Performance of evaporation estimation methods compared with standard 20 m² tank

Desempenho de métodos de estimativa da evaporação em comparação com tanque padrão de 20 m²

The low reliability of evaporation estimates in reservoirs challenges the management of water resources, especially when drought occurs. The evaporation rates measured in buried tanks (20 m² evaporimeters) are close to that of lakes. However, there are few studies in Brazil using long data sets with this type of tank. In this context, this study aimed to evaluate evaporation estimates of free water surface using the method of Penman (1948) and other five empirical equations in comparison with data from a 20 m² tank observed during 10 years. The annual relationship between rainfall and evaporation was 1.0, showing variations in dry years (0.7) and rainy years (1.3). Among all evaluated methods, Linacre (1993) shows the best performance. Camargo et al. (1999) has very good estimates using air temperature as input variable and is a simple and reliable alternative when data are missing.

Key words:
water resources; evaporimeters; free water surface; Penman