Application of the source-area concept of storm runoff to a small Arizona watershed

An attempt to demonstrate the source-area concept of storm runoff by analysis of the rainfall-runoff relation for the watershed of Queen Creek tributary in south-central Arizona was moderately successful. The demonstration was somewhat marred by the necessity to make several simplifying assumptions to eliminate some of the many basin variables of unknown magnitude. The percentage of watershed contributing storm runoff was related to total rainfall received that is, antecedent and storm rainfall on the assumption that the availability of rainfall excess from any subarea was dependent on the saturation, or near saturation, of a permeable upper layer of soil. An average unit hydrograph was used for all computed sizes of the runoff-contributing area.