O São Francisco River is one of the most important water courses in Brazil and considered the national integration river. Its importance goes beyond the water supply (mainly) in the Northeast of Brazil, as has economic, social and cultural value for the country, as many families depend on it for survive. The São Francisco River enables fruit growing, irrigating production, as well as being used in the production of energy in hydroelectric plants.
Read too: Why is there drought in the Northeast?
General features
The São Francisco is a perennial river, that is, it is a river that has flow normally constant and stable throughout the year. Therefore, it does not dry out, regardless of the dry period.
→Extension
The São Francisco River runs through much of the northeastern semiarid, extending through regions with semiarid, arid and humid climates. It has approximately 2,700 kilometers, according to the Brazilian Institute of Geography and Statistics (IBGE), occupying about 8% of the national territory.
→ States traversed
The Rio São Francisco course runs through the states of Minas Gerais, Goiás and the Federal District, Bahia, Pernambuco, Sergipe and Alagoas (where its spillway is located).
→ Bathed municipalities
The river runs through about 507 municipalities, according to IBGE. Examples are the municipalities of Pirapora and Três Marias, in Minas Gerais; Paulo Afonso and Bom Jesus da Lapa, in Bahia; Penedo and Piranhas, in Alagoas; and Petrolina, in Pernambuco.
→ drainage area
The São Francisco River drains an area of approximately 641,000 km2.
→ Flow average
The average flow is 2,846 cubic meters per second, about 1.58% of the national average flow, according to the National Water Agency.
→ Navigability
This is one of the main characteristics of the São Francisco River. This features two regions of greater navigability. They are: the medium stretch, which is about 1,371 km long (between Minas Gerais, Bahia and Pernambuco), and the low stretch, approximately 208 km long (between Alagoas and the mouth — place where the river flows: the Ocean Atlantic).
The source of the São Francisco River is located in the state of Minas Gerais.
Where does the São Francisco River start?
The São Francisco River has its historic spring at the top of Serra da Canastra National Park, in Minas Gerais, in the municipality of São Roque de Minas, a region considered a great cradle of rivers. However, according to the Ministry of the Environment, it was determined that the geographical source of the São Francisco River is in the municipality of Medeiros, in Minas Gerais. The river connects the regions North East and Southeast from Brazil, flowing into the Atlantic Ocean, on the border between the states of Alagoas and Sergipe.
Map of the hydrographic region of the São Francisco River. (Source: National Water Agency/IBGE)
São Francisco River Basin
The São Francisco River Basin is the most extensive among the exclusively national basins and has a total area of 639,219.4 km2, where: 62.5% of this area is located in the Northeast region of Brazil; 36.8% in the Southeast region; and 0.7% in the Midwest region. The basin covers the states of Goiás (and the Federal District), Bahia, Pernambuco, Alagoas, Sergipe and Minas Gerais.
The São Francisco River has 168 tributaries distributed between perennial and intermittent rivers.*
The basin is divided into four physiographic regions (physical characteristics present in an area), according to data from the Ministry of the Environment:
1) Alto São Francisco: it corresponds to a stretch of approximately 702 km in length, located between the areas of the headwaters of the São Francisco River to Pirapora and Montes Claros, in Minas Gerais. It corresponds to 16% of the basin area. The rains in this region are frequent, with annual rainfall between 1,600 mm and 1,100 mm in summer, between the months of October and April.
- Main cities in this area: Metropolitan Region of Belo Horizonte, Ouro Preto and Divinópolis.
2) Middle San Francisco: It corresponds to a stretch of about 1,230 km in length (most of the basin), where the navigable stretch begins, between the area of Pirapora, in Minas, and Remanso, in Bahia. It represents approximately 63% of the basin's area.
- Main cities in this area: Pirapora, Montes Claros, Paracatu, Formosa and Bom Jesus da Lapa.
3) High School San Francisco: It corresponds to the area of the states of Pernambuco and Bahia, going from Remanso to the city of Paulo Afonso, with about 440 km in length. It represents approximately 17% of the basin's area. The average rainfall in this region is between 450 mm and 800 mm annually.
- Main cities in this area: Juazeiro, Ouricuri and Arcoverde.
4) Lower San Francisco: It comprises the area from Paulo Afonso to the mouth between Alagoas and Sergipe, with about 214 km in length. It represents approximately 4% of the basin. The average annual precipitation in this area varies between 1300 mm to 500 mm.
- Main cities in this area: Jeremoabo, Bom Conselho, Nossa Senhora da Glória and Penedo.
The São Francisco Riveris the main watercourse in the basin and features 168 tributaries. The basin covers the area of three biomes, the thick (between the states of Minas Gerais and Bahia); The Caatinga (comprises the northeast of Bahia) and the Atlantic Forest (in the Alto São Francisco region). As for the climate of the area covered by the basin, it is influenced by different air masses and different altitudes and relief. The river is in the intertropical region with high solar incidence, causing the evapotranspiration rate to be high, especially in the northern region of the basin.
Floods and droughts occur in different regions of the basin. Normally, floods (from December to March) are characteristic of the Upper São Francisco, and droughts generally occur in the Middle and Lower Middle São Francisco.
In relation to the social characteristics of the region of the São Francisco River basin: it is an area of high demographic density and with points where there is a population in a situation of poverty. The total population of the basin, according to the IBGE, is of almost 14 million inhabitants (predominantly urban), and the demographic density is approximately 20.0 inhabitants per km2. Most of the population is located in Alto do São Francisco (48.8%), and the region with the lowest concentration of population is Baixo São Francisco (10.7%).
See too: Main hydrographic basins in Brazil
Main tributaries
The São Francisco River has, according to the Ministry of the Environment, 168 tributaries. Among them, 90 are located on the left bank, and 78 on the right bank. Of these 168 tributaries, 99 are perennial, such as the Rio Paracatu, Corrente, Paraopeba and Urucuia. 69 of them are intermittent (rivers that disappear during the dry season).
The main tributaries of the São Francisco River Basin are located on the left bank of both the Upper and Middle São Francisco, due to the sedimentary formation, which allows the rainwater to infiltrate more easily, feeding these rivers.
The main tributaries are:
Paraopeba River |
Abaete River |
Jequitaí River |
Paracatu River |
Rio Verde Grande |
Rio Carinhanha |
Current River |
Rio Pará |
Rio das Velhas |
Pajeú River |
river saltpeter |
Urucuia River |
Transposition of the São Francisco River
The transposition of the São Francisco River is not a current project. The first attempt to cross the river took place in 1847. The idea was presented to Dom Pedro II by engineer Marcos de Macedo, who intended to reduce the problems of drought in the Northeast. However, the project did not come to pass.
Other attempts—in the years 1856, 1886, and 1889—did not succeed. During the administrations of Getúlio Vargas, Itamar Franco and Fernando Henrique Cardoso, the issue of transposing the São Francisco River was also on the agenda, but, again, it did not get off the ground.
The idea of mitigating the effects caused by the drought resurfaced in the government of Luiz Inácio (Lula) da Silva, between 2003 and 2006. The then president ordered the transposition work to be carried out.
The project is currently running and has not been completed. It is a work from the Federal Government and aims to "divert" the waters of the São Francisco based on the construction of canals to make intermittent rivers become perennial rivers, thus reducing the scarcity of water that plagues the Brazilian Northeast. The population — from the states of Ceará, Pernambuco, Paraíba, Rio Grande do Norte and Ceará — would have greater access to the water and, thus, greater possibilities for the development of activities that leverage the lives of people in these regions.
The idea of the São Francisco transposition project is divided into two axes:
1) North Axis: collects water from the São Francisco in the region of Cabrobó, Pernambuco, and distributes it to the interior of the states of Ceará, Pernambuco, Paraíba and Rio Grande do Norte. This stretch will cover 400 km, operating with a continuous flow of 16.4 cubic meters per second.
2) East Axis: it collects water from the São Francisco in the Floresta region of Pernambuco and distributes it to the hinterland and wilderness of Pernambuco and Paraíba. This stretch will cover 220 km, with a continuous flow of 10 cubic meters per second.
It is worth noting that this project is subject to numerous criticisms, since is associated with several negative environmental impacts arising from the works that must be carried out, as well as the logging and the loss of biodiversity in some areas. Some scholars also believe that transposition can damage the river's flow in more near the spring areas, also harming the generation of energy by the hydroelectric plants installed in the area of bowl.
Curiosities about the São Francisco River
- É known as "Old Chico" and also like "Brazilian Nile", because of its floods, which make its banks fertile.
- The São Francisco River was discovered in the year 1501 and is considered the river of national integration, as it connects the Northeast and Southeast regions, playing an important role in the occupation of the territory by allowing the entry of flags.
- Although the largest volume of water that supplies the São Francisco is offered by the Cerrado rivers, they are the Três Marias and Sobradinho dams that guarantee, today, the regularity of the river, even at the dry.
- In the São Francisco River basin, there are about 158 species of fish.
- The São Francisco River region is rich in deposits of various minerals, such as zinc, lead, diamond, slate, manganese, among others.
- Mining and mining cause numerous impacts in the São Francisco River region. Deforestation and sediment deposition compromise the quality of the river.
- O logging and land use for agricultural practices has increased cases of erosion, drastically reducing the basin's retention capacity, which causes flooding.
One of the main importance of the São Francisco River is the generation of electric energy in hydroelectric plants, such as the Xingó Plant.
Importance of the São Francisco River for the Brazilian Northeast
The São Francisco River is extremely important for the water supply of the Northeast and Southeast, being considered one of the essential development factors, mainly in the Northeast Brazilian. As it is located in the northeastern semiarid region, the river is one of the few sources of water in the region.
Many families and fishermen make their living from the river. On its banks, agriculture and livestock are developed. Local vegetation and availability of ores are also relevant factors in the importance of this watercourse.
According to the São Francisco Valley Development Company (Codevasf), its banks are considered a large orchard. Several fruits are cultivated in the river area, where large companies have been installed. Fruits such as papaya, mango and watermelon are grown, which supply the domestic and foreign market.
The São Francisco River is also used for power generation. Big ones hydroelectric plants, like Xingó and Sobradinho, use the power of their water to generate electricity. The energy generated supplies the Northeast region and part of the state of Minas Gerais.
read more: 10 largest hydroelectric plants in the world
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*Image Credits: ANDRE DIB / Shutterstock
By Rafaela Sousa
Graduated in Geography
Source: Brazil School - https://brasilescola.uol.com.br/brasil/rio-sao-francisco.htm