River Congo

The Congo is a giant river in the middle of Africa.

It flows through a huge, green rainforest. It makes a big curve before it reaches the ocean. Two big cities sit across the river from each other.

The Congo River is the second-longest river in Africa, after the Nile, at about 4,700 kilometers. Its farthest source is the Chambeshi River in the highlands of northeastern Zambia. From there it flows in a giant counterclockwise arc, first northwest, then west, then southwest, until it reaches the Atlantic Ocean.

Its basin, all the land that drains into it, covers about 3.46 million square kilometers, almost all of the Democratic Republic of the Congo and much of the Republic of the Congo, the Central African Republic, Zambia and Angola. The basin holds the world's second-largest rainforest. Two capital cities, Kinshasa and Brazzaville, face each other across a wide part of the river called Malebo Pool.

Britannica gives the Congo a length of about 4,700 km and a basin of some 3,457,000 km², taking in almost all of the Democratic Republic of the Congo, most of the Republic of the Congo and the Central African Republic, eastern Zambia, northern Angola and parts of Cameroon and Tanzania. The Chambeshi, rising at 1,760 m between Lakes Tanganyika and Nyasa, is the remotest source, but the Lualaba carries the most water, so either can be called the original main stream.

The Congo and the Amazon are the world's two great rivers flowing out of equatorial zones with rain in almost every month. Upstream of Malebo Pool the basin receives about 1,500 mm of rain a year, more than a quarter of which reaches the Atlantic. The basin is about half the size of the Amazon's, and the Congo's flow of about 41,000 m³/s at its mouth is far less than the Amazon's. With its tributaries it forms Africa's largest network of navigable waterways, about 14,000 km within the DR Congo alone.

The middle of the Congo's land is shaped like a giant, shallow bowl.

Rivers flow down into the bowl from all sides. The Congo rushes over waterfalls, then flows slowly and widely. Near the sea it crashes through wild rapids.

The center of the Congo basin is a huge, shallow depression, like a saucer. For hundreds of millions of years, mud and sand have washed into it from the higher land all around. Rivers flow down its slopes from every side, like the ribs of a fan, and meet in the Congo.

The river has three parts. In the upper Congo, rivers join, widen into lakes and tumble over rapids, such as Boyoma Falls near Kisangani. In the middle Congo, the river flows calmly for more than 1,600 kilometers, sometimes 8 to 13 kilometers wide, dotted with islands. Below Malebo Pool, the lower Congo races through 32 cataracts and rapids before it reaches the sea.

Britannica describes the central cuvette (saucer) as an immense depression of Quaternary alluvium over thick continental sands and sandstones; boreholes show sediment accumulating since at least 570 million years ago, evidence of persistent subsidence, with uplift on the eastern rim influenced by the Western Rift Valley. Tributaries descend concentric slopes of 275 to 460 m toward the center.

The upper Congo is a series of confluences, lakes (Upemba, Bangweulu, Mweru, Tanganyika) and rapids. Below Boyoma Falls, seven cataracts ending at Kisangani, the navigable middle Congo runs more than 1,600 km, splitting into arms between islands and widening to 8 to 11 km, once 13 km, before narrowing through the Chenal, cut hundreds of meters into the sandstone of the Batéké Plateau. The Ubangi, Sangha and Kwa raise the flow from under 7,000 m³/s at Kisangani to nearly the maximum at Kinshasa. Below Malebo Pool, 32 cataracts, including Inga Falls, drop the river from about 275 m to near sea level; the 134 km estuary from Matadi forms the Angola-DR Congo border, and offshore the river continues as a submarine canyon about 200 km long. Fed by rain on both sides of the Equator, its flow is unusually regular.

Hundreds of kinds of fish live in the Congo.

Some live only here and nowhere else. Some are white and blind. Forest elephants, bonobos and lots of birds live in the forest beside the river.

The Congo is full of fish. Scientists from the American Museum of Natural History have found about 320 kinds in just the last 350 kilometers of the river, and about 90 of them live nowhere else. Scientists think the wild rapids act like walls that keep groups of fish apart, so new species can form. One strange fish is white and blind and is thought to live deep in the river.

More than 265 kinds of forest birds have been recorded in the Congo region, and hippos live in the river. In the northwest of the basin, UNESCO protects forests with large numbers of forest elephants. The river also separates two kinds of apes: chimpanzees live north of it, and bonobos live only south of it.

Britannica notes more than 230 fish species in Malebo Pool and its inflows alone, lungfish that survive dry spells in mucus cocoons in drying swamps, and black catfish matching tea-colored marsh water. The American Museum of Natural History reports about 320 species in the lower Congo's 350 km, 90 of them endemic, compared with about 115 in the much longer Upper Nile. Its researchers propose that the rapids isolate fish populations, speeding speciation: two populations of Teleogramma brichardi from opposite banks look alike yet differ by about 5 percent in a DNA section. The blind, colorless Lamprologus lethops is always found dead or dying at the surface; one that died in Stiassny's hand had gas bubbles in its skin and gills, which led the team to suspect it lives at great depth.

The river shapes other animals' ranges too: AMNH notes that common chimpanzees live only north of the Congo and bonobos only south of it, a split biologists suspect began at least 800,000 years ago. Britannica records more than 265 equatorial-forest bird species, migrants from Europe, and rare aquatic mammals: hippopotamus, two otter species and the manatee, confirmed only on the Sangha. In the northwestern basin, the Sangha Trinational World Heritage site (which includes Nouabalé-Ndoki National Park) protects large populations of forest elephants.

Many people along the Congo catch fish.

They use traps, nets and boats. They grow cassava on land beside the river. Big boats carry goods up and down the river, because there are few roads.

Almost all the peoples living along the Congo fish. At Boyoma Falls, the Enya people tie fish traps to poles set right in the rapids. In the marshes, the Ngombe, whose name means water people, fish in the flooded forest. People also build dikes, banks of earth, to grow cassava on land safe from floods.

The river is also a road. Few roads and bridges cross the region, so boats carry farm goods, wood and fuel between towns. Railways built in 1898 and 1934 carry goods around the rapids to the sea. Europeans once called the river the Zaire, from a local word meaning simply river; its modern name comes from the old Kingdom of Kongo.

Britannica describes three river environments, narrow sections, island-studded reaches and floodplain marshes, each with its own fishing: the Enya (Wagenia) at Boyoma Falls and the Manyanga below Malebo Pool attach traps to stakes in the rapids, while marsh peoples such as the Ngombe fish the flooded forests. Cultivators raise dikes, sometimes of monumental size, to grow cassava, sweet potatoes, bananas and yams, and the growth of Kinshasa and Brazzaville has tied fishing to a cash economy.

The DR Congo has some 14,000 km of navigable waterway, but traffic is modest and has declined since independence in 1960; the Ilebo-Kinshasa route still carries Katanga's copper toward the coast. The Matadi-Kinshasa railway (1898) and the Congo-Ocean line from Brazzaville to Pointe-Noire (1934) bypass the cataracts. Europeans who reached the river at the end of the 15th century called it the Zaire, a corruption of a local word for river; the name Congo, from the Kingdom of Kongo, came into use in the early 18th century. Britannica estimates the basin's hydroelectric potential at about one-sixth of the world's known resources, with more than 30,000 MW at Inga alone, where Inga I and II have been built.