Application of Aridity Index in Determination of Potential Evapotranspiration for Estimating Crop Water Use in Iran

Reliable estimation of ETo is very important in managing water resources. FPM is widely used for this purpose in different climatic conditions. In this study by considering aridity index of 30 meteorological stations ETo was estimated by FPM method. Time base was from 1961 to 2010. ETo for the period of 1961-1980 was compared with ETo of the period of 1981-2010. Also ETo mapping for Iran Plato was presented for monthly and yearly basis. The results showed that in 12 stations resent aridity have changed ETo significantly. Average ETo in the last 15 years was 1112 mm/yr compared to the previous 30 years average which was 995 mm/yr. Variation in summer periods were more significant than winter periods.