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FACTS AND FIGURES ABOUT LAKES Lake Superior (United States and Canada) is 563 km long, 257 km wide, and covers an area of more than 82,000 km2, which makes it the largest freshwater lake in the world. Lake Baikal, situated in south-east Siberia, is the oldest (25 million years) and deepest (1,700 m) lake in the world. It contains 20% of the world's total unfrozen freshwater reserve. Known as the 'Galapagos of Russia', its age and isolation have produced one of the world's richest and most unusual freshwater faunas. Lake Toba watershed in Indonesia is the world’s largest volcanic crater lake, covering about 4,000 km. Most freshwater lakes are located at high altitudes, with nearly 50% being located in Canada alone. Many lakes, especially those in arid regions, become salty through evaporation, which concentrates the inflowing salts. The Caspian Sea, the Dead Sea, and the Great Salt Lake are among the world's major salt lakes. Lake Malawi has the largest number of fish species of any lake in the world, estimated at more than 500 species, 90% of which are thought to be unique to the lake. The most important species biologically, and in terms of local livelihoods, are the 400 or more cichlid species, all but 5 of which are endemic to Lake Malawi. The Asia and Pacific region as a whole has more lakes and reservoirs with eutrophication problems (54%) than Europe (53%), Africa (28%), North America (48%) and South America (41%). Straddling the borders of Chad, Niger and Cameroon in West Africa, Lake Chad has been a source of freshwater for irrigation projects in all these countries. Maps drawn from a series of satellite images show a dramatic decrease in the size of the lake over the past 30 years. Since 1963, the lake has shrunk to nearly a 20th of its original size, due both to climatic changes and to high demands for agricultural water. Since 1963, the surface area of Lake Chad has decreased to 1,350 km from approximately 25,000 km An estimated 30 million people depend on Lake Victoria, a lake whose natural resources are under increasing stress. The population on the shore has grown fast over the past century, with corresponding increases in the demand for fish and agricultural products. Following the introduction of gill nets by European settlers at the beginning of the 20th century, populations of indigenous fish species declined. Many were specially adapted to eat algae, decaying plant material and snails that host the larvae of Schistosomes that cause bilharzia in humans. The lake started to eutrophicate and people became more vulnerable to disease. As fish catches declined, non-native species were introduced, thus causing further stress to indigenous fish. The greatest impact resulted from the introduction of nile perch (Lates niloticus) in the 1960s, as the basis of commercial freshwater fisheries. This had repercussions on the local fishing economy and distribution of wealth. Local people who previously met most of their protein requirements from the lake began to suffer from malnutrition and protein deficiency. Although 20,000 tonnes of fish are exported annually to European and Asian markets, local people can afford only fish heads and bones from which the flesh has been removed.
Information from: Source: UNESCO Water Portal, August 2005
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