ESTIMATE OF REFERENCE EVAPOTRANSPIRATION IN THE SEMIARID OF PERNAMBUCO STATE

The objective of this work was determinate the reference evapotranspira o of (ETo) daily at Pesqueira City (PE) in 2007. It was used empirical models of Hargreaves-Samani (EToHS), Linacre (EToLI), Priestley-Taylor (EtoPT), Jensen-Haise (EToJH) and Penman-Monteith (EToPM) as standard to observe the variation of the evapotranspiration in the year. After the evapotranspiration values had been correlated with the EToPM considered in the study, each year weather season. Moreover, the methods had been collated with the determined values of Penman-Monteith with statistical indices (Willmott index). It was verified that the correlations between EToPT and EToJH with EToPM had gotten optimum adjustment, whose coefficients had been 0.95 and 0.97 (in the summer), 0.98 and 0.99 (in the autumn), 0.93 and 0.96 (in the winter) and of 0.78 and 0.84 (in the spring), respectively. The EToPT values were the one that presented better performance in seasons through the statistical test. It concludes that Priestley-Taylor method adjusts well for Pesqueira City (PE), what it evidences that the EToPT could be used in the form proposal for estimate of the ETo of this place.