River flow forecasting using a rainfall disaggregation model incorporatingsmall-scale topographic effects

River flow forecasting using rainfall predictions from a mesoscale weather prediction model in combination with a physically-based rainfall disaggrega tion model incorporating small-scale topographic variability is demonstrate d. Rainfall predicted by the UK Met Office Mesoscale Model on a 16.8 km gri d is disaggregated onto a 2 km grid using a rainfall model which adds the e ffect of small-scale topography. River flow is calculated by a distributed rainfall-runoff model using the output from the rainfall model, A thunderst orm event on 7 June 1996 over the Brue catchment in Somerset, England is us ed to evaluate the models. The rainfall model successfully forecasts the ba nd-shaped rainfall field within the catchment and the error in the total am ount of flow during the storm is only -12%. An error of -40% in the peak fl ow is attributed to the treatment of convective clouds in the model.