TREND ANALYSIS OF HISTORIC DISCHARGE SERIES IN THE AMAZON RIVER HYDROGRAPHIC BASIN

Abstract

Studying flow trends is important to understand hydrological variability and to determine what has influenced their increases or decays. The present work analyzes the spatio-temporal trends of the annual series of average flow in the Amazon River Basin (Brazilian portion) of 92 fluviometric stations through non-parametric Mann-Kendall and Sen's Slope tests for five distinct 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) records the greatest trends of significant increase in the average annual flow from 1998 onwards, reaching the highest values ​​ever observed. Mean flow decay trends were found at six stations in the Tapajós and Madeira sub-basins. The magnitude of trends by Sen's Slope test, of significant or non-significant data, shows that there is behavior of increase in flow rates throughout the Amazon basin, which can be influenced by atmospheric systems operating in the Amazon (such as the Intertropical Convergence Zone, ENOS, General and Upper Circulation in Bolivia) or changes in land use and occupation, such as deforestation of the right bank of the Amazon River.