How lakes disappear

Lake Chad in a 2001 satellite image,
with the actual lake in blue,
and vegetation on top of the old lake bed
in green. Above that, the changes
from 1973 to 1997 are shown.

A lake may be infilled with deposited sediment, and gradually, the lake becomes a wetland, such as a swamp or marsh. An important difference exists between lowland and highland lakes: lowland lakes are more placid, are less rocky/more sedimentary, have a less sloping bottom, and generally contain more plant life. Large water plants (typically reeds) accelerate this closing process significantly because they partially decompose to form peat soils that fill shallows of lakes. Conversely a peat soils in a marsh can naturally burn and reverse this process to recreate a shallow lake. Turbid lakes, and lakes with much plant-eating fish, tend to disappear slower. A "disappearing" lake (barely noticeable on a human timescale) typically has a water's edge with extensive plant mats. They become a new habitat for other plants (like peat moss, when conditions are right) and animals, many of which are very rare. Gradually, the lake closes, and young peat may form, forming a fen. In lowland river valleys (allowing the river to meander), the presence of peat is explained by the closing of historical oxbow lakes. In the very last stages of succession, more trees would grow in, eventually turning the wetland into a forest.

Some lakes can also disappear seasonally; they are called intermittent lakes and are typical of karstic terrain. A prime example of this is Lake Cerknica in Slovenia. On 3 June 2005 in Nizhny Novgorod Oblast, Russia, a lake called Lake Beloye vanished in a short period of time (minutes). News sources reported government officials theorized that this strange phenomena may have been caused by a shift on soil underneath the lake which drained water to channels leading to

The presence of ground permafrost is also important to lake persistence. According to research published in the journal Science ("Disappearing Arctic Lakes," June 2005), thawing permafrost may explain the shrinking or disappearance of hundreds of large Arctic lakes across western Siberia. The idea here is that rising air and soil temperatures thaw permafrost, allowing the lakes to drain away into the ground.

Neusiedler See, located in Austria and Hungary, dried up several times for a number years during the past centuries. As of 2005, it is again rapidly losing water, giving rise to the fear that it will be completely dried up by 2010.

Some lakes disappear because of human development factors. The shrinking Aral Sea is described as being "murdered" by the intended diversion of rivers feeding the lake for irrigation.

From Wikipedia