Llyn Clywedog

Clywedog Dam, high above Llanidloes, was built between 1964 and 1967 to regulate the flow of water in the upper reaches of the River Severn. At the time of completion it was the tallest mass concrete buttress dam in Britain, standing an impressive 235 feet high.









752 feet long, the dam, which has a convex form facing upriver, retains 11,000 million gallons of water. The reservoir is six miles long, 212 feet deep at maximum fill, and has a surface area of 615 acres.

In support of the dam, 15 miles of road were constructed or relaid; two new bridges were built; and a subsidiary dam, the 40 foot high earthen-cored and stone-faced Bwlch y Gle, was constructed to prevent the reservoir spilling around the sides of Bryn y Fan hill.