Evaluation of evapotranspiration of wheat using SEBAL algorithm (Case study: Agricultural Research Station of Haji Abad)

Evapotranspiration (ET), which includes water evaporation from soil surface and vegetation transpiration, represents a fundamental process of the hydrological cycle. For water resource management, especially in arid and semi-arid regions, this is a key element. A lot of empirical methods have been developed in order to estimate ET from meteorological data since 50 years ago. The major problem of this method is that it can be used for evaluation of uniform regions near the station. This could not be extracted for other regions. Nowadays, remote sensing based methods often used for calculation of different parameters of ET, are suitable to extract different parameters of ET at proper temporal and spatial scales.
One of the most famous algorithms for estimation of actual evapotranspiration is Surface Energy Balance Algorithm (SEBAL). This algorithm calculates all fluxes of the energy balance at the earth's surface including net radiation (Rn), soil heat flux (G), and sensible heat flux (H) from satellite images. Finally, actual ET is computed based on the energy balance at the earth surface. The aim of the current study is to evaluate the spatial and temporal variation of actual evapotranspiration of wheat in Agricultural Research Station of Haji Abad using SEBAL algorithm. The area has geographic coordinates 55° 54 'N, 28° 18' E, with an elevation of 900 m above mean sea level. For this purpose, 4 cloud free Landsat 7 / ETM images are used. Landsat 7 Enhanced Thematic Mapper Plus (ETM) in cloud free satellite images were downloaded from the USGS Earth Explorer site [(http://edcsns17.cr.usgs.gov/NewEarthExplorer/)]