Lucy Scott, South African Institute for Aquatic Biodiversity, Grahamstown, South Africa
Musonda Mumba, University College, London, UK; Paul Skelton, South African Institute for Aquatic Biodiversity, Grahamstown, South Africa; and Monica Chundama, WWF Zambia Coordination Office, Lusaka
Major Habitat Type
Tropical and subtropical floodplain rivers and wetland complexes
Drainages flowing into
The Middle Zambezi River.
Main rivers to other water bodies
The Kafue River is about 1,000 km long from its source to the confluence of the two rivers (Beadle 1981). The river is a major tributary of the Zambezi and is found entirely in Zambia. It is a source of potable water for about 40% of the Zambian population and is the major source of water for the capital city, Lusaka (Chabwela & Mumba 1998).
This ecoregion encompasses the Kafue River drainage basin from central Zambia, south to the Kafue gorge where the river enters the Middle Zambezi River. It contains the extensive and seasonally inundated floodplains of the Kafue Flats and the large Lukanga swamp. However, the headwaters of the Kafue, including parts of the Lufupa, Lunga, Luswishi, and upper Kafue rivers are excluded from this ecoregion and contained within the Upper Zambezi Floodplains ecoregion , with which they have faunal affinities.
The aquatic vegetation in permanent water and on the seasonally inundated floodplains of the Kafue flats and Lukanga swamp is characterized by Vossia cuspidata, Polygonium sp., Cyperus papyrus, Potamogeton sp., Apanogeton sp., Typha sp., and Leersia hexandra. Floating rafts of vegetation are known to break away from the banks and float out to open water (Williams 1971; Stuart et al. 1990).
The relatively high rainfall combined with a gentle gradient in the main river has produced extensive swamps and floodplains. The Kafue is termed a ‘reservoir river’ (sensu Jackson 1961, 1963)(Jackson 1961; , meaning that the floodplains regulate the flood, releasing it slowly back to the river so that river levels seldom exhibit large variations in height. Inundation of the floodplains occurs from January to June, following the rains (Williams 1971). The floodplains are inundated to an average depth of 3 m and have water on them for long periods. Marginal vegetation is abundant and provides cover for small and juvenile fish (Williams 1971; Marshall 2000). The 250-km long Kafue floodplain, stretching from Itezhi-Tezhi to the Kafue gorge, is up to 40 km wide during seasonal floods (Hughes & Hughes 1992).
The terrestrial vegetation in the Kafue ecoregion is a diverse mosaic of miombo (Brachystegia / Julbernardia), Acacia/Combretum and mopane woodland, and grasslands dominated by rice grass(Oryza barthii), Echinochloa pyramidalis, Vetivaria nigritana, Acroceras macrum, and Setaria avettae.
Description of endemic fishes
Only one killifish (Nothobranchius kafuensis) and one cyprinid (known only from its type locality; Barbus altidorsalis) are endemic.
Seasonal flooding in the Kafue is the most important ecological process maintaining biodiversity in the region. During periods of inundation, fish migrate out onto the floodplains to spawn, taking advantage of increased habitat and protective vegetative cover. Fish known to use the rich floodplain habitats in this way include the largemouth breams and tilapias, as well as many small barbs. Females of the endemic Kafue killifish (Nothobranchius kafuensis) lay their eggs on the sediments of the floodplain or in pans during the wet season, but hatching is delayed until the following year when water returns.
Justification for delineation
The Kafue is part of the west-Zambezian aquatic faunal arena and has ichthyofaunal affinities with the Okavango, Upper Zambezi, and Cunene Rivers. The Kafue also has some species in common with the southern tributaries of the Congo River, especially the Chambeshi (Bell-Cross 1972; Skelton 1994). The Kafue River has long stretches of rapids in the upper two-thirds of its course, but these present no barrier to fish movement. However, a series of falls downstream in the 48-km long Kafue Gorge create two major physical barriers to fish movement from the middle Zambezi (Bell-Cross 1965, 1972). Observed biogeographic affinities with Zambezian ichthyofauna can be explained by a series of stream captures. Prior to the Pleistocene, the Kafue may have flowed westward to join the Okavango, Upper Zambezi, and Cunene, and later it may have been captured by a tributary of the middle Zambezi (Bell-Cross 1972; Beadle 1981). It is thought to have separated from the Upper Zambezi in the mid-Tertiary, however its headwaters retain ichthyofaunal affinities with the Upper Zambezi and are included in the Upper Zambezi Floodplains ecoregion . The Kafue was separated from the Zambian Congo drainage when the Chambeshi was captured by the Luapula [ecoregion 806], and as a consequence it was not invaded by those Congo River species that invaded the Upper Zambezi (Marshall 2000).
Level of taxonomic exploration
Fair. More research is needed in all aspects pertaining to this ecoregion, especially into the effects of overfishing, other anthropogenic activities and the functioning of the system as a whole.
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