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Reservoir reflections

The Llyn Clywedog is a man made reservoir formed by the construction of the Clywedog Dam. The dam was built between 1965-67 to regulate the flow of water in the Severn, both as a protection against flooding of the upper sections of the river during the winter months and also to ensure the maintenance of a minimum flow in the river during the summer.

 

The construction of the dam and lake throw up a number of interesting statistics. The structure is the tallest mass concrete dam in Britain, standing fully 236 ft (72m) high. It is 750 ft long, and holds back some 11,000 million gallons of water. This apparently equates to some 550 million baths, or 264 billion glasses of water. The weight of concrete used in the construction of the dam is equal to 7 times the tonnage of the QE2 cruise liner, in all some 200,000 cubic metres; enough to build 28 miles of six lane motorway.

 

The lake has a surface area of 615 acres (230 football pitches), is 216 ft deep at its maximum depth and stretches in all a distance of some six miles. At its maximum, it is just 500 yards wide. Some 15 miles of new or improved roads were built around the reservoir at time of construction, along with two new bridges. There is a second, much less visible dam at Bwlch-y-gle. This is an earthen structure faced with stone, about 40ft high and 600ft long which prevents the lake spilling over into the neighbouring valleys on either side of Bryn y Fan hill, the highest of the hills surrounding the lake and a commanding feature to be seen from miles around.

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Uploaded on December 24, 2025
Taken on November 2, 2021