It is very useful, especially ASTER satellite. There is a model called "SEBAL, Surface Energy Balance Algorithm for Land" deals with estimating the evapotranspiration. Also, it can be correlated with the vegetation cover using vegetation indices (VI), such as NDVI and SAVI.
you should also check the phd dissertation prepared by raghuveer kaushik vinukollu titled quantifying global evapotranspiration from remote sensing: estimates, trends and uncertainties for terrestrial hydrology