ارزيابي پنج روش محاسبه تبخير تعرق ماهانه در منطقه شيراز

Evaluation of Five Methods for Monthly Evapotranspiration Calculation in Shiraz Region

The Penman-Monteilh method is the most common equation for estimating reference crop evapotranspiration. But, this method needs many weather parameters. In this study, by using the weather data of Shiraz synoptic station from years 1959 to 2000, four versions of Hargreaves equation were compared with Penman-Monteith method. The results indicated that the original Hargreaves equation was the worst, and the version included monthly rainfall, was the nearest to the Penman-Monteith method. Therefore, the version of Hargreaves with mean monthly minimum and maximum temperature and monthly rainfall, can be used for estimating monthly evapotranspiration in Shiraz region instead of Penman-Monteith method. The important advantage of using this equation is to need less weather parameter. Also, this equation can be used in conditions that some weather parameters were not. measured