Evapotranspiration Estimation Using Remote Sensing Technology Based on SEBAL Algorithm

Abstract

The aim of this study is to obtain the actual evapotranspiration (ETa) values using Surface Energy Balance Algorithm for Land (SEBAL) algorithm, during the year 2008 in Nekooabad agricultural and drainage network and Ben-Saman region located in Gavkhouni basin in Iran. For this purpose, the time series of Moderate Resolution Imaging Spectroradiometer images from Terra satellite are prepared and ETa values of the regions are estimated for this year. In order to evaluate the SEBAL algorithm performance, the algorithm was executed on Nekooabad agricultural network located in Najafabad region with enough land information and three different methods were used to verify the results. (1) Epan-method: The correlation coefficient between obtained ETa by SEBAL algorithm and the reference ET values (ET0) from pan evaporation method is about 86.72 %. (2) Penman–Monteith method: This method is used for result comparison (the correlation coefficient is about 90.47 %). (3) Water balance method: Considering the water withdrawal of the wells, precipitation and inflow and outflow to the region to the water balance equation, the ETa is estimated as the unknown variable. The results are compared with the result of SEBAL algorithm that shows an error of 7.21 %. SEBAL measured the ETa of Ben-Saman region about 228.16 mm, while there is not enough information of land change in recent years about this region. The results indicate that more cooperation is needed for implementing the special plans for water resources allocation to prevent irregular withdrawals.