The Amazon Basin is constantly affected by episodes of drought and floods during phenomena such as El Niño and La Niña, in addition to Multidecadal Atlantic Oscillation, Pacific Decadal Oscillation, the Intertropical Convergence Zone and the South Atlantic Convergence Zone. These extremes precipitation cause severe changes in the flow and precipitation of the rivers of several sub -basins in temporal and spatial scale. In the Pacific Ocean the phenomena of El Niño and La Niña are the main mechanisms of interannual and decadal oscillations, causing extreme hydrometeorological in the Amazon, both temporal and spatial scale. Spatial variations of hydrological regimes of the Amazon tributaries show that during the occurrence of seasonal peak flows in the left margin of the tributaries are offset by the decrease of flow of the tributaries of the right bank . Thus, the length of the left bank of rainfall is behind two months of the rainy season on the right bank. In addition to this variation the hydrometeorological extremes cause environmental, social and economic to the population, especially those with high vulnerability. The objective of this work is to study the hydrometeorological regime and the water balance of the Amazon Basin, determining its role in the return flow of the Amazon River to the Atlantic Ocean, as well as the socioeconomic and environmental risks associated with hydrometeorological events. For this we used monthly and annual data flow and precipitation in the period 1982-2012 (31 years) along the main Amazon river channel and 8 sub-basins, as well as an analysis of social and economic risks was made in municipalities of the Amazon basin. The precipitation trends over the study period were negative, in the southwestern part (Purus) and central (Madeira) of the Amazon Basin, and positive on the east side (Tapajós and Xingu). The Amazon Southwest sub-basins were negative extremes and extreme events (El Niño) throughout the study period. It is concluded that the flow in the channel of the main river in the Amazon basin depends on variations in the tributaries of the right and left bank. Seasonality is influenced in the dry season by the tributaries of the right bank , for matching the negative trend over the period studied , and the rainy season is influenced by the tributaries of the left bank . All these fluviometric variabilities cause risks to the population. Thus, it can be said that the socioeconomic and environmental risk is more dangerous during flood events, particularly in states with smaller spatial scale (Rondônia and Roraima) , and greater vulnerability occurs in states with higher spatial scale (Pará and Amazonas) this can be explained by the lack of public policy.
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