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ARS Home » Plains Area » Temple, Texas » Grassland Soil and Water Research Laboratory » Research » Publications at this Location » Publication #332085
Title: Improved simulation of river water and groundwater exchange in an alluvial plain using the SWAT model

Author
item SUN, X - University Of Toulouse
item BERNARD-JANNIN, L - University Of Toulouse
item GARNEAU, C - University Of Toulouse
item VOLK, M - Helmholtz Centre For Environmental Research
item Arnold, Jeffrey
item SRINIVASAN, R - Texas A&M University
item SAUVAGE, S - University Of Toulouse
item SANCHEZ-PEREZ, J - University Of Toulouse

Submitted to: Hydrological Processes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/10/2015
Publication Date: 7/1/2016
Publication URL: https://handle.nal.usda.gov/10113/63230
Citation: Sun, X., Bernard-Jannin, L., Garneau, C., Volk, M., Arnold, J.G., Srinivasan, R., Sauvage, S., Sanchez-Perez, J.M. 2016. Improved simulation of river water and groundwater exchange in an alluvial plain using the SWAT model. Hydrological Processes. 30:187-202.

Interpretive Summary: Water flow from a river to its flood plain during flooding and groundwater flow from an aquifer to a river have significant impacts on water supply and quality. In this study, the Soil and Water Assessment Tool (SWAT) was modified to simulate water flow to and from a river, flood plain and associated aquifer. The model was validated with measured data from the Garonne River in France to ensure it could reproduce surface and groundwater flows with reasonable accuracy. The new model in SWAT, with river, flood plain and aquifer interactions, provides a decision tool for better management of flood plain lands and groundwater resources.

Technical 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.