A semi-distributed watershed model was developed that conceptualizes the catchment as a cascade of nonlinear storage elements whose geometric dimensions are derived from the Horton-Strahler ordering of the stream network. Each storage element represents quick storm runoff over land or in a channel segment. The physically based groundwater submodel is parameterized through the application of the Brutsaert-Nieber recession flow analysis and it provides continuous baseflow separation. The model requires the calibration of seven parameters from a one year rainfall-runoff record. It was tested on the Mahantango Creek watershed in the Susquehanna River basin, Pennsylvania.