Hydrologic-Response simulations for the R-5 catchment with a comprehensive physics-based model

For approximately 20 years, there has been a concerted effort, by several different research groups, to simulate observed rainfall‐runoff events from the well‐known R‐5 catchment, located near Chickasha, Oklahoma. These prior simulation efforts, with relatively simple models of Horton‐type overland flow, have not been entirely successful, as the streamflow generation process for the R‐5 catchment, as now recognized, may not be totally dominated by the Horton mechanism. In the effort reported here, a new fully coupled comprehensive physics‐based hydrologic‐response model, the Integrated Hydrology Model (InHM), is tested for two R‐5 rainfall‐runoff events. The InHM simulations in this study clearly show, in a hypothesis‐testing mode, that both the Horton and Dunne overland flow mechanisms can be important streamflow generation processes for R‐5 events. The InHM simulations reported here also suggest that accurate accounting of soil water storage can be as important as exhaustive characterization of spatial variations in near‐surface permeability.