The Vyrnwy Dam

Until Vyrnwy, British reservoir dams were earth embankments with a clay core. Vyrnwy is masonry — a solid gravity dam of dressed stone, relying on its own weight to hold back the water — and it was the first large one built in this country.

The numbers

Around 44 metres high and 357 metres long, holding a lake four and a half miles from end to end.

Construction ran from 1881 to 1888 under Thomas Hawksley and George Deacon for Liverpool Corporation, and it was engineering at the edge of what was then understood. The design had to be proved as it was built, and the profile was calculated to keep the masonry in compression throughout.

Water overtops the crest in a continuous sheet when the reservoir is full, which was intended, and it is the reason people photograph it.

The tower

Standing out in the water is the straining tower, where the supply is screened before it enters the aqueduct. It was completed in the early 1890s and it is dressed as a small Gothic castle with a conical roof, connected to the shore by a bridge.

There is no engineering reason for any of that. Victorian municipal waterworks were built to be admired, and Liverpool wanted its ratepayers to see what they had bought. The same instinct produced the architecture of the Elan dams a decade later.

The aqueduct

Water reaches Liverpool by gravity along a line of about 68 miles, through tunnels, siphons and pipe. It has never required pumping and it is still in service.

That is the part that impresses engineers rather than photographers: a survey accurate enough, in the 1880s, to fall consistently across nearly seventy miles of Welsh and English country.

What is underneath

The village of Llanwddyn, with around thirty-seven houses, two chapels, a church, three inns and a school. The churchyard was cleared and the remains reinterred before the valley was flooded.

A replacement village was built below the dam. That is dealt with on the Llanwddyn page and in the article on the drowned valleys.

Now

The estate is managed with the RSPB, which has run a reserve here since 1977 covering the lake, the Berwyn oakwoods and the moorland above. The bird list is one of the better ones in Wales.

There is a road round the lake of about twelve miles, a visitor centre, hides, and a good deal of cycling traffic in summer.

Visiting

Free and open. The best view of the dam is from the road below it, and the best view of the tower is from the eastern shore.

Go when the reservoir is full and overtopping if you can. In a dry summer it is a large lake with a wall at one end.