Comparação de métodos de estimativa da evapotranspiração para Alegrete - RS

Abstract

The performance of the methods to estimate the reference evapotranspiration (ETP) varies according to the local climatic conditions, being this a factor of extreme importance when it comes to the irrigation management of a given crop. The aim of this work is to evaluate the performance of the reference evapotranspiration methods, based on the Penman-Montheith-FAO standard method, in order to select the most appropriate methods for Alegrete / RS, comparing them with the empirical methods Jansen-Heise, Tanner and Pelton, Turc and the "Class A" tank method, in addition to determining and comparing the efficiency of empirical methods with the standard Penman-Montheith-FAO method for the Alegrete region. Meteorological data from the years 2015 and 2016 were used for mean air temperature (tmed), maximum air temperature (tmax), minimum air temperature (tmín), wind speed measured at 2 meters high (U2), relative humidity (RH), precipitation (mm) and evaporation of the "Class A" tank (ECA). The radiation balance (Rn) was estimated. The results show that the Jansen-Heise, Tanner and Pelton, Turc methods presented a "poor" performance for the region, while the "Class A" tank method performed "optimally". For the region under study, it is concluded that the "Class A" tank method can be recommended for the calculation of reference evapotranspiration. The determination of the reference evapotranspiration is considered a procedure of extreme importance to the agricultural sector, since it measures the management and the irrigation system, being easily obtainable due to being affected only by climatic factors. In this way, the choice of the appropriate method for the determination of evapotranspiration is of fundamental importance, being necessary the validation of the models, if they are empirical models.