Madeira: an international River
The River Madeira is an international river and flows not only through the Brazilian states of Rondônia, Acre, Amazonas and Mato Grosso but also through seven Bolivian and three Peruvian departments. It drains 35% of the water from the Andes Mountains from these countries and is the only large Brazilian river with this feature.
The hydrographic system of the Madeira consists of the Upper Madeira, with a stretch from its spring in the Andes Mountains. This includes its main tributary rivers: the Middle Madeira, made up of the segment of waterfalls between Guajará-Mirim (RO), on the border with Bolivia, and the Santo Antonio waterfall, in Porto Velho (RO); and the Lower Madeira, which includes the downstream stretch of the river which goes in the direction of its mouth from the Santo Antônio waterfall.
The main tributaries of the River Madeira are the Guaporé, Mamoré, Beni, Madre de Dios and Abunã rivers. It is the biggest tributary of the Amazon River.
The river has particular features in relation to the kind of topography, climate and soil and has an extremely variable vegetation cover.
In terms of topography, the river passes through different altitudes ranging from 6,500 m to 40 m. In terms of climate, the river receives annual rainfall which varies from 400 mm to 5,000 mm and its banks are extensively flooded in the rainy season.
In terms of the geology of the River Madeira, there are soils from the Precambrian period to more recent quaternary rocks. The vegetation in the surrounding area ranges from low grazing land to dense humid tropical forest.