Zambezi
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The Zambezi (also spelled Zambesi) is the fourth longest river in Africa, and the largest of those flowing eastwards to the Indian Ocean. The area of its basin is 1,570,000 km² (606,000 mi²), slightly less than half that of the Nile. The 2,574 kilometre-long river has its source in Zambia and flows through Angola, along the border of Zambia and Zimbabwe, to Mozambique, where it empties into the Indian Ocean.
The Zambezi's most spectacular feature is Victoria Falls, one of the world's largest waterfalls. Other notable falls include the Chavuma Falls at the border between Zambia and Angola, and Ngonye Falls, near Sioma in Western Zambia. Over its entire course, the Zambezi is spanned by only five bridges: at Chinyingi, Katima Mulilo, Victoria Falls, Chirundu and Tete.
There are two main sources of hydroelectric power on the river. These are the Kariba Dam, which provides power to Zambia and Zimbabwe and the Cabora-Bassa Dam in Mozambique which provides power to South Africa. There is also a smaller power station at Victoria Falls.
Course
Source
The river rises in north-western Zambia, in undulating hills about 1,500 m above sea level, covered with bracken and open forest. Like that of all the rivers of the neighbourhood, the Zambezi's source is a black marshy bog, which quickly collects into a well-defined stream. In the first hundred miles of its course the river is known as the Yambeshe, in sound almost identical with its name in its lower course, though intervening sections are known as Liambeshe, Liarabai, etcetera. Eastward of the source the watershed between the Congo and Zambezi basins is a well-marked belt of high ground, falling abruptly north and south, and running nearly east and west between 11 and 12°S. This distinctly cuts off the basin of the Luapula (the main branch of the upper Congo) from that of the Zambezi. In the neighbourhood of the source the watershed is not so clear, but the two river systems do not connect.
The upper river
After flowing to the south-west for about 240 km (150 miles), the river turns more directly south, and is joined by many tributaries. A few miles above Kakengi, the river widens from 100 to 350 metres. Below Kakengi are a number of rapids ending in the Sapuma cataracts, where the river flows through a rocky fissure. The first of its large tributaries to enter the Zambezi is the Kabompo River, which joins the main stream at 14°26′ S. A little further south is the confluence with the much larger Lungwebungu River. The savanna through which the river has flowed gives way to a more open bush valley, studded with Borassus palms. Dense vegetation is confined to narrow strips of matted forest which skirt the first few hundred yards of the sources of the Zambezi and its tributaries during the first 160 km (100 miles) or so.
From 1500 m at the source, the river drops to about 1100 metres at Kakengia, 350 km (220 miles) downstream. From this point until the Victoria Falls are reached, the level of the Zambezi basin is very uniform, dropping only by another 180 metres. 30 km below the confluence of the Lungwebungu the country becomes flat, and in the rainy season is largely covered by floods. 80 km (50 miles) further down, the Luanginga, which with its tributaries drains a large area to the westward, joins the Zambezi. A few miles higher up on the east the main stream is reinforced by the waters of the Luena.
On the same (eastern) side a little below the junction of the Luanginga and the Zambezi stands Lealui, one of the capitals of the Lozi people who populate the semi-autonomous Zambian region of Barotseland. The chief of the Lozi has two compounds, the other being at Limulunga. Limulunga 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 one of Zambia's best known festivals, the Kuomboka.
The river, which for some distance has had a slight western as well as southern trend, now turns distinctly south-east. From the east the Zambezi continues to receive numerous small streams, but on the west is without tributaries for 240 km (150 miles)., when the great river formerly misnamed the Chobe, but known to the natives as Kwando or Linyante, joins it. Before this junction is effected, the Ngonye Falls offer an interruption to navigation, whilst below the falls are numerous rapids.
South of Ngonye Falls, the river briefly borders Namibia's Caprivi Strip. The strip projects from the main body of Namibia, and results from the colonial era: it was added to German South West Africa expressly to give Germany access to the Zambezi.
Below the junction of the Kwando and the Zambezi the river bends almost due east. The stream has hitherto flowed, in the main, in a gentle steady current, the depth of water, owing to the breadth of the channel, not being great. But as it flows eastward towards the border of the great central plateau of Africa it reaches a tremendous chasm, into which the Victoria Falls plunge.
The middle Zambezi
The Victoria Falls are reached 100 km (60 miles) after the Kwando confluence is passed, and below them the river continues to flow due east for about 200 km (120 miles). It then cuts its way through perpendicular walls of basalt from 20 to 60 m apart. Towering over the rocks which form the banks of the river are precipitous hills, 200-250 m high. The river flows swiftly through the gorge, the current being continually interrupted by reefs. Beyond the gorge are a succession of rapids which end 240 km (150 miles) below Victoria Falls. Over this distance, the river drops 250 metres.
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 m 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 when the river enters Lake Cahora Bassa (also spelled Cabora Bassa). Formerly the site of dangerous rapids known as Kebrabassa, the lake was created in 1974 by the construction of the Cahora Bassa Dam.
The lower river
The lower Zambezi's 650 km (400 miles) from Cahora Bassa to the Indian Ocean present no obstacles to navigation although the river is shallow in many places during the dry season. This shallowness arises from the different character of the river basin. Instead of, as in the case of the middle Zambezi, flowing mainly through hilly country with well-defined banks, the river traverses a broad valley and spreads out over a large area. Only at one point, the Lupata Gorge, 320 km (200 miles) from its mouth, is the river confined between high hills. Here it is scarcely 200 metres wide. Elsewhere it is from 5 to 8 km (3 to 5 miles) wide, flowing gently in many streams. The river bed is sandy, the banks are low and reed-fringed. At places, however, and especially in the rainy season, the streams unite into one broad swift-flowing river.
About 160 km (100 miles) from the sea the Zambezi receives the drainage of Lake Malawi through the Shire River. On approaching the Indian Ocean, the Zambezi splits up into a number of branches and forms a wide delta. Each of the four principal mouths, Milambe, 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 (60 miles) 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.
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.
The region drained by the Zambezi is a vast broken-edged plateau 900-1200 m high, composed in the remote interior of metamorphic beds and fringed with the igneous rocks of the Victoria Falls. At Shupanga, 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 the Victoria Falls. Gold-bearing rocks occur in several places.
Tributaries
The Zambezi has numerous tributaries. Some of the more important ones are described here, in order from source to sea.
The Kabompo rises in the high land which forms the eastern watershed between the Zambezi and Congo systems. It is formed itself by the confluence of the upper Kabompo and the somewhat larger Lunga River, and flows into the Zambezi north of the town of Lukulu.
The Lungwebungu, which enters the Zambezi from the west just south of the confluence with the Kabompo River, is a strong, deep stream 200 metres wide in its upper course, flowing in a valley bordered by white sand covered by thin forest, its floor forming at times an inundated plain 2 to 3 miles wide.
The Cuando River, largest of the western affluents of the Zambezi, was formerly known as the Chobe, a name now given to another tributary. The Kwando has the ruined capital of the Makololo people on its lower course. It rises in Angola, and flows in a generally straight course south-east, forming the border between Zambia and Angola for part of its course, before making a sudden bend to the south, then flowing east to the Zambezi. In this eastward stretch the Kwando flows through a vast reedy swamp or lake studded with alluvial islands for 110 km (70 miles). Apart from its head-streams, it receives most of its tributaries from the west, and at its most southern bend is joined by the Magwekwana, which in time of flood receives some of the surplus water of the Okavango. This surplus water, received after most of the flood water of the Kwando has passed, raises the level of the lake and holds up the waters of the Kwando for some miles above it.
The largest tributary of the middle Zambezi, the Kafue, rises in northern Zambia at an elevation of 1350 metres in thick forest country. The main headstream, which flows first south-east, then south-west, is later joined by the Lunga or Luanga, the united stream then flowing first south, afterwards due east. The Itezhi-Tezhi Dam is an important source of hydroelectric power from the Kafue river, and the river also supports a great deal of wildlife, which is protected by Zambia's largest national park, Kafue National Park. The lower Kafue has a series of waterfalls and cataracts, dropping several hundred feet in 25 km (15 miles).
The next great tributary to the east is the Luangwa which in its upper course runs parallel to the western shores of Lake Malawi, having its source not far from the north-west corner of the lake. The main stream flows in a generally level valley, bounded by steep plateau escarpments, and is for the most part shallow and rapid, though fairly wide. Its tributaries the Lunsefwa and Lukosasi drain a large extent of the western plateau of Zambia. The Luangwa joins the Zambezi a little above the town of Zumbo. The Luangwa Valley is an important wildlife conservation area, and contains North Luangwa National Park and South Luangwa National Park.
For some distance its lower course forms the border between Mozambique and Zambia. From the south the middle Zambezi receives various rivers which water northern Zimbabwe—the Shangani, Sanyati, and Hanyani, besides minor streams. The Mazoe, which rises in Mashonaland, joins the Zambezi below the Cahora Bassa Dam.
Exploration of the River
The Zambezi region was known to the medieval geographers as the empire of Monomotapa and the course of the river, as well as the position of Lakes Ngami and Nyasa, was filled in with a rude approximation to accuracy in the earlier maps. These were probably constructed from Arab information.
The first European to visit the upper Zambezi was 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 discovered the Victoria Falls. During 1858–60, accompanied by Dr (later Sir) John Kirk, Livingstone ascended the river by the Kongone mouth as far as the Falls, besides tracing the course of its tributary the Shire and discovering Lake Malawi.
For the next thirty-five years very little exploration of the river took place, but in 1889 the Chinde channel north of the main mouths of the river was discovered. Two expeditions led by Major A. St Hill Gibbons in 1895–96 and 1898–1900 continued the work of exploration begun by Livingstone in the upper basin and central course of the river. Portuguese explorer Serpa Pinto examined some of the western tributaries of the river and made measurements of the Victoria Falls in 1878.
Wildlife
The river supports large populations of many animals. Hippopotamuses are abundant along most of the calm stretches of the river, and many crocodiles are also present. Monitor lizards are found in many places. Bird life is abundant, with species including heron, pelican, egret and fish eagle present in large numbers. Riverine woodland also supports many large animals, such as buffalo, zebras, giraffes and elephants. However, below Kariba and Cahora Bassa dams, the cessation of annual flooding has seen the area of this habitat greatly reduced and a corresponding reduction in the populations of the large mammals.
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 and other large species. The Zambezi Shark is named for the river but is found around the world. It normally inhabits coastal waters but has been found far inland in many large rivers including the Zambezi. It is an aggressive shark which has been responsible for several attacks on humans.
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 flood plains provide good agricultural land.
Communities by the river fish extensively from it, 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. As well as fishing for food, game fishing is a significant activity on some parts of the river. Between Mongu and Livingstone, several safari lodges cater for 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 1.5 million visitors annually, while Mana Pools and Lake Kariba also draw substantial tourist numbers.
Transport
The river is frequently interrupted by rapids and so has never been an important long distance transport route. However, along short stretches, it is often more convenient to travel by canoe along the river rather than on the unsurfaced roads which are often in very poor condition due to being regularly submerged in flood waters, and many small villages along the banks of the river are only accessible by boat.
There are only five bridges across the river along its entire course, of which one is a footbridge only. However, at many locations pontoons ferry people and vehicles across the river. The bridge at Victoria Falls was the first to be built, and was completed in April 1905. It was initially intended as a link in Cecil Rhodes' Cape to Cairo railway scheme. The bridge is 250 metres across, with a main arch spanning 150 metres, and the top of the bridge is 125 metres above the low-water level of the river. Later bridges were constructed at Chirundu in Zambia (1939, replaced in 2003), Tete in Mozambique (1960s) and Chinyingi in northern Zambia in the 1970s (footbridge only). 2004 saw the completion of a bridge crossing the river from Sesheke in Zambia with Katima Mulilo in Namibia, completing the TransCaprivi Highway and connecting Lusaka in Zambia with Walvis Bay on the Namibian coast.
Ecology
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 force them to 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.
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 constructed 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 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. due to the reduction in emplacement of silt and associate nutrients. Wetland ecosystems downstream of the dam shrank considerably.
Major towns
Along much of the river's length, the population is sparse, but important towns and cities along its course include the following:
- Mongu
- Lukulu
- Katima Mulilo (Namibia), Sesheke (Zambia)
- Livingstone (Zambia), Victoria Falls, Zimbabwe
- Kariba
- Songo
- Tete
External links
References
- Bryan R. Davies, Richard D. Beilfuss and Martin C. Thoms (2000), Cahora Bassa retrospective, 1974–1997: effects of flow regulation on the Lower Zambezi River, Verh. Internat. Verein. Limnol, v. 27, p. 1-9
- Saskia Bourgeois, Thomas Kocher, Peter Schelander (2003), Case study: Zambezi river basin, ETH Seminar: Science and Politics of International Freshwater Management 2003/04
- Carlos Manuel Bento, Richard Beilfuss (2003), Wattled Cranes, Waterbirds, and Wetland Conservation in the Zambezi Delta, Mozambique, report for the Biodiversity Foundation for Africa for the IUCN - Regional Office for Southern Africa: Zambezi Basin Wetlands Conservation and Resource Utilisation Project.
- Dunham, KM (1994), The effect of drought on the large mammal populations of Zambezi riverine woodlands, Journal of Zoology, v. 234, p. 489-526
This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). Encyclopædia Britannica (11th ed.). Cambridge University Press. {{cite encyclopedia}}: Missing or empty |title= (help)
