The river in the outskirts of Porto Velho
|Name origin: Portuguese, "wood river"|
|Part of||Amazon Basin|
|- left||Madre de Dios River|
|- right||Mamoré River, Ji-Paraná River, Aripuana River|
|Source||Confluence of Madre de Dios and Mamoré|
|- location||Near Guayaramerín, Bolivia & Brazil|
|- elevation||180 m (591 ft)|
|- location||Amazonas state, Brazil|
|- elevation||40 m (131 ft)|
|Length||3,250 km (2,019 mi)|
|Basin||850,000 km2 (328,187 sq mi)|
|- average||24,397 m3/s (861,572 cu ft/s)|
|- max||52,804 m3/s (1,864,756 cu ft/s)|
|- min||2,346 m3/s (82,848 cu ft/s)|
The Madeira River is a major waterway in South America, approximately 3,250 km (2,020 mi) long. The Madeira is the biggest tributary of the Amazon. A map from Emanuel Bowen in 1747, held by the David Rumsey Map Collection, refers to the Madeira by the pre-colonial, indigenous name Cuyari:
"The River of Cuyari, called by the Portuguese Madeira or the Wood River, is formed by two great rivers, which join near its mouth. It was by this River, that the Nation of Topinambes passed into the River Amazon."
The mean inter-annual precipitations on the great basins vary from 750 to 3,000 millimetres (30 to 120 in), the entire upper Madeira basin receiving 1,705 millimetres (67.1 in). The greatest extremes of rainfall are between 490 to 7,000 millimetres (19 to 280 in). At its head, the Madeira on its own is still one of the largest rivers of the world, with a mean inter-annual discharge of 18,000 cubic metres per second (640,000 cu ft/s), i.e. 536 cubic kilometres (129 cu mi)/yr, approximately half the discharge of the Congo River. The mean inter-annual contribution of the Bolivian Andes is 4,170 cubic metres per second (147,000 cu ft/s), i.e. 132 cubic kilometres (32 cu mi)yr, representing 25% of the discharge of the entire upper Madeira basin. On the further course towards the Amazon, the mean discharge of the Madeira increases up to 31,200 cubic metres per second (1,100,000 cu ft/s).
Between Guajará-Mirim and the falls of Teotônio, the Madeira receives the drainage of the north-eastern slopes of the Andes from Santa Cruz de la Sierra to Cuzco, the whole of the south-western slope of Brazilian Mato Grosso and the northern slope of the Chiquitos sierras. In total, the catchment area is 850,000 km2, almost equal in area to France and Spain combined. The waters flow into the Madeira from many large rivers, the principal of which, (from east to west), are the Guaporé or Itenez, the Baures and Blanco, the Itonama or San Miguel, the Mamoré, Beni, and Mayutata or Madre de Dios, all of which are reinforced by numerous secondary but powerful affluents. The climate of the upper catchment area varies from humid in the western edge with the origin of the river's main stem by volume (Río Madre de Dios, Río Beni) to semi arid in the southernmost part with the andine headwaters of the main stem by length (Río Caine, Río Rocha, Río Grande, Mamoré).
All of the upper branches of the river Madeira find their way to the falls across the open, almost level Mojos and Beni plains, 90,000 km2 (35,000 sq mi) of which are yearly flooded to an average depth of about 3 feet (0.91 m) for a period of from three to four months.
The falls of Teotônio and of San Antonio are exceeding the more famous Boyoma Falls in Africa by volume and total drop. From these rapids, the Madeira flows northward forming the border between Bolivia and Brazil for approximately 100 km (62 mi). Below the confluence of the Rio Abunã, the Madeira meanders north-eastward through the Rondônia and Amazonas states of north west Brazil to its junction with the Amazon. At its mouth is Ilha Tupinambaranas, an extensive marshy region formed by the Madeira’s distributaries.
The Madeira river rises more than 15 m (50 ft) during the rainy season, and ocean vessels may ascend it to the Falls of San Antonio, near Porto Velho, Brazil, 1,070 km (660 mi) above its mouth; but in the dry months, from June to November, it is only navigable for the same distance for craft drawing about 2 m (from 5 to 6 feet) of water. The Madeira-Mamoré Railroad runs in a 365 km (227 mi) loop around the unnavigable section to Guajará-Mirim on the Mamoré River.
Two large dams (see below) are under construction as part of the IIRSA regional integration project. The dam projects include large ship-locks capable of moving ocean going vessels between the impounded reservoir and the downstream river. If the project is completed, "more than 4,000 km of waterways upstream from the dams in Brazil, Bolivia, and Peru would become navigable.".
A subspecies of boto (Amazon river dolphin) inhabits the Madeira river system. Approximately 750 fish species are known from the Madeira River basin, making it one of the freshwater systems with the highest species richness in the world.
In popular culture
The river is the fifth title of the album Aguas da Amazonia.
In July 2007, plans have been approved by the Brazilian Government to construct two hydroelectric dams on the Madeira River, the Santo Antonio Dam near Porto Velho and the Jirau Dam about 100 km upstream. Both the Jirau and Santo Antonio dams are run-of-the-river projects that do not impound a large reservoir. Both dams also feature significant environmental re-mediation efforts (such as fish ladders). As a consequence, there has not been strong environmental opposition to the implementation of the Madeira river complex. However, critics point out that if the fish ladders fail, "several valuable migratory fish species could suffer near-extinction as a result of the Madeira dams."  There are also concerns with deforestation and pressure on conservation areas and indigenous peoples' territories. The Worldwatch institute has also criticized the fast-track approval process for "kindler, gentler dams with smaller reservoirs, designed to lessen social and environmental impacts", claiming that no project should "fast-track the licensing of new dams in Amazonia and allow projects to circumvent Brazil's tough environmental laws".
- "Madeira (river)". Talktalk.co.uk (encyclopedia). Accessed May 2011.
- Seyler, Patrick; Laurence Maurice-Bourgoin, Jean Loup Guyot. "Hydrological Control on the Temporal Variability of Trace Element Concentration in the Amazon River and its Main Tributaries". Geological Survey of Brazil (CPRM). Retrieved 16 July 2013.
-  Water and Salt Balances of the Bolivian Amazon, UNESCO
- Maria del Carmen Vera-Diaz (2009). Effects of Energy and Transportation Projects on Soybean Expansion in the Madeira River Basin (Report). Conservation Strategy Fund. http://conservation-strategy.org/files/Madeira%20soy%20final_draft2_0.pdf. Retrieved July 7, 2011.
- Ekström, J. (23 December 2007) Hydroelectric dam constructions in Amazonas. Retrieved 6 February 2013.
- "Brazil Engineers a Critic-Proof Dam". Wall Street Journal. October 6, 2010. Retrieved 2 April 2011.
- "Greenwashing Hydropower". World Watch (Worldwatch Institute) 23 (1): 8–18. 2010.
- "Madeira River Basin: Hydropower dams in the heart of the Amazon". World Wildlife Fund Global. Retrieved 7 July 2011.
- BBC News Online. 2007. Brazil gives Amazon dams go-ahead. 10 July. Available from: http://news.bbc.co.uk/2/hi/americas/6286804.stm. Accessed 16 July 2007.
- Survival International, Madeira River
|Wikimedia Commons has media related to Madeira River.|
- Beach, Chandler B., ed. (1914). "Madeira, a river of South America". The New Student's Reference Work. Chicago: F. E. Compton and Co.
- The Amazon and Madeira Rivers: Sketches and Descriptions from the Note-Book of an Explorer from 1875