Influência de fenômenos climáticos sobre o regime hidrológico no médio rio Negro (Amazonas – Brasil)

Abstract

Knowledge of the hydrological conditions of a river is one of the main factors for an efficient management of the local water infrastructure, being important in the development of hydrological forecasting tools and techniques, which seek to identify ways to mitigate environmental risks in cases of climatic extremes. Climatic occurrences have a profound influence on the water regime, more specifically on flows and precipitation, as they act directly on the amount of water present, causing changes in periods of droughts and floods. In view of this and having as a study area the stretch between the cities of São Gabriel da Cachoeira and Barcelos, region of the middle Rio Negro (Amazonas), this research aimed to analyze how the climatic phenomena ENOS (El Niño and La Niña) and Dipole of the Atlantic (Positive Dipole and Negative Dipole) interfere on the flow regime. Along with the verification of their actions on the local climate variability, through precipitation. Initially, data collection was carried out regarding the flows recorded between the years 1978 and 2017 (historical series). Subsequently, the ENSO phenomenon was determined based on its Niño Oscillation Index (ION), for the Atlantic Dipole the TNA (Tropical Northern Atlantic) and TSA (Tropical Southern Atlantic) indices were used, obtaining the Inter -hemispheric (GIH). Through these indices, it was possible to visualize how their occurrences influenced the flows annually, and monthly with the intensities of the phenomena, making the analysis more precise and punctual. Statistical analyzes were also performed with the Grubbs, Shapiro-Wilk and Spearman Correlation tests, considering the interactions between the flow values and the climatic indices. Thus, it was identified that in El Niño years there were most of the lowest flows in the historical series. In contrast, in La Niña years, most of the highest flows were recorded, following the logic of effects generated by these ENSO phases. As for the Atlantic Dipole, its phases also followed the regularities, when in years of Positive Dipole, the flows were among the lowest in the series, while the Negative Dipole recorded the highest flows. The simultaneous occurrences also deserve emphasis, since the El Niño, together with the Positive Dipole, reduced the flows and the La Niña, together with the Negative Dipole, implies its intensification and increase, the flows and precipitations, showed a significant and directly proportional correlation between them, however weak.