Analysis of potential evapotranspiration using 11 modified temperature-based models

The evapotranspiration was estimated using 11 temperature-based models and was compared with the FAO Penman-Monteith model. The results showed that the modified Hargreaves-Samani models estimate the evapotranspiration better than the other models in the most provinces of Iran. However, the values of R2 were less than 0.98 for 15 provinces of Iran. Therefore, the models were calibrated and precision of estimation was increased (the values of R2 were less than 1.00 (with respect to two decimal numbers) for only five provinces in the modified models). The temperature-based models estimated the evapotranspiration in the north east and south west provinces of Iran better than other provinces. The best precise methods were the modified Hargreaves-Samani 1 method for AL (before calibration) and the Hargreaves-Samani method for AR, the Modified Hargreaves-Samani 2 method for SE and GH, the modified Hargreaves-Samani 1 for FA, and the modified Hargreaves-Samani 3 for MZ (after calibration).