Elan Valley reservoirs
Birmingham Corporation needed drinking water for the Midlands and the Elan Valley Water Scheme was planned to the west of Rhayader.
At the time the Elan Valley had one hundred occupants who needed to be moved and only landowners received compensation. The scheme affected eighteen cottages and farmhouses, a school, a church and two manor houses. The nineteenth century poet, Percy Byshe Shelley had stayed in both Nantgwillt House and Cwm Elan House before they were submerged.
This was an ambitious civil engineering project and the construction phase lasted thirteen years from 1893 to 1906. The main features of the first phase of the scheme included the Caban Coch reservoir and dam, the Pen-y-Garreg reservoir and dam, and Craig Goch reservoir and dam. The Foel tower stands 52 metres above the Frankley Reservoir in Birmingham and the water is transferred through an aqueduct that is 117 kilometres long. Between the Garreg Ddu and Caban Coch reservoirs the Garreg Ddu dam is a submerged structure that has the appearance of a viaduct. It holds back water upstream so that it can be extracted at the Foel tower.
The work was substantially complete when the scheme was officially opened by King Edward VII and Queen Alexandra on 21 July 1904. The scheme is still supplying Birmingham's water. Between 1948 and 1952 the Claerwen dam was built to double the capacity of the original scheme to 345.5 million litres of water per day. The dam is 56 metres high and is supported on thirteen elliptical arches and it has stone parapets.
Since 1997 four Francis turbines and one Kaplan submersible hydropower turbine have been installed at the bases of all the dams and the Foel tower. The maximum energy output is 4.2 megawatts.
The Elan Estate is now owned by Dŵr Cymru / Welsh Water who are responsible for the Visitor Centre, the dams and reservoirs, the woodlands and most of the Elan Valley Trail. The Estate covers an area of 80 square kilometres that includes twelve Sites of Special Scientific Interest, and a National Nature Reserve.