride was chosen as a conservative tracer to test simulated water exchanges. The simulated water exchange quantity from SWAT‐LUD was compared with the output of a two‐dimensional distributed model, surface–subsurface water exchange model. The results showed that simulated groundwater levels in the LU adjoining the river matched the observed data very well. Additionally, SWAT‐LUD model was able to reflect the actual water exchange between the river and the aquifer. It showed that river water discharge has a significant influence on the surface–groundwater exchanges. The main water flow direction in the river/groundwater interface was from groundwater to river; water that flowed in this direction accounted for 65% of the total exchanged water volume. The water mixing occurs mainly during high hydraulic periods. Flooded water was important for the surface–subsurface water exchange process; it accounted for 69% of total water that flowed from the river to the aquifer. The new module also provides the option of simulating pollution transfer occurring at the river/groundwater interface at the catchment scale. Copyright © 2015 John Wiley & Sons, Ltd. |
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| Keywords: | SWAT model landscape unit water exchange floodplain Garonne River |
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