A giant of the 1930s
Work began in 1929 and the dam came into service in 1934. It is a gravity dam: it holds back the water by its weight alone, 75 metres thick at the base and 225 metres long at the top. Together with the underground power station at Brommat, opened in 1933 by President Albert Lebrun, it then formed one of the largest hydroelectric schemes in Europe. Thousands of workers from all over Europe and North Africa laboured on it, and at least fifty of them lost their lives.
The lake covers about 1,000 hectares and holds nearly 300 million cubic metres of water. The power house at the foot of the dam now produces up to 183 MW. Sarrans is part of the chain of dams along the Truyère gorges, down to Couesques, below Valon.
The viewpoint and the power station tour
The dam's old lookout post has been turned into an open-air information area. Panels explain how the dam works, its history and the wildlife of the gorges, a Natura 2000 site. Access is free all year round, the viewpoint is wheelchair accessible, and there are picnic tables for visitors.
In summer, EDF opens the power station on Friday afternoons, in small groups of twelve for an hour and a half. You must book at least 48 hours ahead (+33 5 65 44 81 61), be at least 8 years old, and bring an identity document and closed shoes. To round it off, the open-air exhibition in the grounds of Brommat castle tells the story of how the dams were built between 1910 and 1934: it is free and open all year.
Tréboul, the village under the lake
In 1934, the filling of the lake drowned the farms at the bottom of the valley and the village of Tréboul, in the Cantal, along with its 14th- and 15th-century stone bridge. This two-arched bridge replaced a ford on an old Roman road and was long used as a toll point. It has been a listed historic monument since 1927. The small chapel nearby was taken down and rebuilt higher up before the valley was flooded.
The old bridge can only be seen when the lake is drained. That happened in 1979, and again from May to October 2014, to inspect the dam and dig a drainage tunnel at its base. The Truyère went back to its old bed, and visitors could get close to the bridge, the dry-stone walls and the remains of the houses. The rest of the time, you have to make do with the suspension bridge built above it in the 1930s, about 55 minutes from Valon.
Getting there
From Valon, allow 26 minutes (about 26 km) towards Brommat. The road runs along the top of the dam, between Brommat and Sainte-Geneviève-sur-Argence.
Our tip
On hot days, visit the viewpoint in the morning, then head off for a swim at the Laussac peninsula, on the same lake, ten minutes' drive away.