"Closed sea" redirects here. For the legal concept in opposition to 'freedom of the seas', seeMare clausum.
The endorheic basin that feeds water intoÜüreg Lake, MongoliaNASA photo of the endorheicTarim Basin, China
Anendorheic basin (/ˌɛndoʊˈriː.ɪk/EN-doh-REE-ik; alsoendoreic basin andendorreic basin) is adrainage basin that normally retains water and allows no outflow to other external bodies of water (such asrivers andoceans). Instead, the water drainage flows into permanent and seasonal lakes and swamps thatequilibrate throughevaporation. Endorheic basins are also calledclosed basins,terminal basins, andinternal drainage systems.
Endorheic regions contrast withopen lakes (exorheic regions), where surface waters eventually drain into the ocean.[1] In general, water basins with subsurface outflows that lead to the ocean are not considered endorheic;[2][3][4] butcryptorheic.[5] Endorheic basins constitute localbase levels, defining a limit of theerosion anddeposition processes of nearby areas.[6] Endorheic water bodies include theCaspian Sea, which is the world's largest inland body of water.[7]
Endorheic lakes (terminal lakes) are bodies of water that do not flow into an ocean or a sea. Most of the water that falls to Earthpercolates into the oceans and the seas by way of a network of rivers, lakes, andwetlands.[9] Analogous to endorheic lakes is the class of bodies of water located in closed watersheds (endorheic watersheds) where the localtopography prevents the drainage of water into the oceans and the seas.[10][11] These endorheic watersheds (containing water in rivers or lakes that form a balance of surface inflows, evaporation and seepage) are often called sinks.[12]
Endorheic lakes are typically located in the interior of a landmass, far from an ocean, and in areas of relatively low rainfall. Their watersheds are often confined by natural geologic land formations such as a mountain range, cutting off water egress to the ocean. The inland water flows into dry watersheds where the water evaporates, leaving a high concentration of minerals and other inflow erosion products. Over time this input of erosion products can cause the endorheic lake to become relatively saline (a "salt lake"). Since the main outflow pathways of these lakes are chiefly through evaporation and seepage, endorheic lakes are usually more sensitive to environmental pollutant inputs than water bodies that have access to oceans, as pollution can be trapped in them and accumulate over time.[7]
TheOkavango Delta (centre) of southern Africa, where theOkavango River spills out into the empty trough of theKalahari Desert. The area was a lake fed by the river during the Ice Ages (national borders are superimposed).
Endorheic regions can occur in any climate but are most commonly found indesert locations.[13] This reflects the balance betweentectonic subsidence and rates of evaporation and sedimentation. Where the basin floor is dropping more rapidly than water and sediments can accumulate, any lake in the basin will remain below the sill level (the level at which water can find a path out of the basin). Low rainfall or rapid evaporation in the watershed favor this case. In areas where rainfall is higher,riparian erosion will generally carve drainage channels (particularly in times of flood), or cause the water level in the terminal lake to rise until it finds an outlet, breaking the enclosed endorheichydrological system's geographical barrier and opening it to the surrounding terrain.[14][15] TheBlack Sea was likely such a lake, having once been an independent hydrological system before theMediterranean Sea broke through the terrain separating the two.[16]Lake Bonneville was another such lake, overflowing its basin in theBonneville flood.[17] TheMalheur/Harney lake system inOregon is normally cut off from drainage to the ocean, but has an outflow channel to theMalheur River. This is presently dry, but may have flowed as recently as 1,000 years ago.[18]
Examples of relatively humid regions in endorheic basins often exist at high elevation. These regions tend to be marshy and are subject to substantial flooding in wet years. The area containingMexico City is one such case, with annual precipitation of 850 mm (33 in) and characterized by waterlogged soils that require draining.[19]
Endorheic regions tend to be far inland with their boundaries defined by mountains or other geological features that block 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.[7] Continents vary in their concentration of endorheic regions due to conditions of geography and climate. Australia has the highest percentage of endorheic regions at 21 per cent while North America has the least at five per cent.[20] Approximately 18 per cent of the Earth's land drains to endorheic lakes or seas, the largest of these land areas being the interior of Asia.
Aerial view of the endorheicAltiplano basin at the boundary between the cities ofEl Alto (left) andLa Paz (right). Note the topographic contrast between the plateau and the descending valley.
In deserts, water inflow is low and loss to solar evaporation high, drastically reducing the formation of completedrainage systems. In the extreme case, where there is no discernible drainage system, the basin is described asarheic.[13] 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 extensivesalt pans (also called salt flats, salt lakes,alkali flats, dry lake beds, or playas). These areas tend to be large, flat hardened surfaces and are sometimes used foraviationrunways, orland speed record attempts, because of their extensive areas of perfectly level terrain.
Both permanent and seasonal endorheic lakes can form in endorheic basins. Some endorheic basins are essentially stable because climate change has reduced precipitation to the degree that a lake no longer forms. Even most permanent endorheic lakes change size and shape dramatically over time, often becoming much 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 disruption of ecosystems.
Even within exorheic basins, there can be "non-contributing", low-lying areas that trap runoff and prevent it from contributing to flows downstream during years of average or below-average runoff. In flat river basins, non-contributing areas can be a large fraction of the river basin, e.g.Lake Winnipeg's basin.[21] A lake may be endorheic during dry years and can overflow its basin during wet years, e.g., the formerTulare Lake.
Because the Earth's climate has recently been through a warming and drying phase with the end of the Ice Ages, many endorheic areas such asDeath Valley that are now dry deserts were large lakes relatively recently. During the last ice age,the Sahara may have contained lakes larger than any now existing.[22]
Climate change coupled with the mismanagement of water in these endorheic regions has led to devastating losses inecosystem services and toxic surges of pollutants.[23] The desiccation of saline lakes produces fine dust particles that impair agriculture productivity and harm human health.[24][25]Anthropogenic activity has also caused a redistribution of water from these hydrologically landlocked basins such that endorheic water loss has contributed tosea level rise, and it is estimated that most of the terrestrial water lost ends up in the ocean.[26] In regions such as Central Asia, where people depend on endorheic basins and other surface water sources to satisfy their water needs, human activity greatly impacts the availability of that water.[27]
Major endorheic basins of the world. Basins are shown in dark grey; major endorheic lakes are shown in black. Coloured regions represent the major drainage patterns of the continents to the oceans (non-endorheic).Continental divides are indicated by dark lines.
Much ofWestern andCentral Asia is a giant endorheic region made up of a number ofcontiguous closed basins. The region contains several basins and terminal lakes, including:
TheCaspian Sea, the largest lake on Earth. A large part of western Russia, drained by theVolga River, is part of the Caspian basin.
Lake Urmia in Western Azerbaijan Province of Iran.
TheAral Sea, whose tributary rivers have been diverted, leading to a dramatic shrinkage of the lake. The resulting ecological disaster has brought the plight of internal drainage basins to public attention.
Though a large portion of Europe drains to the endorheicCaspian Sea, Europe's wet climate means it contains relatively few terminal lakes itself: any such basin is likely to continue to fill until it reaches an overflow level connecting it with an outlet or erodes the barrier blocking its exit.
There are some seemingly endorheic lakes, but they are cryptorheic, being drained either through manmadecanals, viakarstic phenomena, or other subsurface seepage.[clarification needed]
There are also multiple small endoreic lake in the mountains inFrance : Allos Lake, Anterne Lake, Eychauda Laye, La Beunaz Lake, Cassière Lake, Lessy Lake, Peyre Lake, Tardevant Lake, Confins Lake, Rouites Lake, Grand Ban Lake and Flaine Lake as an example.
Crater Lake, inOregon, a cryptorheic lake with subsurface drainage to theWood River. It is filled directly by rain and snow and has very little mineral or salt buildup.
Several lakes on the westernChilcotin Plateau sit on the divide between the Fraser River drainage to the east and the Homathko drainage to the west. Such examples includeChoelquoit Lake,Eagle Lake, andMartin lake.
Don Juan Pond inWright Valley is fed by groundwater from a rock glacier and remains unfrozen throughout the year.
Lake Vanda inWright Valley has a perennial ice cover, the edges of which melt in the summer, allowing flow from the longest river in Antarctica, theOnyx River. The lake is over 70 m deep and is hypersaline.
Lake Bonney is inTaylor Valley and has a perennial ice cover and two lobes separated by the Bonney Riegel. Glacial melt and discharge fromBlood Falls feed the lake. Its unique glacial history has resulted in hypersaline brine in the bottom waters and fresh water at the surface.
Lake Hoare, inTaylor Valley, is the freshest of the Dry Valley lakes, receiving its melt almost exclusively from the Canada Glacier. The lake has an ice cover and forms a moat during the Austral summer.
Lake Fryxell is adjacent to theRoss Sea inTaylor Valley. The lake has an ice cover and receives its water from numerous glacial meltwater streams for approximately six weeks out of the year. Its salinity increases with depth.
Some of Earth's ancient endorheic systems and lakes include:
TheBlack Sea, until its merger with the Mediterranean.
TheMediterranean Sea itself and all its tributary basins, during itsMessinian desiccation (approximately five million years ago) as it became disconnected from the Atlantic Ocean.
Tularosa Basin and Lake Cabeza de Vaca in North America. The basin was formerly much larger than it is today, including the ancestralRio Grande north of Texas, which fed a large lake area.
Ebro andDuero basins, draining most of northern Spain during theNeogene and perhapsPliocene. Climate change and erosion of the Catalan coastal mountains, as well as the deposition of alluvium in the terminal lake, allowed the Ebro basin to overflow into the sea during the middle-to-lateMiocene.
^Galat, D. L.; Lider, E. L.; Vigg, S.; Robertson, S. R. (1981). "Limnology of a large, deep, North American terminal lake, Pyramid Lake, Nevada, U.S.A.".Salt Lakes. pp. 281–317.doi:10.1007/978-94-009-8665-7_22.ISBN978-94-009-8667-1.
^Nichols, Gary (7 December 2007). "Fluvial Systems in Desiccating Endorheic Basins".Sedimentary Processes, Environments and Basins. pp. 569–589.doi:10.1002/9781444304411.ch23.ISBN9781444304411.
^National Research Council Staff (1995). Mexico City's Water Supply: Improving the Outlook for Sustainability. Washington, D.C., US: National Academies Press.ISBN978-0-309-05245-0.
