بررسي دقت و عملكرد تبخير- تعرق پتانسيل محاسبه شده به روشهاي هارگريوز- ساماني و تشتك تبخير در ايستگاههاي سينوپتيك استان خراسان

Accuracy and Behavior of Hargreaves-Samani and Evaporation Pan Methods in Estimation of Evapotranspiration in Khorasan

Estimation of crop water use through prediction of Evapotranspiration (}:To) is one of the methods for improving water use efficiency. The Food and Agriculture Organization (FAO) of the United Nations has suggested the FAO Penman-Monteith method as a standard procedure for the calculation of ETo, and also for calibration of other methods. This method requires radiation, air temperature, humidity and wind speed. In some stations air temperature is the only available climatic data, therefore, adapting a method like Hargreaves-Samani that only use temperature data is nceessarv. An investigation was carried out on synoptic stations of Khorasan province to obtain the most suitable method for estimating ETo when temperature is the only available data and also to study the accuracy of Evaporation pan method. These methods were compared with the FAO Penman-Monteith method. The results showed that although the Evaporation pan method uses many climatic data but still it does not produce accurate or desirable result. For the condition of minimum data (temperature only) a calibrated method for Hargreaves-Samani is proposed and recommended to he used.