Estimation of Actual Evapotranspiration flora pasture by Remote Sensing and SEBAL method

Estimation of Actual Evapotranspiration of Pasture Plants using SEBAL Algorithm (Case Study: Ahar County)Abstract The present study was an attempt to calculate the actual evapotranspiration rate of thyme, mint, and alfalfa pastures using the SEBAL method in the Ahar region, which is located south of Arsbaran forests and has numerous pastures of different species. For this purpose, 6 Landsat 8 satellite images were used between 2017 and 2020, which were in the initial and final periods of growth. The results were compared with the Penman-Monteith method. The results indicated that, based on the SEBAL method, the mint crop had the lowest rate of evapotranspiration in the initial period of crop growth on 2021/5/29, with a numerical value of 2.84 mm per day, and the alfalfa crop also in the initial crop growth period on 2019/6/11 has the highest rate of evapotranspiration with a numerical value of 3.49 mm per day. Additionally, in the final period of growth in the SEBAL method, the mint crop on 2018/8/28 had the lowest rate of evapotranspiration with a numerical value of 6.18 mm per day. Also, the thyme crop had the highest evapotranspiration rate in the final product growth period on 2022/7/19, with a numerical value of 7.41 mm per day. Finally, based on the comparisons made between the studied methods in the initial and final periods of growth in terms of squared mean error, mean absolute deviation, and coefficient of determination, it can be concluded that the SEBAL method compared to the Penman-Monteith method has an error rate with RMSE of 0.717, MAD of 0.658, and the coefficient of determination of 0.84 mm per day, which is acceptable.Keywords: Evapotranspiration, SEBAL, Pasture, Water requirement, Ahar County