The Kafue Flats are a broad floodplain wetland on the Kafue River in central Zambia, stretching about 240 km east to west from the Itezhi-Tezhi Dam to Kafue town and the head of the Kafue Gorge, up to 50 km wide and roughly 6,500 km² in area across Southern, Central and Lusaka provinces. They are a landscape of seasonally flooded grassland, lagoons, ox-bow lakes and permanent swamp over black clay soil, flooded to less than a metre in the rains and cracking dry by the end of the dry season. In 1991 about 6,000 km² of the flats, matching the Kafue Flats Game Management Area, was listed as a Wetland of International Importance under the Ramsar Convention, and two national parks, Lochinvar (428 km²) and Blue Lagoon (about 500 km²), protect the southern and northern sides. The flats are best known for the Kafue lechwe, an antelope found nowhere else, and for one of Africa's most important populations of the vulnerable wattled crane.
Locally the flats are called Butwa, and the Batwa (Twa), now a small fishing minority on higher ground by the river channel, are thought to have been their first inhabitants. Their wildlife only makes sense against their shape: the Kafue River falls just 40 m along the whole length, from about 1,030 m at Itezhi-Tezhi to 990 m at Kafue town, so the river spreads sideways rather than running fast. The floodplain belongs to the Zambezian flooded grasslands ecoregion, ringed by miombo, mopane and acacia woodland. Its heavy black soils crack widely when dry and turn sticky when wet, forming a gilgai surface of small ridges 20–60 cm high around circular hollows 2–7 m across. The animals below are the ones that depend most on that slow sheet of floodwater.
Kafue lechwe: 250,000 in 1931, about 38,000 by 2005
The Kafue lechwe (Kobus leche kafuensis) is a subspecies of the southern lechwe confined to the Kafue Flats. Males carry long, lyre-shaped horns; both sexes have hind legs that are long in proportion, which helps them run through knee-deep water, and they use that water as protection from predators. They graze on aquatic plants and on grasses of the flooded meadows, following the edge of the water as it advances and retreats.
In 1931 an estimated 250,000 lechwe lived on the flats, one of the highest animal densities recorded anywhere, equivalent to about 11,000 kg of animal per km². By 2005 the count had fallen to about 38,000, a figure that stayed broadly stable at the next census, completed in 2009. The decline is attributed to the Itezhi-Tezhi Dam and the change in the timing and depth of flooding, to illegal hunting and to the growing numbers of people and cattle sharing the floodplain.
Lechwe mate during the rains, from November to February, and after a gestation of seven to eight months most calves are born between July and September. A flood that comes late, or a dry season in which water is released unpredictably, falls directly on that breeding cycle.
Lochinvar's 428 km² of lechwe grassland and wattled cranes
The south bank's main refuge is Lochinvar National Park, designated in 1972 on a former cattle ranch named after a loch in Galloway, Scotland. The Kafue River marks its northern boundary, and its 428 km² run from the floodplain and Chunga Lagoon up to wooded hills dominated by termite mounds, Faidherbia albida and Combretum trees. Ranchers long ago killed off the large predators, which is one reason antelope do well here; blue wildebeest, kudu, oribi and bushbuck share the park with the lechwe. Zebra and lechwe are the two dominant large mammals of the flats as a whole.
The same grassland is the stronghold of the wattled crane (Bugeranus carunculatus), listed as vulnerable on the IUCN Red List. It lives in eleven countries of eastern and southern Africa, and more than half of the world's wattled cranes are found in Zambia, although the single largest concentration is in Botswana's Okavango Delta. Lochinvar holds one of the highest numbers of the species in Africa. On the Kafue Flats as a whole, wattled cranes fell from between 2,000 and 3,000 birds in the 1970s to fewer than 1,000 by 2002, again linked to the altered flood regime that changes the shallow wet grassland where they feed and nest.
Lochinvar also preserves some of the oldest evidence of people on the flats. At the Gwisho hot springs, inside the park on the southern edge of the flats at about 977 m, J. Desmond Clark began excavations in 1957 and Creighton Gabel continued them in 1960–61, uncovering unusually well-preserved plant and animal remains with stone tools. Sebanzi Hill holds the remains of an Iron Age village, and the park also has hot springs and echoing rocks.
Chunga Lagoon and the birds of a 450-species Important Bird Area
BirdLife International lists the Kafue Flats as an Important Bird and Biodiversity Area, with more than 450 bird species recorded, including large breeding colonies hidden deep in the swamps. Lochinvar alone has more than 400 species. Waterbirds dominate: resident herons, egrets and storks, and seasonal migrants. The flats also hold a high density of breeding raptors, especially vultures, including the lappet-faced vulture.
Other species of conservation concern recorded here include the crowned crane, the slaty egret, the lesser kestrel and the corn crake. Chunga Lagoon, inside Lochinvar, shows how the river has changed: because Itezhi-Tezhi now releases water through most of the dry season, Chunga stays permanently flooded instead of shrinking each year. The spread of invasive weeds and rising human use are listed alongside the dams as the main threats to the flats' birds.
Sitatunga, zebra and buffalo in the 500 km² Blue Lagoon park
The north bank has its own refuge. Blue Lagoon National Park, about 500 km² in Central Province, lies roughly 100 km west of Lusaka (120 km by road) off the Lusaka–Mongu road; the Kafue's main channel runs about 10 km south of its boundary. Like Lochinvar it was a farm before it became a park in the 1970s, and its old farmhouse is now the reception. There is no direct road between the two parks; travellers go back via Lusaka.
Herds of Kafue lechwe use the flooded ground, Grant's zebra, reedbuck and African buffalo graze the drier parts, and the swamps hold sitatunga. The sitatunga is an amphibious antelope that lives in tall, dense swamp vegetation, feeding on sedges, bulrushes and aquatic grasses; unlike the lechwe, it depends on permanent swamp rather than on the seasonal flood. Blue wildebeest, roan, greater kudu and hippo are present in small numbers, mainly in and around the two parks. Outside them, the roughly 6,000 km² Kafue Flats Game Management Area allows people to live and use resources under regulation, a lower level of protection than the parks.
Itezhi-Tezhi, Kafue Gorge and the flood the wildlife depends on
Every species above is adapted to one rhythm: rains from November to December raising the river, a peak flood in April or May, then a slow drain that left little surface water by October or November. Two hydroelectric dams changed it. The Kafue Gorge Dam at the eastern end was completed in 1972 with 600 MW of generation and a reservoir of 785 million m³; its power station has since grown to 990 MW. To feed it through the dry season, a second dam about 62 m high was built at the Itezhi-Tezhi gap upstream between 1974 and 1977, holding about 5,700 million m³ in a reservoir of roughly 370–390 km² that floods part of Kafue National Park. Water takes about eight weeks to travel down the flats between the two.
The designers intended a managed flood of 300 m³/s through March to keep the floodplain working. In practice power demand, and erratic rainfall since 1990, meant that release often did not happen. Instead the flats received sudden pulses of water and a substantial dry-season flow. The documented results are lower fish production, disrupted breeding of lechwe and sitatunga, less dry-season grazing, and woody plants invading the grassland. In June 2004 an agreement was reached with the power company to return to a more natural release pattern, and since 2016 Itezhi-Tezhi has also housed its own 120 MW power station.
Ila cattle camps, fishing camps and Nakambala sugar on the edges
The wildlife shares the flats with people and livestock. The Ila and Balundwe (Plateau Tonga), in at least 21 chieftaincies, arrived 200 to 300 years ago and move cattle from woodland villages onto the floodplain as the water recedes. Seasonal fishers come from the Bemba north and the Lozi west; by 2004 there were at least 11 major permanent fishing camps, each with 500 or more fishermen.
On the southeastern edge at Mazabuka, the Nakambala Sugar Estate, Zambia's largest sugar producer, irrigates about 20,000 hectares with its outgrowers and draws more than 720,000 m³ of water a day; Kafue Sugar farms another 9,000 hectares north of the flats. Fertiliser runoff can trigger algal blooms and weed growth that reduce fish. Similar pressures shape the lechwe and shoebill country of the Bangweulu Wetlands in the north, but on the Kafue Flats the decisive factor for the lechwe, the cranes and the sitatunga remains how much water the dams let through, and when.