Llyn Clywedog has a capacity of 50,000 million litres, a surface area of 250 hectares and a maximum water depth of 66 metres. Clywedog Reservoir was created between 1964 and 1967. The main Clywedog Dam (NPRN 305772) is 72 metres (237 ft) tall. The smaller dam at Bwlch- y-Gle (NPRN 309936) prevents the waters from flowing into an adjacent valley. The reservoir maintains water supply and generates a small amount of electricity.

Claire Parry, RCAHMW, 16 June 2011

Source: Association for Industrial Archaeology: A Guide to the Industrial Archaeology of Mid-Wales, 1984