Estimativa da evapotranspiração para uma bacia hidrográfica no semiárido brasileiro.

Abstract

Evapotranspiration - ET is an important term in the water cycle that integrates atmospheric demands and surface conditions and one of the main variables of the hydrological cycle, as the main responsible for the loss of water in hydrographic basins, ET has a great influence on the hydrological processes. The main objective of this study was to evaluate the performance of the SWAT Soil and Water Assesssment Tool hydrological model in the simulation of evapotranspiration estimates for the Piranhas-Açu River Basin (BHRPA) in the state of Rio Grande do Norte, Northeast semiarid region Brazilian. The results of the hydrological simulation allowed to analyze the behavior and seasonal variability of ET on a basin scale. The SWAT model was used without calibration and presented a good performance in the ET simulation, offering coherent information when compared to those estimated by the water balance method - BH, indicating that it has an expressive potential for continuously monitoring the spatial ET, that can be used to determine the behavior of the hydrological cycle. The ET values of the simulation with the SWAT and of three more products of estimates of different methods were compared with estimates by the method of BH for localities inserted in the BHRPA, the spatial distribution of the average of the annual accumulated values of the simulation for the components was also performed hydrological. The ET estimates for the period from January 2002 to December 2011 used in this work are derived from hydrological simulation with SWAT, from global scale ET products MOD16 (Moderate resolution Imaging

Spectroradiometer) and GLDAS (Global Land Data Assimilation System) and the regional R- SSEB model (Simplified Modeling for Power Balance estimate the area in regional Scale).

Despite the differences between the ET from the evaluated methods and the one calculated by the BH method, in general it was possible to identify that the simulation with the SWAT model showed more coherent evapotranspiration results, indicating an expressive potential for spatial monitoring of the ET continuously. Considering the spatial distribution of the averages of the annual accumulated hydrological components, through hydrological simulation, described in the work, it is concluded that there may be possible interferences of vegetation cover, use and types of soil in the evapotranspiration process, as well as influences of evapotranspiration in the hydrological components simulated with SWAT.