Pluviometric behavior and trends in the Legal Amazon from 1986 to 2015.

The Amazon region is of interest to the scientific community because it has the largest tropical rainforest in the world and has plentiful water and solar energy which are essential for climate regulation. In this context we analyzed the annual and seasonal rainfall of the Brazilian Legal Amazon Region over a period of 30 years (1986 to 2015) using data from 268 pluviometric stations from the ANA HIDROWEB database to provide information for the management and planning of the water resources. The spatial and temporal dynamics of the rainfall were analyzed using these data along with isohyet maps of the estimates of rainfall and rainfall volume; the trends and magnitudes of rainfall were analyzed by nonparametric Mann–Kendall and Sen's slope tests respectively. The results indicated a mean precipitation of 2070 mm/year. The Legal Amazon is a region with wide rainfall variability both spatially (the precipitation trend increases from the south to the north of the region) and temporally (both seasonally and interannual). The statistical tests indicated both positive and negative trends in and magnitudes of precipitation. In general an average decrease in precipitation of 5 mm per year was estimated in the Legal Amazon. In addition the rainfall behavior is not homogeneous and is influenced by atmospheric systems and phenomena especially the most intense ENSO events. Important changes are occurring in pluviometry and have the potential to cause hydrological and climatic risks. [ABSTRACT FROM AUTHOR]