Summary of site:
Karst areas are characterised by rivers and streams that drain into sink holes, potholes, caves and rock fractures, and then follow underground courses before surfacing or ‘resurging’ elsewhere. The link between the water source and the resurgence can be established by dye testing and results are often surprising.
Holywell is a large-scale resurgence with water welling up from a boulder and sand bed. The origin of the water is unknown and although there is speculation that it could originate in the Reyfad Cave catchment 7.5km to the north, there is as yet no direct proof.