The Hydrologic Model System (HMS), a physically based distributed model, was used to simulate the soil moisture variation during a storm event in the Upper West Branch, a subbasin of the Susquehanna River Basin. The model was calibrated by comparing the simulated temporal daily variation in soil moisture with field data. Data from the Mahantango Watershed within the Susquehanna River Basin were used to drive the HMS for the temporal simulation of soil moisture as a function of soil texture, vegetation, and topography. Spatially distributed data sets with a resolution of 1 km were prepared for the simulations and used to examine the soil moisture variation as caused by the spatial variability in soil texture, vegetation type, and topography. The Pennsylvania State-National Center for Atmospheric Research Mesoscale Meteorological Model (MM5) coupled with the HMS was used to simulate the basin response of hydrologic processes to a storm event. The effect of infiltration on the soil moisture along the flow pathway in the river basin and the overall hydrologic response with observed precipitation compare well with observations. The simulated hydrologic response with the MM5-simulated precipitation slightly underestimates the actual response. ¿ 2001 American Geophysical Union