Sink (geography)

Sink (geography)

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Encyclopedia
A geographic sink is a depression within an endorheic basin where water collects with no visible outlet. Instead of discharging
Discharge (hydrology)
In hydrology, discharge is the volume rate of water flow, including any suspended solids , dissolved chemical species and/or biologic material , which is transported through a given cross-sectional area...

, the collected water is lost due to evaporation and/or penetration
Standard Penetration Test
The standard penetration test is an in-situ dynamic penetration test designed to provide information on the geotechnical engineering properties of soil...

 (water sinking underground, e.g., to become groundwater
Groundwater
Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock...

 in an aquifer
Aquifer
An aquifer is a wet underground layer of water-bearing permeable rock or unconsolidated materials from which groundwater can be usefully extracted using a water well. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology...

). If the sink has karstic terrain
Karst topography
Karst topography is a geologic formation shaped by the dissolution of a layer or layers of soluble bedrock, usually carbonate rock such as limestone or dolomite, but has also been documented for weathering resistant rocks like quartzite given the right conditions.Due to subterranean drainage, there...

, water will sink at a higher rate than the surface evaporation, and conversely if the lakebed or sink bed has a layer of soil that is largely impervious to water (hardpan
Hardpan
In soil science, agriculture and gardening, hardpan or ouklip is a general term for a dense layer of soil, usually found below the uppermost topsoil layer. There are different types of hardpan, all sharing the general characteristic of being a distinct soil layer that is largely impervious to water...

), evaporation will predominate. Since dry lakes in sinks with hardpan have little penetration, they require more severe aridity/heat to eliminate collected water at a comparable rate as for a similar sink with appreciable penetration.

Depending on losses, precipitation, and inflow
Inflow (hydrology)
In hydrology, the inflow of a body of water is the source of the water in the body of water. It can also refer to the average volume of incoming water in unit time. It is contrasted with outflow....

 (e.g., a spring, a tributary, or flooding); the temporal result
Hydrology
Hydrology is the study of the movement, distribution, and quality of water on Earth and other planets, including the hydrologic cycle, water resources and environmental watershed sustainability...

 of a lake in a sink may be a persistent lake
Lake
A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...

, an intermittent lake, a playa
Dry lake
Dry lakes are ephemeral lakebeds, or a remnant of an endorheic lake. Such flats consist of fine-grained sediments infused with alkali salts. Dry lakes are also referred to as alkali flats, sabkhas, playas or mud flats...

 lake (temporarily covered with water), or an ephemeral
Ephemeral
Ephemeral things are transitory, existing only briefly. Typically the term is used to describe objects found in nature, although it can describe a wide range of things....

lake.