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Max Planck Encyclopedia of Public International Law [MPEPIL]

Zambezi River

George (Rock) Pring, Katie Allison

Rivers — Water — Indigenous peoples — Sustainable development — Natural resources

Published under the auspices of the Max Planck Foundation for International Peace and the Rule of Law under the direction of Rüdiger Wolfrum.

A.  Introduction

The Zambezi River is one of the world’s great international watercourses, the largest river in southern Africa and ‘the most shared resource’ in the region (Mafuta). Thus far, the sharing has been done without a comprehensive treaty governing international regulation of the use of water (Water, International Regulation of the Use of). Water development in the basin has chiefly involved ‘national single-purpose projects [which] have rarely taken into consideration the interests of other users or countries or the consequential environmental impacts’ (Hoekstra 185). Nevertheless, there have been no major conflicts over water, because the limits of the basin’s abundant water supplies are still far from being reached. Development pressures on the Zambezi are multiplying and if all current development plans go forward, conflicts will be inevitable (ibid). To avoid this, the Zambezi Basin States are developing basin governing bodies and plans aimed at establishing equitable utilization of this shared resource (Equitable Utilization of Shared Resources).

B.  Physical

The Zambezi starts on the Central African Plateau in the far northwest corner of Zambia and drains much of the south-central region of the continent. It flows over 2500 km—although some sources rate it considerably longer—in an S-shaped course, south and east, before emptying into the Indian Ocean. It drains a total area of nearly 1,400,000 km2 in eight States: Zambia (42.5% of the basin), Angola (17.4%), Zimbabwe (15.8%), Mozambique (12%), Malawi (8%), Tanzania (2.1%), Botswana (0.9%), and Namibia (1.3%)—with some authorities adding a very small portion of a ninth State, the Democratic Republic of Congo (less than 0.1%). The basin covers about 4.5% of the continent.

The upper Zambezi rises in wetlands in the Kalene hills of Zambia, separated by a thin watershed from the headwaters of the Congo River to the north. The Zambezi crosses the border into Angola, where it flows southwest and south for 280 km. It re-enters Zambia, flowing south through marshy floodplains, where it is enlarged by major tributaries, then swings east forming the border for about 130 km between Zambia on the north and on the south the Caprivi Strip, the long, thin, colonial-era extension of Namibia designed to give it a finger-hold on the Zambezi. At the eastern tip of the Caprivi Strip, Namibia, Botswana, Zambia, and Zimbabwe come together, and the Kwando—also called Cuando, Linyanti, Chobe—joins the Zambezi. The river then continues, forming the border between Zambia and Zimbabwe, before plunging over Victoria Falls, marking the beginning of the middle Zambezi. Two lakes formed by large dams—the Kariba (on the Zambia-Zimbabwe border) and the Cahora Bassa (in Mozambique)—cover much of this middle reach of the river, which continues to form the Zambia–Zimbabwe border. Here it receives its major tributaries, the Kafue and Luangwa, and crosses into Mozambique. The lower course begins at the Cahora Bassa Dam as the river descends from the plateau to the coastal plain, where its last large tributary joins it, the Shire. Finally, the river spreads out as much as 8 km, splits into a wide delta, and empties into the Indian Ocean.

The Zambezi Basin lies in the tropics. Annual rainfall decreases from almost 1800 millimetres per year (‘mm/y’) in the upper basin to less than 550 millimetres per year (‘mm/y’) in the south. The average rainfall is about 930 mm/y, but much of this is lost given the area’s high evaporation rates. The variable climate, rainfall, and evaporation account for the river’s highly variable flows, which range from severe floods to droughts that can vary from year to year. In 2006, the basin States suffered a drought, and in 2007, one of their worst floods ever.

The Zambezi’s water flow is some 10 times greater than the Orange River, but only about 1/10 that of the Congo River. The average annual discharge is 18 km3/y where the upper Zambezi flows from Angola back into Zambia, 33.5 km3/y at the eastern end of the Caprivi Strip, 77.5 km3/y as it enters Lake Cahora Bassa, and 106 km3/y as it enters the sea. Maximum flows occur in March–April, and can drop to less than 10% of the maximum before the rainy season starts in November. The basin’s dams have tempered medium-level floods, to the detriment of the flood-dependent flora, fauna, and ecosystems downstream, but not extreme floods. A vast amount of water is lost from the large dams through evaporation (Conley 12).

Vegetation along the upper and middle Zambezi is predominantly savannah, grasslands, and forests. The lower course contains evergreen forests, dense bush, and mangrove swamps. The basin supports large populations of mega-fauna, including crocodiles, hippopotamuses, elephants, buffalo, giraffes, lions, and many different types of ungulates, as well as several hundred species of fish. The reduction in annual flooding below the large dams has caused a reduction in habitat and populations of the large mammals.

Pollution of land, air, and water resources are major problems in parts of the basin (see SADC and others). Increasing rates of urbanization and industrialization are primary factors. Point source water pollution occurs from untreated municipal sewage, industry, power generation, and mining; non-point source water pollution occurs from agriculture, urban stormwater runoff, landfill leachate, soil erosion, and gold panning (ibid).

C.  History of Human Use

African tribes and kingdoms have populated the basin since prehistoric times, practising subsistence and irrigated agriculture and leaving legacies of stone ruins, sophisticated water works, and thousands of small gold mines (McNaughton para. 6). The first non-Africans to arrive in the basin were Arab traders looking for ivory, gold, and slaves starting in the 10th century CE. The Portuguese followed for similar reasons in the 16th century, but failed to penetrate far up the river. Scottish missionary Dr David Livingstone, immortalized by the journalist Henry Stanley, explored and mapped most of the river in the 1850s, but the river’s source was not finally found and surveyed until the 20th century.

Colonialism in the 19th and 20th centuries brought urban and hydropower development. After World War II, the influence of South Africa’s apartheid, independence movements in the region, civil war, and human rights problems have had a destabilizing influence on all basin States, although some bilateral water resources development continued.

10  Basin countries have built three major dams, primarily for hydroelectricity and flood control. In the 1950s, the Kariba Dam, one of the largest in the world, was built to provide electricity for Zambia and Zimbabwe. In the 1970s, Portugal and others built the Cahora Bassa Dam downstream in Mozambique, primarily to supply electricity over a 1400 km transmission line to South Africa. Also in the 1970s, the Zambian government authorized the Itezhi-Tezhi Dam on the Kafue River tributary as a regulating dam for hydropower. The dams have proved controversial for displacing tens of thousands of indigenous peoples, altering the riverine ecosystems, and flooding vast areas, including a national park.

11  Demand for water in the basin is growing in all sectors due to spiralling population growth and economic development (see SADC and others). Angola and Zambia have adequate water supplies for the future, but the basin States Namibia and Botswana are already facing shortages, and Zimbabwe, Mozambique, and Tanzania will do so by 2025 (ibid). Poverty is viewed as ‘one of the root causes of environmental degradation in the region’, with millions of people living in poverty in both rural and urban areas of the basin (ibid).

12  Water development and environmental management in the Zambezi Basin has not been integrated basinwide, but proceeded ‘as disparate parts within eight national boundaries defined during colonialism’ (SADC and others). Past regional co-operation has focused on specific hydropower or irrigation projects, without giving priority to social, ecological, or integrated water management factors (ibid). The Southern African Development Community (‘SADC’), of which all basin States are parties, now presses for regional co-operation.

D.  International Legal Regime

13  While there is yet no basinwide treaty on equitable allocation of the Zambezi’s waters, the riparian States have created a basinwide commission and a planning process to lead to a comprehensive agreement. A number of bilateral and multilateral agreements starting in the 19th century have led to this point.

14  In an 1890 agreement between colonial powers, Great Britain ceded to Germany the long strip of land called the Caprivi Strip to give its colony, today’s Namibia, a riparian claim to the Zambezi; this colonial gerrymandering causes other basin States to question Namibia’s riparian rights, but it has not abandoned its claims. In an 1891 treaty, Britain and Portugal ‘defin[ed] their respective spheres of influence’ in the region, using the Zambezi and tributaries as boundaries (Art. VII Treaty between Great Britain and Portugal defining the Spheres of Influence of the two countries in Africa).

15  Multi-State co-ordinated development of the Zambezi began in the 1940s under the Central African Federation (‘CAF’), consisting of Southern Rhodesia (later Zimbabwe), Northern Rhodesia (later Zambia), and Nyasaland (later Malawi). Planning for the Kariba Dam began in the 1950s, with funding from the World Bank (World Bank Group) to the CAF’s Federal Power Board. In 1963, Northern and Southern Rhodesia entered into a treaty establishing the Central African Power Corporation (‘CAPCO’) to replace the Federal Power Board and operate the Kariba complex. In 1987, after independence, Zambia and Zimbabwe replaced CAPCO with the Zambezi River Authority (‘ZRA’) to operate the Kariba complex, investigate and develop new dams, and monitor environmental data. The ZRA has proposed some new projects and worked on benefit sharing and water quality, but its scope presently does not allow it to serve as a basinwide co-ordinating structure (see SADC and others). The Cahora Bassa hydroelectric dam project began with a 1969 bilateral agreement between Portugal and South Africa, and it was completed in 1974. Mozambique achieved independence the following year, and a new agreement between Portugal, Mozambique, and South Africa ensued in 1984.

16  In 1987, the predecessor of today’s SADC brought together the eight basin States, as well as the Zambezi-interested non-basin States of South Africa, Lesotho, and Swaziland, to adopt the Zambezi Action Plan for the Environmentally Sound Management of the Common Zambezi River System (‘ZACPLAN’). Its purpose is to develop a management plan for the basin as a whole, to assure equitable sharing and sustainable development. This forum has lead to the identification of 19 Zambezi Action Plan Projects (‘ZACPRO’), but co-ordination and progress have been limited (Nakayama 110).

17  Botswana and Namibia created a comprehensive sub-basin agreement in 1990 for their shared Kwando-Linyanti-Chobe tributary system. The two States created a Joint Permanent Water Commission for co-operative development and utilization of those water resources, but without involving other downstream States that could be affected.

18  The SADC has developed one of the most progressive examples of a regional water treaty, the 2000 Revised SADC Protocol on Shared Watercourse Systems in the Southern African Development Community Region (‘Revised Protocol’), covering the 15 international river basins in the SADC region, which has been ratified by all SADC members, including the Zambezi Basin States. The protocol is a ‘revised’ version of an earlier 1995 SADC Water Protocol, designed to upgrade the earlier one with the more progressive concepts of the intervening 1997 UN Convention on Non-navigational Uses of International Watercourses.

19  The revised protocol sets out the principles for joint management of watercourses shared by two or more SADC Member States—including surface water and surface-connected groundwater. Its preamble acknowledges the principles in the 1996 Helsinki Rules, the 1997 UN Convention on the Law of the Non-Navigational Uses of International Watercourses, and Agenda 21 noting ‘the need for co-ordinated and environmentally sound development of the resources of shared watercourses in the SADC Region in order to support sustainable socio-economic development’ (preamble Revised Protocol). It adopts something close to a ‘community-of-interests’ approach (McCaffrey 156) and includes a long list of progressive commitments, including promoting ‘sustainable development’ (Art. 3 (1) Revised Protocol), ‘equitable and reasonable utilisation’ (Art. 3 (7) ibid), open utilization of shared watercourses (Art. 3 (2) ibid), respect for international water law (Art. 3 (3) ibid), balancing development and environmental protection (Art. 3 (4) ibid), close co-operation (Art. 3 (5) ibid), information exchange (Art. 3 (6) ibid), notice of development projects (Art. 4 ibid), dispute settlement (Art. 7 ibid), and the rule against ‘causing of significant harm’ (Art. 10 ibid). It pledges them to establish appropriate river basin management institutions, such as river commissions (Art. 5 (3) ibid). It empowers States to enter into more specific basin agreements that apply the protocol’s principles (Art. 6 ibid). The SADC Revised Protocol has worked very successfully, and the SADC plays an important role in overseeing its implementation.

20  Eight of the basin States signed a 2004 agreement to create a Zambezi River Basin Commission (‘ZAMCOM’). ZAMCOM is to be a comprehensive basinwide body, empowered to promote the equitable and reasonable use of Zambezi Basin water, co-ordinate management and development of its water resources, provide information, and advise on planning, dispute avoidance, and harmonization of national water polices and legislation. It will consist of a Council of Ministers to adopt policies and decisions, a Technical Committee to implement the Council’s directives, and a Secretariat to provide technical and administrative services. It is still in the formative stages, however, since it must be ratified by at least six of the basin States to come into force. As of 2007, Angola, Botswana, Mozambique, and Namibia had ratified the treaty, but not the key States of Zambia and Zimbabwe or Malawi and Tanzania. Whether those States join and whether all can incorporate the undertakings in their national plans remains to be seen (Bos).

E.  Future for the Basin

21  According to the SADC, there are two possible future scenarios for the Zambezi Basin: ‘the beaten track on which society has been traveling all along or a new highway towards a state of sustainability’ (SADC and others). The ‘beaten track’ has been defined by national boundaries, interests, and projects, without taking a basinwide ‘ecosystem’ approach of sustainable development (ibid).

22  The basin States face severe challenges including the flood-drought climate, spiralling population, endemic poverty for the majority, unemployment, food and energy insecurity, human and technologic capacity issues, human rights issues, and inadequate financial resources. Out-of-basin areas, such as South Africa and Namibia, view the Zambezi as a future source of water. All of these factors combine to place growing demands on the water resource in all sectors, with consequent impacts on water quantity and quality, biodiversity loss, and land and wetlands degradation. Some basin States are already facing water shortages in the near term or water stress, and all have water quality and dry season quantity problems. The situation ‘could end up being a disaster if planning for the next 25 years does not start now’ (SADC and others).

23  There are promising signs for the future. The SADC is ‘one of the most successful regional organizations ever to operate in … the entire developing world’ (SADC and others). Its Revised Protocol on Shared Watercourses sets a model foundation on which to build a modern basin management agreement. The fledgling Zambezi Basin Commission shows promise, if the remaining basin States will ratify it.

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