Evapotranspiração de referência na microbacia hidrográfica do Rio Caiabi, afluente da margem direita do Rio Teles Pires

Abstract

Solar radiation is closely linked to physical, chemical and biological processes, its variation changes the temperature and air circulation, allowing applications in plant growth, climatic changes and water requirements. Evapotranspiration is a simultaneous process of water loss through soil evaporation and transpiration of plants, and is related to the water requirement of the crops. the knowledge of the amount of water required by the crops is very important for the design of irrigation systems. The main objective of this work was to evaluate simplified models of estimation of reference evapotranspiration (ETo), and to calibrate the global radiation estimation model proposed by Bristow and Campbell (1984), in the Caiabi river sub-basin region, a right bank afluent of Teles Pires’s river. The meteorological data were obtained from the databases of three automatic meteorological stations (Davis Vantage Pro2), installed in different points of the sub-basin. The models evaluated were: Hargraves and Samani; Camargo; Makkink; Turc and Solar Radiation. The performance indexes used were: Mean Bias Error (BEM), Root Mean Square Error (RMSE) and Willmott's d index. The global radiation model of Bristow and Campbell presented the coefficients a, b and c with 0.7479, 0.0417 and 1.3208 for the rainy season and 0.5172, 0.0246 and 1.7776 for the dry season. For the rainy season the best model was the Hargreaves and Samani With an MBE of -0,0102 and the worst model was Camargo,for the dry season the best models were those of Camargo and Makkink with an MBE of -0.0219 and 0.0134 respectively and the worst model was that of Hargreaves and Samani.