EVALUATION OF BASIN-SCALE HYDROLOGIC RESPONSE TO A MULTI-STORM SIMULATION

Abstract

Understanding how hydrologic systems of large river basins respond to atmospheric forcing is crucial to regional climate and hydrology studies. A hydrologic model system (HMS) was linked to a regional climate model (RCM) to model a series of storm events passing over the Susquehanna River Basin and to simulate various hydrologic processes in soil hydrology, land surface hydrology, and ground-water hydrology using observed and modeled storm events. The RCM is designed to link to general circulation models and to provide fine spatiotemporal output for hydrologic and other applications. The hydrologic models were calibrated to the observed data (e.g. soil moisture and streamflow) at the basin and subbasin-scales. The HMS-simulated hydrologic response to observed precipitation from a six-storm sequence compares well to the observed. The subgrid-scale spatial variability in precipitation and hydraulic conductivity is included in HMS simulations with RCM-modeled precipitation. Nested 108-36-12km RCM domains are used for the multi-storm simulation. The 12km RCM-modeled precipitation is then downscaled to a 1km hydrologic grid resolution for HMS simulation. Simulations of the six-storm sequence by the RCM produce precipitation fields that appear realistic in general, but that diverge in detail from observed precipitation in both time and space. HMS proves to be sensitive to these details, so the simulated streamflow does not accurately reproduce observed streamflow. The results suggest potential value in improving on the current versions of RCM and HMS for regional climate and hydrology system modeling.