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The shores of Lake Hart , an endorheic desert lake in South AustraliaIn geography, an endorheic basin is a watershed from which there is no outflow of water (either on the surface as rivers, or underground by flow or diffusion through rock or permeable material). The term has Greek roots, endo, "inside" and rhein, "to flow". Any rain (or other precipitation) that falls inside an endorheic basin remains there permanently, leaving the system only by evaporation. Endorheic basins are also called "internal drainage systems".
Although, in theory, endorheic basins can occur in any climate, in practice they are most commonly found in hot desert locations. In places with a higher rainfall, the riparian erosion of the water's flow will generally carve drainage channels (particularly in times of flood), breaking through to the larger enclosing hydrological system, and breaking the watershed barrier between the endorheic system and the surrounding terrain. The Black Sea is such a lake, having once been an independent hydrological system in its own right before the Mediterranean Sea broke through the terrain separating the two.
In hot deserts, the net inflow is low and loss to solar evaporation high, drastically slowing the formation of complete drainage systems. The closed nature of this water flow often leads to the concentration of salts and other minerals in the lake; minerals leached from the surrounding rocks are deposited in the endorheic basin, and left behind when the water that bore them there evaporates. Thus endorheic basins often contain extensive salt pans (alkali flats) or playas. These areas, which tend to be large, hard surfaced, and fairly flat, are sometimes used for aviation (as large cheap runways) or for breaking land speed records.
Both permanent and seasonal endorheic lakes can form in endorheic basins, and some endorheic basins are essentially in stasis, the climate having changed to reduce precipitation to such an extent that a lake no longer forms. Even with endorheic lakes that exist permanently, most change size and shape dramatically over time, often becoming dramatically smaller (or breaking into several smaller parts) during the dry season. As humans have expanded into previously unliveable desert areas, the river systems that feed many endorheic lakes have been altered by the construction of dams and aqueducts. As a result many endorheic lakes in developed or developing countries have contracted dramatically. This often results in dramatic increases in salinity, higher concentrations of pollutants, and the consequent disruption of the lake's ecosystem.
A false-colour satellite photo of Australia's Lake Eyre
Image credit: NASA's Earth Observatory
1 Notable endorheic basins and lakes
- Much of western and Central AsiaCentral Asia is a region of Asia. Various definitions of its exact composition exist. Definitions Under one definition, Central Asia covers about 9,029,000 km2, or 21% of the continent. Under this definition Central Asia includes the following countries: is a single, giant inland basin. It contains a number of lakes, including:
- The Caspian SeaThe Caspian Sea is a landlocked sea in Asia. It is bordered by Russia ( Dagestan, Kalmykia, Astrakhan Oblast), Republic of Azerbaijan, Iran ( Guilan, Mazandaran and Golestan provinces), Turkmenistan, and Kazakhstan, with the central Asian steppes to the n, the largest lake on Earth.
- The Aral SeaThe Aral Sea is an endorheic inland sea in Central Asia; it lies between Kazakhstan in the north and Karakalpakstan, an autonomous region of Uzbekistan, in the south. Since the 1960s, the Aral Sea has been shrinking, as the rivers that feed it were divert. Here the diversion of the sea's tributary rivers has led to a dramatic shrinkage of the lake, and the resulting ecological disaster has brought the plight faced by internal drainage basins to public attention.
- Eastern KazakhstanKazakhstan ( Kazakh: #x49A;қ Qazaqstan Russian: Kazakhstan , also spelled Kazakstan is a country that stretches over a vast expanse of Asia and a former republic of the now extinct USSR. It has borders with Russia, the People's Republic of China, and's Lake BalkhashLake Balkash (sometimes written as Lake Balqash is a large lake in southeastern Kazakhstan, the second largest in Central Asia after the Aral Sea. It is part of the huge west/central asian endorheic basin that includes the Caspian and Aral seas. The lake
- The Dead SeaThe Dead Sea ( Hebrew , Arabic ) is an endorheic lake of saline water (area: ca. 1050 kmē or 401 sq mi), fed by the Jordan River, surrounded by Jordan, Israel and the West Bank. The Dead Sea is the saltiest and deepest hypersaline lake in the world. The s in the Middle EastThe Middle East is a geographical and cultural area comprising the lands around the southern and eastern parts of the Mediterranean Sea, a territory that extends from the eastern Mediterranean Sea to the Persian Gulf. The Middle East is a subregion of Afr, the saltiest major body of water in the world (so salty that a person can float unaided in it).
- The Lake Eyre BasinThe Lake Eyre Basin drains about one sixth of Australia. It is the largest internal drainage system in the world, and covers roughly 1. 2 million square kilometres, including much of inland Queensland, large portions of South Australia and the Northern Te is the largest endorheic system in the world. It includes much of the landmass of arid inland Australia drains into the highly variable Lake Eyre.
- One of the few endorheic lakes in cold desert locations, Antarctica's Lake Vida remains liquid because its salinity is seven times that of seawater.
- The US's Great Basin, which covers much of Nevada and Utah, and includes:
- California's Salton Sea, a lake accidentally created in 1905 when irrigation canals ruptured, filling a desert endorheic basin and recreating an ancient saline sea.
