Calibration, sensitivity and validation of a physically-based rainfall-runoff model

Abstract The Institute of Hydrology Distributed Model version 4 is a physically-based rainfall runoff model using numerical solutions to surface and subsurface flow equations for periods of storm hydrograph generation. Calibration of the model for a small catchment, the Tanllwyth in central Wales, is described and an investigation reported into the sensitivity of model simulations to changes in values of key physical variables, namely hydraulic conductivity, porosity, initial moisture potentials and surface roughness. The best-fit physical parameter values are transposed temporally to different storm events in the catchment and, in addition, these parameter values are transposed spatially to a physiographically similar adjacent catchment.