Clywedog Dam, with another at Bwlch-y-gle (nprn 309936), was built between 1964 and 1967 to create Llyn Clywedog or Clywedog Reservoir (nprn 309930) and thus regulate the flow of the River Severn. It is of mass-concrete construction, standing 72m high and 231m long.
B.A.Malaws, RCAHMW, 27 January 2004.