A watershed is a collection of land drained by a major river, its tributaries and sub-tributaries. The IBGE (Brazilian Institute of Geography and Statistics) classifies rivers into nine basins, presented below.
It is the largest watershed in the world, with 7,050,000 km², being more than half located in Brazilian lands. It also covers lands from Bolivia, Peru, Colombia, Venezuela, Guyana, French Guiana and Suriname. Its main river, the Amazon, is born in Peru with the name of Vilcanota and later receives the names of Ucaiali, Urubamba and Marañon. When it enters Brazil, it is renamed Solimões and, after meeting the Rio Negro near Manaus, receives the name of Amazon River.
Northeast Basin *
It covers several large rivers of regional significance, such as: Acaraú, Jaguaribe, Piranhas, Potengi, Capibaribe, Una, Pajeú, Turiaçu, Pindaré, Grajaú, Itapecuru, Mearim and Parnaíba. The Parnaíba River forms the border of the states of Piauí and Maranhão, from its sources in the Tabatinga mountain range to the Atlantic Ocean, and represents an important waterway for the transport of agricultural products from the region.
With an area of over 800,000 km2, the Tocantins-Araguaia river basin is the largest watershed entirely situated in Brazilian territory. The Tocantins River is born at the confluence of the Maranhão and Paraná (GO) rivers, while the Araguaia is born in Mato Grosso. In this basin is located the Tucuruí (PA) plant, which supplies projects for the extraction of iron and aluminum.
It stands out for its navigability, being widely used for cargo transportation. Thus, it becomes important for the integration of Mercosur countries. Its waters bathe Brazilian, Paraguayan and Argentine lands.
It is the most industrialized and urbanized region of the country. In the Paraná basin resides almost one third of the Brazilian population, being the main urban agglomerations the metropolitan regions of São Paulo, Campinas and Curitiba. The Paraná River, with approximately 4,100 km, has its sources in the Southeast, separating the lands of Paraná from Mato Grosso do Sul and Paraguay. The Paraná River is the main watercourse of the basin, but its tributaries and formers are also very important, such as the Grande, Paranaíba, Tietê, Paranapanema, Iguaçu rivers, among others. This river basin is the one with the largest hydroelectric production in the country, housing the largest hydroelectric plant in the world: the Itaipu Plant in the State of Paraná, a joint project between Brazil and Paraguay.
São Francisco Basin
It is born in Minas Gerais, in the Serra do Canastra, crossing the states of Bahia, Pernambuco, Alagoas and Sergipe. The São Francisco River is the main watercourse of the basin, about 2,700 km long and 168 tributaries. Of great political, economic and social importance, especially for the northeast of the country, it is navigable for about 1,800 km, from Pirapora, in Minas Gerais, to the waterfall of Paulo Afonso. The main population cluster of the São Francisco basin corresponds to the Metropolitan Region of Belo Horizonte, in the Alto São Francisco region.
Southeast-South Basin *
It is composed by rivers of the importance of Jacuí, Itajaí and Ribeira do Iguape, among others. They have regional importance, by participating in activities such as waterway transportation, water supply and electric power generation.
It is formed by the Uruguay River and its tributaries, flowing into the Silver River estuary, already outside the Brazilian territory. The Uruguay River is formed by the Canoas and Pelotas rivers and serves as a border between the states of Santa Catarina and Rio Grande do Sul. It also forms the border between Brazil and Argentina and between Argentina and Uruguay. It empties into the ocean after covering 1,400 km. Uruguay's hydrographic region has great hydroelectric potential, having one of the largest energy / km² ratios in the world.
Eastern Basin *
Like the northeast basin, this basin has several large rivers of regional importance. Among them, we have the rivers Pardo, Jequitinhonha, Paraíba do Sul, Vaza-Barrels, Itapicuru, das Contas, Paraguaçu, among others. The Paraíba do Sul River, for example, is located between the states of São Paulo, Rio de Janeiro and Minas Gerais, presenting along its course several hydroelectric projects, large riverside cities and important industries, such as Companhia Siderúrgica Nacional.
* They are called grouped basins because they do not have a main river to name them.