The abundant presence of rivers is a characteristic of Brazilian hydrography: the country has some of the largest hydrographic basins in the world.
Brazil is bathed by long and flowing rivers, due to the hot and humid climate. The relief, on the other hand, interferes with the presence of numerous waterfalls and, mainly, with the direction in which the rivers flow. The slopes direct most of the basins to the Atlantic Ocean.
Water resources are poorly distributed throughout the territory, the scarcity areas are limited to the northeast region. However, the country has about 15% of all surface fresh water in the world.
In the Brazilian territory there are plateau rivers (mostly), which cross areas of rugged relief and, therefore, have waterfalls. These favor the generation of hydroelectric energy. There are also plain rivers , which cross areas of relief with gentle unevenness. These are rivers that favor navigation.
According to Plus-Size-Tips, there is a predominance of the tropical rainfall regime (the rains that determine the variation in the volume of water in rivers), in which the floods coincide with the wettest season of the year, summer, which extends from December to March.
There is also a predominance of exorreic rivers , those that flow into the ocean, and perennial , rivers that never dry up. Many mouths (mouths) of our rivers have the shape of an estuary.
Brazil Hydrography Division
Resolution 32/2003 of the National Water Resources Council established the National Hydrographic Division into 12 Hydrographic Regions.
Amazon Hydrographic Region
The region is part of the Amazon basin , but is limited to Brazilian territory. With an extension of 3.870 thousand km², which is equivalent to 45% of the territory, it covers the states of Acre, Amapá, Amazonas, Mato Grosso, Rondônia, Roraima and Pará
Its main river, the Amazon , has a total length of 7100 km and changes its name several times along its route. Initially, in Peruvian territory, it is called the Apurinac river; later its name changes to Ucayali River. On the Brazilian border, it is renamed Solimões. From the city of Manaus, it receives the name of Amazonas.
The northern region is a likely frontier for exploring the Brazilian hydroelectric potential, of which more than 60% can still be used.
Tocantins-Araguaia Hydrographic Region
Considered the largest hydrographic basin located entirely in Brazil, the Tocantins-Araguaia basin drains 10.8% of the national territory, having an area of 920 thousand km². It crosses lands in the states of Goiás, Mato Grosso, Pará, Maranhão and Tocantins. The second largest hydroelectric power plant in the country was built there, the Tucuruí plant.
However, this basin offers more than 3,000 km of navigable stretches. Because of this, there is a great controversy regarding the use of its waters for navigation of large vessels. The Tocantins-Araguaia waterway project has been deeply questioned for crossing areas of environmental protection and indigenous lands and for threatening an aquatic ecosystem of great biodiversity.
Parnaíba Hydrographic Region
The Parnaíba basin drains 3.9% of Brazil, has an area of 333,056 km² and crosses the lands of the states of Ceará, Maranhão and Piauí.
Its main river is the Parnaíba , 1700 km long, making it the largest navigable river in the northeast. It forms the largest open sea delta on the American continent, the delta of the guarás.
Western Northeast Atlantic Hydrographic Region
This region drains 3% of the national territory, having an approximate area of 274,300 km², comprising the state of Maranhão and a small part of Pará.
An important river in the basin is the Mearim , with 930 km, located about 160 km from the capital of Maranhão. Its waters are widely used for irrigation of various crops such as rice. However, studies show that there is excess contamination of these waters with pesticides used indiscriminately in agricultural production.
East Northeast Atlantic Hydrographic Region
The region occupies an area of about 286,800 km² (3.4% of the national territory), covering 6 states: Alagoas, Ceará, Paraíba, Pernambuco, Piauí and Rio Grande do Norte.
The Jaguaribe River is part of this basin. It is born in the Serra da Joaninha, in the state of Ceará, crossing a stretch of 610 km of land with water shortage due to the semiarid climate. Also noteworthy are the Beberibe and Capibaribe rivers that cross the city of Recife, capital of the state of Pernambuco. A significant part of the old historic center of the city was built along these watercourses.
San Francisco Hydrographic Region
With 638,466 km 2 , the São Francisco basin is the second largest hydrographic basin totally located in Brazilian territory. It comprises the states: Bahia, Minas Gerais, Pernambuco, Alagoas, Sergipe, Goiás, and the Federal District.
The São Francisco River is born in the Serra da Canastra, in Minas Gerais, and is of great importance as it is a perennial river that crosses the semi-arid northeastern hinterland. It links the Northeast and the Southeast, the two regions that historically correspond to the oldest settlement centers and are today the most populous in the country. Because of this connection, the São Francisco is known as the “river of national integration”. It crosses lands in the states of Minas Gerais, Bahia, Sergipe and Alagoas.
It is a typical plateau river, with numerous waterfalls along its course. However, there are some navigable stretches, and the development of irrigable agriculture on its banks is notable.
East Atlantic Hydrographic Region
This region is mainly formed by the Jequitinhonha, Pardo and Contas rivers. It occupies an area of 388,160 km², of which 69% are in Bahia , 26% in Minas Gerais , 4% in Sergipe and 1% in Espírito Santo .
The Jequitinhonha River crosses northeastern Minas Gerais and southeastern Bahia and is the most important water resource in the region. However, the environmental changes caused by men caused deforestation in their headwaters, while mining silted up their watercourses.
Added to this is the fact that the river valley has water scarcity, which has generated a process of economic abandonment and, consequently, social exclusion. This explains the intense rural exodus to the big cities and a growing demographic depletion in the region.
Southeast Atlantic Hydrographic Region
The main rivers in the region are Paraíba do Sul, Doce and Ribeira do Iguape. It has an area of 214,629 km² which is equivalent to 2.5% of the country and comprises 5 states: Espírito Santo, Minas Gerais, Paraná, Rio de Janeiro and São Paulo.
Extending 853 km, the Doce river is formed by the Piranga and Carmo rivers, which originate on the slopes of the Mantiqueira and Espinhaço mountains. It has great economic prominence, as along its valley there is the largest steelmaking complex in Latin America and the largest open pit mining company on the planet: Vale, formerly known as Companhia Vale do Rio Doce.
The Ribeira valley is constituted by the presence of the Lagoon of Iguape Estuarine Complex and by the area crossed by the Ribeira do Iguape river , which rises in the Paranapiacaba mountain range, Paraná, and constitutes the main water resource in the region. Despite the valley being sandwiched between two of the most developed states in the country, São Paulo and Paraná, there was an important environmental preservation in the area.
In addition to the remnants of the Atlantic Forest , the Ribeira valley has one of the greatest speleological heritages in the country. However, there is no consistent economic organization in favor of sustainable management and, therefore, the region has the lowest socioeconomic indicators in São Paulo and Paraná.
South Atlantic Hydrographic Region
This region, whose most important rivers are the Capivari and Itajaí , drains 2.2% of the national territory, with an area of 187,552 km² and crossing 4 important states: Paraná, Santa Catarina, São Paulo and Rio Grande do Sul.
The Itajaí valley is located in the north of the state of Santa Catarina and is home to an area of great influence from German colonization, being an important textile center. Sometimes, there were great floods in the valley, which brought destruction to cities like Itajaí, Joinville and Blumenau.
Paraná Hydrographic Region
Its largest river is the Paraná , a typical plateau river, which has excellent water potential. Its waters feed the turbines of the second largest hydroelectric plant in the world, Itaipu.
The region drains 10% of the national territory and occupies an area of 879,873 km², crossing the states of: DF, GO, MS, MG, PR, SC and SP.
Hydrographic Region of Paraguay
The Paraguay basin is strongly influenced by the low altitudes of the local relief, which slows the flow of water and causes its overflow during the flood period, flooding vast areas. Due to the low slope, the waters that fall upstream of the river take up to four months to cross the entire plain. The Pantanal is part of it.
Its largest river, the Paraguay , is typically plain, with great navigability. It joins the Paraná River forming the Prata River.
The region has an area of 363,446 km², covering part of the states of Mato Grosso and Mato Grosso do Sul.
An important waterway is operating in this basin: the Tietê-Paraná . With 2,400 km of navigability, it was completed thanks to the construction of the Três Irmãos and Jupiá locks. In addition to facilitating the integration between Paraná, São Paulo, Minas Gerais, Goiás and Mato Grosso do Sul, it makes it possible to link Brazil with Argentina, Paraguay and Uruguay, its partners in Mercosur .
Uruguay’s Hydrographic Region
The waters of the Paraguay River join those of another river, in another basin, that of the Uruguay River , which originates in Brazil and flows into the Prata estuary, on the border between Argentina and Uruguay, making up the Platina Basin with the others . The Uruguay River has a high plateau course, therefore with good hydroelectric potential, and its middle and lower courses have important navigable stretches. However, it is underutilized.
The region has, in Brazilian territory, approximately 274,300 km² (3% of the national territory) and covers portions of the states of Rio Grande do Sul and Santa Catarina.