Zambezi

The Zambezi River (also spelled Zambeze and Zambesi) 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 the 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 (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.Dorling Kindersley, pp. 84–85

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 , in a distance of about . From this point to the Victoria Falls, the level of the basin is very uniform, dropping only by another in a distance around .

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.

Abouy 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 20 to 60 m (66 to 200 ft) apart in hills 200 to 250 m (660 to 820 ft) 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 240 km (150 mi) 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 (15°37' S), 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 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. 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 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.

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

The Zambezi Delta has extensive seasonally and permanentlybflooded 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, 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 (''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'').

Reptiles include Nile crocodile (''Crocodylus niloticus''), Nile monitor lizard (''Varanus niloticus''), 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'').

Several butterfly species are endemic.

Climate

The north of the Zambezi basin has mean annual rainfall of 1100 to 1400 mm, which declines towards the south, reaching about half that figure in the south-west. The rain falls in a 4-to-6-month summer rainy season when the intertropical convergence zone moves over the basin from the north between October and March. Evaporation rates are high (1600 mm-2300 mm), and much water is lost this way in swamps and floodplains, especially in the south-west of the basin.

Wildlife

The river supports large populations of many animals. Hippopotamuses are abundant along most of the calm stretches of the river, as well as Nile crocodiles. Monitor lizards are found in many places. Birds are abundant, with species including heron, pelican, egret, lesser flamingo, and African fish eagle present in large numbers. Riverine woodland also supports many large animals, such as buffalo, zebras, giraffes, and elephants.

The Zambezi also supports several hundred species of fish, some of which are endemic to the river. Important species include cichlids, which are fished heavily for food, as well as catfish, tigerfish, yellowfish, and other large species. The bull shark is sometimes known as the Zambezi shark after the river, not to be mistaken with ''Glyphis'' freshwater shark genus that inhabit the river, as well.

Tributaries

''Upper Zambezi: 507,200 km², discharges 1044 m³/s at Victoria Falls, comprising:''

: ''Northern Highlands catchment, 222,570 km², 850 m³/s at Lukulu:''
:* Chifumage River: Angolan central plateau
:* Luena River: Angolan central plateau
:* Kabompo River: 72,200 km², NW highlands of Zambia
:* Lungwebungu River: 47,400 km², Angolan central plateau
:''Central Plains catchment, 284,630 km², 196 m³/s (Victoria Falls–Lukulu):''
:* Luanginga River: 34,600 km², Angolan central plateau
:* Luampa River/ Luena River, Zambia: 20,500 km², eastern side of Zambezi
:* Cuando /Linyanti/Chobe River: 133,200 km², Angolan S plateau & Caprivi

''Middle Zambezi cumulatively 1,050,000 km², 2442 m³/s, measured at Cahora Bassa Gorge''

: (Middle section by itself: 542,800 km², discharges 1398 m³/s (C. Bassa–Victoria Falls)
:''Gwembe Catchment, 156,600 km², 232 m³/s (Kariba Gorge–Vic Falls):''
:* Gwayi River: 54,610 km², NW Zimbabwe
:* Sengwa River: 25,000 km², North-central Zimbabwe
:* Sanyati River: 43,500 km², North-central Zimbabwe
:''Kariba Gorge to C. Bassa catchment, 386200 km², 1166 m³/s (C. Bassa–Kariba Gorge):''
:* Kafue River: 154,200 km², 285 m³/s, West-central Zambia & Copperbelt
:* Luangwa River: 151,400 km², 547 m³/s, Luangwa Rift Valley & plateau NW of it
:* Panhane River: 23,897 km², North-central Zimbabwe plateau

''Lower Zambezi cumulatively, 1,378,000 km², 3424 m³/s, measured at Marromeu''

: (Lower section by itself: 328,000 km², 982 m³/s (Marromeu–C. Bassa))
:* Luia River: 28,000 km², Moravia-Angonia plateau, N of Zambezi
:* Luenha River/ Mazoe River: 54,144 km², 152 m³/s, Manica plateau, NE Zimbabwe
:* Shire River , 154,000 km², 539 m³/s, Lake Malawi basin
: Zambezi Delta, 12,000 km²

Total Zambezi river basin: 1,390,000 km², 3424 m³/s discharged into delta

''Source: Beilfuss & Dos Santos (2001)'' The Okavango Basin is not included in the figures because it only occasionally overflows to any extent into the Zambezi.

Because of the rainfall distribution, northern tributaries contribute much more water than southern ones; for example: The Northern Highlands catchment of the upper Zambezi contributes 25%, Kafue 8%, Luangwa and Shire Rivers 16% each, total 65% of Zambezi discharge. The large Cuando basin in the south-west, though, contributes only about 2 m³/s because most is lost through evaporation in its swamp systems. The 1940s and 1950s were particularly wet decades in the basin. Since 1975, it has been drier, the average discharge being only 70% of that for the years 1930 to 1958.

Geological history

Up to the Late Pliocene or Pleistocene (more than two million years ago), the upper Zambezi flowed south through what is now the Makgadikgadi Pan to the Limpopo River. The change of the river course is the result of epeirogenic movements that lifted up the surface at the present-day water divide between both rivers.

Meanwhile, east, a western tributary of the Shire River in the East African Rift's southern extension through Malawi eroded a deep valley on its western escarpment. At a slow rate, the middle Zambezi started cutting back the bed of its river towards the west, aided by grabens (rift valleys) forming along its course in an east–west axis. As it did so, it captured several south-flowing rivers such as the Luangwa and Kafue.

Eventually, the large lake trapped at Makgadikgadi (or a tributary of it) was captured by the middle Zambezi cutting back towards it, and emptied eastwards. The upper Zambezi was captured , as well. The middle Zambezi was about lower than the upper Zambezi, and a high waterfall formed at the edge of the basalt plateau across which the upper river flows. This was the first Victoria Falls, somewhere down the Batoka Gorge near where Lake Kariba is now.

History

Etymology

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 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. 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.

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.

In a curious note, 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". 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". 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".

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".

Exploration

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.

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.

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.

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. In 1884, 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. He considered that the nearby high and cool Kalene Hill was a particularly suitable place for a mission. Arnot was accompanied by Portuguese trader and army officer António da Silva Porto.

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.

Economy

The population of the Zambezi River Valley is estimated to be about 32 million. About 80% of the population of the valley is dependent on agriculture, and the upper river's floodplains provide good agricultural land.

Communities by the river fish it extensively, and many people travel from far afield to fish. Some Zambian towns on roads leading to the river levy unofficial "fish taxes" on people taking Zambezi fish to other parts of the country. Game fishing, as well as fishing for food, is a significant activity on some parts of the river. Between Mongu and Livingstone, several safari lodges cater to tourists who want to fish for exotic species, and many also catch fish to sell to aquaria.

The river valley is rich in mineral deposits and fossil fuels, and coal mining is important in places. The dams along its length also provide employment for many people near them, in maintaining the hydroelectric power stations and the dams themselves. Several parts of the river are also very popular tourist destinations. Victoria Falls receives over 100,000 visitors annually, with 141,929 visitors reported in 2015. Mana Pools