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Author
Chege, David MatheaDate
2009
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Show full item recordAbstract
The Africa continent is endowed with many lakes. There are two categories of lakes; those that form inland drainage, most of which are salty e.g. Okavango in Botswana and Shots in the Atlas mountains, and those drained by rivers which are mainly fresh water e.g. L. Victoria drained by R. Nile and L. Ngami by R. Zaire. African lakes are categorised according to their formation. Rift Valley lakes were formed when the floor of the valley was filled with water. Most of these lakes are long, narrow and deep with steep cliff-like edges. They are mostly salty due to their inland drainage. They do not have an outlet to the sea except L. Tanganyika drained by R. Lukuya during the wet season, L. Malawi by R. Shire and L. Naivasha which has an Underground outlet. Warping lakes were formed by the down warping of the ancient plateau. The depression so formed was later filled with water to form lakes. Examples include L. Victoria in East Africa, L. Kyoga in Uganda and L. Chad in Chad. Volcanic crater lakes were formed through volcanic activities. When the volcanoes erupted, the lava cooled inside a vent and a depression formed due to the subsidence of lava. This later filled with water to form a crater lake e.g. Ngorongoro crater in Tanzania. Deposition lakes are mainly ox-bow lakes formed at the old stage of the river before the mouth. Once a pronounced meander is separated from the main steam by deposition and erosion, an ox-bow lake is formed. Examples include L. Narugi on R. Tana in Kenya and L. Kilombero in Tanzania. Glacial lakes were formed in depressions or basins resulting from glacial erosion as huge blocks of ice glide down the mountain side. They are known as corries or tarns e.g. the Teleki Tarn on Mt. Kenya. Wind eroded lakes are found in huge depressions created by wind erosion in the desert sands. Once the water table is reached the depressions fill with water. Due to excessive evaporation, the lakes turn into muddy swamps with small water points known as oases. An example of such desert depressions is the Quattara in Egypt. Sometimes these oases may dry up completely forming salt flats known as playas. Man-made lakes are formed as a result of damming of rivers where multi-purpose river projects have been established. They are important for production of Hydro-electric power (H.E.P), transport, fishing, irrigation and regulating flooding. AVAILABILITY:Pages
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