The Significance of Spatial Variability of Rainfall on Runoff

A key issue in rainfall-runoff modelling is to assess the importance of the spatial representation of rainfall on streamflow generation. Distributed models have the potential to represent the effects of spatially variable inputs such as rainfall making them an appropriate tool to investigate the role of spatial rainfall on runoff. This paper explores the importance of spatial rainfall representation for rainfall-runoff modelling as a function of catchment scale and type. The study investigated the effect of catchment scale and type using 9 gauged catchments ranging in size from 30 to 1040 km2. Regional relationships between known catchment characteristics and model parameters have been developed to overcome the task of estimating model parameter values at ungauged subcatchments. The results indicate the importance of considering the effect of spatial rainfall in most of the catchments with the significance of spatial effects increasing at small spatial scales. Finally, the importance of spatial variability is enhanced when impermeable areas are investigated.