For proper estimation of the quantity of surface runoff generated in a watershed, understanding of the complex relationships between rainfall and runoff processes is necessary.GIS based model systems are increasingly becoming popular tools due to its capability to handle the spatial variation of hydrological and physiographic inputs of the watershed. This book focused on application of a GIS based semi-distributed watershed model (HEC-HMS) in the Woldiya watershed in Ethiopia to establish rainfall-runoff modelling for the determination of important hydrologic design parameters (peak discharge...