Comparison of different types of Hargreaves equation for estimating monthly evapotranspiration in the south of Iran

The Penman-Monteith is the most desirable method for estimating reference crop potential evapotranspiration (ETo). However, this method needs full weather data, but only a few stations with complete weather data exist in the south of Iran. On the other hand, the Hargreaves equation is a more simple equation for estimating ETo, and some new types of this equation have been proposed recently. In this study, using the weather data of 14 stations in the south of Iran, different types of the Hargreaves equation for monthly ETo estimates were compared with the Penman-Monteith method. By using the obtained results, monthly ETo can be estimated with appropriate type of Hargreaves equation for different places by considering the average ratios between monthly estimated ETo with Penman-Monteith to the appropriate type of Hargreaves equation. The results showed that the original type of Hargreaves equation was only better than the other types of this equation in three stations with humid climate and low value of win...