Comparing evapotranspiration obtained from some of pan evaporation equations using ASCE Standard Penman-Monteith model in an arid climate

The present study aimed at investigating four different models to estimate pan evaporation coefficient (Kp) to measure alfalfa-reference evapotranspiration. To this end the values of pan coefficient obtained from Cuenca, Allen and Priutt, Snyder and Orang equations in Kerman with arid climate were calculated. Then, the values of alfalfa-reference evapotranspiration (ET0) were measured using pan evaporation daily data in a period of five months (from 23/07/2013 to 21/12/2013) on experimental farm of Shahid Bahonar University of Kerman. Based on the daily weather data provided by the automatic weather station in this farm ( during the study), ET0 was calculated using ASCE standard Penman-Monteith model and was used as an index to measure alfalfa-reference evapotranspiration obtained from the four stated models. The results indicated that d-index in Allen and Priutt model was closer to 1 (0.823) with fewer errors compared to those of the other models (RMSE=1.607 and MAE=1.412). Accordingly, among the four models under investigation, Allen and Priutt is suggested to estimate evapotranspiration using pan evaporation in such a climate.