Zambezi

The Zambezi and its river basin.

The river rises in a black marshy dambo in dense undulating miombo woodland 50 kilometres (31 mi) north of Mwinilunga and 20 kilometres (12 mi) south of Ikelenge in the Ikelenge District of North-Western Province, Zambia, at about 1,524 metres (5,000 ft) above sea level.[13] The area around the source is a national monument, forest reserve and Important Bird Area.[14]

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 (the main branch of the upper Congo) from the Zambezi. In the neighborhood of the source, the watershed is not as clearly defined, but the two river systems do not connect.[15]

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.[16]

The river flows to the southwest into Angola for about 240 kilometres (150 mi), then is joined by sizeable tributaries such as the Luena and the Chifumage flowing from highlands to the north-west.[15] 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 400 metres (1,300 ft) 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 400 metres (1,300 ft) in elevation from its source at 1,500 metres (4,900 ft) to the Chavuma Falls at 1,100 metres (3,600 ft), in a distance of about 400 kilometres (250 mi). From this point to the Victoria Falls, the level of the basin is very uniform, dropping only by another 180 metres (590 ft) in a distance of around 800 kilometres (500 mi).[17]

The first of its large tributaries to enter the Zambezi is the Kabompo River in the northwestern 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.[18]

Thirty kilometres 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. Eighty kilometres further down, the Luanginga, which with its tributaries drains a large area to the west, joins the Zambezi. A few kilometres higher up on the east the main stream is joined in the rainy season by overflow of the Luampa/Luena system.[15]

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 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.[15] 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.

Victoria Falls, the end of the upper Zambezi and beginning of the 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 200 kilometres (120 mi), cutting through perpendicular walls of basalt 20 to 60 metres (66 to 200 ft) apart in hills 200 to 250 metres (660 to 820 ft) high. The river flows swiftly through the Batoka Gorge, the current being continually interrupted by reefs. It has been described[19] 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 which end 240 km (150 mi) below Victoria Falls. Over this distance, the river drops 250 metres (820 ft).

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 the Kafue are the two largest left-hand tributaries of the Zambezi. The Kafue joins the main river in a quiet deep stream about 180 metres (590 ft) wide. From this point the northward bend of the Zambezi is checked, and the stream continues due east. At the confluence of the Luangwa (15°37' S) it enters Mozambique.[20]

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.[21]

The lower Zambezi's 650 km 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, 320 km from its mouth, is the river confined between high hills. Here it is scarcely 200 m wide. Elsewhere it is from 5 to 8 km 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 160 km 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.[15] Each of the four 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 2 m at the entrance and 4 m further in, and is the branch used for navigation. 100 km 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.[22]

Annotated view of the Zambezi river delta from space.[24]

NASA false-colour image of the upper Zambezi and Barotse (Balozi) floodplain during an extreme flood in 2003.

The Zambezi Delta has extensive seasonally- and permanently-flooded grasslands, savannas, and swamp forests. Together with the floodplains of the Buzi, Pungwe, and Save rivers, the Zambezi's floodplains make up the World Wildlife Fund's Zambezian coastal flooded savanna ecoregion in Mozambique. The flooded savannas lie close to the Indian Ocean coast. Mangroves fringe the delta's shoreline.

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, 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. However, the shrinking of the wetlands resulted in uncontrolled hunting of animals such as buffalo and waterbuck during the Mozambican Civil War.

Although the region has seen 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 (Panthera leo), leopard (Panthera pardus), cheetah (Acinonyx jubatus), spotted hyena (Crocuta crocuta) and side-striped jackal (Canis adustus). The floodplains are a haven for migratory waterbirds including pintails, garganey, African openbill (Anastomus lamelligerus), saddle-billed stork (Ephippiorhynchus senegalensis), wattled crane (Bugeranus carunculatus), and great white pelican (Pelecanus onocrotalus).[25]

Reptiles include Nile crocodile (Crocodylus niloticus), Nile monitor lizard (Varanus niloticus) and African rock python (Python sebae), the endemic Pungwe worm snake (Leptotyphlops pungwensis) and three other snakes that are nearly endemic; floodplain water snake (Lycodonomorphus whytei obscuriventris), dwarf wolf snake (Lycophidion nanus) and swamp viper (Proatheris).[25]

There are a number of endemic butterflies.

The first European to come across the Zambezi river was Vasco da Gama in January 1498, who anchored at what he called Rio dos Bons Sinais ("River of Good Omens"), now the Quelimane or Quá-Qua, a small river on the northern end of the delta, which at that time was connected by navigable channels to the Zambezi river proper (the connection silted up by the 1830s). In a few of the oldest maps, the entire river is denoted as such. By the 16th century, a new name emerged, the Cuama river (sometimes "Quama" or "Zuama"). Cuama was the local name given by the dwellers of the Swahili coast for an outpost located on one of the southerly islands of the delta (near the Luabo channel). Most old nautical maps denote the Luabo entry as Cuama, the entire delta as the "rivers of Cuama" and the Zambezi river proper as the "Cuama River".

In 1552, Portuguese chronicler João de Barros noted that the same Cuama river was called Zembere by the inland people of Monomatapa.[30] The Portuguese Dominican friar João dos Santos, visiting Monomatapa in 1597 reported it as Zambeze (Bantu languages frequently shifts between z and r) and inquired into the origins of the name; he was told it was named after a people.

Map by Willem Janszoon Blaeu, dated 1635, showing the course of the Zambezi, and its source in a great lake.

"The River Cuama is by them called Zambeze; the head whereof is so farre within Land that none of them know it, but by tradition of their Progenitors say it comes from a Lake in the midst of the continent which yeelds also other great Rivers, divers ways visiting the Sea. They call it Zambeze, of a Nation of Cafres dwelling neere that Lake which are so called." —J. Santos Ethiopia Oriental, 1609[31]

Thus the term "Zambezi" is after a people who live by a great lake to the north. The most likely candidates are the "M'biza", or Bisa people (in older texts given as Muisa, Movisa, Abisa, Ambios and other variations), a Bantu people who live in what is now central-eastern Zambia, between the Zambezi River and Lake Bangweolo (at the time, before the Lunda invasion, the Bisa would have likely stretched further north, possibly to Lake Tanganyika). The Bisa had a reputation as great cloth traders throughout the region.[32]

In a curious note, the Goese-born Portuguese trader Manuel Caetano Pereira, who traveled to the Bisa homelands in 1796, was surprised to be shown a second, separate river referred to as the "Zambezi".[33] This "other Zambezi" that puzzled Pereira is most likely what modern sources spell the Chambeshi River in northern Zambia.

The Monomatapa notion (reported by Santos) that the Zambezi was sourced from a great internal lake might be a reference to one of the African Great Lakes. One of the names reported by early explorers for Lake Malawi was "Lake Zambre" (probably a corruption of "Zambezi"), possibly because Lake Malawi is connected to the lower Zambezi via the Shire River. The Monomatapa story resonated with the old European notion, drawn from classical antiquity, that all the great African rivers—the Nile, the Senegal, the Congo, and the Zambezi—were all sourced from the same great internal lake. The Portuguese were also told that the Mozambican Espirito Santo "river" (actually an estuary formed by the Umbeluzi, Matola and Tembe rivers) was sourced from a lake (hence its outlet became known as Delagoa Bay). As a result, several old maps depict the Zambezi and the "Espirito Santo" rivers converging deep in the interior, at the same lake.

However, the Bisa-derived etymology is not without dispute. In 1845, W.D. Cooley, examining Pereira's notes, concluded the term "Zambezi" derives not from the Bisa people, but rather from the Bantu term "mbege"/"mbeze" ("fish"), and consequently it probably means merely "river of fish".[34] David Livingstone, who reached the upper Zambezi in 1853, refers to it as "Zambesi" but also makes note of the local name "Leeambye" used by the Lozi people, which he says means "large river or river par excellence". Livingstone records other names for the Zambezi—Luambeji, Luambesi, Ambezi, Ojimbesi and Zambesi—applied by different peoples along its course, and asserts they "all possess a similar signification and express the native idea of this magnificent stream being the main drain of the country".[35]

In Portuguese records, the "Cuama River" term disappeared and gave way to the term "Sena River" (Rio de Sena), a reference to the Swahili (and later Portuguese) upriver trade station at Sena. In 1752, the Zambezi delta, under the name "Rivers of Sena" (Rios de Sena) formed a colonial administrative district of Portuguese Mozambique. But common usage of "Zambezi" led eventually to a royal decree in 1858 officially renaming the district "Zambézia".

Satellite image showing Victoria Falls and subsequent series of zigzagging gorges

The Zambezi region was known to medieval geographers as the Empire of Monomotapa, and the course of the river, as well as the position of lakes Ngami and Nyasa, were generally accurate in early maps. These were probably constructed from Arab information.[36]

The first European to visit the inland Zambezi river was the Portuguese degredado António Fernandes in 1511 and again in 1513, with the objective of reporting on commercial conditions and activities of the interior of Central Africa. The final report of these explorations revealed the importance of the ports of the upper Zambezi to the local trade system, in particular to East African gold trade.[37]

The first recorded exploration of the upper Zambezi was made by David Livingstone in his exploration from Bechuanaland between 1851 and 1853. Two or three years later he descended the Zambezi to its mouth and in the course of this journey found the Victoria Falls. During 1858–60, accompanied by John Kirk, Livingstone ascended the river by the Kongone mouth as far as the falls and also traced the course of its tributary the Shire and reached Lake Malawi.[36]

For the next 35 years very little exploration of the river took place. Portuguese explorer Serpa Pinto examined some of the western tributaries of the river and made measurements of the Victoria Falls in 1878.[36] In 1884 the Scottish-born Plymouth Brethren missionary Frederick Stanley Arnot traveled over the height of land between the watersheds of the Zambezi and the Congo and identified the source of the Zambezi.[38] He considered that the nearby high and cool Kalene Hill was a particularly suitable place for a mission.[39] Arnot was accompanied by the Portuguese trader and army officer António da Silva Porto.[40]

In 1889 the Chinde channel north of the main mouths of the river was seen. Two expeditions led by Major A. St Hill Gibbons in 1895 to 1896 and 1898 to 1900 continued the work of exploration begun by Livingstone in the upper basin and central course of the river.[36]

Two locals in the Zambezi river near Victoria falls, Zambia.

Sewage effluent is a major cause of water pollution around urban areas, as inadequate water treatment facilities in all the major cities of the region release untreated sewage into the river. This has resulted in eutrophication of the river water and has facilitated the spread of diseases of poor hygiene such as cholera, typhus and dysentery.[49]

The construction of two major dams regulating the flow of the river has had a major effect on wildlife and human populations in the lower Zambezi region. When the Cahora Bassa Dam was completed in 1973, its managers allowed it to fill in a single flood season, going against recommendations to fill over at least two years. The drastic reduction in the flow of the river led to a 40% reduction in the coverage of mangroves, greatly increased erosion of the coastal region and a 60% reduction in the catch of prawns off the mouth because of the reduction in emplacement of silt and associated nutrients. Wetland ecosystems downstream of the dam shrank considerably. Wildlife in the delta was further threatened by uncontrolled hunting during the civil war in Mozambique.[50][51]

The proposed Kavango–Zambezi Transfrontier Conservation Area was to cover parts of Zambia, Angola, Namibia, Zimbabwe and Botswana, including the Okavango Delta in Botswana and Victoria Falls. Funding was boosted for cross-border conservation along the Zambezi in 2008. The project received a grant of €8 million from a German nongovernmental organisation. Part of the funds are to be used for research in areas covered by the project. However, Angola has warned that landmines from their civil war may impede the project.[52]

The river currently passes through Ngonye Falls National Park, Mosi-oa-Tunya National Park, and Lower Zambezi National Park (in Zambia); the Zambezi National Park, Victoria Falls National Park, Matusadona National Park, Mana Pools National Park, and the Middle Zambezi Biosphere Reserve (in Zimbabwe).

As of 2017 the situation of overfishing in the upper Zambezi and its tributaries was considered dire, in part because of weak enforcement of the respective fisheries acts and regulations. The fish stocks of Lake Liambezi in the eastern Caprivi Strip were found to be depleted, and surveys indicated a decline in the whole Zambezi-Kwando-Chobe river system. Illegal fishing (by foreign nationals employed by Namibians) and commercially minded individuals, exploited the resources to the detriment of local markets and the communities whose culture and economy depend on these resources.[53]

Namibian officials have consequently banned monofilament nets and imposed a closing period of about 3 months every year to allow the fish to breed. They also appointed village fish guards and the Kayasa channel in the Impalila conservancy area was declared a fisheries reserve. The Namibian ministry also promotes aquaculture and plans to distribute thousands of fingerlings to registered small-scale fish farmers of the region.[53]

In September 2007, epizootic ulcerative syndrome (EUS) killed hundreds of sore-covered fish in the river. Zambia agriculture minister Ben Kapita asked experts to investigate the outbreak to probe the cause to find out if the disease can be transmitted to humans.[54]