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 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 factors specific to a cave – such as the sea tide, changes in

river A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and becomes dry at the end of its course without reaching another body of ...

flow, or the relationship with the local

water table The water table is the upper surface of the zone of saturation. The zone of saturation is where the pores and fractures of the ground are saturated with water. It can also be simply explained as the depth below which the ground is saturated. T ...

– 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 Swildon's Hole is an extensive cave in Priddy, Somerset. At in length, it is the longest cave on the Mendip Hills. It has been found to be connected to Priddy Green Sink and forms part of the Priddy Caves Site of Special Scientific Interest (SSS ...

). 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 search for and recovery of divers or, as in the 2018 Thai cave rescue, other ...

(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 (from grc, σίφων, síphōn, "pipe, tube", also spelled nonetymologically 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 a ...

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, Greece Greece,, or , romanized: ', officially the Hellenic Republic, is a country in Southe ...

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 locally also known as ''vrtače'' and shakeholes, and to openi ...

, 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 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 expl ...

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.

External links

Sump Rescue
{{caves Caving Hydrology

Exploration past a sump

Diving

Draining

See also

External links