Options for Reference Evapotranspiration Estimation in Northern Espírito Santo and Eastern Minas Gerais States, Brazil

Due to the misuse and management of drinking water sources, in the last few decades there has been increasing waste of this resource and, as a consequence, the state of Espírito Santo, Brazil, has experienced a period of water crisis that has resulted in a fall in production in several agricultural sectors. In view of this, it is proposed that measurements related to water management should be carried out, such as the estimation of reference evapotranspiration (ET0), with the objective of optimising water use in agriculture by more efficient management, based on the collection and calculation of daily climatic data. Thus, this study aimed to estimate reference evapotranspiration (ET0) using six different methods and to compare the results with the values ​​estimated by the Penman-Monteith-FAO 56 (PM) method in the municipalities of Aimorés, MG and Linhares, ES, Brazil. The methods of Hargreaves-Samani (HS), Solar Radiation FAO (RS-FAO), Makkink (MKK), Jense-Haise (JH), Linacre (LIN) and simplified Penman (PS) were investigated. For both cities, the results were similar in terms of method performance, especially PS and RS-FAO, with the highest indexes and efficiency, as well as smaller errors, followed by HS and MKK, both with indexes smaller than the most efficient methods. However, it was necessary to apply linear adjustment, using the coefficients "a" and "b". The LIN method is not recommended for either city, since the results using this method were unsatisfactory for most analyses.