Comparative performance of empirical methods to estimate the reference evapotranspiration in Aquidauana, MS, Brazil

Estimating the reference evapotranspiration is quite useful when managing irrigation, as before picking the right method; it is necessary to analyse local’s climatic conditions. Therefore, the aim of this study was to evaluate the performance of empirical methods to estimate ET 0 , comparing them with FAO reference evapotranspiration from Penman-Monteith equation, for the region of Aquidauana, Brazil. The empirical methods used were Camargo (CM), Hargreaves-Samani (HS), Jensen-Haise (JH) and Priestley & Taylor (PT). The climatic variables were obtained from a station of the National Institute of Meteorology (INMET), located in Aquidauana, MS, collected between January of 2008 and December of 2014. In order to compare the values of ET 0 obtained from the empirical equations with the standard method of Penman-Monteith, it was considered the following parameters: regression equation (a and b), coefficient of determination (r 2 ), Willmott’s index (d) and C-index (c), as both for dry and rainy period. The method of Priestley & Taylor was the one that presented the closest value to Penman-Monteith equation, followed by the method of Jensen-Haise. The methods of Hargreaves-Samani and Camargo are not recommended to the region of Aquidauana, MS.