Ayat Rohina - Postgraduate in watershed management engineering, Payam Noor University part-time instructor, DehDasht branch, Kohkiloie Va Boirahmad, Iran.
Mohammad Karami - Postgraduate in watershed management engineering, Islamic azad university of Arsanjan branch, Arsanjan, Fars, Iran.
Ayob Bahranifard - Postgraduate in watershed management engineering, Islamic azad university of Arsanjan branch, Arsanjan, Fars, Iran.
Mohsen Dehghan - Postgraduate in watershed management engineering, Islamic azad university of Arsanjan branch, Arsanjan, Fars, Iran.

Sensitivity analysis to determine variations in evapotranspiration is much important considering a known variation in one of climatic variables. In this study, sensitivity of evapotranspiration from Penmann-Mantith, Penmann-Kimberly (1996), Penman-Kimberly (1972) and Penmann (1984) and Hargrivs (1985) approaches to three climatic variations (maximum temperature, wind speed, solar radiation) was studied in station Fasa for an interval of 22 years (1982-2003).In this research, in order to represent the effect of climatic variables on evapotranspiration, variation percentage standard was used. The results showed that, in most approaches, the most sensitivity was to net radiation, maximum temperature and wind speed, respectively. The results of this study are applicable for measurement of climatic variations in order to estimate evapotranspiration

Potential evapotranspiration, Sensitivity analysis, Variation coefficient, Fasa synoptic station