Hydrology of the Congo River ( about one-sixth of the known world hydro energy resources)


The Congo has a regular flow, which is fed by rains throughout the year. At Kinshasa the flow has for many years remained between the high level of 2,310,000 cubic feet (65,000 cubic metres) per second, recorded during the flood of 1908, and the low level of 756,000 cubic feet (21,000 cubic metres) per second, recorded in 1905. During the unusual flood of 1962, however, by far the highest for a century, the flow probably exceeded 2,600,000 cubic feet (73,000 cubic metres) per second.

At Brazzaville and Kinshasa, the river’s regime is characterized by a main maximum at the end of the year and a secondary maximum in May, as well as by a major low level during July and a secondary low level during March and April. In reality, the downstream regime of the Congo represents climatic influence extending over 20° of latitude on both sides of the Equator a distance of some 1,400 miles (2,250 km). Each tributary in its course modifies the level of the main stream. Thus, for example, the low level in July at Malebo Pool results from two factors: a drought that occurs for several months in the southern part of the basin at that time, as well as a delay before the floods of the Ubangi tributary flowing down from the north arrive, which does not happen before August. The Congo basin is so vast that no single meteorologic circumstance is capable of disturbing the slow movement of the waters’ rise and fall. The annual fluctuations may alter drastically, however, when floodwaters from different tributaries that normally coincide with each other arrive at different times.

Lake Tanganyika, apart from brief seiches caused by wind drift and sudden changes in atmospheric pressure, may experience considerable variations in its water level from year to year. In 1960, for example, its waters flooded parts of KalemiDemocratic Republic of the Congo, and BujumburaBurundi. A series of particularly rainy years followed by a blocking of the outlet by floating vegetation may explain this phenomenon.



Typical climate in regions through which the Congo flows is that of Yangambi, a town situated on the river’s right bank slightly north of the Equator and a little downstream of Kisangani. Humidity is high throughout the year, and annual rainfall amounts to 67 inches (1,700 mm) and occurs fairly regularly; even in the driest month the rainfall totals more than 3 inches (76 mm). Temperatures are also uniformly high throughout the year, and there is little diurnal variability. The average temperature at Yangambi is in the mid-70s F (mid-20s C).

From the pluviometric equator (an imaginary east-west line indicating the region of heaviest rainfall), which is situated slightly to the north of the geographic equator, the amount of rainfall decreases regularly in proportion to latitude. The northernmost points of the basin, situated in the Central African Republic, receive only from 8 to 16 inches (200 to 400 mm) less during the course of a year than points near the Equator. The dry season, however, lasts for four or five months, and there is only one annual rainfall maximum, which occurs in summer. In the far southern part of the basin, at a latitude of 12° S, the climate becomes definitely Sudanic in character, with marked dry and wet seasons of approximately equal length and with rainfall of about 49 inches (1,250 mm) a year.



Plant life

The Congo basin is home to the second largest rainforest in the world. The equatorial climate that prevails over a significant part of the Congo basin is coextensive with a dense evergreen forest. The Congolese forest spreads out over the central depression, extending continuously from about 4° N to about 5° S; it is interrupted only by clearings, many of which have a natural origin. The forest region is bordered on either side by belts of savanna (grassy parkland). The forest and savanna often meet imperceptibly, blending together in a mosaic pattern; more rarely, strips of forest invade the grassland. Farther away from the Equator, and to the extent that the Sudanic features of the climate become evident, the wooded savanna region, with its thin deciduous forest, is progressively reached.

As it courses through the solid mass of the Congolese forest, the Congo and its tributaries are bordered by discontinuous grassy strips. Meadows of Echinochloa (a type of grass), papyrus, and Cyperaceae (sedge) occupy abandoned river channels, fringe the banks, or, behind a curtain of forest, blanket the depressions in the centre of the islands, They also spring up on sandbanks, as well as on the downstream ends of islands that are fertilized by the floods. A shrub, Alchornea, frequently marks the transition to the high forest that grows on the levees behind the banks.


Animal life

The animal life of the Congo basin is identified to a certain extent with that of the equatorial forest, which is sharply distinct from the wildlife of the savannas. Within this equatorial domain, the Congo and its principal tributaries form a separate ecological milieu. The animal population of the great waterways often has fewer affinities with the neighbouring marshes or the forests on dry land than it has with other river systems, whether of the coastal region or the savannas.

Numerous species of fish live in the waters of the Congo; more than 230 have been identified in Malebo Pool and the waters that flow into it alone. The riverine swamps, which often dry up at low water, are inhabited by lungfish, which survive the dry periods buried and encysted in cocoons of mucus. In the wooded marshlands, where the water is the colour of black tea, the black catfish there assume the colour of their environment. The wildlife of the marshes and that of the little parallel streams do not mix with the wildlife of the river itself.

The waters of the Congo contain various kinds of reptiles, of which crocodiles are the most striking species. Semiaquatic tortoises are also found, as are several species of water snakes.

The forest birdlife constitutes, together with the birdlife of the East African mountains, the most specifically indigenous birdlife found on the African continent. In the Congo region more than 265 species typical of the equatorial forest have been recorded. Occasionally or seasonally, however, nontypical birds may be observed. Seabirds, such as the sea swallow, fly upstream from the ocean. Migratory birds from Europe, including the blongios heron and the Ixobrychus minutus (little bittern), pass through the region. Species with a wide distribution within Africa, such as the Egyptian duck, also have been sighted. Ducks, herons, storks, and pelicans are abundantly represented.

Aquatic mammals are rare, consisting of the hippopotamus, two species of otters, and the manatee. The manatee (sea cow), which lives entirely in the water, has been officially identified only on the Sangha tributary but appears to have given rise to some curious legends on the lower Congo, including its association with a creature called Mami Wata (a kind of siren), stories of which were carried by African slaves to the Americas.



The people and the economy

Life of the river peoples

Three types of environments are found, either juxtaposed or in succession, along the river and its tributaries: the narrower sections, bordered by firm ground; the wider stretches, dotted with islands and accompanied by backwaters; and the zones where flooding occurs or where there are extensive marshes.

Almost all the river peoples engage in fishing. Along the narrow sections, where rapids often occur, fishing is only of interest to a small number of villages. The Enya (Wagenia) of Boyoma Falls and the Manyanga living downstream from Malebo Pool attach fish traps to stakes or to dams built in the rapids themselves. Fishing of a very different nature, notably by poison, is conducted in the marshy areas, where the population is more extensive than might be imagined. Among these peoples are the Ngombe—“water people”—who inhabit the Itimbiri-Ngiri and the triangle formed by the Congo and the Ubangi. Other fisherfolk of the marshes dwell in the lagoons and the flooded forests of the region where the confluence of the Congo and the Alima, Likouala, and Sangha occurs.

Enya (Wagenia) fishing in the rapids of the Congo River near Kisangani, Democratic Republic of the Congo.


Despite unfavourable conditions, all these peoples are also cultivators. They raise dikes, often of monumental size, to plant cassava (manioc) on the land thus sheltered from flooding. Other minor crops, such as sweet potatoes, bananas, and yams, are also found. The Congo basin has the continent’s most important timber resources, but the timber industry is developing slowly, mainly because the interior is so inaccessible and because the cost of transporting timber to the coast is so high.

Few modes of existence have undergone such profound changes as a result of contact with the modern world as has that of the river’s fisherfolk. The growth of the towns on the banks of Malebo Pool as well as the taste of urban dwellers for river fish have served to stimulate fishing by tying it to a cash economy. It is not just a question of villagers smoking fish that they sell to passing traders. Increasingly numerous fishing crews sail up the Congo, the Ubangi, and the Kasai, well above their confluences, to fish in the shallows.



The Congo is an important navigational system in Africa. Within the territorial limits of the Democratic Republic of the Congo alone, there are some 8,700 miles (14,000 km) of navigable waterway. Of this total, 650 miles (1,050 km) are accessible at all seasons to barges with capacities between 800 and 1,100 tons, depending upon the height of the water. The amount of goods transported by water—consisting mainly of agricultural produce, wood, minerals, and fuel—is very modest in comparison with the traffic on European rivers (for example, the commercial traffic from the port of Kinshasa does not reach a million tons), but river transport remains essential for communications with regions that are inaccessible by road, especially in the cuvette. The three principal routes, all of which converge on the downstream terminus at Kinshasa on the Malebo Pool, run from Kisangani, from Ilebo (formerly Port-Francqui) on the Kasai, and from Bangui on the Ubangi. River transport, however, falls short of the role it could play in development. It has actually declined since the states of the Congo basin became independent in 1960, because of serious problems with aging equipment, a lack of maintenance of the infrastructure, and the poor functioning of the public waterway agencies. In the Democratic Republic of the Congo only the section from Ilebo to Kinshasa is still important, because it constitutes the river link (the other link being a railway between Kinshasa and Matadi) used to transport the copper production of Katanga to the coast.

This network has fostered economic development in inland areas, far from the coast. Varied activities include the production of palm oil on the banks of the Kwilu, centred on the port of Kikwit, and the establishment of plantations of robusta coffee in the Kisangani area.

Before such developments could be undertaken, however, it was necessary to overcome the barrier to the sea formed by the Congo’s lower course. That feat was accomplished in 1898 with the opening of the railway between Matadi and Léopoldville (now Kinshasa) and in 1934 by the completion of the Congo-Ocean rail line on the right bank between Brazzaville and Pointe-Noire.

While the river system facilitates navigation, it also hinders land transportation. Only a small number of bridges cross the Congo and its tributaries. The Kongolo rail-and-road bridge over the Lualaba was reconstructed in 1968, and a bridge over the Congo at Matadi was opened in 1983. Numerous projects to improve the situation nevertheless exist, notably a link between Kinshasa and Brazzaville. This project has long been under discussion, although to financial obstacles are added difficulties caused by political dissension. Several times since the two countries gained independence in 1960, dissension has interrupted the ferry traffic between the two capitals.


It has been estimated that the hydroelectric potential of the Congo basin amounts to about one-sixth of the known world resources, but only a fraction of this potential has been harnessed. The single site of Inga, just upriver from Matadi, has a power potential estimated at more than 30,000 megawatts. Two hydroelectric projects, called Inga I and Inga II, have been completed there since the independence of the Democratic Republic of the Congo. Further development of the region’s hydropower potential, as outlined in the ambitious “Grand Inga” scheme, would create one of the world’s largest hydroelectric power systems.

Study and exploration

The question of the source of the Congo confronted European explorers from the time that the Portuguese navigator Diogo Cão encountered the river’s mouth in 1482, which he believed to be a strait providing access to the realm of the mythical Prester John, a Christian priest-king. It is virtually certain that, well before the Welsh explorer Henry Morton Stanley arrived in 1877, some 17th-century Capuchin missionaries reached the shores of Malebo Pool. This exploit, however, was not followed up, even by the amply supplied expedition led by James Kingston Tuckey, which was sent out by the British Admiralty in 1816 but was decimated and had to retrace its footsteps even before it had surmounted the cataracts. Preposterous hypotheses about the river continued to be entertained, connecting, for example, the upper Niger to the Congo or maintaining that the Congo and the Nile both flowed from a single great lake in the heart of Africa.

Even after the European discovery of Lake Tanganyika by the British explorers Richard Burton and John Speke (1858), then of the Lualaba (1867) and of Lake Bangweulu (1868) by the Scottish explorer David Livingstone, uncertainty remained—uncertainty that Stanley was to dissipate in the course of his famous expedition in 1876 and 1877 that took him by water from the Lualaba to the Congo’s mouth over a period of nine months. In the interior of the Congo basin and above all on the right bank, the final blank spaces on the map could not be filled in until about 1890, when the exploration of the upper course of the Ubangi was completed.

Lake Tanganyika

Lake Tanganyika near Bujumbura, Burundi.

Kay Honkanen/Ostman Agency



Source : https://www.britannica.com/place/Congo-River/Hydrology

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