REAL EVAPOTRANSPIRATION ESTIMATE IN WATERSHEDS IN BRAZILIAN SAVANA

Abstract

The evapotranspiration is the phenomenon responsible for defining the transference of water from the soil-plant system to the atmosphere. It can be estimated through images obtained through remote sensing techniques, allowing the planning of proper water use, besides contributing to studies regarding environmental changes. The research has as objective to apply the SEBAL (Surface Energy Balance Algorithms of Land) model to estimate the real evapotranspiration from biophysical parameters measured by remote sensing and geoprocessing in different watersheds. After the implementation of SEBAL in 38 Landsat8 scenes from May 2018 to September 2019, a very good performance index was observed for daily and seasonal data, whereas for the instantaneous evapotranspiration the model still demands adjustments. The daily reference values (ETo) varied from 1.97 mm in winter to 8.16 mm in summer, while the real evapotranspiration values (ETr) varied from 3.68 mm in winter to 7.08 mm in spring, with the ETr presenting itself 33% inferior to the reference values. Considering the rainfall, the ETr corresponds to 74% of the annual value and indicates that the model is able to estimate these values in scale of 1:150.000 with inferior errors to 15%.