Ecoregion Description

557: Kafue

Major Habitat Type:

tropical and subtropical floodplain rivers and wetland complexes

Author:

Lucy Scott, South African Institute for Aquatic Biodiversity, Grahamstown, South Africa

Reviewers:

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

Countries:

Zambia; Zimbabwe

Boundaries:

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 [556], with which they have faunal affinities. 

Drainages flowing into:

The Middle Zambezi River.

Main rivers or 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).

Climate:

Rainfall in the ecoregion is highly seasonal, averaging 600-900 mm annually, with the majority falling in the summer months of November through February. The maximum temperature varies from 20°C to 45°C, depending on the season.

Freshwater habitats:

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).

Terrestrial Habitats:

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.

Fish Fauna:

The rivers, floodplains and swamps of the Kafue ecoregion support a moderately rich freshwater fauna, but these habitats support few fish endemics compared to other large river and floodplain ecoregions. However, near-endemism is high for large riverine cichlids within this ecoregion, and about 60 species of fish live in its waters (Bell-Cross 1972). 

Description of endemic fishes:

Only one killifish (Nothobranchius kafuensis) and one cyprinid (known only from its type locality; Barbus altidorsalis) are endemic. 

Other noteworthy aquatic biotic elements:

The Kafue Flats supports the highest abundance of waterbirds within the Zambezi basin (Mundy 2000) and the area is an Important Bird Area (Fishpool & Evans 2001). For instance, the most significant population of the vulnerable wattled crane (Grus carunculatus) congregates in the Kafue Flats. The vulnerable slaty egret (Egretta vinaceigula) has also been recorded in the flats and probably also breeds here. Congregations of long-tailed cormorant (Phalacrocorax africanus), cattle egret (Bubulcus ibis), African openbill (Anastomus lamelligerus), fulvous whistling duck (Dendrocygna bicolor), comb duck (Sarkidiornis melanotos), collared pratincole (Glareola pratincola), Caspian plover (Charadrius asiaticus), and ruff (Philomachus pugnax) are also known (Fishpool & Evans 2001).

 Several migratory mammals graze on the grasses that grow seasonally on the floodplains. About half of all of the 100,000 remaining lechwe (Kobus leche leche and Kobus l. kafuensis)in Africa occur in the Kafue floodplain (Cotterill 2000). The red lechwe (K. l. leche) occupies extensive areas of the dry floodplain in parts of Kafue National Park and is probably beneficial to the fishery by increasing the floodplain fertility (Williams 1971). The Kafue lechwe (K. l. kafuensis) is endemic to the Kafue Flats and inhabits low-lying land in the vicinity of the Kafue Gorge and Itezhi-Tezhi Dam (Williams 1971; Stuart et al. 1990).

Ecological phenomena:

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 [556]. 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.

References/sources:

Beadle, L. C. (1981). "The inland waters of tropical Africa" England: Longman Group Limited.

Bell-Cross, G. (1972). "The fish fauna of the Zambezi River system" Arnoldia (Rhodesia) 5(29) 1-19.

Bell-Cross, G. (1965). "Physical barriers separating the fishes of the Kafue and Middle Zambezi River systems" Fisheries Research Bulletin of Zambia 4 97-101.

Chabwela, H. N. W.,Mumba, W. (1998)"Integrating water conservation and population strategies on the Kafue Flats" In de Sherbinin, A.;Dompka, V. (Ed.). Water and population dynamics. Washington, D.C., USA: American Association for the Advancement of Science.

Cotterill, F. (2000)"Reduncine antelope of the Zambezi Basin" In Timberlake, J. (Ed.). Biodiversity of the Zambezi Basin wetlands. (pp. 145-199) Harare, Zimbabwe: Biodiversity Foundation for Africa, Bulawayo/The Zambezi Society.

Fishpool, L. D. C.,Evans, M. I. (Ed.) (2001). "Important Bird Areas in Africa and associated islands: Priority sites for conservation" Newbury and Cambridge, UK: Pisces Publications and BirdLife International (Birdlife Conservation Series No. 11).

Hughes, R. H.,Hughes, J. S. (1992). "A directory of African wetlands" Gland, Switzerland, Nairobi, Kenya, and Cambridge, UK: IUCN, UNEP, and WCMC.

Jackson, P. B. N. (1963). "Ecological factors affecting the distribution of freshwater African fishes in tropical Africa" Annals of the Cape Provincial Museums (Natural History) 2 223-228.

Jackson, P. B. N. (1961). "Kariba studies. Ichthyology: The fish of the Middle Zambezi" UK: Manchester University Press.

Marshall, B. E. (2000)"Fishes of the Zambezi Basin" In Timberlake, J. (Ed.). Biodiversity of the Zambezi Basin wetlands. (pp. 393-460) Harare, Zimbabwe: Biodiversity Foundation for Africa, Bulawayo/The Zambezi Society.

Mundy, P. (2000)"Wetland birds of the Zambezi Basin" In Timberlake, J. (Ed.). Biodiversity of the Zambezi Basin wetlands. (pp. 213-278) Harare, Zimbabwe: Biodiversity Foundation for Africa, Bulawayo/The Zambezi Society.

Skelton, P. H. (1994). "Diversity and distribution of freshwater fishes in East and Southern Africa" Annals of the Royal Central Africa Museum (Zoology) 275 95-131.

Stuart, S. N., Adams, R. J., et al. (1990) Biodiversity in Sub-Saharan Africa and its islands: Conservation, management and sustainable use, Occasional Papers of the IUCN Species Survival Commission No. 6. Gland, Switzerland: IUCN.

Williams, R. (1971). "Fish ecology of the Kafue River and flood plain environment" Fisheries Research Bulletin of Zambia 5 305-330.