The Barotse Floodplain also known as the Bulozi Plain, Lyondo or the Zambezi Floodplain is one of Africa's great wetlands, on the Zambezi River in the Western Province of Zambia. It is a designated Ramsar site, regarded as being of high conservation value.
The name recognises the floodplain as spawning the culture and way of life of the Lozi people, "Rotse" being a variant of Lozi, and "Ba" meaning "people". They became a powerful kingdom in Central/Southern Africa under their King or Litunga, Lewanika, whose realm extended up to 300 km from the plain and was called Barotseland.
Topography and area
The region is a flat plateau at an elevation of about 1000 m tilting very slightly to the south. The Zambezi and its headwaters rise on the higher ground to the north, which enjoys good rainfall (1400 mm annually) in a rainy season from October to May. A flood moves down the river reaching a flat region, formed from Kalahari sands, about five hundred kilometres across. To the south around the Ngonye Falls harder rock is found at the surface and has resisted the river's tendency to cut a channel down into it, and so acts a bit like a dam. Behind it the floodplain has formed. Below the falls the river falls nearly twice as fast as it does on the plain, and flows more swiftly in a narrower valley less prone to flooding.
The floodplain stretches from the Zambezi's confluence with the Kabompo and Lungwebungu Rivers in the north, to a point about 230 km south, above the Ngonye falls and south of Senanga. Along most of its length its width is over 30 km, reaching 50 km at the widest, just north of Mongu, principal town of the plain, situated at its edge. The main body of the plain covers about 5500 km², but the maximum flooded area is 10 750 km² when the floodplains of several tributaries are taken into account, such as the Luena Flats. The Barotse Floodplain is the second largest wetland in Zambia after the Lake Bangweulu system, which differs in having a large permanent lake and swamps, and a much smaller area which dries out annually.
The satellite photo was taken in April 2004 at the peak of the flood, Note that the northern part of the plain, near Lukulu, is less flooded, the land there varies a bit more in height and the water tends to keep to the many river channels.
Flood levels and timing
- See also Climate of Zambia
The peak of the flood occurs on the floodplain about 3 months after the peak of the rainy season in January–February. The flood usually peaks in April, and recedes in May to July, when grasses quickly grow on the exposed plain. At the river's lowest water in November the floodplain still contains about 537 km² of lagoons, swamps and channels. The flood leaves behind a fertile grey to black soil overlaying the Kalahari sands, enriched by siltdeposited by the flood as well as humus from vegetation killed by the initial flood, and from decaying aquatic plants left to dry out in the mud. It provides a good soil, but in the late dry season it bakes hard in the heat of the sun.
As the floods recede, water is left behind in lagoons, swamps, and oxbow lakes.
The floodplain is in the Zambezian flooded grasslands ecoregion, and is bordered by slightly higher sandy ground on which grow dry grasslands (Western Zambezian grasslands) with woodland savanna (Zambezian Baikiaea woodlands) to the east and south, and patches of evergreen forest (Cryptosepalum dry forests) in the north and east.
The flood provides aquatic habitats for fish such as tigerfish and bream, crocodiles, hippopotamus, waterbirds, fish-eating birds, and lechwe, the wading antelope. After the flood, the plain is a habitat for grazing animals such as wildebeest, zebra, tsessebe and small antelope such oribi and steenbok, and their predators. These herbivores have been displaced in most areas by the cattle grazed by the Lozi, but they have provided a large game reserve on the dry grassland to the west, the Liuwa Plain National Park, once the Litunga's hunting grounds, established as a game reserve by Lewanika in the 19th century. In addition the entire western of the Zambezi within the country is a Game Management Area.
Human ecology of the plain
About 250,000 people live on the plain with a similar number of cattle, migrating to grasslands at the edge of the floodplain when the flood arrives. The floodplain is one of the most productive areas for raising cattle in the country.
The Lozi also catch fish, eating about five times as much as the national average. At the height of the flood they use fish traps and spears for fishing, and they use gill nets in the lagoons left behind by the falling flood. Fish spawn just before the flood, the first floodwaters are naturally hypoxic (low in oxygen) which kills most fish, while eggs survive.
November to January are lean months. Stored produce from the previous growing season is almost used up and in any case would need to be transported during the migration, while the new season's crops and grasses are not yet productive, and at the same time fishing stops for the spawning season. Hunting and trapping animals, which might have filled the gap, is no longer available to most people, and trapping waterbirds is one of the few alternatives to buying flour.
The floodplain determines and dominates the way of life, economy, society and culture of the Lozi, who are skilled boat-builders, paddlers and swimmers. The annual migration with the flood is celebrated in the Kuomboka ceremony held at Mongu, capital of Barotseland and its successor, the Western Province.
In the occasional very wet year such as 2005, lives and property are lost in floods on the Barotse Plain. More often, however, it is a very good example of the principle that natural annual flooding by rivers is valuable and productive for wildlife and human populations, while damming rivers to control floods, as has happened with the Kafue Flats, is potentially damaging to the environment.
Development on or affecting the plain
Development on the plain has been restricted until now to—
- the canal dug in colonial times to connect a small harbour at Mongu to the Zambezi's channel in the dry season
- small villages and compounds constructed on mounds, such as Lealui
- a few dry season tracks
- pontoon ferries at Sandaula, Libonda and Lukulu
- some intensive rice and sugarcane plantations.
Tight control over access to the floodplain by the Litunga and the homogeneity of the indigenous people have slowed commercial development by outsiders.
Barotse Floodplain causeway
A new project, the Mongu-Kalabo road, will have more far-reaching consequences. Around 2002 construction started of a 46-kilometre causeway across the centre of the floodplain to take a paved highway from Mongu to Kalabo, via the ferry across the main river channel at Sandaula, which would then be replaced by a 500-metre bridge. Originally intended to be completed in 2006, it has been delayed by the difficulty of building on the floodplain. There is no rock in the region, and the causeway has been built from sand and gravel scooped out from shallow depressions next to it. Higher than usual floods washed away large sections. The contractor was a Kuwait-based company which acknowledged that conditions were difficult. The Times of Zambia reported that the company underestimated the floodplain environment, and abandoned the contract. Subsequent modifications have been made to raise the road height and to increase the number and size of culverts, and this in turn led to funding problems. In November 2007 it consisted of earth causeways from Mongu to some distance beyond Lealui, and from the ferry at Sandaula to Kalabo. No information is available on the impact the structure will have on flood flow patterns, river channels, silt deposition, or on fish and wildlife movements.
- "Seasonal Flooding in Southern Africa". NASA/Visible Earth, Credit: Jacques Descloitres, MODIS Rapid Response Team, NASA/GSFC.
- "Zambezi Floodplain Ramsar Information Sheet", in Ramsar Sites Information Service, Wetlands International. Retrieved 22 November 2007.
- "Barotse Floodplain, Zambia: local economic dependence on wetland resources." Case Studies in Wetland Valuation #2: IUCN, May 2003.
- Welcomme, R.L. (Comp.) (1979): ”The inland fisheries of Africa." CIFA Occas.Pap., (7): 69 p. Published by Food and Agricultural Organization of the United Nations, Rome.
- Bulletin 74 (August 2004), Consolidated Contractors Company of Kuwait.
- Sylvia Mweetwa: "Road financiers to extend agreement." Ndola: Times of Zambia, 5 April 2007.
- Google Earth has high resolution images of the causeways, showing some washed-out sections, and the ferry. Retrieved 20 November 2007.
- Chris McIntyre (2004). Zambia: The Bradt Travel Guide online at www.zambia-travel-guide.com. Retrieved 21 November 2007.
- Map references
- "Zambia 1:1,500,000 2nd Edition", Terracarta/International Travel Maps, Vancouver, 2000.
- MSN Encarta World Atlas online retrieved 19 November 2007.