Wikipedia
The Tapajós is a river in Brazil. It runs through the Amazon Rainforest and is a major tributary of the Amazon River. When combined with the Juruena River, the Tapajós is approximately long. For most of its length it runs through Pará State, but the upper (southern) part forms the border between Pará and Amazonas State. The source is at the Juruena– Teles Pires river junction. The Tapajós River basin accounts for 6% of the water in the Amazon Basin, making it the fifth largest in the system.
From the lower Arinos River (a tributary of Juruena) to the Maranhão Grande falls are a more or less continuous series of formidable cataracts and rapids; but from the Maranhão Grande to the mouth of Tapajós, about , the river can be navigated by large vessels.
For its last it is between wide and much of it very deep. The valley of the Tapajós is bordered on both sides by bluffs. They are from high along the lower river; but a few miles above Santarém, they retire from the eastern side and do not approach the Amazon floodplain until some miles below Santarém.
The eastern border of Amazônia National Park is formed by the Tapajós River. From Itaituba and southwest a part of the Trans-Amazonian highway (BR-230) follows the river, while a part of BR-163 runs parallel to the river from Santarém and south.
The South American pole of inaccessibility is located close to the sources of Tapajós's tributaries, near town Utiariti
The Tapajós is named after the Tapajós Indians, a tribe of Native Americans from Santarém.
The Tapajós is one of three major clearwater rivers in the Amazon Basin (the others are Xingu and Tocantins; the latter arguably outside the Amazon). Clearwater rivers share the low conductivity and relatively low levels of dissolved solids with blackwater rivers, but differ from these in having water that at most only is somewhat acidic (typical pH ~6.5) and very clear with a greenish colour. About 325 fish species are known from the Tapajós River basin, including 65 endemics. Many of these have only been discovered within the last decade, and a conservative estimate suggests more than 500 fish species eventually will be recognized in the river basin.
Those fish, along with many other endemic species flora and fauna are threatened by the many dams that are planned on the river. The largest of those projects is the São Luiz do Tapajós mega dam, whose environmental licensing process has been suspended - not yet cancelled - by IBAMA due to its expected impacts on indigenous and river communities. The Washington Post has referred to this issue as the next battle over saving the Amazon as a result of its controversy involving Indigenous communities, the Brazilian government, large multinationals and international environmental organizations.
Tapajós is the name for a proposed new Brazilian state, which would consist of the western part of the current state of Pará. The proposal was defeated in a referendum in 2011 and by law could not be revived until 2015; as of 2016, no new such proposal has been made. Although voters within the territory of the proposed state voted strongly in favor, the vote was strongly negative among the much larger population in what would have remained of Pará.