A sump, or siphon, is a passage in a cave that is submerged under water.
A sump may be static, with no inward or outward flow, or active, with continuous through-flow. Static sumps may also be connected underwater to an active stream passage. When short in length, a sump may be called a duck; however, this can also refer to a section or passage with some (minimal) airspace above the water.
Depending on
hydrological
Hydrology () is the scientific study of the movement, distribution, and management of water on Earth and other planets, including the water cycle, water resources, and drainage basin sustainability. A practitioner of hydrology is called a hydro ...
factors specific to a cave – such as the
sea tide, changes in
river
A river is a natural stream of fresh water that flows on land or inside Subterranean river, caves towards another body of water at a lower elevation, such as an ocean, lake, or another river. A river may run dry before reaching the end of ...
flow, or the relationship with the local
water table
The water table is the upper surface of the phreatic zone or zone of saturation. The zone of saturation is where the pores and fractures of the ground are saturated with groundwater, which may be fresh, saline, or brackish, depending on the loc ...
– sumps and ducks may fluctuate in water level and depth (and sometimes in length, due to the shape of adjacent passage).
Exploration past a sump
Diving
Short sumps may be passed simply by holding one's breath while ducking through the submerged section (for example, Sump 1 in
Swildon's Hole). This is known as "free diving" and can only be attempted if the sump is known to be short and not technically difficult (e.g. constricted or requiring navigation). Longer and more technically difficult sumps can only be passed by
cave diving
Cave-diving is underwater diving in water-filled caves. It may be done as an extreme sport, a way of exploring flooded caves for scientific investigation, or for the underwater search and recovery, search for and recovery of divers or, as in th ...
(as happened repeatedly in the exploration of
Krubera Cave).
Draining
When practical, a sump can also be drained using buckets, pumps or
siphon
A siphon (; also spelled syphon) is any of a wide variety of devices that involve the flow of liquids through tubes. In a narrower sense, the word refers particularly to a tube in an inverted "U" shape, which causes a liquid to flow upward, abo ...
s. Pumping the water away requires the inward flow of water into the sump to be less than the rate at which the pump empties it, as well as a suitable place to collect the emptied water. Upstream sumps have been successfully emptied using hoses to siphon water out of them, such as at the
Sinkhole Dersios
The Dersios sinkhole (Greek: Σπηλαιοκαταβόθρα "Ο Δέρσιος" ''Spilaiokatavothra "O Dhersios"'') is a sinkhole in Arcadia (regional unit), Arcadia, Greece.
The sinkhole, which has a depth of , has been known since antiquity ...
during exploration in 2005. The water was sent deeper into the
sinkhole
A sinkhole is a depression or hole in the ground caused by some form of collapse of the surface layer. The term is sometimes used to refer to doline, enclosed depressions that are also known as shakeholes, and to openings where surface water ...
, and the emptied sumps revealed virgin passage behind them. During a rescue from beyond a downstream sump at
Sarkhos Cave in 2002, water was pumped upstream into a
dam
A dam is a barrier that stops or restricts the flow of surface water or underground streams. Reservoirs created by dams not only suppress floods but also provide water for activities such as irrigation, human consumption, industrial use, aqua ...
constructed a few metres above the flooded passage.
Some manuals also mention the use of
explosives
An explosive (or explosive material) is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure. An exp ...
or other forms of force to empty sumps, but the
ecological damage done to the fragile cave environment usually rules out the use of such methods.
See also
*
References
External links
Sump Rescue
{{caves
Caving
Hydrology