We have received the following message from Dwr Cymru Welsh Water. Although they say they “do not envisage any problems with any increased flooding risk downstream”, the last time they did this the water level did reach the top of the ledge at the Porth yr Ogof main entrance (although it quickly subsided), so it could affect cave and gorge users…

“As responsible reservoir undertakers Dŵr Cymru Welsh Water are planning on testing the operation of the reservoir scour valve(s) at Ystradfellte on 11/05/2023. The test involves a short opening of the bottom outlet valve(s) of the reservoir to ensure its efficient functioning. This is a statutory requirement by Welsh Water under the Reservoirs Act 1975 of which DCWW has received consent to carry out from NRW as per consent NRWWIA201 dated 16th December 2020 and provides consent until the 21st January 2026. We are writing to you to inform you that we do not envisage any problems with any increased flooding risk downstream or the possible release of turbid water during this short release and there are no algal blooms present. This will be a Partial operation and releases will be low.”