This study aimed to evaluate the real daily evapotranspiration - ETr by remote sensing and to compare it with ETr according to the Bowen ratio technique in the Tapacurá River basin, Pernambuco state, Brazil. The Surface Energy Balance Algorithm for Land (SEBAL) was used with data from Moderate Resolution Imaging Spectroradiometer (MODIS) and meteorological data obtained in a field experiment inside the basin from January 2010 to August 2011. The ETr from SEBAL ranged between 0 and 6 mm d-1, with the highest values registered in the Tapacurá reservoir and the smallest in urban areas inside the basin. The ETr from the Bowen ratio in a pasture area ranged from 3.6 to 4.9 mm d-1. The SEBAL provided good results of the daily evapotranspiration when compared with ETr estimated according to the Bowen ratio technique, resulting in Mean Absolute Error, Relative Error and Average Root Mean Square Error, respectively of 0.40 mm d-1; 9.63% and 0.51 mm d-1. It was concluded that, despite the intense presence of clouds in the region, it was possible to obtain the real daily evapotranspiration in Tapacurá River basin based on MODIS images with good precision.
energy balance; water resource; Bowen ratio
