The Central African Republic (CAR) lies entirely within the tropical zone of Central Africa. Completely landlocked, it is bordered by Chad, Sudan, Zaire, the Congo, and Cameroon. The land consists of an undulating plateau varying in altitude from 2,000 to 2,500 ft. The land is well drained by two river systems: the Ugangi and its tributaries in the southern and the tributaries of the Shari and Longone rivers in the north.
Topography of the Central African Republic
The rivers in CAR are crucial natural resources, serving as waterways and supporting the local ecosystems and communities. These rivers flow into three main drainage basins.
Key Rivers and Their Significance
Most of the rivers in the Central African Republic are part of the huge Congo River basin.
The Ubangi River
The Ubangi River, also spelled Oubangui, is the largest right-bank tributary of the Congo River in the region of Central Africa. The headwaters of the Oubangui River begin in the Central African Republic. The Ubangi is formed by the union of the Bomu (Mbomou) and Uele (Welle) rivers. Then it flows west. The total length of the Ubangi, with the Uele, is approximately 1,400 miles (2,250 km). Its mean discharge at Bangui is estimated at 151,147 cubic feet (4,280 cubic metres) per second.
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The Oubangui River, with a catchment of over 777,000 km², is a major tributary of the Congo River. Forested floodplains line the Oubangui as it flows west along the border. The Oubangui eventually joins the Congo, which, at this point, is a slow flowing, braided maze of alluvial islands, sand banks, and floating beds of grass.
The lower course of the Oubangui River is characterised by lower levels of endemism than other rivers within the inner Congo basin. However, upstream areas and rapids, which are often located in savanna regions harbor some endemics, though these species are known only from small collections. High habitat diversity and hydrogeographic barriers have shaped the ichthyofauna of the Oubangui drainage. Numerous waterfalls separate upstream and downstream sections of the main river and its tributaries.
Ubangi River Basin
The Mbomou River
The Mbomou River is a very important river that forms much of the border between the Central African Republic and the Democratic Republic of the Congo. The Chinko River and its affluent the Vivado, the Ouarra and its affluent the Goangoa, the Kerre, and the Mbokou rivers all begin in the far southeastern corner of CAR and flow down gentle slopes to join the Mbomou River. The Mbomou flows along the border of CAR and DRC for several hundred kilometers until it is joined by the Kotto River; below this confluence the river is called the Oubangui.
The Chari River
Lake Chad is a large, shallow lake in Africa. The Chari River is the main river that feeds Lake Chad.
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Other Rivers
The Lom River starts in the Central African Republic and flows into the Sanaga River.
Drainage Basins
A drainage basin is like a giant bowl where all the rain and smaller streams eventually flow into one larger river or lake. The rivers in CAR flow into three main areas, called drainage basins.
Congo River Basin
Most of the rivers in the Central African Republic are part of the huge Congo River basin. The Congo River itself flows through countries like the Democratic Republic of the Congo and the Republic of the Congo. The Oubangui ecoregion encompasses the entirety of the Oubangui basin (with the exception of the Uelé basin) and a portion of the mainstem Congo River from its confluence with the Oubangui downstream to Malebo Pool.
Lake Chad Basin
The northern border of this ecoregion marks the divide between the Congo River and Lake Chad basins and the eastern border is the divide between the Congo and Nile basins.
Gulf of Guinea
The Gulf of Guinea is a large part of the Atlantic Ocean, located off the coast of West Africa.
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Ecological Aspects
The area between longitude 16° E and the Ubangi consists of flat, swampy valleys and low divides descending east and southeast from the western hills to the Congo River. Much of the region is covered with dense equatorial rainforest, and large portions of the region that lie northeast and southwest of the Sangha River are permanently inundated.
A variety of vegetation types covers the terrestrial landscape of the Oubangui ecoregion. In the Sudanian zone in the north, savanna predominates with some semi-humid forest, cropland, and gallery forest interspersed. Primary tropical rainforest blankets the landscape in the southern equatorial latitudes; dense evergreen forest occurs in the west-central areas and freshwater swamp forest occurs along the lower course of the Oubangui River.
Northeast of its confluence with the Congo, the Oubangui is joined by the Giri River and spreads out across a large floodplain, forming the Giri or Bangala Swamp. These swamps have black, acidic waters (pH 3.5-5.2) derived from the surrounding floodplain forests.
Right-bank tributaries of the Congo River below its junction with the Oubangui include the Likouala aux Herbes, Sangha, Likouala, Alima, Nkeni, and Lefini rivers. Swamp forests predominate on the floodplains in this section, creating over 6,800 km² that include parts of the Likouala aux Herbes swamps. The Likouala-aux-Herbes drains Lac Telé, a shallow lake possibly formed by a meteorite crater.
There are twelve endemic fishes known from this ecoregion, including rivulines, cichlids, mochokids, and cyprinids. Some of these rapids may have been formed after river capture of Nilo-Sudanic catchments by the Oubangui drainage.
