Sump (cave)

A sump is a term used in caving to describe a submerged passage in a cave.

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). Longer sumps can only be passed by cave diving (as happened repeatedly in the recent exploration of Voronya-Krubera).

When practical a sump can also be drained using buckets, pumps or siphons. 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 at the Sinkhole Dersios during 2005. The water was sent deeper into the sinkhole and the emptied sumps revealed virgin passage behind them. During the rescue at Sarkhos Cave in 2002, the water was collected by pumping slightly above the flooded sump through the construction of a suitable watertight area some meters higher than the sump.

Some manuals mention the use of explosives 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.