The total quantity of water stored in wetlands is estimated at 100,000 million cubic metres. Apart from artificial wetlands, most of which have been formed by blocking gorges, valleys and streams for water abstraction and other developments, natural wetland systems have formed along the main river and its tributaries, wherever the river stretch encounters depressions and wide valleys. The wetlands have historically attracted large population communities due to the diverse means of livelihood they provide, and they continue to be areas of vast opportunities for modern development, therefore posing enormous challenges for their effective management.

TYPES AND FUNCTIONS
Wetlands in the Zambezi Basin fall within five broad categories: artificial lakes, natural lakes, riverine and freshwater marshes, estuarine, and marine wetlands.

Artificial Lakes

Artificial lakes or reservoirs have been constructed to optimise the potential of the river basin to support economic development through hydropower generation, irrigation, water supply, fisheries, navigation, tourism and recreation. The main artificial lakes in the Zambezi Basin are Itezhi-tezhi, Kafue, Kariba and Cahora Bassa. All were constructed for the installation of hydropower generation, although they are also being utilised for fisheries, tourism and navigation, and to a lesser extent for irrigation and water supply.

Natural Lakes

The main natural lake in the Zambezi Basin is Lake Malawi/Nyasa/Niassa (as it is known respectively in Malawi, Tanzania and Mozambique), the third largest natural lake in Africa after Lakes Victoria and Tanganyika, with a surface area of about 28,000 sq km. The lake provides a livelihood to a large portion of the population of Malawi, primarily through fisheries but also through tourism and other means. The lake outlet at Liwonde forms the beginning of the Shire river along which hydropower and extensive irrigation developments have been established. Hence the lake supports power generation for Malawi as well.

Riverine And Freshwater Marshes

Wetlands under this category are found along the main river channel and its tributaries, wherever the slope is sufficiently gentle and stable and the valley sufficiently wide to allow continuous settlement of sediment and growth of permanent vegetation. Riverine wetland and freshwater marshes are periodically flooded during seasons of high flow, and are generally regarded as key components for regeneration of plant and animal life forms including fish, birds and other aquatic species endemic to the river system. Major riverine and freshwater marshes in the Zambezi Basin are the Barotse plains and Kafue flats in Zambia, Eastern Caprivi in Namibia, the Chobe-Linyanti swamps in Botswana, Lukanga swamps in Zambia, and Elephant marshes in southern Malawi. Dombos which are common in Zambia and Zimbabwe also fall under this category of wetlands.

Estuarine

The Zambezi delta, covering some 15,000 sq km, is the main estuarine wetland in the basin. The delta was formed as a result of slowing of the river flow as it enters the Indian Ocean, depositing sediment to form an alluvial fan spanning an area of 18, 000 sq km and extending more than 100 km inland. The area, however, shrank to 15,000 sq km upon construction of Cahora Bassa dam. The Marromeu complex which is part of the Zambezi delta is being declared a wetland of international importance under the Ramsar Convention by the government of Mozambique. Other minor estuarine systems found in the basin are those formed where the main river or its tributaries enter lakes and reservoirs. Notable of these are the estuarine wetlands found along Lake Malawi and Lake Kariba.

Marine

The marine wetland system in the Zambezi Basin occurs along the coastline of Mozambique, adjacent to the delta. This area is fertile in coastal fisheries, which earn substantial income for communities in the area. The marine wetland system also supports mangrove, sea grass and coral reef resources, which are exploited by local communities and commercial companies.

MAIN VALUES

Wetlands are recognised throughout the world as valuable areas, harbouring some of the most welldocumented civilisations, and the Zambezi basin wetlands are no exception. Key values of wetlands in the basin include: water flow regulation, soil and sediment nutrient retention and distribution, supporting diverse plant and animal life and related products, as well as water purification. Other values of an indirect nature include supporting energy production, aquifer recharge, cultural, traditional and religious, aesthetic and tourism, and climate-change mitigation. Wetlands derive their values mainly from the steady and consistent supply of water and nutrients, and subsequently through dense vegetation growth and its decomposition. This nature of wetlands is maintained within a fragile ecological balance, which if disturbed leads to them losing their values.

Water flow regulation

Wetlands in the basin provide a reliable and consistent source of water even through dry seasons. In the Kafue, the Kafue flats complement the Itezhitezhi reservoir to ensure a relatively steady supply of water for production of hydropower at Kafue Gorge. Due to the vegetation and flat terrain, wetlands also reduce the magnitude of floods, thus protecting infrastructure, communities and reducing the erosive capacity of rivers and streams. The flow regulation property of wetlands also translates into retention of water during the wet season and its release into rivers and streams during the dry season (as baseflow), and providing an opportunity for infiltration of the water into groundwater (aquifer recharge).

Soil and sediment nutrient retention and distribution

Wetlands act as a trap for soil and sediment nutrients gathered by the river and streams in the upper catchment. The nutrients are enriched by the decomposing vegetation of the wetland and combined with the water retention capacity of wetlands, this attribute of wetlands makes them particularly suitable for cultivation and farming. In the Zambezi Basin, the floodplains in the Chobe/Caprivi, Zambezi delta, Elephant marshes (in the Lower Shire) and Kafue flats are extensively used for agricultural production. A sizeable proportion of the 520,000 sq km of land area cultivated in the Basin falls under subsistence floodplain farming.

Water flow regulation

Supporting plant and animal life Arguably the most prominent and visible value of wetlands in the SADC region, including the Zambezi Basin, is their ability to support diverse plant and animal life. Communities living in the vicinity of wetlands derive significant benefit from harvesting of different products including reeds, grasses, fish, wood, clay, wildlife and birds, for direct consumption, for sale to markets within and outside the wetland, or for processing into higher value products.

Water purification

The water purification ability of wetlands, like nutrient retention, is derived from the flat nature of wetlands, their thick vegetation and the presence of fine sediment and clay in the system. The chemical properties of clays and fine sediment in wetlands favour the trapping of both floating and dissolved pollutants in water. Wetlands also remove pollution from water through direct absorption by vegetation. The main sources of pollutants and sewage effluent in the Zambezi Basin exist in the upper reaches of the river, from mining activities in the Copperbelt of Zambia; in the middle reaches from cities and urban settlements (notably Lusaka, Victoria Falls, Harare, Lilongwe, Blantyre); commercial farming in the middle and lower reaches of the river; and mining (commercial and smallscale gold-panning) in the middle reaches. The existence of vast areas of wetlands have protected most communities from widespread pollution and ensured availability of potable water.

Cultural, traditional and religious

Wetlands are valued by communities as places for worshipping, performing traditional practices and religious rituals. Practices such as baptising are conducted in wetlands, and wetlands provide a rich source of traditional medicines. In the upper Zambezi, the rich traditions of the Lozi, eg the cattle- moving and hunting ceremonies, are closely linked to the high flood and flood recession on the wetlands of the Zambezi river.

Aesthetic and tourism

The aesthetic value of wetlands is mainly derived from the diverse plant and animal life they support. This feature attracts tourism, which in turn provides income for communities in the areas surrounding wetlands. The Zambezi Basin, through its wetlands attracts many tourists to areas such as Victoria Falls, Chobe, Caprivi, Lake Malawi, Kariba and the Zambezi delta.

Climate change mitigation

The continued emission of carbon products into the atmosphere from industry is expected to influence the well-established climatic patterns in the world in general. Wetlands, because they support large expanses of vegetation, contribute to alleviation of the adverse effects of climate change, mainly because vegetation uses carbon dioxide in its growth. Climate change is also expected to increase the magnitude of extreme weather patterns, both droughts and floods. Therefore, through the flow regulation and retention of water, wetlands will play a more crucial role in maintaining livelihoods of communities who are already vulnerable to extreme weather events.

Reconciling hydropower generation with ecosystem maintenance

There is evidence that upstream regulation of water flows to the Zambezi delta is negatively affecting the economic potential and ecological function of the estuarine wetland. Studies by the International Crane Foundation demonstrate that due to regulation of approximately 90 percent of water flows of the Zambezi through upstream hydroelectric installations at Kariba (closed in 1959) and Cahora Bassa (closed in 1975), flow regimes (wet season flooding, flood recession and dry season low flow) at the delta have been significantly altered. This has caused a reduction in fish spawning areas, direct losses in prawn production, disappearance of flow in some channels, salt water intrusion, vegetation of some channels, increased poaching due to accessibility of areas previously under constant flood, intensive veldt burning, and encroachment of flood-prone river banks by communities thus exposing them to destructive flood events. A reservoir management strategy has been developed to help restore the ecological integrity of the Zambezi Delta.

Source: SADC Wetlands Conservation Project Phase II, Stakeholder workshop for development of a wetland management plan: Marromeu Complex Estuarine Wetland, Beira, 13-14 February 2003

WETLAND MANAGEMENT

Wetlands the world over are damaged through unwise exploitation of their resources and erosion of their values. Rehabilitation is very costly if ever accomplished. In the Zambezi Basin, wetlands are threatened by pollution from industry, sewage effluent discharge, pollution from largescale farming practices, mining, reservoir development for hydropower installations, largescale water abstraction for use in the basin and potentially outside, drainage for farming, invasive alien plants, and over utilisation beyond limit of natural regeneration.

Efforts to promote integrated management of wetlands in the basin have been supported by agencies such as SADC, through ZACPLAN (a project seeking to develop an integrated water resources management of the entire river basin), IUCN through the Wetlands Conservation and Sustainable Utilisation project and the SADC Wetlands Conservation Project Phase II, WWF through initiatives in the Kafue flats promoting partnerships for sustainable use of wetland resources, and the International Crane Foundation through their research on migratory bird species and the effects of infrastructure development on wetlands.

Most basin states have ratified the Ramsar Convention and as part of their obligations under the Convention have designated specific wetlands as wetlands of international importance. The designation obliges the country to develop a wetland management plan for the designated area. Botswana, Malawi, Namibia, Tanzania and Zambia have ratified the Convention, but only Zambia has designated specific wetlands as Ramsar sites (Lochnivar and Blue lagoon on the Kafue flats, Lukanga swamps, Liuwa swamps, Luangwa floodplain, Busanga swamps). Mozambique is planning to accede to the Convention and intends to designate the Marromeu complex on the Zambezi delta as a Ramsar site. Countries have also established policies and institutions to promote wise-use of the resources.

CONCLUSION

Integrated management of wetlands presents challenges, mainly because of the wide spectrum of stakeholders benefiting from the systems. The institutional arrangements for effective management are a key component. It is recommended that institutional arrangements that give clear roles, visibility and actively involve all sectors of the community, government, enterprises and the commercial sector be established for all significant wetlands. Gender considerations are of cardinal importance in establishing effective management frameworks for wetlands.

Transboundary co-operation, joint management and compatible approaches among countries sharing wetlands are crucial to successful management of wetlands. Information sharing is also very critical for transparency, trust building and sustainable initiatives. Support for research to ensure understanding of wetland dynamics and to support policy formulation and decision making is encouraged.

REFERENCES

Davies, B and Day, J.A., 1998. Vanishing Waters. University of Cape Town Presss

Chenje, M. (ed), 2000. State of the Environment Zambezi Basin 2000/Estado do Ambiente Bacia do Zambeze 2000, and the Summary/Sumário. SADC, IUCN, SARDC, ZRA and Sida. Maseru, Lusaka and Harare

Hirji, R., Johnson, P., Maro, P. and Matiza Chiuta, T. (eds) 2002. Defining and Mainstreaming Environmental Sustainability in Water Resources Management in Southern Africa, and A Summary. SADC, IUCN, SARDC, World Bank and Sida

SADC Wetlands Conservation Project Phase II, 2002, unpublished reports