Anendorheic lake (also called asink lake orterminal lake) is a collection of water within anendorheic basin, or sink, with no evident outlet.[1] Endorheic lakes are generallysaline as a result of being unable to get rid ofsolutes left in the lake byevaporation.[2] These lakes can be used as indicators ofanthropogenic change, such asirrigation orclimate change, in the areas surrounding them. Lakes with subsurface drainage are calledcryptorheic.
The two main ways that endorheic lakes accumulate water are through river flow into the lake (discharge) andprecipitation falling into the lake.[2] The collected water of the lake, instead ofdischarging, can only be lost due to eitherevapotranspiration orpercolation (water sinking underground, e.g., to becomegroundwater in anaquifer). Because of this lack of an outlet, endorheic lakes are mostly salt water rather than fresh water. The salinity in the lake gradually builds up through years as water evaporates and leaves its solutes behind.[citation needed]
Depending on water losses, precipitation, andinflow (e.g., a spring, a tributary, or flooding), thetemporal result of a lake in a sink may change. The lake could be a persistentlake, anintermittent lake, aplaya lake (temporarily covered with water), or anephemeral lake, which completely disappears (e. g. by evaporation) before reappearing in wetter seasons.[3] These terms (playa, ephemeral lake, etc.) are sometimes used interchangeably, but there has been activity tending towards defining meanings for each term.[4]
Many endorheic lakes exist inarid orsemi-arid climates.[5] Because these climates have limited rainfall, but also a high possibility of evaporation, endorheic lakes in these regions often experience flux in their water levels. This flux can be aggravated byanthropogenic intrusions (e.g.global warming).
InCentral Asia, a large percentage of water for farming comes from surface water, like endorheic lakes, rather than precipitation.[2] Because of the overall lack of precipitation, farming in this area can only be sustained by irrigation. Massive amounts of irrigation in agrarian Central Asia have led to the reduction in size of endorheic lakes. TheAral Sea was once the second largest endorheic lake in the world, butanthropogenic effects such as bad irrigation practices have led to this lake's drastic decrease in size and transition into adesert, theAralkum Desert.[6]
Endorheic lakes, because of the closed nature of their systems, are sensitive to new conditions.[2] Records of previous environmental change are preserved inlake sediments in endorheic lakes that are being affected byclimate change; these natural records can give information about past climates and conditions of the lake. Research on these lake sediments could lead to these lakes becoming archives of theeffects of climate change. There is early evidence that in regions affected by irrigation the majority of endorheic lake area may have already been lost.[7]
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