Observational data obtained at various points in the mountains of Southern California indicate that a considerable part of the basin's precipitation is lost to the atmosphere by evapotranspiration. Occasionally the engineer is called upon to obtain the arcal distribution of this basin-wide loss. Currently one of the most promising methods for accomplishing this distribution in Southern California is based on the well-known P/E factor, where P represents the moisture availability and E the opportunity for evapotranspiration. The moisture availability is based on the precipitation and the opportunity for evapotranspiration on the evaporation from a type-A Weather Bureau pan. Where evaporation records are not available, suitable substitute values can often be estimated from regional temperature, humidity, and wind records.
Additional publication details
Distribution of natural water loss in the mountains in the mountains of southern California