Estimation of actual evapotranspiration Mediterranean ecosystems of Chile by ASTER and MODIS data

The estimation of the spatial distribution of evapotranspiration (ET), at the landscape scale, allows deepen our understanding of the biophysical functioning of a territory, which is essential in ecosystems with frequent water limitations, which in addition, are poorly instrumented and documented. In this sense, daily ET was estimated in a Mediterranean rainfed landscape of the Central Chile, based in meteorological in situ data, and two satellite scenes (ASTER and MODIS). The surface energy balance model S-SEBI was calibrated to estimate the evaporative fraction, from the spatial contrast of reflectance and surface temperatures from ASTER. The atmospheric profiles from MODIS (MOD07) and the maximum and minimum air temperature from meteorological stations were considered to obtain net radiation, considering the topographic heterogeneity derived from a digital elevation model taken from ASTER as well. Results reflected the heterogeneity of the landscape, with an ET of 5.8 ± 1.8 and 6.4 ± 2.1 mm.d-1, en both scenes, depicting the variability of land use, which encompass bare soils, crops, forests and water bodies. The use of the S-SEBI model represents an efficient procedure in the prediction of the actual ET in vast territories. This information is essential in the calculation of the water balance and water consume in areas, where the hydric resources are unknown and the in situ measurements scarce. The carrying out of this methodology represents a valuable alternative for the decision-making in the territorial planning of the hydric resources.