Estimation of Evapotranspiration in Ardestan, Center of Iran

Knowing the rate of evapotranspiration (ET) from surface water resources such as lakes and reservoirs is essential for the precise management of water balance. Ardestan city with hot and dry climate is in Isfahan province (center of Iran), so in this region, water is very important. In this study, monthly ET was determined by several methods and equations for Ardestan city from 1993-2006. Monthly data were obtained from IMO (Iran Meteorological Organization) weather station, located in the Ardestan, for all of these years. FAO Penman Monteith (FAO-56 PM) method has been accepted by many researchers and international institutes as the reference and Standard method. Accurate different methods include Penman Fao, BlaneyCriddle, linacre, Thorenthwaite, Hargreaves-Samani, Irmak, Turc and jensen-haise are applied and then their results were compared with FAO-56 PM method. The results indicate that the Blaney-Criddle model is the most appropriate for this particular study area, with an average RMSE of 1.34 mm d and MAE of 1.00 mm d and 1 1 a correlation coefficient of 0.952. For all the years, ET rates were low in winter and fall and highest during the summer. Also, the regression relationship ET = 0.345×T with (R =0.90) of between mean temperature and 2 FAO-56 PM method were determined.