Zambezi
The Zambezi is the fourth-longest river in Africa, the longest east-flowing river in Africa and the largest flowing into the Indian Ocean from Africa. Its drainage basin covers, slightly less than half of the Nile's. The river rises in Zambia and flows through eastern Angola, along the north-eastern border of Namibia and the northern border of Botswana, then along the border between Zambia and Zimbabwe to Mozambique, where it crosses the country to empty into the Indian Ocean.
The Zambezi's most noted feature is Victoria Falls. Its other falls include Chavuma Falls at the border between Zambia and Angola and Ngonye Falls near Sioma in western Zambia.
The two main sources of hydroelectric power on the river are the Kariba Dam, which provides power to Zambia and Zimbabwe, and the Cahora Bassa Dam in Mozambique, which provides power to Mozambique and South Africa. Additionally, two smaller power stations are along the Zambezi River in Zambia, one at Victoria Falls and the other in Zengamina, near Kalene Hill in the Ikelenge District.
Course
Origins
The river rises in a black, marshy dambo in dense, undulating miombo woodland north of Mwinilunga and south of Ikelenge in the Ikelenge District of North-Western Province, Zambia, at about above sea level. The area around the source is a national monument, forest reserve, and important bird area.Eastward of the source, the watershed between the Congo and Zambezi Basins is a well-marked belt of high ground, running nearly east–west and falling abruptly to the north and south. This distinctly cuts off the basin of the Lualaba from the Zambezi. In the neighborhood of the source, the watershed is not as clearly defined, but the two river systems do not connect.
The region drained by the Zambezi is a vast, broken-edged plateau 900–1,200 m high, composed in the remote interior of metamorphic beds and fringed with the igneous rocks of the Victoria Falls. At Chupanga, on the lower Zambezi, thin strata of grey and yellow sandstones, with an occasional band of limestone, crop out on the bed of the river in the dry season, and these persist beyond Tete, where they are associated with extensive seams of coal. Coal is also found in the district just below Victoria Falls. Gold-bearing rocks occur in several places.
Upper Zambezi
The river flows to the southwest into Angola for about, then is joined by sizeable tributaries such as the Luena and the Chifumage flowing from highlands to the north-west. It turns south and develops a floodplain, with extreme width variation between the dry and rainy seasons. It enters dense evergreen Cryptosepalum dry forest, though on its western side, Western Zambezian grasslands also occur. Where it re-enters Zambia, it is nearly wide in the rainy season and flows rapidly, with rapids ending in the Chavuma Falls, where the river flows through a rocky fissure. The river drops about in elevation from its source at to the Chavuma Falls at, over a distance of about. From this point to the Victoria Falls, the level of the basin is very uniform, dropping only by another across a distance of around.The first of its large tributaries to enter the Zambezi is the Kabompo River in the North-Western Province of Zambia. The savanna through which the river flows gives way to a wide floodplain, studded with Borassus fan palms. A little farther south is the confluence with the Lungwebungu River. This is the beginning of the Barotse Floodplain, the most notable feature of the upper Zambezi, but this northern part does not flood so much and includes islands of higher land in the middle.
About 30 km below the confluence of the Lungwebungu, the country becomes very flat, and the typical Barotse Floodplain landscape unfolds, with the flood reaching a width of 25 km in the rainy season. For more than 200 km downstream, the annual flood cycle dominates the natural environment and human life, society, and culture. About 80 km further down, the Luanginga, which with its tributaries drains a large area to the west, joins the Zambezi. A short distance higher up on the east, the main stream is joined in the rainy season by overflow of the Luampa/Luena system.
A short distance downstream of the confluence with the Luanginga is Lealui, one of the capitals of the Lozi people, who populate the Zambian region of Barotseland in the Western Province. The chief of the Lozi maintains one of his two compounds at Lealui; the other is at Limulunga, which is on high ground and serves as the capital during the rainy season. The annual move from Lealui to Limulunga is a major event, celebrated as one of Zambia's best-known festivals, the Kuomboka.
After Lealui, the river turns south-southeast. From the east, it continues to receive numerous small streams, but on the west, it is without major tributaries for 240 km. Before this, the Ngonye Falls and subsequent rapids interrupt navigation. South of Ngonye Falls, the river briefly borders Namibia's Caprivi Strip. Below the junction of the Cuando River and the Zambezi, the river bends almost due east. Here, the river is broad and shallow and flows slowly, but as it flows eastward towards the border of the great central plateau of Africa, it reaches a chasm into which the Victoria Falls plunge.
Middle Zambezi
The Victoria Falls are considered the boundary between the upper and middle Zambezi. Below them, the river continues to flow due east for about, cutting through perpendicular walls of basalt apart in hills high. The river flows swiftly through the Batoka Gorge, the current being continually interrupted by reefs. It has been described as one of the world's most spectacular whitewater trips, a tremendous challenge for kayakers and rafters alike. Beyond the gorge are a succession of rapids that end below Victoria Falls. Over this distance, the river drops.At this point, the river enters Lake Kariba, created in 1959 following the completion of the Kariba Dam. The lake is one of the largest man-made lakes in the world, and the hydroelectric power-generating facilities at the dam provide electricity to much of Zambia and Zimbabwe.
The Luangwa and Kafue rivers are the two largest left-hand tributaries of the Zambezi. The Kafue joins the main river in a quiet, deep stream about wide. From this point, the northward bend of the Zambezi is checked, and the stream continues due east. At the confluence of the Luangwa, it enters Mozambique.
The middle Zambezi ends where the river enters Lake Cahora Bassa, formerly the site of dangerous rapids known as Kebrabassa; the lake was created in 1974 by the construction of the Cahora Bassa Dam.
Lower Zambezi
The lower Zambezi's from Cahora Bassa to the Indian Ocean is navigable, although the river is shallow in many places during the dry season. This shallowness arises as the river enters a broad valley and spreads out over a large area. Only at one point, the Lupata Gorge, from its mouth, is the river confined between high hills. Here, it is scarcely wide. Elsewhere it is from wide, flowing gently in many streams. The river bed is sandy, and the banks are low and reed-fringed. At places, however, and especially in the rainy season, the streams unite into one broad, fast-flowing river.About from the sea, the Zambezi receives the drainage of Lake Malawi through the Shire River. On approaching the Indian Ocean, the river splits up into a delta. Each of the primary distributaries, Kongone, Luabo, and Timbwe, is obstructed by a sand bar. A more northerly branch, called the Chinde mouth, has a minimum depth at low water of at the entrance and further in, and is the branch used for navigation. About further north is a river called the Quelimane, after the town at its mouth. This stream, which is silting up, receives the overflow of the Zambezi in the rainy season.
Discharge
Average, minimum and maximum discharge of the Zambezi River at Marromeu. Period from 1998 to 2022.Delta
The delta of the Zambezi is today about half as broad as it was before the construction of the Kariba and Cahora Bassa dams controlled the seasonal variations in the flow rate of the river. Before the dams were built, seasonal flooding of the Zambezi had quite a different impact on the ecosystems of the delta from today, as it brought nutrient-rich fresh water down to the Indian Ocean coastal wetlands. The lower Zambezi experienced a small flood surge early in the dry season as rain in the Gwembe catchment and north-eastern Zimbabwe rushed through while rain in the upper Zambezi, Kafue, and Lake Malawi basins, and Luangwa to a lesser extent, is held back by swamps and floodplains.The discharges of these systems contribute to a much larger flood in March or April, with a mean monthly maximum for April of per second at the delta. The record flood was more than three times as big, per second being recorded in 1958. By contrast, the discharge at the end of the dry season averaged just per second.
In the 1960s and 1970s, the building of dams changed that pattern completely. Downstream, the mean monthly minimum–maximum was per second; now it is per second. Medium-level floods especially, of the kind to which the ecology of the lower Zambezi was adapted, happen less often and have a shorter duration. As with the Itezhi-Tezhi Dam's deleterious effects on the Kafue Flats, this has these effects:
- Fish, bird, and other wildlife feeding and breeding patterns were disrupted.
- Less grassland remains after flooding for grazing wildlife and cattle.
- Traditional farming and fishing patterns were disrupted.
Ecology of the delta
Although the dams have stemmed some of the annual flooding of the lower Zambezi and caused the area of floodplain to be greatly reduced, they have not removed flooding completely. They cannot control extreme floods, and they have only made medium-level floods less frequent. When heavy rain in the lower Zambezi combines with significant runoff upstream, massive floods still happen, and the wetlands are still an important habitat. The shrinking of the wetlands, though, resulted in uncontrolled hunting of animals such as buffalo and waterbuck during the Mozambican Civil War.
Although the region has had a reduction in the populations of the large mammals, it is still home to some, including the reedbuck and migrating eland. Carnivores found here include lion, leopard, cheetah, spotted hyena, and side-striped jackal. The floodplains are a haven for migratory waterbirds, including pintails, garganey, African openbill, saddle-billed stork, wattled crane, and great white pelican.
Reptiles include Nile crocodile, Nile monitor lizard, African rock python, the endemic Pungwe worm snake, and three other snakes that are nearly endemic - floodplain water snake, dwarf wolf snake, and swamp viper.
Several butterfly species are endemic.