Systematic Procedure for Evaluating Partial Areas of Watershed Runoff

A method is presented by which the proportions of a watershed that contribute surface runoff in different storms and at different times during the same storm can be determined by analysis of rainfall and runoff records. The method is a modification of a method described in an earlier paper, which eliminates the need for subjective selection of particular runoff events for analysis. The method is illustrated using data from a 16.8‐ha watershed in Queensland, Australia, and the estimates of runoff from the different source areas are compared with actual records of runoff from the whole watershed. Runoff occurred from the entire watershed area on only three occasions in the 15‐yr study period, about 10% of runoff events. In about two‐thirds of runoff events, runoff came only from the 15% of the watershed that has the smallest surface storage capacity.