Hydroclimatic variables associated with El Nino and La Nina events at the Curuá-Una hydroelectric reservoir, Central Amazonia

ABSTRACT The anomalies of Sea Surface Temperature (SST) influence rainfall and therefore the regime of the rise and fall in the level of the rivers in the Amazon region. The aim of this study was to investigate the influence of the El Nino-Southern Oscillation (ENSO) on hydroclimatic variables and identify the existence of trends on these variables in the Curuá-Una hydroelectric reservoir in the West of the State of Pará. It was used 27 years of monthly precipitation and water flow data to identify possible trends using a non-parametric test (Mann Kendall, p<0.05), and the standardized precipitation index (SPI) was also calculated. The results indicate a positive tendency of the influence of the ENSO on hydroclimatic variables, although it was observed that the rainfall did not increase over the period of 1977 to 2004. The SPI indicates that extreme events of precipitation are related to El Nino and La Nina and that lower precipitation periods were more intense in the decades of the 80´s and 90's. The results show that El Nino events can directly affect the water balance at the micro-watershed of Curuá-Una, as was observed in 2015.