Comparison of different methods for daily estimating reference evapotranspiration for the region of Uberaba

Abstract

This study had the objective to carry out a comparative study of Blaney Criddle, Hargreaves-Samani and Radiation methods with the standard method (Penman-Monteith FAO 56) for the climate conditions in the city of Uberaba, located in the “Triângulo Mineiro” region of the state of Minas Gerais, Brazil. A set of 10 years daily data (1996 to 2005) of maximum and minimum temperatures, wind speed, insolation and relative humidity was used. In order to compare the evapotranspiration values estimated by the empirical equations with the universal standard Penman-Monteith method (FAO56), the parameters of the regression equation a and b, determination coefficient, Pearson’s correlation coefficient, mean bias error, the mean absolute error, root mean squared error, the index of agreement and the index of confidence or performance were considered. The methods were evaluated for two seasons: (1) low evaporative demand, in the months of April and September and, (2) high evaporative demand, in the months of October and March. In both cases, the Blaney Criddle equation was shown to be more accurate. The Hargreaves-Samani method presented the worst performance for the studied climate conditions.