Análise da tendência de precipitação e vazão na bacia hidrográfica do Rio Amazonas

Abstract

Studying rainfall and flow trends is important to understand hydrological variability and to determine what has influenced increases or decays. The present study analyzes the trends of the space-time annual series of precipitation (total annual precipitation and maximum annual precipitation) and flow (averages, maximums and minimums) in the Amazon River Basin through non-parametric Mann-Kendall and Sen's tests. Slope for five different periods (1975-2014, 1980-2014, 1985-2014, 1995-2014 and 2000-2014). The results indicate that the series of average flows are increasing in the Amazon Basin for all analyzed periods. In the sub-basins of the right bank of the Amazon River, Tapajós and Madeira, the most recent period (2000-2014) registered the greatest trends of increase in the average annual flow from 1998 (year of strong El Niño) and that reached the largest values already observed. In the maximum flow series, the Óbidos station had an increasing rate of increase for the five periods analyzed for extreme flood events, which directly affect the population residing in these areas. Mean flow decay trends were found at six stations in the Tapajós and Madeira sub-basins. As for precipitation, there are significant trends of increase and decay distributed in several distinct regions of the basin. The stations with the highest positive precipitation trends had a significant increase since 1997, reaching the highest peaks in 2013. The comparison of the magnitude of the trends by the Sen's Slope test shows that there is a behavior of increasing flow rates in the entire Amazon basin and in terms of precipitation there are areas of increase and decrease, that is, precipitation is not the only variable that influences the flows of the Amazon River basin.