Evapotranspiration in the Brazilian municipalities surrounding the Itaipu Binacional reservoir: characterization process and estimation methods

Abstract

Seeking to contribute with the management of water resources in the Itaipu Binacional reservoir region, this research aimed to characterize the dynamics of evapotranspiration and evaluate the performance of different mathematical methods, which determine reference evapotranspiration (ETo) from air temperature values. Fifteen municipalities were analyzed. After obtaining the data series, ETo was estimated using six methods: Camargo (C), Hargreaves-Samani (HG-S), Jensen-Haise (JH), Penman-Monteith with missing data (PMm), Thornthwaite-Camargo (TW-C) and Penman-Monteith (PM) – the latter was the reference method. The performance of the methods was analyzed by several statistical indexes. Daily ETo values ranged from 2 to 10 mm d-1, with an annual mean of 5.78 mm d-1. We also observed that it is determined predominantly by radioactive parameters, which annually represent 76% of the evapotranspiration process, while aerodynamic parameters represent 24%. Among the ETo estimation methods, HG-S and PMm were the most suitable for estimating.