The UK and Welsh Governments have introduced new measures to safeguard water supply and resources on both sides of the border.
The protocol meets a key commitment made during the passage of the Wales Act 2017, paving the way to remove the Secretary of State powers to intervene on water policy.
It ensures there is no serious adverse impact on water resources, water supply or water quality in Wales arising from the action or inaction of the Secretary of State or public bodies exercising functions in England and vice versa.
The new measures, which will come into force on 1st April 2018, replace these intervention powers with a reciprocal agreement between the UK and Welsh Governments.
Welsh Secretary of State Alun Cairns said: “From today onwards, no action or inaction by either the UK or Welsh Governments relating to water resources, water supply or water quality should have serious adverse impacts for consumers on either side of the border.
“This protocol demonstrates how far we have come from the events of 52 years ago, which resulted in the flooding of the Tryweryn Valley. Today’s agreement puts cross-border arrangements for water on a footing fit for the 21st century and underlines what can be achieved when two governments work together for Wales’ future prosperity.”