An Inter-comparison of Two Coupled Hydrogeological Models

Benchmarking coupled surface-subsurface flow models becomes more important as they are increasingly used for operational purposes (e.g. in water management) and long-term analysis (e.g. in climate change research). For this reason we inter-compare the hydrogeological models HydroGeoSphere and OpenGeoSys and present results with emphasis on the parametrization of the surface-soil water coupling fluxes and the numerical soil grid resolution. The numerical models simulate surface and subsurface water interactions by coupling a diffusive waver shallow water equation for 2D flow on the surface with a Richards’ equation for 1D / 3D flow in the variably saturated subsurface. The governing flow equations are spatially discretized with finite element and finite volume methods. As a main difference, HydroGeoSphere assembles the governing partial differential equations monolithically (fully implicit coupling), while OpenGeoSys performs a coupling iteration in a partitioned matrix assembly. The software inter-comparison is currently based on classic lab and field experiments with relevance to overland and stream flow generation in natural catchments: Comparative examples include the field study by Warrick (1971) on infiltration with ponding, the lab experiments by Smith and Woolhiser (1971) on Horton overland flow, and the field study at the Borden site by Abdul and Gillham (1985) on the effect of the capillary fringe on stream flow (Dunne flow) generation.