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

river basin A drainage basin is an area of land in which 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, th ...

, 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 2014 ...

and Araguaia. The basin extends to the states of

and

Goiás Goiás () is a Brazilian States of Brazil, state located in the Central-West Region, Brazil, Central-West region. Goiás borders the Federal District (Brazil), Federal District and the states of (from north clockwise) Tocantins, Bahia, Minas Ge ...

(58%),

Mato Grosso Mato Grosso ( – ) is one of the states of Brazil, the List of Brazilian states by area, third largest by area, located in the Central-West Region, Brazil, Central-West region. The state has 1.66% of the Brazilian population and is responsible ...

(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 st ...

(13%),

Maranhão Maranhão () is a States of Brazil, state in Brazil. Located in the country's Northeast Region, Brazil, Northeast Region, it has a population of about 7 million and an area of and it is divided into 217 municipalities. Clockwise from north, it ...

(4%), in addition to the

Federal District A federal district is a specific administrative division in one of various federations. These districts may be under the direct jurisdiction of a federation's national government, as in the case of federal territory (e.g., India, Malaysia), or the ...

(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), just after the

Pará River The Pará River (), also called Parauaú River, Jacaré Grande River, Marajó River Channel, Macacos River Channel, Santa Maria River Channel and Bocas Bay, is a watercourse and immense estuarine complex that functions as a canal between the ...

, 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 A distributary, or a distributary channel is a stream channel that branches off and flows a main stream channel. It is the opposite of a ''tributary'', a stream that flows another stream or river. Distributaries are a result of river bifurc ...

channel, that is, a link between the Tocantins River and the

Amazon Delta The Amazon Delta (Portuguese language, Portuguese: delta do Amazonas) is a vast river delta formed by the Amazon River and the Tocantins River (through the Pará River distributary channel) in northern South America. It is located in the Federat ...

. 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 region, altitudes are less than 10m. The Tocantins basin is the second largest in energy production in

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

. 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 ...

, 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