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Improved Representation of Groundwater–Surface Water Interactions Using SWAT+gwflow and Modifications to the gwflow Module
Yimer, E.A.; Bailey, R.T.; Leda Piepers, L.; Nossent, J.; Van Griensven, A. (2023). Improved Representation of Groundwater–Surface Water Interactions Using SWAT+gwflow and Modifications to the gwflow Module. Water 15(18): 3249. https://dx.doi.org/10.3390/w15183249
In: Water. MDPI: Basel. e-ISSN 2073-4441
Peer reviewed article  
Available in  Authors 
    Waterbouwkundig Laboratorium: Open Repository 392560 [ OWA ]
Keywords
    Development tools and software
    Literature and desktop study
    Numerical modelling
    Water management > Hydrology > Physically based models
    Water management > Risk > Low water strategies
    Water management > Water quantity > Water system knowledge
    Belgium, Dijle R. [Marine Regions]
Author keywords
    ground–surface water interaction; groundwater–soil interaction; geohydrological modeling; inter-model comparison; SWAT+; gwflow
Project Top | Authors 
  • PhD - Predicting Impact Climate Change on Drought in the Scheldt River Basin
Authors  Top 
  • Yimer, E.A.
  • Bailey, R.T.
  • Leda Piepers, L.
  • Nossent, J.
  • Van Griensven, A.
Abstract
    Recent water availability and scarcity problems have highlighted the importance of surface– groundwater interactions. Thus, groundwater models are coupled with surface water models. However, this solution is complex, needing code modifications and long computation times. Recently, a new groundwater module (gwflow) was developed directly inside the SWAT code to tackle these issues. This research assesses gwflow’s capabilities in representing surface–groundwater system inter actions in the Dijle catchment (892.54 km2), a groundwater-driven watershed in Belgium. Additional developments were made in SWAT+gwflow to represent the interaction between the groundwater and soil (gwsoil). The model was calibrated for monthly mean streamflow at the catchment outlet (1983 to 1996) and validated for two periods (validation 1: 1975 to 1982 and validation 2: 1997 to 2002). It was found that the SWAT+gwflow model is better at representing the total flow (NSE of 0.6) than the standalone SWAT+ (NSE of 0.4). This was confirmed during two validation periods where the standalone model scored unsatisfactory monthly NSE (0.6 and 0.1), while the new model’s NSE was 0.7 and 0.5. Additionally, the SWAT+gwflow model simulations better depict the groundwater via baseflow and attain proper water balance values. Thus, in a highly groundwater-driven catchment, the simplified representation of groundwater systems by the standalone SWAT+ model has pitfalls. In addition, the modification made to the gwflow module (gwsoil) improved the model’s performance, which, without such adjustment, overestimates the streamflow via saturation excess flow. When including the gwsoil mechanism, thereby providing a more accurate representation of water storage and movement, groundwater is transferred to the soil profile, increasing the overall soil water content and thereby increasing lateral flow. This novel modification can also have implications for other distributed hydrological models to consider such exchanges in their modeling scheme.
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