Dwr Cymru will be carrying out a 3900l/s (3.9cumec) ‘scour test’ at Ystradfellte reservoir at 10am tomorrow (Wed 24 Jan).

The test should last only a few minutes, so the impact may not be significant – but if there are delays in the valve operation it is possible that water level could  rise at the cave by as much as half a metre.

Groups should therefore be diligent and exercise caution in the cave tomorrow morning.

Apologies for the short notice…