Optimization of SAVI index and Estimation of ETa Using Landsat8 Satellite Images

Actual evapotranspiration (ETa) estimation is a main factor for irrigation scheduling, hydrological balance, design and management of irrigation systems and crop yield prediction. Therefore many researchers have been tried to achieve ETa in different spatial and temporal scales. Remote sensing is one of the newest methods that can be used for this purpose. Therefore, In present study, spatial distribution of daily Eta at a part of Mashhad plain was estimated using Landsat 8 satellite images on 9 June, 25 June, 28 August and 13 September 2013. For this purpose, soil adjusted vegetation index (SAVI) was optimized for SEBAL algorithm. The results showed that there was a correlation between normalized difference vegetation index (NDVI) and ETa in study events. Also, standard deviation of SAVI was the least for L=1 (correction factor of soil background effects). Therefore it can be concluded that optimum amount of L for study region is one. Also the trend of ETr was similar to ETa. It can be concluded that plant cover in agriculture lands had no limitation for accessible of water in study region.