Effects of catchment size on runoff relationships

Abstract

Much hydrological research has been carried out on small drainage basins. The transfer of results to large catchments is of obvious practical importance. Factors that affect hydrological relationships between small and large catchments are reviewed, including the various processes and mechanisms by which runoff occurs, catchment characteristics such as land use, soils and geology, the variation of geomorphological characteristics with catchment size, small-scale nonhomogeneity of hydrological characteristics, and data errors. Hydrological responses of small catchments are likely to be different from and more variable than those of large catchments. While general relationships will exist between small and large catchments in a region, no simple or closely defined relations are likely. The transfer of many types of relationships from one region to another is also likely to be invalid. The findings of the review are illustrated by the results of an investigation of relationships between small and large catchments in eastern Australia involving annual rainfall-runoff relations, unit hydrograph parameters and storm loss rates.