Now-a-days, many people are concerned with the shortage of drinking water, particularly in arid and semi-arid areas. In that sense, the rational and optimized use of the water is a need, mainly for agricultural and industrial activities. Among the many methods of estimating evapotranspiration (ET), the remote sensing is regarded as the one that can efficiently and economically provides regional and local coverage of actual ET. The objective of the present study was the determination and mapping of ET in Alto Piranhas Basin, according to orbital satellite images and SEBAL/METRIC algorithms. The ET estimation was obtained from the latent heat flux as the residue of the energy balance equation (BE). The BE was calculated from physical parameterizations of the radiance in the visible, infra-red and thermal bands. The ET values were validated with data obtained in a field experiments carried out in a 300 ha irrigated banana orchard located in a semi-arid land of Northeast Brazil. When applied to high resolution orbital images the SEBAL/METRIC estimates showed to be in good agreement with surface data and high efficiency in the estimation of daily evapotranspiration.