An Evaluation of Potential Evapotranspiration Estimates for Selected Sites within Arizona

Abstract

The purpose of this investigation was to develop empirical relationships between pan evaporation and meteorological factors, under varied climatic conditions. Linear regression equations relating potential evapotranspiration and pan evaporation were derived for five stations in Arizona from January to December, 1983. Five climatological models (temperature, temperature-radiation, net radiation, solar radiation, and Penman combination) were applied to data collected from Mesa, Tucson (Campus Agricultural Center and UA 1), Oracle Agricultural Center, and Yuma. At each site high correlations were found between predicted values and open pan evaporation when data were grouped into monthly and weekly periods, although coefficients of variation were markedly different. Of the five methods, the net radiation equation, which required local calibration showed the poorest agreement between the empirical and measured values. Improvement in comparisons between empirical and measured values was observed with the temperature, radiation-temperature, and solar radiation methods. The Penman combination equation corresponded most closely to measured values.