Evaluation of SEBAL Algorithm for Estimation of Real Evapotranspiration in Vardij area

The aim of this study was to evaluate the remote sensing algorithm (SEBAL) for estimating actual evapotranspiration in Vardij area in Tehran province. For this purpose Landsat 8 satellite images on June 10th, July 12th, August 13th and September 14th, 2018 and July 15th, 2019 were used. The reference evapotranspiration value (alfalfa plant) was calculated using evapotranspiration obtained from the SEBAL algorithm for the three points where alfalfa was previously cultivated. Using the meteorological station data, reference evapotranspiration was estimated by the experimental methods of FAO Penman- Monteith, Penman -Wright, Hargreaves Samani and Blani Cridel. The values obtained from SEBAL algorithm were compared with the mentioned methods and it was observed that in the study area the Hargreaves Samani method (MAE = 0.472 and RMSE = 0.62) was closer to the remote sensing method. Next in rating is the FAO Penman Monteith method (MAE = 1 and RMSE = 1.26). Finally, the evapotranspiration obtained from SEBAL algorithm was compared with the value obtained from portable lysimeter and the results showed good correlation, so that absolute difference value was 0.81 (mm/day), and it can be concluded that the remote sensing method is suitable for estimating evapotranspiration in the study area.