Improved simulation of river water and groundwater exchange in an alluvial plain using the SWAT model

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.

Spatio-temporal analysis of factors controlling nitrate dynamics and potential denitrification hot spots and hot moments in groundwater of an alluvial floodplain

“…In addition, modelling studies have shown the importance of river-aquifer exchanges for groundwater composition Peyrard et al, 2008;Sun et al, 2015) and the impact of agricultural practices on nitrate leaching into the shallow aquifer (Jégo et al, 2012).…”

“…Floodplain environments are characterised by strong surface water-groundwater interactions that are important for aquifer water composition (Amoros et al, 2002;Sun et al, 2015). Nitrate contamination in shallow aquifers can therefore be mitigated by the dilution resulting from mixing with river water containing low nitrate concentrations (Pinay et al, 1998;Baillieux et al, 2014).…”

Simulation of Hydrology and Nutrient Transport in the Hetao Irrigation District, Inner Mongolia, China

“…In recent years, intensive human activities such as irrigation have begun to be considered, and several studies have applied SWAT to model lowland and irrigation areas. For example, Volk and coworkers [14,15] identified land use and land management scenarios that would reduce the total nitrogen concentration in Upper Ems River basin, which is a predominantly flat landscape with sandy soils. Schmalz and coworkers [16] assessed the nutrient transport and dominant hydrologic processes in lowland catchments, concluding that surface runoff and shallow groundwater strongly influence the hydrology and nutrient dynamics, especially at the adjacent floodplains.…”

Impact of river water levels on the simulation of stream–aquifer exchanges over the Upper Rhine alluvial aquifer (France/Germany)

“…Regional alluvial aquifers are characterized by strong interactions between groundwater and surface water (Winter 1999;Woessner 2000;Sanford 2002;Sophocleous 2002;Thierion et al 2012;Sun et al 2016). Groundwater feeds rivers during dry periods, while rivers contribute to the recharge of aquifers under conditions of high water level that are associated with large precipitation or snowmelt.…”

“…Stream-aquifer exchanges can be represented either through a physically based approach considering the hyporheic zone as a continuum interface, or by using a conductance model (Kollet and Maxwell 2006;Rushton 2007;Flipo et al 2014). A conductance model computes the flux as the product between a transfer coefficient, depending on the riverbed characteristics, with the hydraulic head gradient between the river and the aquifer-for example, Sun et al (2016) used the Soil and Water Assessment Tool (SWAT) semi-distributed model to study river water and groundwater exchange in an alluvial plain by using a new module based on conductance. In contrast, Kollet and Maxwell (2006) used an integrated surface-water/groundwater flow model that directly couples the governing equations of overland flow and variably saturated groundwater flow, thereby avoiding the need to define a transfer coefficient.…”