LIMITATIONS OF TEMPERATURE-BASED METHODS IN ESTIMATING CROP EVAPOTRANSPIRATION IN ARID-ZONE AGRICULTURAL-DEVELOPMENT PROJECTS

The methods of Blaney-Criddle and Thornthwaite were used to estimate evapo-transpiration and the estimates were compared with similar estimates provided by the Doorenbos and Pruitt method as well as with the measured values of Class A pan evaporation. It was concluded that Thornthwaite underestimates under the arid conditions. Blaney-Criddle method, though developed in arid areas and can provide good estimates of the mean values in an arid area, has an insufficient sensitivity to the inter-annual variation of the evaporative demand of the atmosphere. The development of a vast irrigation project in a previously barren arid land allowed the examination of the effect of the release of latent heat in the estimates of evapotranspiration. © 1979.