Estimating the reference evapotranspiration values by using FAO-56PM in Aydoghmush river basin

Food and Agriculture Organization(FAO), has offered the Penman model (FAO-56PM) as a standard model to estimate reference evapotranspiration of crops. The lack of some climatological variables such as solar radiation, relative humidity and wind speed can be a major obstacle in estimating evapotranspiration by FAO-56PM. To overcome this problem, a series of relations and equations is used in the form of the Penman model. By considering these facts, assessmentthe accuracy and validity of this model in different regions, is important. In this studythe equations for estimating the parameters of wind speed , relative humidity and solar radiation were used, and finally the potential evapotranspiration was estimated in the Aydoghmush basin. For this purpose, data of 5 climatological stations in Aydoghmush river basinwas used. Comparing estimated and obtained evapotranspiration values, determined that there is a small difference between ETO values in both cases. In this study, the highest and lowest values of RMSE and MBE have been estimated from 0.227 to 0.971 and -0.271 to 0.724 respectively. According to the results it can be said that by using the computational data evapotranspiration values can be estimated with the greatest accuracy.