Estimation of actual evapotranspiration by using MODIS images (a case study: Tajan catchment)

Evapotranspiration (ET) is one of the most effective variables to determine water balance in a region. Accurate estimation of ET flux is vital for agricultural scheduling and water resource management. One of the ways for estimation of ET is applying energy budget methods in which parameters are determined by using remote-sensing technique. The surface energy balance algorithm for land (SEBAL) is one of the most important algorithms for estimation of ET using satellite images. This model estimates ET via estimation of all energy components in the surface such as net radiation flux, soil heat flux and sensible heat flux. This paper aims to investigate accuracy of actual ET estimation using SEBAL algorithm in comparison with calculated values by Food and Agriculture Organization (FAO) Penman-Monteith in Tajan catchment and area of Sari Dasht Naz Agricultural Corporation, Iran. In this investigation, seven images of moderate resolution imaging spectroradiometer (MODIS) were used from February to July 2011. The obtained results show that there is not a significant difference between SEBAL and FAO Penman-Monteith methods for estimation of hourly and daily ET (P-value>0.05). In addition, hourly and daily ET can be estimated with acceptable accuracy, RMSE=0.091mm and RMSE=1.49mm, respectively.