Portal:Lakes
The Lakes Portal
A portal dedicated to Lakes
Introduction
A lake is a naturally occurring, relatively large and fixed body of water on the Earth's surface. It is localized in a basin or interconnected basins surrounded by dry land. Lakes lie completely on land and are separate from the ocean, although they may be connected with the ocean by rivers, such as Lake Ontario. Most lakes are freshwater and account for almost all the world's surface freshwater, but some are salt lakes with salinities even higher than that of seawater. Lakes vary significantly in surface area and volume.
Lakes are typically larger and deeper than ponds, which are also water-filled basins on land, although there are no official definitions or scientific criteria distinguishing the two. Lakes are also distinct from lagoons, which are shallow tidal pools dammed by sandbars at coastal regions of oceans or large lakes. Most lakes are fed by springs, and both fed and drained by creeks and rivers, but some lakes are endorheic without any outflow, while volcanic lakes are filled directly by precipitation runoffs and do not have any inflow streams.
Natural lakes are generally found in mountainous areas (i.e. alpine lakes), dormant volcanic craters, rift zones and areas with ongoing glaciation. Other lakes are found in depressed landforms or along the courses of mature rivers, where a river channel has widened over a basin formed by eroded floodplains and wetlands. Some parts of the world have many lakes formed by the chaotic drainage patterns left over from the last ice age. All lakes are temporary over long periods of time, as they will slowly fill in with sediments or spill out of the basin containing them. (Full article...)
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Lake Chad (Arabic: بحيرة تشاد, Kanuri: Sádǝ, French: Lac Tchad) is an endorheic freshwater lake located at the junction of four countries: Nigeria, Niger, Chad, and Cameroon in western and central Africa respectively, with a catchment area of 1×10 6 km2 (390,000 sq mi). It is an important wetland ecosystem in West-Central Africa. The lakeside is rich in reeds and swamps, and the plain along the lake is fertile, making it an important irrigated agricultural area. The lake is rich in aquatic resources and is one of the important freshwater fish producing areas in Africa.
Lake Chad is divided into deeper southern parts and shallower northern parts. The water source of the lake mainly comes from rivers such as the Chari River that enter the lake. The water level varies greatly seasonally, and the area of the lake also changes dramatically. During the African humid period, the area of Lake Chad reached 400,000 km2 (150,000 sq mi). Due to the increasingly arid climate, the lake surface gradually shrank. In the 19th century, Lake Chad still had an area of 28,000 km2 (11,000 sq mi). However, due to climate change and human water diversion, Lake Chad has been greatly reduced since the mid-1970s, and its area has fluctuated between 2,000 and 5,000 km2 (770 and 1,930 sq mi). (Full article...)General topics
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Lake stratification |
Lake types |
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External media
- World Lake Database. International Lake Environment Committee Foundation. – provides a searchable database
- Global Lakes and Wetlands Database. World Wide Fund for Nature. – available for free download