Lac de Villerest, reservoir in France

Lac de Villerest is a 770-hectare reservoir on the Loire upstream of Roanne, held back by a dam at Villerest and Commelle-Vernay. It runs 36 km through a valley between green hills, with a small cluster of pale buildings on the left shore and a low promontory ending in a single small tree on the right. A dark metal railing crosses the foreground.

Construction of the Villerest dam began in 1976 and the structure entered service in 1985, creating the reservoir on the Loire upstream of Roanne. The dam stands on the communes of Villerest and Commelle-Vernay. Its main purpose is to cut flood peaks and support low flows downstream, in conjunction with the Naussac dam; hydroelectric production is secondary.

The lake's name comes from Villerest, the commune where the dam stands with Commelle-Vernay. Each year in mid-June the Roanne-Villerest Triathlon is held here; its 2013 edition was the 28th. The Villerest beach has supervised swimming in summer, water activities, mini-golf and a playground.

Free parking is available near the lake and local buses provide access for those without a car. The swimming season works best in summer when water is warm and supervised, while walking trails remain accessible year-round for visitors of all abilities.

Fishing is restricted here: the Loire water is polluted enough that selling the catch is banned and eating it is advised against, as noted in 2008. The reservoir's main job is flood control and low-water support for the downstream Loire, working together with the Naussac dam; hydropower comes second.