Calibration guide for watershed modeling with distributed groundwater modeling: Application for the SWAT+ model

Authors: ABBAS, SALEM - Colorado State University; BAILEY, RYAN - Colorado State University; ALMAHAWIS, MOHAMMED - Colorado State University; WHITE, JEREMY - Intera, Inc; Arnold, Jeffrey; White, Michael

Submitted to: Hydrological Sciences Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/24/2024
Publication Date: 8/15/2024
Citation: Abbas, S.A., Bailey, R.T., Almahawis, M.K., White, J.T., Arnold, J.G., White, M.J. 2024. Calibration guide for watershed modeling with distributed groundwater modeling: Application for the SWAT+ model. Hydrological Sciences Journal. https://doi.org/10.1080/02626667.2024.2393414.
DOI: https://doi.org/10.1080/02626667.2024.2393414

Interpretive Summary: Coupled surface-subsurface hydrologic models are important tools for the prediction of water movement in the environment and how that is impacted by human and natural disturbances. These model must be calibrated to be useful and that is a difficult process. In this research SWAT+ is coupled with gwflow and the system is evaluated in 6 hydrologically different basins in the US. Model behavior and response to parameter adjustments are used to develop a system of heuristics which function as a guidance protocol for model calibration.

Technical Abstract: A standard calibration protocol for coupled surface-subsurface hydrologic models can facilitate model applications to watersheds worldwide. Using a protocol, specific issues in the temporal distribution of streamflow can be targeted for improvement by modifying identified parameter values (channel, soil, landscape, aquifer). The protocol can improve the model's capacity to enhance accuracy of simulating peak flows, baseflows, and other crucial characteristics with minimal user effort. In this study, we introduce a calibration protocol (simple guide for parameter value changes) for the integrated surface-subsurface hydrologic model SWAT+, using the new distributed groundwater module gwflow. To create a general protocol, calibration guidelines are provided for six watershed types, using representative watersheds across the United States. Each watershed type has a unique hydrologic feature: tile drainage with high baseflow and low peak flow (Winnebago River), tile drainage with low peak flow (Boone River), groundwater discharge with low baseflow (Nanticoke River), irrigation-related groundwater pumping with low peak flow (Cache River), and snowmelt-dominant runoff (Cache la Poudre River and Arkansas Headwaters River) with variations in initial simulated streamflow patterns, such as high peak flow, leftward discharge shift, low peak flow, and high baseflow. Each model was tested based against measured monthly streamflow and annual groundwater head, using automated calibration and sensitivity analysis, to establish the protocol. This protocol can be applied not only to SWAT+, but also to other coupled surface-subsurface models with integrated land surface, soil, aquifer, and surface water processes and feedback.