Subterranean river

File:Burger OtokKriznaJama.jpg

A subterranean river in the Cross Cave system of Slovenia. (Scale shown by people in photograph.)

A subterranean river (also known as an underground river) is a river or watercourse that runs wholly or partly beneath the ground, one where the riverbed does not represent the surface of the Earth.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> It is distinct from an aquifer, which may flow like a river but is contained within a permeable layer of rock or other unconsolidated materials. A river flowing below ground level in an open gorge is not classed as subterranean.<ref>William Herbert Hobbs, Earth Features and Their Meaning: An Introduction to Geology for the Student and the General Reader, Macmillan, 1912, pages 182 and 189.</ref>

Some natural rivers may be entirely subterranean, collecting in and flowing through cave systems. In karst topography, rivers that originate above ground can disappear into sinkholes, continuing underground until they reappear on the surface downstream, possibly having merged with other subterranean rivers. The longest subterranean river in the world is the Sistema Sac Actun cave system in Mexico.<ref>"Underwater cave is the world’s biggest", Mexico Daily News, January 15, 2018, https://mexiconewsdaily.com/news/underwater-cave-is-worlds-biggest/ Template:Webarchive</ref>

Subterranean rivers can also be the result of covering over a river or diverting its flow into culverts, usually as part of urban development.<ref name="heggen">Richard J. Heggen: Underground Rivers from the River Styx to the Rio San Buenaventura with Occasional Diversions Template:Webarchive, University of New Mexico.</ref> Reversing this process is known as "daylighting" a watercourse and is a major form of visible river restoration. Successful examples include the Cheonggyecheon in the centre of Seoul.<ref>Template:Cite news</ref><ref>Template:Cite news</ref>

Some fish (colloquially known as cavefish) and other troglobite organisms are adapted to life in subterranean rivers and lakes.<ref>William B. White and David C. Culver (eds), Encyclopedia of Caves, 2nd ed, Academic Press, 2012, Template:ISBN, p. 468.</ref>

Examples of subterranean rivers also occur in mythology and literature.

Natural examples

File:Buna source.jpg

The cave of source of the Buna can be entered by boat and dived through a cave system serving as an effluence of the Zalomka.

File:Caves entranceexit.jpg

The Puerto Princesa cave can be entered by boat.

File:La chute d'entrée de la Gorge du Diable.jpg

Devil's Throat Cave subterranean river from above

There are many natural examples of subterranean rivers. Among them:

• In Bosnia and Herzegovina: Unac; Mušnica-Trebišnjica-Krupa/Ombla (Ombla springs out of huge cave near Dubrovnik, Croatia and after just ca. 30 meters empties into Adriatic Sea's ria called Rijeka Dubrovačka); Zalomka-Buna/Bunica/Bregava; Vrljika-Trebižat; Lištica-Jasenica; Šuica-Ričina<ref name="Dinarides-devonkarst.org.uk">{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref><ref name="Ponor-Dobrelji-devonkarst.org.uk">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

• In Bulgaria:
  • Banderishka reka, subterranean section below Kutelo Peak, Pirin Mountain
  • Struma River subterranean currents in Duhlata cave, Vitosha Mountain
  • Negovanka River subterranean currents in Emen cave, Veliko Tarnovo Province
  • Trigradska reka, subterranean section where Devil's Throat Cave and Trigrad Gorge, Rhodope Mountains
• The Camuy River located in the northwestern region of Puerto Rico is one of the<ref>{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref> largest underground river systems in the world.

• The Cross Cave system in Loška Dolina, Slovenia includes 22 subterranean lakes
• The Lost River in the Appalachian Mountains of West Virginia disappears underground and reappears as the Cacapon River
• The Mojave River in southern California flows underground in most places
• The Phong Nha-Kẻ Bàng National Park in Vietnam has an underground river flowing through its cave system
• The Puerto Princesa Subterranean River on the island of Palawan, Philippines flows underground before emerging into the South China Sea<ref>{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref>

• The Punkva in Moravian Karst, Moravia, Czech Republic underground river flowing through cave system - Punkva Caves and Macocha gorge.
• The Santa Fe River in northern Florida drops into a large sinkhole in O'Leno State Park and reappears in the adjacent River Rise Preserve State Park, Template:Convert downstream.
• The Reka in Slovenia, which disappears in the Škocjan Caves, re-emerges as part of the Timavo in Italy.<ref>Template:Cite journal</ref>

Artificial examples

File:Effra vauxhall 2.jpg

The Effra is one of the subterranean rivers of London. It empties into the Thames by Vauxhall Bridge, from which this photograph was taken.

In many cities there are natural streams which have been partially or entirely built over. Such man-made examples of subterranean urban streams are too numerous to list, but notable examples include:

• The Bièvre underneath Paris, France
• The Boyanska reka (Boyana river), partially underneath Sofia, Bulgaria
• Castle Frank Brook, Garrison Creek, Russell Creek, and Taddle Creek, and other subterranean urban streams in Toronto
• The River Farset, which Belfast is named after, which runs in tunnels underneath the city.
• The Fleet and other subterranean rivers of London
• The Frome underneath Bristol
• The Hobart Rivulet in Tasmania
• Mill Creek in Philadelphia
• The Neglinnaya River, which runs through a series of tunnels underneath the central part of Moscow
• The Park River underneath Hartford
• The Spirit Lake Outlet Tunnel underneath Harry's Ridge in Skamania County, Washington, United States
• The River Team underneath the Team Valley Trading Estate, Gateshead, United Kingdom
• The Tank Stream underneath Sydney, Australia
• The Zenne underneath Brussels, following the covering of the Zenne between 1865 and 1871

• Subterranean rivers of London
• Subterranean rivers in Hong Kong

Ecology

Some fish (popularly known as cavefish) and other troglobite organisms are adapted to life in subterranean rivers and lakes.

Mythology and literature

File:Gustave Doré - Dante Alighieri - Inferno - Plate 9 (Canto III - Charon).jpg

In Dante's Inferno, Charon ferries souls across the subterranean river Acheron.

Greek mythology included the Styx, Phlegethon, Acheron, Cocytus, and Lethe as rivers within the Underworld. Dante Alighieri, in his Inferno, included the Acheron, Phlegethon, and Styx as rivers within his subterranean Hell. Similar references were made in John Milton's Paradise Lost. The river Alph, running "Through caverns measureless to man / Down to a sunless sea" is central to the poem Kubla Khan, by Samuel Taylor Coleridge.

The characters in Jules Verne's Journey to the Center of the Earth encounter a subterranean river:

"Hans was not mistaken," he said. "What you hear is the rushing of a torrent."

"A torrent?" I exclaimed.

"There can be no doubt; a subterranean river is flowing around us."<ref>Jules Verne, Journey to the Center of the Earth, translated by Frederick Amadeus Malleson, 1877, at Project Gutenberg.</ref>

Several other novels also feature subterranean rivers.<ref name="heggen"/> The subterranean rivers of London feature in the novel Drowning Man by Michael Robotham as well as in the novel Thrones, Dominations by Dorothy L. Sayers and Jill Paton Walsh in which a character remarks:

"You can bury them deep under, sir; you can bind them in tunnels, but in the end where a river has been, a river will always be."<ref>Dorothy L. Sayers and Jill Paton Walsh, Thrones, Dominations, Hodder and Stoughton, 1998, p. 313.</ref>

See also

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