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a river in Brazil; a right tributary of the Amazon. The Tapajóz measures 2,200 km long from its source, the Juruena River; it drains an area of 487,000 sq km. It is formed by the confluence of the Juruena (about 1,000 km long) and Teles Pires (Sao Manuel) rivers, which originate in the Serra dos Parecis upland and flow through the western part of the Brazilian Highlands, forming numerous rapids and waterfalls. The Tapajóz flows through the Amazonian Lowland, forming more rapids. In the lower course, the river reaches a width of 15 km.
The Tapajóz is fed by rain. There is high water from November through March, with a rise in the water level of 7–8 m; low water occurs from May through October. The mean flow rate is 15,500 cu m per sec. The Tapajóz is navigable for a distance of 300 km from the mouth, as far as the city of Sāo Luís.