The paper deals with the application, calibration and validation of the conceptual rainfall-runoff model for local catchment conditions. The Watershed Model is applied to Kanshi River basin in north Pakistan. Model applied, calibrated and verified using thirteen years data from 1971 to 1983. Conceptual mathematical models are a useful tool for stream flow simulation. The calibration of such models has attracted the attention of hydrologists since unique and optimal parameters are difficult to obtain. The calibration of a conceptual model is discussed through a simple conceptual Watershed Model whose parameters are determined using a trial and error technique.