BIOPHYSICAL ASPECTS

Location
The Zambezi Basin (located between 8^oS and 20^oS latitude, and 16.5^oE and 36^oE longitude), drains an area of about 1.3 million square kilometres (sq km), and covers about 23.4 percent of the total area of its riparian countries. The Zambezi River flows over a distance of nearly 3,000 km, dropping in altitude from its source in the Kalene Hills of North Western Zambia, 1,585 metres above sea level, to its delta in the Indian Ocean, 200 km north of the Mozambican port of Beira. The river's major tributaries include the Luena and Lungue-Bungo in Angola; the Chobe in Botswana; Shire in Malawi; Luiana in Namibia; Kabompo, Kafue and Luangwa in Zambia; and Manyame, Sanyati and Gwayi in Zimbabwe.

Climate and geology
Most of the basin lies about 400 m above sea level, with subdued topography. This results in extremely hot summer and low winter temperatures. The basin mainly consists of Karoo sediments. The Karoo rocks host all known coal reserves in the basin while the thick sedimentary rocks have a potential for the production of petroleum and natural gas.

Water resources
The basin features various surface and groundwater sources. These include wetlands such as the Kafue flats (about 7,000 sq km) and the Lukanga swamp (about 2,600 sq km) both

The Zambezi River Basin has eight riparian states; Angola, Botswana, Malawi, Mozambique, Namibia, Tanzania, Zambia and Zimbabwe. This makes it the second most shared basin within the Southern African Development Community (SADC) region after the Congo. along the Kafue River, and the Barotse floodplains in the Upper Zambezi. The floodplains regulate the Zambezi River water delivery throughout the year, absorbing water during the rains and slowly releasing it downstream over time. There are also major natural lakes including, Lake Malawi (referred to as Lake Nyasa in Tanzania and Lake Niassa in Mozambique) and Lake Bangweulu (Zambia). Two major artificial lakes: Lake Kariba (shared by Zambia and Zimbabwe) and Lake Cahora Bassa (Mozambique) were created after damming the Zambezi River.

Biodiversity
The biodiversity of the basin includes a wide range of terrestrial and aquatic environments. Main forest types include miombo, mukwa and Zambezi teak while woodlands include mopane and mahogany, and these support different animal and aquatic species. Important endemics include Lake Malawi's fish fauna, the "underground trees" (suffrutices) of the Barotse floodplains and the Reduncine antelopes. Bird species such as the wattled crane depend on the wetlands for their survival. The biodiversity is, to some extent, protected by conservation areas such as national parks and game reserves. These include the Kameia National Park (Angola), Chobe National Park (Botswana), Nyika National Park (Malawi), Caprivi Game Reserve (Namibia), Kafue, Luangwa and Lower Zambezi National Parks (Zambia) and Hwange and Mana Pools National Parks (Zimbabwe).

HUMAN ASPECTS

Socio-economic
About 31.7 million people live within the basin. In addition, a number of major settlements have been established, including the capital cities of Lilongwe (Malawi), Lusaka (Zambia) and Harare (Zimbabwe). The basin provides land for settlement, farming, grazing and cultural activities. The larger part of the basin is utilised for agriculture and wildlife conservation. These and other sectors provide the local people with employment and supplementary cash from selling surplus produce and community-based wildlife management activities. The main industries in the industrial sector include mining, hydroelectricity and thermal power generation, tourism, textiles, chemicals, pharmaceuticals, furniture, rubber, cement, and fisheries.

Political
Shared watercourses are a potential source of conflict between or among the basin countries. Conflicts usually arise over water usage, especially the amounts abstracted. However, if managed well, shared watercourses are a potential source of regional integration. Due to the need to promote regional cooperation in managing shared watercourses, in August 1995 the SADC members signed a Protocol on Shared Watercourse Systems. The protocol aims at promoting cooperation in the utilisation of resources of shared watercourse systems within the SADC region and is yet to be ratified.

THE RIPARIAN STATES

Angola
Approximately 11.6 percent of the total area in Angola is taken up by the basin and falls within Moxico Province. Main tributaries to the Zambezi River include the Lumbane, Luena, Lungue-Bungo and Macondo. The average annual rainfall in the province ranges from 1,200-1,400 mm. Agricultural activities are mainly subsistence crop and fish-farming. There are no hydro-power stations in the basin although nine potential sites have been identified. Three out of the country's 12 major protected areas fall within the basin; Kameia National Park, and Luiana and Mavinga Reserves.

Environmental problems include deforestation and soil erosion, resulting from agricultural activities and fuelwood-harvesting. The damming of the Zambezi River and its tributaries is likely to result in losses of biodiversity.

Botswana
An estimated 14.4 percent of Botswana's total area is taken up by the basin which is located within the Chobe District. On average, the District receives annual rainfall of about 650 mm. The main water consumers are wildlife and irrigation agriculture from the Chobe River that drains into the Zambezi River. Chobe National Park (the country's largest) is situated within the basin. The Shashe Dam, linked to the major settlements of Botswana by the North-South Carrier pipeline, can meet water demands until 2020. However, beyond this period more water will be required from the Zambezi River system.

As will be the situation in other riparian countries, drawing water from the Zambezi River system may cause the over-abstraction of the Zambezi waters to supply increasing populations and major settlements.

Malawi
Approximately 93.2 percent of the total area of Malawi is taken up by the basin. The country's average annual rainfall varies between about 700-1,625 mm. Lake Malawi, the most outstanding basin feature, is ranked the world's ninth largest in area (28,800 sq km) and fifth largest in volume with about 8,400 cubic metres (cu m). The Shire River is the only outlet of Lake Malawi and drains into the Zambezi River. The navigable lake and river also provide effective goods and passenger transport as well as fisheries. The need for increased food production in Malawi has translated into higher water demand for irrigation. Fuelwood provides up to 90 percent of Malawi's energy needs, with petroleum and hydro-power contributing four and three percent respectively. Several other potential sites for hydro-power generation have been identified with some already under construction. Almost all of Malawi's protected areas fall within the basin.

Due to a high fuelwood demand, high levels of deforestation and soil erosion are being experienced. Unsustainable damming may also lead to downstream impacts, including impairment of ecosystems, loss of biodiversity, reductions in fish production and sedimentation.

Mozambique
An estimated 17.5 percent of Mozambique's total area is taken up by the basin which passes through the Tete province, forming its southern border with Manica province as well as the border between the provinces of Sofala and Zambezia.

The basin represents approximately half of the country's freshwater resources. Rainfall ranges between 1,000-1,400 mm. In the valleys, average annual rainfall is below 600 mm. Features of importance include Lakes Niassa and Cahora Bassa. The Cahora Bassa, completed in 1977, was constructed mainly to supply hydro-power to South Africa. The lakes provide fisheries and also serve as a transport routes for goods and passengers. Coal mining is one of the major industrial activities within the basin while other deposits include gold, graphite, uranium, copper, iron and asbestos. The basin constitutes about two-thirds of total irrigable land in the country. Proposals for the construction of the Mepanda Ucua and Baroma reservoirs downstream of Cahora Bassa are underway.

Environmental problems include pollution from mining and sewage from Tete city, resulting from the inadequate disposal facilities. Population increase around major settlements has also led to deforestation and increased soil erosion.

Namibia
Approximately three percent of Namibia's total area is taken up by the basin and falls within the Caprivi region. The average annual rainfall is 680 mm. Due to flat gradients in the tributaries of Kwando-Linyanti-Chobe Rivers, backwater effects are significantly experienced. The basin water supplies the urban centres of Katima Mulilo, Chinchimane, Linyanti, and Bukalo as well as most rural areas that are networked by hand-dug wells and boreholes.

Irrigation agriculture also consumes a significant proportion of the basin waters and if not checked, this may lead to the over-abstraction of the basin waters.

Tanzania
An estimated three percent of Tanzania's total area is taken up by the basin and is represented by Lake Nyasa's catchment area. The lake's main river network comprises the Songwe, Ruhuhu and Kiwira. The average annual rainfall ranges between 800-2,600 mm. Major economic activities include agriculture and fish-farming. As such, unsustainable abstraction of Lake Nyasa waters may lead to negative downstream effects along the Shire River and ultimately on the Zambezi River, affecting fisheries and irrigation agriculture.

Due to a high fuelwood demand, high levels of deforestation and soil erosion are being experienced. Floods are also a threat to this part of the basin.

Zambia
Approximately 71.6 percent of Zambia's total area is taken up by the basin and most of the country's rivers flow into the Zambezi River. The average annual rainfall ranges between 710-1,475 mm. However, in the north average annual rainfall varies between 1,000-1,400 mm. Irrigation agriculture takes up most of the basin waters, followed by domestic and industrial uses. Almost the country's entire energy needs are met from the hydro-power stations which include the Kafue gorge, Kariba North Bank and Victoria Falls. The upper Zambezi and Lake Kariba are also used in transporting goods and services. Tourism activities are dominated by the Victoria Falls and wildlife.

Environmental problems include water pollution from, mining, industrial and domestic activities within major cities, and reduction of wilderness values due to over-development at tourism "hot-spots" such as the Victoria Falls. Planned irrigation projects within the basin may also lead to unsustainable use of the basin waters, while the rapidly growing population may result in more settlements being established within the basin. Increased settlements may also lead to land degradation and ultimately increased erosion, deforestation and siltation with resultant effects on ecosystems and possible loss of biodiversity.

Zimbabwe
An estimated 64.3 percent of Zimbabwe's total area is taken up by the basin. In the north-eastern parts of the country some areas receive over 1,500 mm annually while in the southernmost parts, average annual rainfall is less than 500 mm. Irrigation agriculture takes up most of the basin waters, followed by domestic and industrial uses. Tourism activities are dominated by the Victoria Falls and wildlife. Five major power stations are located within the basin (South Kariba Hydropower Station, Hwange, Bulawayo, Harare and Manyati thermal stations which derive coal energy from the same catchment). Proposals have been put forward to build another hydropower plant at Batoka Gorge upstream of Lake Kariba and the Sengwa Thermal Power Station in Gokwe North District.

Environmental problems include pollution from mining, industrial and domestic activities within major cities and reduction of wilderness values due to over-development at tourism "hot-spots" such as the Victoria Falls and Mana Pools. The damming of the basin tributaries, especially for irrigation water may have downstream impacts such as sedimentation which could impair ecosystems and result in possible loss of biodiversity. Other activities dependent on the abundance of water such as fish production would also be adversely affected.