The Amazon’s “Wood River” floods a plain the size of a country
The Madeira runs about 1,450 kilometres, or 3,250–3,380 kilometres if measured as the Madeira–Mamoré system, making it one of the Amazon’s great white-water feeders. Portuguese called it the Wood River; upper plains the size of 90,000 square kilometres still flood about a metre deep each year.
Formed where the Madre de Dios and Mamoré meet, it traces the Bolivia–Brazil border to the Abuna before turning northeast through Rondônia toward the Amazon. Between Guajará-Mirim and Teotônio falls it gathers Andes drainage from Santa Cruz to Cuzco plus Mato Grosso and Chiquitos slopes. Upper-basin rainfall averages about 170.5 centimetres, with extremes from 49 to 700. Mojos and Beni plains stay inundated three to four months annually.
In the rainy season the river climbs more than 15 metres, letting ocean-going ships reach the San Antonio falls near Porto Velho, 1,070 kilometres upstream, though the dry months from June to November restrict that run to shallower craft. Barges loaded at Porto Velho, where Cargill and Amaggi run terminals, now carry close to four million tons of grain downriver to Itacoatiara. Its distributaries end in the marshy Ilha Tupinambaranas.
Andean sediment makes the main river turbid whitewater, while tributaries such as the Aripuanã and Ji-Paraná run clear and the Manicoré black. More than 900 fish species live in the basin, one of the richest freshwater systems anywhere, and the Bolivian river dolphin exists only in its upper reaches. Historical notes recall Topinambá peoples using the corridor into the Amazon. In 2006 Brazil created the 283,117-hectare Rio Madeira Sustainable Development Reserve along the north bank opposite Novo Aripuanã.
In July 2007 Brazil approved two hydroelectric projects, Jirau and, roughly 100 kilometres downstream by Porto Velho, Santo Antônio, both run-of-the-river designs with fish ladders; critics warn that if the ladders fail, valuable migratory fish could be pushed close to extinction. Philip Glass even named a track on his album Aguas da Amazonia after the river.
Source: Madeira River
