OVERVIEW OF THE IMPACT OF MINING ON THE ... - IIED pubs

or fuelwood production. Similar patterns are also associated with the development of mining operations and
satellite towns in remote regions of the basin (Chenje, 2000).
3.1.4 Hydrological characteristics, water availability and patterns of water use
The quantity and timing of rainfall received in the Zambezi basin controls the quantity, timing and duration of
flows in the different tributary rivers. The uneven distribution of rainfall in the basin is reflected in the very
uneven distribution of water resources in the basin states. In turn, these influence the types of economic
activities undertaken by the residents in each country. The uneven distribution of water across the basin has
led to tensions and occasional disputes between some of the basin states regarding what can be constituted as
a “fair and equitable share” of the available water resources (Ashton, 2000).
The Zambezi and its larger tributaries are all perennial with seasonal cyclical patterns of high and low flows.
The Luangwa River in Zambia shows a very marked seasonality, and in dry years, flows cease altogether. The
western and southwestern parts of the basin that receive the lowest rainfalls have mainly seasonal or episodic
rivers that have no surface flow during the dry winter months (Chenje, 2000).
The available information on flows in the Zambezi River show the presence of a distinct long-term cycle, with a
period estimated at some 70-80 years. At Victoria Falls, flow measurements show that high flows average
some 3,500 Million m 3 /second, whilst low flows are some 60% below this level. In recent years (1985-1999),
however, dry season flows at Victoria Falls have been exceptionally low and parts of the Victoria Falls have
dried out completely for periods of several weeks.
The demand for water in the Zambezi basin is both high and unevenly spread. In particular, water demands by
industry, mining and the agricultural sector account for over 75% of all water used. Coupled with high
evaporation losses from Lakes Kariba and Cahora Bassa, flows in the lower reaches of the Zambezi River are
usually relatively small, unless they have been “boosted” by the arrival of a tropical cyclone (e.g. the cyclone
that arrived in 2000 and flooded large areas of Mozambique).
Flows in the lower Shire River are fed by outflows from Lake Malawi. Recent declines in the level of Lake
Malawi have resulted in significantly decreased outflows and, as a result, the Shire River has contributed
relatively little water to flows in the lower Zambezi River.
Large areas of important wetlands are found in several areas of the Zambezi basin (Timberlake, 1998). These
wetlands absorb and attenuate flows from upstream catchment areas, releasing this “trapped” water slowly over
a period of several months and maintaining flows during the dry winter months. The most important wetland
areas in the Zambezi basin are the Zambezi Floodplains in Barotseland, the Chobe-Linyanti Swamps in
northeastern Namibia and Botswana, the Busanga Swamps on the Lunga River (a tributary of the Kafue River),
and the Lukanga Swamps and the Kafue Floodplain on the Kafue River. Smaller wetland areas are located on
the lower reaches of the Luangwa River, as well as the Elephant Marsh near the town of Chiromo on the lower
Shire River in Malawi and Mozambique (Timberlake, 1998).
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