The Congo River, also called the Zaire River in the past, is the second-longest river in Africa, after the Nile. It is the third-largest river in the world by the amount of water it carries, following the Amazon and Ganges–Brahmaputra rivers. It is the deepest river recorded, with depths measured at about 220 meters (720 feet). The Congo–Lualaba–Luvua–Luapula–Chambeshi River system has a total length of 4,700 kilometers (2,900 miles), making it the ninth-longest river in the world. The Chambeshi River is a tributary of the Lualaba River, and the Lualaba is the name of the Congo River upstream of Boyoma Falls, covering 1,800 kilometers (1,100 miles).

When measured with its main tributary, the Lualaba, the Congo River has a total length of 4,370 kilometers (2,720 miles). It is the only major river that crosses the equator twice. The Congo Basin covers an area of about 4,000,000 square kilometers (1,500,000 square miles), which is 13% of Africa’s total land area.

Name

The name Congo/Kongo comes from the Kingdom of Kongo, which was once located on the southern side of a river. The kingdom was named after the Bantu Kongo people, who were called "Esikongo" in the 17th century. South of the Kingdom of Kongo was another kingdom called Kakongo, which was mentioned in 1535. In 1564, Abraham Ortelius labeled a city at the river's mouth as "Manicongo" on his world map. The names of the Kongo people may come from a word meaning a public gathering or meeting place. The modern name "Bakongo" for the Kongo people was used starting in the early 20th century.

The name Zaire comes from a Portuguese version of a Kikongo word, "nzere," which means "river." This word is a short form of "nzadi o nzere," meaning "river swallowing rivers." The river was called Zaire during the 16th and 17th centuries. Over time, the name "Congo" gradually replaced "Zaire" in English during the 18th century. By the 19th century, "Congo" was the preferred name in English writing, though some sources still used "Zaire" or "Zahir" as the name used by local people. The Democratic Republic of the Congo and the Republic of the Congo are named after the river. The earlier Republic of the Congo, which became independent in 1960 from the Belgian Congo, also used this name. The Republic of Zaire, which existed from 1971 to 1997, was named after the river's name in French and Portuguese.

Basin and course

The Congo River's drainage basin covers 4,014,500 square kilometers (1,550,000 square miles), an area almost the same size as the European Union. The river's discharge at its mouth varies between 23,000 and 75,000 cubic meters per second (810,000 to 2,650,000 cubic feet per second), with an average of 41,000 cubic meters per second (1,400,000 cubic feet per second). Each year, the river carries 86 million tonnes of suspended sediment to the Atlantic Ocean and an additional 6% of bedload.

The river and its tributaries flow through the Congo rainforest, the second-largest rainforest in the world, after the Amazon rainforest in South America. The Congo is the third-largest river by discharge volume (41,860 cubic meters per second at its mouth), following the Amazon (219,530 cubic meters per second) and the Ganges–Brahmaputra–Meghna (43,950 cubic meters per second at its delta). It has the second-largest drainage basin of any river, after the Amazon, and is one of the deepest rivers in the world, with depths exceeding 220 meters (720 feet). Because its drainage basin includes areas both north and south of the Equator, the river's flow remains stable, as at least one part of the river always experiences a rainy season.

The Congo River's sources are located in the highlands and mountains of the East African Rift, as well as in Lake Tanganyika and Lake Mweru, which feed the Lualaba River. The Lualaba River becomes the Congo River below Boyoma Falls. The Chambeshi River in Zambia is generally considered the source of the Congo, following the global practice of identifying the longest tributary as the river's origin, similar to how the Nile River's source is determined.

The Congo River flows generally northwest from Kisangani, just below Boyoma Falls, then turns gradually southwestward, passing Mbandaka. It joins the Ubangi River and flows into the Pool Malebo (Stanley Pool). Kinshasa (formerly Léopoldville) and Brazzaville are located on opposite sides of the river at the Pool, where the river narrows and flows through several cataracts in deep canyons (known collectively as the Livingstone Falls), passing Matadi and Boma before reaching the sea at Muanda.

The Lower Congo refers to the section of the river from the Atlantic coast to the twin cities of Brazzaville and Kinshasa. In this section, two major tributaries flow on the left (south) side of the river. The Kwilu River originates in the hills near the Angolan border and enters the Congo about 100 kilometers upstream from Matadi. The Inkisi River flows northward from the Uíge Province in Angola and joins the Congo at Zongo, approximately 80 kilometers (50 miles) downstream from the twin capitals. Due to the large number of rapids, especially the Livingstone Falls, this section of the river is not continuously navigable by riverboats.

Drainage basin

The Congo basin is found in ten countries and makes up about 13% of Africa. The highest point in the Congo basin is located in the Ruwenzori Mountains, at a height of around 4,340 meters (14,240 feet) above sea level.

Distribution of the Congo basin area between countries:

Tributaries

Lower Congo (River Mouth to Kinshasa)
Below Kinshasa, starting from the river's mouth near Banana, several major rivers flow into the Congo River. These include:

• M'pozo (left)
• Kwilu (left)
• Inkisi (left)
• Foulakary (right)
• Djoué (right)

Middle Congo (Kinshasa to the Boyoma Falls)
Between Kinshasa and the Boyoma Falls, the following rivers join the Congo River:

• Nsele (left)
• Lufimi (left)
• Mary (right)
• Kwa–Kasai (left)
• Fimi
• Lukenie
• Lokoro—Lake Mai-Ndombe
• Kwango
• Culio
• Wamba
• Kwilu
• Kwenge
• Inzia
• Loange
• Sankuru
• Lubilanji
• Lubefu
• Lubudi
• Lulua
• Chicapa
• Luachimo
• Lubembe
• Chiumbe
• Léfini (right)
• Léfini River
• Nkeni (right)
• Alima (right)
• Likouala – Mossaka (right)
• Sangha (right)
• Likouala aux Herbes
• Ngoko
• Boumba
• Kadéï (570 km, 41,000 km², 466 m³/s)
• Mambéré
• Ubangi (right)
• Ubangi River
• Giri
• Lua
• Lobaye
• Mbali
• Ouaka
• Kotto
• Mbomou
• Man on the Mbomou River, between Bangassou and Ndu
• Chinko
• Mbari
• Bili
• Uele
• Uele River
• Kibali
• Dungu
• Bomokandi
• Uere
• Irebu—Lake Tumba (left)
• Ruki (left)
• Momboyo
• Busira
• Salonga
• Tshuapa or Ruki (left)
• Lomela
• Ikelemba (left)
• Lulonga (left)
• Lopori
• Maringa
• Moeko (right)
• Mongala (right)
• Itimbiri (right)
• Aruwimi (right)
• Ituri
• A river flowing through the Ituri Rainforest
• Nepoko
• Lukombe (left)
• Lomami (left)
• Lomami River
• Lindi (right)
• Tshopo
• Cascades of the Tshopo River
• Maiko (right)

Upper Congo (Lualaba; upstream from the Boyoma Falls)
Above the Boyoma Falls, the following rivers flow into the Lualaba River:

• Lilu (right)
• Ruiki (left)
• Lilo (left)
• Lowa (right)
• Oso
• Ulindi (right)
• Lugulu
• Kasuku (left)
• Ambe (right)
• Elila (right)
• Loho (left)
• Lubutu (left)
• Kunda (right)
• Luama (right)
• Luika (right)
• Lukuga (right)
• Rusizi (Lake Tanganyika)
• Ruzizi River
• Malagarasi (Lake Tanganyika)
• Ugalla
• Gombe
• Moyowosi
• Luvidjo (left)
• Luvua (right)
• Kalungwishi (Lake Mweru)
• Luapula (Lake Mweru; 740 km, 173,386 km², 741 m³/s)
• Chambeshi (Lake Bangweulu, Bangweulu swamp; 500 km, 44,427 km², 185 m³/s)
• Kalumengongo (right)
• Lovoi (left)
• Lufira (right)
• Lubudi (left)
• Lufupa (left)

Economic importance

The Livingstone Falls stop ships from reaching the ocean, but most of the Congo River above the falls is easy to travel on in parts, especially between Kinshasa and Kisangani. Large river boats used the river until recently. The Congo River remains a key route for transportation in an area with few roads or railways. Railways now go around the three major falls, and much of Central Africa’s trade moves along the river. Goods include copper, palm oil (as kernels), sugar, coffee, and cotton.

The Congo River is the strongest river in Africa. During the rainy season, more than 50,000 cubic metres (1,800,000 cubic feet) of water flow into the Atlantic Ocean every second. This means the river and its smaller rivers have great potential to produce power from water. Scientists say the Congo Basin holds 13 percent of the world’s possible hydropower. This could supply all of Sub-Saharan Africa’s electricity needs.

There are about 40 hydropower plants in the Congo Basin. The largest are the Inga dams, located about 200 kilometres (120 miles) southwest of Kinshasa. The project began in the early 1970s, when the first dam was completed. The original plan called for building five dams with a total power generation of 34,500 megawatts (MW). So far, only Inga I and Inga II have been built, producing 1,776 MW.

In February 2005, South Africa’s state-owned power company, Eskom, proposed expanding power generation by improving the existing dams and building a new one. This would increase the facility’s maximum output to 40,000 megawatts (MW). It is feared that these new dams might cause many native fish species in the river to become extinct.

Natural history

The Congo River's current path formed between 1.5 and 2 million years ago during the Pleistocene era. During this time, many of the river’s upper tributaries, such as the Uele and upper Ubangi from the Chari system, and the Chambeshi River and some upper Kasai River tributaries from the Zambezi system, were likely captured from neighboring river basins.

The formation of the Congo River may have caused the bonobo and the common chimpanzee to become separate species from their most recent common ancestor. The bonobo lives only in the humid forests of the region, along with other species like the Allen’s swamp monkey, dryas monkey, aquatic genet, okapi, and Congo peafowl.

The Congo River Basin has a very high number of aquatic species, many of which are found only in this area. As of 2009, nearly 800 fish species had been recorded in the Congo River Basin (excluding Lake Tanganyika, which is connected but ecologically different). Large parts of the basin, such as the Salonga National Park area (about the size of Belgium), had not been studied at all by 2006. Scientists regularly discover new fish species in the basin, and many more remain unknown.

The Congo River has the highest fish diversity of any African river system. Other rivers, such as the Niger, Volta, and Nile, have about 240, 140, and 130 fish species, respectively. The Congo Basin has such varied habitats as river rapids, deep rivers, swamps, and lakes that it is often divided into multiple ecoregions. For example, the Livingstone Falls cataracts region has over 300 fish species, including about 80 that are found nowhere else. The southwestern part of the basin (Kasai River basin) has more than 200 fish species, with about a quarter being unique to the area.

Some of the most common fish families in the river include Cyprinidae (carp, such as Labeo simpsoni), Mormyridae (elephantfish), Alestidae (African tetras), Mochokidae (squeaker catfishes), and Cichlidae (cichlids). The giant tigerfish, a large predator, is also native to the river. Some unusual endemic species include Lamprologus lethops, a blind and pale fish that lives at depths of up to 160 meters; Heterochromis multidens, a cichlid more closely related to American cichlids than African ones; and Caecobarbus geertsii, the only known cavefish in Central Africa. The basin is also home to many endemic frogs and snails. Plans for new hydroelectric dams on the river could threaten the survival of many of these unique species.

Several turtle species and crocodiles, including the slender-snouted, Nile, and dwarf crocodile, live in the Congo River Basin. African manatees are found in the lower parts of the river.

The Democratic Republic of Congo (DRC) and the Republic of Congo (RoC) have faced repeated flooding along the Congo River and its tributaries during the rainy season. These floods cause erosion, landslides, and harm to human settlements, farming, and health. As global temperatures rise and rainfall becomes more intense and longer, the Congo River is expected to face greater challenges from climate change.

Between October 2019 and January 2020, heavy rains affected 16 of the 26 provinces in the DRC and eight of the 12 departments in the RoC, leading to the 2019–2020 Congo River floods. The rains caused the Congo and Ubangi rivers to overflow, resulting in widespread flooding, landslides, and the displacement of hundreds of thousands of people.

History

The entire Congo Basin is home to Bantu people, who are divided into hundreds of different ethnic groups. Bantu people began moving into the middle Congo area around 500 BC and reached the upper Congo by the first century AD. Some of the original people who lived in the region before the Bantu arrived, called the Pygmies/Abatwa of the Ubangian group, still live in the remote forest areas of the Congo Basin.

By the 13th century, three main groups of states existed in the western Congo Basin. In the east were the Seven Kingdoms of Kongo dia Nlaza, which were among the oldest and most powerful. These likely included Nsundi, Mbata, Mpangu, and possibly Kundi and Okanga. South of these was Mpemba, which stretched from modern-day Angola to the Congo River. It included kingdoms such as Mpemba Kasi and Vunda. To the west of Mpemba, across the Congo River, were three smaller states: Vungu (led by its ruler), Kakongo, and Ngoyo.

The Kingdom of Kongo was created in the late 14th century when the kingdoms of Mpemba Kasi and Mbata merged along the lower Congo River. Its control was limited to what is now the Kongo Central province. European exploration of the Congo began in 1482 when Portuguese explorer Diogo Cão discovered the river’s estuary (likely in August 1482). He marked the site with a stone pillar called a Padrão, which still exists in pieces today. Cão traveled up the river briefly and made contact with the Kingdom of Kongo. The full path of the river remained unknown for many years.

The upper Congo Basin is located west of the Albertine Rift. Its connection to the rest of the Congo was unknown until 1877. The far northeast of the Congo Basin was reached by the Nilotic expansion between the 15th and 18th centuries, by ancestors of the Southern Luo-speaking Alur people. In 1796, Francisco de Lacerda followed the Zambezi River and reached the upper part of the Congo Basin (the Kazembe region in the upper Luapula Basin).

The upper Congo River was first reached by the Arab slave trade in the 19th century. Nyangwe was established as a slavers’ outpost around 1860. In March 1871, David Livingstone became the first European to reach Nyangwe. Livingstone aimed to prove that the Lualaba River connected to the Nile, but on July 15, he witnessed the killing of about 400 Africans by Arab slavers in Nyangwe. This experience made him too distressed to continue his mission, so he returned to Lake Tanganyika.

Europeans had not reached the central parts of the Congo Basin from the east or west until Henry Morton Stanley’s expedition in 1876–77, supported by the Committee for Studies of the Upper Congo. At the time, one of the last unanswered questions about Africa was whether the Lualaba River fed the Nile (as Livingstone believed), the Congo, or even the Niger River. Stanley’s first trans-Africa journey, funded in 1874, began in Zanzibar and reached the Lualaba River on October 17, 1876. He traveled overland to Nyangwe, a lawless area with tribes known for cannibalism, where Tippu Tip controlled the slave trade. Stanley hired Tippu Tip’s men to guard him for about 90 days.

The group left Nyangwe through the thick Matimba forest and reached the Lualaba River again on November 19. Because the forest was so difficult to travel through, Tippu Tip turned back with his party on December 28, leaving Stanley with 143 people, including eight children and 16 women, and 23 canoes. Stanley’s first meeting with a local tribe was with the cannibal Wenya. He reported 32 encounters with unfriendly tribes on the river, some of which were violent, even though he tried to negotiate peaceful passage. The tribes were wary because their only experience with outsiders was with slave traders.

On January 6, 1877, after traveling 640 kilometers (400 miles), Stanley reached Boyoma Falls (later called Stanley Falls), which consisted of seven cataracts over 100 kilometers (60 miles). It took until February 7 to reach the end of the falls. There, Stanley learned the river was called Ikuta Yacongo, proving he had reached the Congo River and that the Lualaba did not connect to the Nile.

From this point, the tribes had firearms, likely due to Portuguese influence. After traveling about 1,900 kilometers (1,200 miles) over four weeks, Stanley reached Stanley Pool (now Pool Malebo), the site of modern cities Kinshasa and Brazzaville. Further downstream were the Livingstone Falls, named after Livingstone despite him never visiting the Congo. These falls included 32 rapids and drops totaling 270 meters (900 feet) over 350 kilometers (220 miles). Stanley began descending the falls on March 15, a journey that took five months and cost many lives. From the Isangile Falls, five falls from the bottom, Stanley and his group left the river by canoe and traveled overland to the Portuguese outpost of Boma.

On August 3, Stanley reached the village of Nsada. He sent four men with letters to Boma for supplies. On August 7, relief arrived from the Liverpool trading firm Hatton & Cookson. On August 9, Stanley reached Boma, 1,001 days after leaving Zanzibar on November 12, 1874. The group then had 108 people, including three children born during the trip. Stanley likely lost 132 people due to disease, hunger, drowning, killing, or desertion.

Kinshasa was founded as a trading post by Stanley in 1881 and named Léopoldville in honor of Leopold II of Belgium. The Congo Basin was claimed by Leopold II as the Congo Free State in 1885, where many atrocities occurred until the region became the Belgian Congo.

General and cited sources

• Cana, Frank Richardson (1911). "Congo." In Chisholm, Hugh (ed.). Encyclopedia Britannica. Volume 6 (11th edition). Cambridge University Press. Pages 914–917.
• Forbath, Peter (1979). The River Congo: The Discovery, Exploration and Exploitation of the World's Most Dramatic River. New York: E. P. Dutton. ISBN 0-525-47573-7.
• Jeal, Tim (2007). Stanley: The Impossible Life of Africa's Greatest Explorer. London: Faber & Faber. ISBN 978-0-571-22102-8.