Zambezi
The
Zambezi (also spelled
Zambesi) is the fourth-longest
river in
Africa, and the largest flowing into the
Indian Ocean. The area of its
basin is
1,570,000 km² (606,000
miles²), slightly less than half that of the
Nile. The 2,574 km (1,600 mile) long river has its source in
Zambia and flows through
Angola, along the border of
Namibia,
Botswana, 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.
Source
The river rises in a black marshy
bog in north-western
Zambia, in undulating forested hills about 1,500 metres (4,900 ft) above
sea level. 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-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 as clearly defined, 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 south, and is joined by many
tributaries. A few miles above
Kakengi, the river widens from 100 to 350 metres (330 to 1,150 ft), and below Kakengi are a number of
rapids ending in the
Chavuma Falls, where the river flows through a rocky fissure. The first of its large tributaries to enter the Zambezi is the
Kabompo River in the north-western province of Zambia. 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
palm trees. Dense vegetation is confined to narrow strips of matted forest which skirt the first few hundred metres of the sources of the Zambezi and its tributaries during the first 160 km (100 miles) or so.
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Zambezi River in North Western Zambia |
From 1500 metres (4,900 ft) at the source, the river drops to about 1100 metres (3,600 ft) at Kakengi, 350 km (220 miles) downstream. From this point until the
Victoria Falls, the level of the basin is very uniform, dropping only by another 180 metres (590 ft). Thirty kilometers (19 miles) below the confluence of the Lungwebungu the country becomes flat, and in the
rainy season is largely covered by
floods. Eighty kilometers (50 miles) 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 by the
Luena.
A short distance downstream of the confluence with the Luanginga is
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 as one of Zambia's best known festivals, the
Kuomboka.
After Lealui, the river turns to the south-east. From the east it continues to receive numerous small streams, but on the west is without tributaries for 240 km (150 miles), when the
Cuando River joins it. Before this, the
Ngonye Falls and subsequent rapids interrupt navigation. 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 Cuando and the Zambezi the river bends almost due east. Here, the river is very broad and shallow, and flows fairly 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.
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 km (120 miles), cutting through perpendicular walls of
basalt 20 to 60 metres (65 to 200 ft) apart in hills 200 to 250 metres (650 to 820 ft) 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 (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.
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 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 (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, 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.
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The Zambezi's delta |
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 river 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 metres at the entrance and 4 metres 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 900â€"1200 metres 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.
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 200 metres wide in its upper course, flowing in a valley bordered by white sand covered in thin forest, its floor forming at times an inundated plain 2 to 3 miles wide.
The
Cuando River, largest of the river's western tributaries, has the ruined capital of the
Makololo people on its lower reaches. It rises in
Angola, and forms the border between Zambia and Angola for part of its course, before curving to the south, then flowing east into the Zambezi. In this eastward stretch the Cuando flows through a vast reedy
swamp studded with alluvial islands for 110 km (70 miles), 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 Cuando has passed, raises the level of the lake and holds up the waters of the Cuando for some miles above it.
The largest tributary of the middle Zambezi, the
Kafue, rises in Zambia's
Copperbelt Province near the border with
Democratic Republic of Congo at an elevation of 1350 metres in thick forest country. The main headstream is later joined by the
Lunga River or Luanga. 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 large tributary to the east is the
Luangwa, which rises near the north-west corner of
Lake Malawi and in its upper course runs parallel to its western shores. The Luangwa flows in a generally level valley, bounded by steep plateau escarpments, and is generally shallow and rapid, though fairly wide. Its tributaries the
Lunsemfwa River and
Lukasashi River drain a large area 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. The Luangwa defines the border between Zambia and Mozambique for about 75 km before it joins the Zambezi.
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.
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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 given broadly accurately in early 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 1858â€"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, 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 to 1896 and 1898 to 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.
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
African 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,
yellowfish and other large species. The
bull shark is sometimes known as the Zambezi Shark after 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.
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The river and its floodplain near Mongu in Zambia |
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.
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Victoria Falls Bridge. 1975 photo. |
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 unimproved 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.
Victoria Falls Bridge was the first to be built, and was completed in April 1905. It was initially intended as a link in
Cecil Rhodes' scheme to build a
railway from Cape Town to Cairo. The bridge is 250 m (820 ft) across, with a main arch spanning 150 m (490 ft), and the top of the bridge is 125 m (410 ft) 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.
 |
Lake Cahora Bassa in Mozambique, one of the river's major sources of hydroelectric energy |
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 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.
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* Bento C.M., Beilfuss R. (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.
* Bourgeois S., Kocher T., Schelander P. (2003),
Case study: Zambezi river basin, ETH Seminar: Science and Politics of International Freshwater Management 2003/04
* Davies B.R., Beilfuss R., Thoms M.C. (2000), "Cahora Bassa retrospective, 1974â€"1997: effects of flow regulation on the Lower Zambezi River,"
Verh. Internat. Verein. Limnologie, 27, 1-9
* Dunham KM (1994),
The effect of drought on the large mammal populations of Zambezi riverine woodlands, Journal of Zoology, v. 234, p. 489-526
* Wynn S. (2002), "The Zambezi River - Wilderness and Tourism",
International Journal of Wilderness, 8, 34.
*
Information and a map of the Zambezi's watershed*
Map of the Zambezi River basin at Water Resources eAtlas*
Zambezi River Authority*
The Zambezi Society*
Map of Africa's river basins
