Two ways in from Machynlleth
The Elan Valley lies south-west of Rhayader in Powys, and there are two sensible ways to reach it from the Dyfi valley. The gentler one goes east over the tops to Llanidloes — the Dylife mountain road, past Llyn Clywedog — and then south on main roads to Rhayader, where the valley road turns off. The wilder one goes south to Devil’s Bridge and inland over the Cwmystwyth mountain road, arriving at Pont ar Elan at the head of Craig Goch and working down the chain of reservoirs from the top. Both are long days; the second is single track for much of its length and is not for anything towing.
Whichever way you come, the place does not look like a Welsh valley at all: five great masonry dams hold back a staircase of lakes in bare hill country, all of it built to send water to Birmingham, 73 miles away.
Why a Welsh valley supplies an English city
The Birmingham Corporation Water Act of 1892 gave the city compulsory purchase powers over the Elan and Claerwen valleys. Work ran from 1893 to 1906 and was substantially complete by 1904, when Edward VII and Queen Alexandra came to open the reservoirs. Water still leaves at the Foel Tower and travels the whole way to Frankley reservoir outside Birmingham by gravity alone, down an aqueduct of about 73 miles — roughly 117 kilometres — falling 52 metres at a gradient of one in 2,300. No pumps, then or now.
The human cost was borne locally. The Royal Commission records that more than a hundred people were evicted, and that landowners were compensated while tenants and smallholders were not. Under the water went farms, a church and a school, and two mansions: Cwm Elan and Nantgwyllt, the second of which the poet Percy Bysshe Shelley had stayed in and hoped to take. The navvies who built the dams lived in a purpose-built model village with electricity and flushing toilets, and a 28-mile railway carried the stone; when the works finished the trackbed became a walking and cycling route.
The five dams
Four dams were built on the Elan in the first scheme. Caban Coch, begun in 1893 and first flooded in 1896, is the lowest and largest sheet of water, holding around 35,530 megalitres across some 606 hectares. Above it, Garreg Ddu is the oddity: a submerged dam whose masonry arches carry the road across the lake but whose real job only shows in a drought, when it holds back enough water to keep the aqueduct running. Then come Pen y Garreg at roughly 6,055 megalitres and Craig Goch, the highest and the most photographed, at about 9,220 megalitres, its curved crest and little arched parapet standing over the top of the valley.
The fifth dam is a different generation. Claerwen, in the side valley to the west, was built between 1946 and 1952 and opened by Queen Elizabeth II; at around 48,694 megalitres it holds more than all four Elan dams together, taking the system to roughly 100,000 megalitres. It is faced in stone to match its Victorian neighbours, so most visitors never guess it is fifty years younger.
The visitor centre, and what is there now
The Elan Valley Visitor Centre sits below Caban Coch dam at Elan Valley, Rhayader, Powys, LD6 5HP, telephone 01597 810880. It is run by Dŵr Cymru Welsh Water, which also established the Elan Valley Trust to look after the estate’s long-term conservation. Welsh Water’s own site gives it as open daily except Christmas Day, with an information desk, an exhibition on the valley, a dog-friendly café, a gift shop, toilets, free wifi, a cycle hub with bike hire, room hire and an adventure playground. Opening hours are not published on the page, so ring ahead if you are relying on the café — and note that road closures do happen for events; the Rali Ceredigion has closed roads around the valley for a weekend in the past.
From the centre, the Elan Valley Trail runs 6.2 miles (10 km) up the line of the old Birmingham Corporation Railway to Craig Goch, past Garreg Ddu and Pen y Garreg. Welsh Water describes it as easy, mostly flat and suitable for all users including wheelchairs and pushchairs, tarmac for the first mile to Garreg Ddu and track beyond, about three hours each way on foot. It crosses and shares the road in places, so care is needed at busy times — but it is far and away the best way to see the dams without driving between them.
One of the darkest skies in Wales
In 2015 the Elan Valley estate became an International Dark Sky Park — the first privately owned one anywhere — covering 180 square kilometres, with a quality lighting plan to keep it that way. It sits between the Bannau Brycheiniog dark sky reserve to the south and Eryri to the north. In practice that means arriving before dark, parking somewhere legal and signed rather than on a verge, and taking a torch and warm clothing. The road home over the mountains after dark is a different proposition from the road out in daylight, so if you plan to stargaze, plan to return via Rhayader.
The road round the reservoirs
The valley road from Rhayader up past Caban Coch, across the Garreg Ddu arches and on beside Pen y Garreg to Craig Goch is narrow but two-way for most of its length, with gates, cattle grids, sheep on unfenced verges and many blind bends. It is well used by cyclists — the dams are a fixture of Mid Wales road cycling — and by walkers crossing between the trail and the road. Beyond Craig Goch the tarmac continues to Pont ar Elan and becomes the single-track Cwmystwyth crossing. Caravans and motorhomes are fine along the valley road but should turn back rather than continue over the mountain; our practical page sets out why.
Practical Information
Reach the Elan Valley from Machynlleth either via Llanidloes and Rhayader, or over Cwmystwyth from Devil’s Bridge; allow a full day either way. Check current visitor centre opening and any event road closures with the Elan Valley website first. There is no fuel in the valley — Rhayader is the place for that. The reservoirs are working water supply, so keep to paths, roads and car parks and away from dam structures and open water. In winter the upper valley is exposed and the mountain crossings can be impassable. More routes on the driving routes hub.
Day trips