Precipitation Analysis and the Influence of the El Niño Phenomenon on the Transboundary Basin of the Madeira River.

The current paper aims at analyzing the behavior of monthly precipitation in the Brazilian and Bolivian parts of the basin of the Madeira river, one of the most important sub-basins of the Amazon basin. Both parts account for 93 % of its total, and studies on this topic are lacking. The research was based on data from 41 rainfall stations considering a historic series from 1978 to 1998, which encompasses two of the largest El Niño events (1982-1983 and 1997-1998), hence its influence on the precipitation of the region was assessed as well. To study precipitation behavior, rainfall was regionalized using data clustering methods (Ward and K-means), with the basin being divided into five regions of homogeneous rainfall. Both methods were applied to the regions and showed similar results, providing a higher reliability for the clusters obtained. The results of the analysis show the homogeneous regions of the basin, the spatial variability of precipitation, seasonality and the influence of the phenomenon on the region. [ABSTRACT FROM AUTHOR]