SWAT Literature Database for Peer-Reviewed Journal Articles

Title:A new physically-based spatially-distributed groundwater flow module for SWAT+ 
Authors:Bailey, R.T., K. Bieger, J.G. Arnold and D.D. Bosch 
Volume (Issue):7(4) 
Article ID:75 
URL (non-DOI journals): 
Broad Application Category:hydrologic only 
Primary Application Category:groundwater and/or soil water impacts/processes 
Secondary Application Category:model and/or data interface 
Watershed Description:327 km^2 Little River Experimental, a tributary of the Upper Suwannee River located in south-central Georgia, U.S. 
Calibration Summary: 
Validation Summary: 
General Comments:The authors do not explicitly identify the modified version of SWAT+ as SWAT+gwflow in the text, but they later use that model name in the following study so that name is used here: Yimer, E.A., R.T. Bailey, B.V. Schaeybroeck, H.V.D. Vyver, L. Villani, J. Nossent and A. van Griensven. 2023. Regional evaluation of groundwater-surface water interactions using a coupled geohydrological model (SWAT+gwflow). Journal of Hydrology: Regional Studies. 50: 101532. DOI: 10.3390/w15183249. 
Abstract:Watershed models are used worldwide to assist with water and nutrient management under conditions of changing climate, land use, and population. Of these models, the Soil and Water Assessment Tool (SWAT) and SWAT+ are the most widely used, although their performance in groundwater-driven watersheds can sometimes be poor due to a simplistic representation of groundwater processes. The purpose of this paper is to introduce a new physically-based spatially-distributed groundwater flow module called gwflow for the SWAT+ watershed model. The module is embedded in the SWAT+ modeling code and is intended to replace the current SWAT+ aquifer module. The model accounts for recharge from SWAT+ Hydrologic Response Units (HRUs), lateral flow within the aquifer, Evapotranspiration (ET) from shallow groundwater, groundwater pumping, groundwater–surface water interactions through the streambed, and saturation excess flow. Groundwater head and groundwater storage are solved throughout the watershed domain using a water balance equation for each grid cell. The modified SWAT+ modeling code is applied to the Little River Experimental Watershed (LREW) (327 km2) in southern Georgia, USA for demonstration purposes. Using the gwflow module for the LREW increased run-time by 20% compared to the original SWAT+ modeling code. Results from an uncalibrated model are compared against streamflow discharge and groundwater head time series. Although further calibration is required if the LREW model is to be used for scenario analysis, results highlight the capabilities of the new SWAT+ code to simulate both land surface and subsurface hydrological processes and represent the watershed-wide water balance. Using the modified SWAT+ model can provide physically realistic groundwater flow gradients, fluxes, and interactions with streams for modeling studies that assess water supply and conservation practices. This paper also serves as a tutorial on modeling groundwater flow for general watershed modelers. 
Keywords:SWAT+; groundwater; modeling; groundwater–surface water interactions