ENDORHEIC BASIN

An 'endorheic basin' (from Greek ''endo'' 'inside' + ''rhein'' 'to flow'; also ''terminal'' or ''closed basin'') is a closed watershed that retains water and allows no outflow to other bodies of water such as rivers or oceans. Normally the water accruing in drainage basins flows out through surface rivers or by underground diffusion through permeable rock to the oceans. However, in an endorheic basin rain (or other precipitation) that falls within it does not flow out but may only leave the drainage system by evaporation and seepage. Endorheic basins are also called internal drainage systems. Some of the largest lakes in the world are endorheic. Good examples are the Aral Sea and the Caspian Sea, the world's largest saline body of water.^[1]

Contents

Occurrence

Notable endorheic basins and lakes

Asia

Australia

Africa

North America

Europe

South America

Ancient

References

External links

Occurrence

Endorheic basins can occur in any climate but are most commonly found in hot desert locations. In areas where rainfall is higher, riparian erosion will generally carve drainage channels (particularly in times of flood), breaking the enclosed endorheic hydrological system's geographical barrier and opening it to the surrounding terrain. The Black Sea was 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.^[2]
Endorheic basins tend to be far inland with their watershed confined by mountains or other geological features that severs their access to oceans. Since the inflowing water can evacuate only through seepage or evaporation, dried minerals or other products collect in the basin, eventually making the water saline and also making the basin vulnerable to pollution. Continents vary in their concentration of endorheic basins due to conditions of geography and climate. Australia has the highest percentage of area not draining to the ocean at 64 percent while North America has the least at 10 percent.^[3] Approximately 18 percent of the earth's land drains to endorheic lakes or seas, the largest of these land areas being the interior of Asia.
In hot deserts water inflow is low and loss to solar evaporation high, drastically reducing the formation of complete drainage systems. Closed water flow areas often lead to the concentration of salts and other minerals in the basin. Minerals leached from the surrounding rocks are deposited in the basin, and left behind when the water evaporates. Thus endorheic basins often contain extensive salt pans (also called salt flats, salt lakes, alkali flats or playas). These areas tend to be large, flat hardened surfaces and are sometimes used for aviation runways or land speed record attempts.
Both permanent and seasonal endorheic lakes can form in endorheic basins. Some endorheic basins are essentially stable, climate change having reduced precipitation to the degree that a lake no longer forms. Even the 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 uninhabitable 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, resulting in increased salinity, higher concentrations of pollutants, and the subsequent disruption of the lake's ecosystem.

Notable endorheic basins and lakes

Major endorheic basins of the world. Basins are shown in dark gray; major endorheic lakes are shown in black.

One of the few endorheic lakes in a cold desert location, Antarctica's Lake Vida remains liquid because its salinity is seven times that of seawater.

Asia

Caspian Sea, a giant inland basin

Much of western and Central Asia is a single, giant inland basin. It contains a number of lakes, including:

★ The Caspian Sea, the largest lake on Earth. In fact, a large part of Eastern Europe drained by the Volga River also belongs to its basin.

★ The Aral Sea, whose tributary rivers have been diverted, leading to a dramatic shrinkage of the lake. The resulting ecological disaster has brought the plight faced by internal drainage basins to public attention.

★ Lake Balkhash (Kazakhstan)

★ Lop Nur, in the southeastern portion of Xinjiang Uygur Autonomous Region in northwestern China

★ Issyk-Kul, Son-Kul and Chatyr-Kul lakes in Kyrgyzstan

★ Sistan Basin covering areas of Iran and Afghanistan

★ Tarim Basin in Xinjiang Uyghur Autonomous Region

★ Sambhar Lake in Rajasthan, north-western India
The Dead Sea, the lowest surface point on Earth and one of its saltiest bodies of water, lies between Israel and Jordan.

Australia

Australia, being very dry and having exceedingly low runoff ratios due to its ancient soils, has a great prominence of variable, endorheic drainages. The most important are:

★ Lake Eyre Basin, which drains into the highly variable Lake Eyre and includes Lake Frome.

★ Lake Torrens, to the west of the Flinders Ranges in South Australia.

★ Lake Corangamite, a highly saline crater lake in western Victoria.

★ Lake George, formerly connected to the Murray-Darling Basin

A false-colour satellite photo of Australia's Lake Eyre
Image credit: ''NASA's Earth Observatory''

Africa

★ Lake Turkana in Kenya

★ The Okavango Delta, an endorheic inland delta in the Kalahari Desert of Botswana

★ Lake Ngami in Botswana

★ Lake Chad (between Chad and Cameroon), fed by the Chari and Logon rivers

★ Etosha pan in Namibia's Etosha National Park

★ Qattara Depression in Egypt

★ Chott Melrhir in Algeria

★ Afar Depression in Eritrea, Ethiopia and Djibouti

North America

Great Salt Lake,Satellite photo (2003} after five years of drought

★ The Valley of Mexico. In Pre-Columbian times, the Valley was substantially covered with five lakes, including Lake Texcoco, Lake Xochimilco, and Lake Chalco.

★ Crater Lake in Oregon

★ Devil's Lake (North Dakota)

★ Devil's Lake (Wisconsin)

★ 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.

★ The Great Divide Basin in Wyoming, a small endorheic basin which straddles the Continental Divide.

★ The United States' Great Basin, which covers much of Nevada and Utah, includes:

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★ The Black Rock Desert in Nevada, location of the Thrust2 and ThrustSSC landspeed record runs, and the annual home to the Burning Man festival

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★ Groom Dry Lake in Nevada, location of the secret Area 51 base

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★ Utah's Great Salt Lake, the largest terminal lake in the Western Hemisphere.

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★ Utah's Sevier Lake

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★ Pyramid Lake in Nevada

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★ Mono Lake in California

★ New Mexico has a number of desert endorheic basins including:

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★ The Tularosa Basin, a rift valley;

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★ Zuni Salt Lake, a maar;

★ Bolsón de Mapimí, in northern Mexico;

★ Guzmán Basin, in northern Mexico southwestern New Mexico;

Europe

★ Neusiedlersee in Austria

★ Lake Trasimeno in Italy
Minor additional endorheic lakes exist throughout the mediterranean countries Spain (e.g. Laguna de Gallocanta), Italy and Greece.

South America

★ Altiplano basin, one of the largest and second highest in the world.

★ Lake Valencia (Spanish: Lago de Valencia) the second largest lake in Venezuela.

Ancient

Some of the Earth's ancient endorheic systems include:

★ The Black Sea, until its merger with the Mediterranean

★ The Mediterranean Sea itself and all its tributary basins, during its Messinian dissecation (5 m.y. BP aprox.) as it became disconnected from the Atlantic Ocean.

★ Lake Lahontan in the western US

★ Ebro and Duero basins, draining most of northern Spain during the Neogene and perhaps Pliocene.

★ Lake Bonneville (Utah)

References

1. Endorheic Lakes: Waterbodies That Don't Flow to the Sea
2. Major drainage basins of the world

3. Saline Lake Ecosystems of the World

External links

★ Primer on endorheic lakes

★ The Silk Roads and Eurasian Geography