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

Abstract

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 ET₀, 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 ET₀ 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 (r²), 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.