The Tocantins basin, or Araguaia-Tocantins basin, is a Brazilian

river basin A drainage basin is an area of land where all flowing surface water converges to a single point, such as a river mouth, or flows into another body of water, such as a lake or ocean. A basin is separated from adjacent basins by a perimeter, the ...

, almost entirely located between the 2ºS and 18ºS parallels and the 46ºW and 56ºW meridians. The main rivers in the basin are

Tocantins Tocantins () is one of the 26 states of Brazil. It is the newest state, formed in 1988 and encompassing what had formerly been the northern two-fifths of the state of Goiás. Tocantins covers and had an estimated population of 1,496,880 in 20 ...

and Araguaia. The basin extends to the states of

and

Goiás Goiás () is a Brazilian state located in the Center-West region. Goiás borders the Federal District and the states of (from north clockwise) Tocantins, Bahia, Minas Gerais, Mato Grosso do Sul and Mato Grosso. The state capital is Goiânia. ...

(58%),

Mato Grosso Mato Grosso ( – lit. "Thick Bush") is one of the states of Brazil, the third largest by area, located in the Central-West region. The state has 1.66% of the Brazilian population and is responsible for 1.9% of the Brazilian GDP. Neighboring ...

(24%),

Pará Pará is a Federative units of Brazil, state of Brazil, located in northern Brazil and traversed by the lower Amazon River. It borders the Brazilian states of Amapá, Maranhão, Tocantins (state), Tocantins, Mato Grosso, Amazonas (Brazilian state) ...

(13%),

Maranhão Maranhão () is a state in Brazil. Located in the country's Northeast Region, it has a population of about 7 million and an area of . Clockwise from north, it borders on the Atlantic Ocean for 2,243 km and the states of Piauí, Tocantins and ...

(4%), in addition to the

Federal District A federal district is a type of administrative division of a federation, usually under the direct control of a federal government and organized sometimes with a single municipal body. Federal districts often include capital districts, and they e ...

(1%). It is the largest hydrographic basin entirely Brazilian.Caderno da Região Hidrográfica do Tocantins-Araguaia
Brasília: Ministério do Meio Ambiente, Secretaria de Recursos Hídricos, 2006. For water resource management purposes, it is inserted in the Tocantins-Araguaia hydrographic region.

General characteristics of the basin

Its length is approximately 2,500 km, from its water source, in the Serra Dourada, to the mouth, in the bay of Marajó (Pará). It has an elongated configuration in the longitudinal direction, which follows the two fluvial axes —

and Araguaia — which join at the northern end of the hydrographic basin. The Tocantins River flows into the Marajoara Gulf (or

Marajó Bay The Marajó Bay, or Marajoara gulf and Amazon gulf, is an recessed body of water of the Brazilian coast located in the state of Pará. It is roughly in size, and is a receptacle for the waters of the Pará River distributary channel, the waters ...

), just after the

Pará River The Pará River (), also called Parauaú River, Jacaré Grande River, Marajó River Channel, Macacos River Channel, Ribeirão Santa Maria, Santa Maria River Channel and Bocas Bay, is a watercourse and immense Estuary, estuarine complex that fun ...

, which flows south of the island of Marajó, being one of the formators of the Great Amazon Estuary. The Pará River is considered a distributary channel, that is, a link between the Tocantins River and the

Amazon Delta Amazon Delta ('' pt, delta do Amazonas'' is a huge river delta formed by the Amazon River and Tocantins River (through the Pará River distributary channel), in northern South America. It is located in the Brazilian states of Pará and Amapá and ...

. The relief is considered a monotope, with altitudes varying between 350m and 500m, except in the river springs, where it reaches more than 1,000m. In the

Tucuruí Tucuruí is a municipality in the state of Pará in the Northern region of Brazil. The city is served by Tucuruí Airport. The name Tucuruí is a Tupi word that means "river of ants" or "river of locusts". It's the concatenation of two tupi word ...

region, altitudes are less than 10m. The Tocantins basin is the second largest in energy production in Brazil. The average discharge from the hydrographic basin, in Tucuruí, is estimated at 12,000 m³/s, with the contribution of the Araguaia and Tocantins rivers being similar, and that of the

Itacaiúnas River The Itacaiúnas River is a river of Pará state in north-central Brazil. Part of the river basin is in the Tapirapé-Aquiri National Forest, a sustainable use conservation unit created in 1989. See also *List of rivers of Pará List of rivers i ...

, much lower (600 m³/s). The basin covers approximately 767,000 km² (about 7.5% of the national territory) distributed, mainly between the Araguaia (382,000 km²), Tocantins (343,000 km²) and Itacaiúnas (42,000 km²) rivers, the largest contributor to the lower Tocantins course.Rodrigues, J. A. M
Impactos antrópicos no regime hidrológico de tributários do Rio Tocantins (Dissertação de Mestrado em Recursos Hídricos em Sistemas Agrícolas)
Lavras: Universidade Federal de Lavras, 2017.

References

{{reflist South American drainage basins of the Atlantic Ocean Drainage basins of Brazil