Caves under North Clare and South Galway could extend 30 miles under Galway Bay and reach the Aran Islands, researchers have discovered.
Rain falling in the Burren and filtering through the limestone appears to be then travelling in underground rivers to the coast and under Galway Bay, before emerging in springs on Inishmaan, and in the bay itself, according to work by a group from NUI Galway.
Geologists have found large networks of underground rivers hidden under the seabed and, while the current research project is wrapping up, additional funding would enable them to identify targets in the subsurface that could be drilled out and water abstracted from them to supply the Aran Islands.
“I would never suggest there is an unending supply of water you could hit there, but there is good potential for hitting a water resource that might augment the water that falls on Inishmaan, or that might help with dealing with water supply on the smaller islands because they are nearer to the coast,” according to Dr Tiernan Henry, lecturer in Environmental Geology, School of Natural Sciences.
“If you look at the geological map and what is going on underground between Gort and the sea, and the sea and the Aran Islands, it is essentially the same system, there just happens to be some seawater sitting on part of it,” added Dr Henry.
“From a geological perspective, it is the same rock and, from a hydrogeological perspective, we know in the South Galway and North Clare areas where those caves have been identified. They have been dived by cavers, so if that rock continues to Galway Bay, why should those cave systems stop right at the coastline? There is no particular reason they should stop there,” he told The Clare Champion.
NUI Galway’s Earth and Ocean Sciences researchers concluded the water is likely to be flowing for several miles, before emerging as ‘freshwater rivers’ out of the seabed of Galway Bay.
This water flow is caused by rain falling on the land. It runs through the limestone and then goes out under the sea. They confirmed that the network of underground rivers stretches up to 30 miles long and is 70ft wide in places and could explain why Inishmaan, unlike many other islands, does not experience water shortages.“We were told about a well at a local hotel on Inishmaan that had an excellent supply of fresh water. The islands can have water problems, they are always short but this well went deep into the rock and was getting more water than falls on the whole island,” Dr Henry outlined.
The pure-bedded limestones that form the Aran Islands are found throughout north Clare and south and east Galway. These rocks are particularly susceptible to dissolution by rainfall and time, forming the distinctive drainage patterns of turloughs, swallow holes and sinking rivers.
Almost all of the freshwater in these areas flows in discrete zones within the rock, discharging in springs found at the coast and in the bays and sea. The means by which these passages and conduits form is well known and well understood but where they form, and the shapes they take, are less easy to predict.
“There is no particular issue with the quality because South Galway North Clare is largely agricultural and there is no big industrial activity. The agriculture is largely extensive, you don’t have huge farming units and also because of the Burren in particular, with the Burren Life project, where there is a lot of farmers actively engaging in positive environmental practices, which are having positive environmental impacts. A lot of what farmers are doing, doing the right thing at their location, has positive knock-ons downstream and any water moving through the system is positively affected by it too, so what we do see is there is nutrient loading into the bays, so the nutrients are coming off the land but not at levels that are of concern,” Dr Henry explained.
“This is something that has been happening for a long, long time. The biological systems in the bay have adjusted to this but the amount of fresh water discharging into Galway Bay, compared to its size, any impact would be instantly diluted because there is so much saltwater there,” he added.
With further research Dr Henry believes water running through the cave systems from Clare and Galway could augment, or even secure, fresh water supply on the smaller Aran Islands.
The research was funded by the Griffiths Award and supported by the University’s Ryan Institute for Environmental, Marine and Energy Research.
By Nicola Corless
A native of Ennis, Colin McGann has been editor of The Clare Champion since August 2020. Former editor of The Clare People, he is a journalism and communications graduate of Dublin Institute of Technology.