Print version ISSN 0103-8478
PILAU, Felipe Gustavo; BATTISTI, Rafael; SOMAVILLA, Lucindo and RIGHI, Evandro Zanini. Perfomance of methods for estimating reference evapotranspiration in the municipalities of Frederico Westphalen and Palmeira das Missões, State of Rio Grande do Sul, Brazil. Cienc. Rural [online]. 2012, vol.42, n.2, pp. 283-290. ISSN 0103-8478. http://dx.doi.org/10.1590/S0103-84782012000200016.
The estimation of reference evapotranspiration (ETo), used in water balance, allows to determine soil water content, assisting on irrigation management. The present study aimed to compare simple ETo estimating methods with the Penman-Monteith (FAO), in the folowing time scales: daily, 5, 10, 15 and 30 days and monthly in the counties of Frederico Westphalen and Palmeira das Missões, in the Rio Grande do Sul state, Brazil. The methods tested had their efficiency improved by increasing the time scale of analysis, keeping the same performance for both locations. The highest and lowest ETo values occurred in December and June, respectively. Most methods underestimated ETo. For any of the time scales Makking and Radiaton FAO24 methods can replace the Penman-Monteith for estimating ETo.
Keywords : climatic elements; empirical methods; evapotranspiration.