Este artigo traz uma perspectiva histórica da evolução do conhecimento sobre a reciclagem de precipitação e fornece uma visão crítica do estado da arte atual. São retratadas as principais fontes de umidade para a precipitação na Amazônia e o transporte de vapor d'água sobre a América do Sul. A quantificação do mecanismo de reciclagem é um indicador da importância dos processos de superfície e do clima no ciclo hidrológico, assim como da sensibilidade climática relacionada às alterações nesses processos. Os aspectos climatológicos da reciclagem na América do Sul mostram que a contribuição advectiva é mais importante para a precipitação sobre a Amazônia e o Nordeste do Brasil, ao passo que na região Centro-Sul a contribuição local tem importante papel na precipitação. Estima-se que a reciclagem de precipitação na Amazônia é da ordem de 20-35%. A advecção de umidade domina o fornecimento de vapor d'água em grande parte da região amazônica, entretanto, o papel da evapotranspiração local na reciclagem é mais importante no setor sul da bacia. Embora os estudos sobre reciclagem tenham produzido novos conhecimentos acerca da interação entre os processos de superfície e o ciclo hidrológico, os efeitos das mudanças climáticas globais nesse mecanismo ainda não estão completamente compreendidos.

The North region is the second region in Brazil with the highest incidence rate of diarrheal diseases in children under 5 years old. The aim of this study was to investigate the relationship between rainfall and water level during the rainy season principally with the incidence rate of this disease in a southwestern Amazon basin. Rainfall estimates and the water level were correlated and both of them were correlated with the diarrheal incidence rate. For the Alto Acre region, 2 to 3 days’ time-lag is the best interval to observe the impact of the rainfall in the water level (R = 0.35). In the Lower Acre region this time-lag increased (4 days) with a reduction in the correlation value was found. The correlation between rainfall and diarrheal disease was better in the Lower Acre region (Acrelândia, R = 0.7) and rainfall upstream of the city. Between water level and diarrheal disease, the best results were found for the Brasiléia gauging station (Brasiléia, R = 0.3; Epitaciolândia, R = 0.5). This study’s results may support planning and financial resources allocation to prioritize actions for local Civil Defense and health care services before, during and after the rainy season.

The biodiversity and productivity of the Amazon floodplain depend on nutrients and organic matter transported with suspended sediments. Nevertheless, there are still fundamental unknowns about how hydrological and rainfall variability influence sediment flux in the Amazon River. To address this gap, we analyzed 3069 sediment samples collected every 10 days during 1995-2014 at five gauging stations located in the main rivers. We have two distinct fractions of suspended sediments, fine (clay and silt) and coarse (sand), which followed contrasting seasonal and long-term patterns. By taking these dynamics into account, it was estimated, for first time, in the Amazon plain, that the suspended sediment flux separately measured approximately 60% fine and 40% coarse sediment. We find that the fine suspended sediments flux is linked to rainfall and higher coarse suspended sediment flux is related with discharge. Additionally this work presents the time lag between rainfall and discharge, which is related to the upstream area of the gauging. This result is an important contribution to knowledge of biological and geomorphological issues in Amazon basin.

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