Potential Evapotranspiration in Arid Regions

Abstract

The concept of potential evapotranspiration, as applied to arid regions, is examined using an energy balance approach suggested by Budyko. Using data for Yuma, Ariz., it is shown that a 50 per cent increase in the relative humidity of the air above an irrigated field is accompanied by a 10 to 15 per cent decrease in potential evapotranspiration, a negligible decrease in the net radiation, and a temperature increase of the surface relative to the air of 2 to 3C. The estimated annual potential evapotranspiration at Yuma is about 2000 mm, which is 30 to 50 per cent higher than estimates based on Thornthwaite's method.