Assessing the response of subgrid hydrologic processes to atmospheric forcing with a hydrologic model system

Abstract

An integrated hydrologic model system (HMS) was developed and used to study hydrologic processes and systems responding to various climatic forcings. The modeling system operates with a time step of minutes to days to facilitate coupling with a mesoscale meteorological model (MM). The major emphasis with HMS is on the interaction among climate, land surface, surface water, and ground water. HMS utilizes spatially detailed information on climate, soil type, land use, digital elevation, and hydrologic parameters. The focus of this study was to improve the presentation of rainfall-runoff partitioning by implementing subgrid-scale spatial variability in precipitation and hydraulic conductivity. The practical application of HMS is demonstrated in the hydrologic simulation of a major sub-basin of the Susquehanna River Basin in Pennsylvania. Questions concerning data preparation, model calibration, and subgrid-scale spatial variability are addressed in the hydrologic simulation. The simulation without considering subgrid-scale spatial variability using both observed and MM5-simulated precipitations significantly underestimates the streamflow. The simulated and observed streamflows compare well in the simulation with consideration of the subgrid-scale spatial variability in hydraulic conductivity using observed precipitation. With the implementation of subgrid-scale spatial variability in precipitation and hydraulic conductivity, the simulated results using MM5-simulated precipitation were improved in terms of fit between the simulated and observed streamflows.