Lake Makgadikgadi
Encyclopedia
Lake Makgadikgadi is an ancient lake
that existed in what is now the Kalahari Desert
in Botswana
. It may have once covered as much as 80,000 km² and was 30 m deep. The Okavango
, Zambezi
, and Cuando
rivers once all emptied into the lake.
into the Indian Ocean
.
Approximately 2 million years ago, the formation of the fault known as the Kalahari-Zimbabwe axis, which runs from the Zimbabwe
capital Harare
through its second-largest city Bulawayo
and ends in the eastern side of the Kalahari, created an enormous basin and forced these rivers to flow into and fill up the basin. Lake Makgadikgadi was thus created.
As the millennia passed, the lake was filled to capacity and began to overflow. About 20,000 years ago, as a result, it began to drain northwards and then eastwards. This caused the middle and lower Zambezi Rivers to connect, resulting in the formation of Victoria Falls
. With the water now able to flow out of the basin, Lake Makgadikgadi was able to drain partially and its average level decreased.
A drier climatic period followed which caused an increase in evaporation and a decrease in the flow of the rivers that fed it. By about 10,000 years ago the drying of Lake Makgadikgadi was in an advanced stage. Sediment
and debris from the Okavango River and windblown sand were gradually filling the lake.
The formation of the Gumare fault lowered the land. As a result, the water of the Okavango River spread out over a much larger area of land than it previously did, forming the now characteristic fan-shaped inland delta of the Okavango, which further reduced the water that flowed into Lake Makgadikgadi and hastened its demise.
Today the only remains of Lake Makgadikgadi are the Okavango Delta
, the Nxai Pan
, Lake Ngami
, Lake Xau, the Mababe Depression, and the two main Makgadikgadi pans
of Sua
and Nwetwe.
, Zambezi River, Okavango River
and Limpopo River
- as many as 100 to 400 new species, of which approximately 25 survive today. The lake's sheer size may have provided the ancestors of these fish with an extremely wide range of new ecological niches to exploit and thus could have served as the stimulus for the evolution of the new species, which they may have done in record time before the lake drained completely. The theory further says that the new species, after having evolved within the confines of the lake, could have escaped with the lakewater as it drained, and populated the rivers of the region to evolve into the cichlids that exist today.
In current times this land is desiccated most of the year and is a seasonal wetland
in the rainy summer months.
Lake
A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...
that existed in what is now the Kalahari Desert
Kalahari Desert
The Kalahari Desert is a large semi-arid sandy savannah in Southern Africa extending , covering much of Botswana and parts of Namibia and South Africa, as semi-desert, with huge tracts of excellent grazing after good rains. The Kalahari supports more animals and plants than a true desert...
in Botswana
Botswana
Botswana, officially the Republic of Botswana , is a landlocked country located in Southern Africa. The citizens are referred to as "Batswana" . Formerly the British protectorate of Bechuanaland, Botswana adopted its new name after becoming independent within the Commonwealth on 30 September 1966...
. It may have once covered as much as 80,000 km² and was 30 m deep. The Okavango
Okavango River
The Okavango River is a river in southwest Africa. It is the fourth-longest river system in southern Africa, running southeastward for . It begins in Angola, where it is known as the Cubango River...
, Zambezi
Zambezi
The Zambezi is the fourth-longest river in Africa, and the largest flowing into the Indian Ocean from Africa. The area of its basin is , slightly less than half that of the Nile...
, and Cuando
Cuando River
The Cuando River is a river in south-central Africa flowing through Angola and Namibia's Caprivi Strip, into the Linyanti Swamp on the northern border of Botswana...
rivers once all emptied into the lake.
Origin and History
Approximately 3 million years ago, strong easterly winds brought about the formation of elongated dunes which ran from east to west across the middle of the Kalahari Desert. During wetter times, these dunes channeled the flow of the great rivers of the area, the Okavango, Chobe, and Zambezi, eastwards with the Limpopo RiverLimpopo River
The Limpopo River rises in central southern Africa, and flows generally eastwards to the Indian Ocean. It is around long, with a drainage basin in size. Its mean annual discharge is 170 m³/s at its mouth...
into the Indian Ocean
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...
.
Approximately 2 million years ago, the formation of the fault known as the Kalahari-Zimbabwe axis, which runs from the Zimbabwe
Zimbabwe
Zimbabwe is a landlocked country located in the southern part of the African continent, between the Zambezi and Limpopo rivers. It is bordered by South Africa to the south, Botswana to the southwest, Zambia and a tip of Namibia to the northwest and Mozambique to the east. Zimbabwe has three...
capital Harare
Harare
Harare before 1982 known as Salisbury) is the largest city and capital of Zimbabwe. It has an estimated population of 1,600,000, with 2,800,000 in its metropolitan area . Administratively, Harare is an independent city equivalent to a province. It is Zimbabwe's largest city and its...
through its second-largest city Bulawayo
Bulawayo
Bulawayo is the second largest city in Zimbabwe after the capital Harare, with an estimated population in 2010 of 2,000,000. It is located in Matabeleland, 439 km southwest of Harare, and is now treated as a separate provincial area from Matabeleland...
and ends in the eastern side of the Kalahari, created an enormous basin and forced these rivers to flow into and fill up the basin. Lake Makgadikgadi was thus created.
As the millennia passed, the lake was filled to capacity and began to overflow. About 20,000 years ago, as a result, it began to drain northwards and then eastwards. This caused the middle and lower Zambezi Rivers to connect, resulting in the formation of Victoria Falls
Victoria Falls
The Victoria Falls or Mosi-oa-Tunya is a waterfall located in southern Africa on the Zambezi River between the countries of Zambia and Zimbabwe.-Introduction:...
. With the water now able to flow out of the basin, Lake Makgadikgadi was able to drain partially and its average level decreased.
A drier climatic period followed which caused an increase in evaporation and a decrease in the flow of the rivers that fed it. By about 10,000 years ago the drying of Lake Makgadikgadi was in an advanced stage. Sediment
Sediment
Sediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....
and debris from the Okavango River and windblown sand were gradually filling the lake.
The formation of the Gumare fault lowered the land. As a result, the water of the Okavango River spread out over a much larger area of land than it previously did, forming the now characteristic fan-shaped inland delta of the Okavango, which further reduced the water that flowed into Lake Makgadikgadi and hastened its demise.
Today the only remains of Lake Makgadikgadi are the Okavango Delta
Okavango Delta
The Okavango Delta , in Botswana, is the world's largest inland delta. It is formed where the Okavango River empties onto a swamp in an endorheic basin in the Kalahari Desert, where most of the water is lost to evaporation and transpiration instead of draining into the sea...
, the Nxai Pan
Nxai Pan
Nxai Pan is a large salt pan topographic depression which is part of the larger Makgadikgadi Pans in northeastern Botswana. This landform is a major part of the Nxai Pan National Park, and is a seasonal home to large herds of zebra...
, Lake Ngami
Lake Ngami
Lake Ngami is an endorheic lake in Botswana north of the Kalahari Desert. It is seasonally filled by the Taughe River an affluent of the Okavango River system flowing out of the western side of the Okavango Delta. It is one of the fragmented remnants of the ancient Lake Makgadikgadi...
, Lake Xau, the Mababe Depression, and the two main Makgadikgadi pans
Makgadikgadi Pan
The Makgadikgadi Pan is a large salt pan in the middle of the dry savanna of northeastern Botswana. It is one of the largest salt flats in the world...
of Sua
Sua
This article is about a topic in Central American religion; for other uses of Sua, see Sua .Sua was a hero-god of the Muyscas of Central America, also called Bachica or Nemquetaha. The name signifies "day" or "east." He taught them the arts of life, and, like Quetzalcoatl, disappeared. Like the...
and Nwetwe.
Ecology
Lake Makgadikgadi is theorized to have been the birthplace of the vast number of cichlids that once swam the Congo RiverCongo River
The Congo River is a river in Africa, and is the deepest river in the world, with measured depths in excess of . It is the second largest river in the world by volume of water discharged, though it has only one-fifth the volume of the world's largest river, the Amazon...
, Zambezi River, Okavango River
Okavango River
The Okavango River is a river in southwest Africa. It is the fourth-longest river system in southern Africa, running southeastward for . It begins in Angola, where it is known as the Cubango River...
and Limpopo River
Limpopo River
The Limpopo River rises in central southern Africa, and flows generally eastwards to the Indian Ocean. It is around long, with a drainage basin in size. Its mean annual discharge is 170 m³/s at its mouth...
- as many as 100 to 400 new species, of which approximately 25 survive today. The lake's sheer size may have provided the ancestors of these fish with an extremely wide range of new ecological niches to exploit and thus could have served as the stimulus for the evolution of the new species, which they may have done in record time before the lake drained completely. The theory further says that the new species, after having evolved within the confines of the lake, could have escaped with the lakewater as it drained, and populated the rivers of the region to evolve into the cichlids that exist today.
In current times this land is desiccated most of the year and is a seasonal wetland
Wetland
A wetland is an area of land whose soil is saturated with water either permanently or seasonally. Wetlands are categorised by their characteristic vegetation, which is adapted to these unique soil conditions....
in the rainy summer months.