Ladybower Reservoir

Ladybower Reservoir is a large Y-shaped, artificial reservoir, the lowest of three in the Upper Derwent Valley in Derbyshire, England. The River Ashop flows into the reservoir from the west; the River Derwent flows south, initially through Howden Reservoir, then Derwent Reservoir, and finally through Ladybower Reservoir. The reservoir is owned by Severn Trent.

The area is now a tourist attraction, with the Fairholmes visitors' centre located at the northern tip of Ladybower. The east arm of the reservoir, fed by the Ladybower Brook, is overlooked by Hordron Edge stone circle.

Design and construction

Ladybower was built between 1935 and 1943 by the Derwent Valley Water Board to supplement the other two reservoirs in supplying the water needs of the East Midlands. It took a further two years to fill, which was done by 1945. The dam differs from the Howden Reservoir and Derwent Reservoir in that it is a clay-cored earth embankment and not a solid masonry dam. Below the dam is a cut-off trench deep and wide filled with concrete, stretching into the hills each side, to stop water leaking around the dam. The dam wall was built by Richard Baillie and Sons, a Scottish company. The two viaducts, Ashopton and Ladybower, needed to carry the trunk roads over the reservoir, were built by the London firm of Holloways, using a steel frame clad in concrete. The project was delayed when the Second World War broke out in 1939, making labour and raw materials scarce, but construction was continued due to the strategic importance of maintaining supplies. King George VI, accompanied by his wife, Queen Elizabeth, formally opened the reservoir on 25 September 1945.

During the 1990s, the wall was raised and strengthened to reduce the risk of over-topping in a major flood. The original dam wall contains 100,000 tons of concrete, over one million tons of earth, and 100,000 tons of clay for the core. The upstream face is stone-faced. Materials were brought to the site on the Derwent Valley Water Board's own branch line and their sidings off the mainline in the Hope Valley.

The dam's design is unusual in having two totally enclosed bellmouth spillway overflows (locally named the "plugholes") at the side of the wall. These are stone and of diameter with a drop of . The plugholes regulate water levels in the reservoir by draining away excess water when they overflow. The water is then carried to the River Derwent through tunnels. The overflows originally had walkways around them, but they were dismantled many years ago. The plugholes typically overflow in winter months if there has been wet or snowy weather in the nearby hills. According to Severn Trent, the reservoir’s operating company, the overflowing plug holes attract many visitors each year.

Water usage

The water is used for river control and to compensate for the water retained by all three dams, along with supply into the drinking water system and hydroelectricity generation. Drinking water must be pumped to treatment works rather than using gravity flow as in the other two reservoirs, increasing costs. The drinking water is treated at Bamford water treatment works by Severn Trent Water. Treated water flows south down the long Derwent Valley Aqueduct to a covered service reservoir at Ambergate to supply clean water to the cities of Nottingham, Derby and Leicester in the East Midlands of England. The aqueduct passes through the park of Chatsworth House. The path of the aqueduct is marked by a series of valve houses built of stone and domed steel access chambers. A tunnel carries some of the water from the Derwent Valley eastwards through the hill and into the lower of the two Rivelin Dams

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