Lag na Sionna
|Location||Derrylahan townland, Glangevlin, County Cavan|
|Primary inflows||Shannon Cave|
|Primary outflows||River Shannon|
|Catchment area||12.8 km2 (4.9 sq mi)|
|Max. length||16 m (52 ft)|
|Max. width||16 m (52 ft)|
|Max. depth||14.6 m (48 ft)|
Shannon Pot or Legnashinna (from Irish: Lag na Sionna, meaning "hollow of the Shannon") is a pool in the karst landscape near Cuilcagh Mountain in County Cavan, Ireland. An aquifer-fed naturally fluctuating pool, it is the traditional source of the River Shannon.
The pool itself is about 16 m (52 ft) wide, and has been dived to −14.6 metres (−48 ft).
According to legend, the Shannon is named after Sionnan, who was the granddaughter of Manannán mac Lir, the god of the sea. She came to this spot to eat the forbidden fruit of the Tree of Knowledge, which was planted by the druids. As she began to eat it, the waters of the pool sprang up and overwhelmed her. She was drawn down into the pool and its water began to flow over the land, forming the River Shannon.
Diving and exploration
Shannon Pot was first explored by divers Roger Solari and John Elliot on multiple dives in 1971, to a depth of firstly 6, then 9 metres (30 ft). At this point the water was found to emerge from a 2-metre (6.6 ft) wide slit, up to 300 mm (0.98 ft) in height. Their progress was hampered by submerged tree branches, equipment problems and poor visibility in the dark brown water. The pot was later explored by Martyn Farr, among others, but no further progress was made until the late 2000s.
In December 2008 and January 2009 the pot was dived again by Alasdair Kennedy and Paul Doig, and subsequently by Artur Kozłowski. After widening the slit and continuing downwards past a loose cobblestone slope, Kozłowski discovered an unstable chamber. A strong current was found to emerge from a tight, unstable shaft in the floor. Doig and Kennedy surveyed the chamber to a depth of 14.6 metres (48 ft).
Surveys have defined a 12.8 km2 (4.9 sq mi) immediate catchment area covering the slopes of Cuilcagh. This area includes Garvagh Lough, 2.2 km to the northeast of the pot. Water from Garvagh drains into Pollnaowen[n 1] sink, before emerging at Shannon Pot.
The highest point in the catchment is a spring at Tiltinbane on the western end of the Cuilcagh mountain ridge; this sources an unnamed stream which itself feeds into Shannon Cave. Further sinks that source the pot include Pollboy and, through Shannon Cave, Pollahune in County Cavan and Polltullyard and Tullyrrakeeragh in Fermanagh.
Surveys suggest that Shannon Pot may once have had a much bigger catchment area. In times of high flow it has been shown to be hydrologically linked to Badger Pot and Pigeon Pot located 10.6 km north of the Shannon Pot in the Cuilcagh Mountain near Florencecourt Forest Park, Fermanagh.
- 'Poll nm1:' hole, pit, sink, leak, aperture (The Pocket Oxford Irish Dictionary – Irish-English)
|Wikimedia Commons has media related to Shannon Pot.|
- LaMoreaux, Dr. Philip E.; Tanner, Judy T., eds. (2001). Springs and Bottled Waters of the World: Ancient History, Source, Occurrence, Quality and Use. Berlin: Springer-Verlag. pp. 166–168. ISBN 3-540-61841-4.
- Kozłowski, Artur; Kennedy, Alasdair; Doig, Paul (2009). "A back door to hell – breakthrough in the Shannon Pot". Irish Speleology. 18: 13–14.
- "Log na Sionna / Shannon Pot". Archived from the original on 2016-03-04. Retrieved 2017-09-14.