Lac du Val-Joly, Artificial lake in the Avesnois, Nord, France

Lac du Val-Joly is an artificial lake near the Belgian border in northern France, set within a natural park. The water is surrounded by forests and rolling green hills, with walking paths along the shores and spots for observing wildlife.

Work on the dam began in 1966 and the lake was filled in 1969, flooding the valley of the Helpe Majeure at Eppe-Sauvage. The 18-metre-high, 315-metre-long reinforced concrete dam holds 4.5 million cubic metres of water. The reservoir was made to regulate the river and to cool the EDF thermal power station at Pont-sur-Sambre.

The lake's name comes from the Val-Joly forest and estate; since 2008 the departmental park has been a tourist resort. Anglers fish for carp, pike and zander, and the lake is restocked regularly, with over a tonne of roach and 200,000 fry added in 2002 alone.

The lake lies in the Helpe Majeure valley at Eppe-Sauvage, 2 km from the Belgian border, with 19 km of shoreline shaped by the old river bed. The dam is 18 m high and 315 m long. The water is hypereutrophic, with summer cyanobacteria and low oxygen below 3 m, so check conditions before swimming.

The lake's water is held by a single reinforced-concrete dam, 18 metres high and 315 metres long, built in the 1960s. It was also meant to supply cooling water to the former EDF thermal power station at Pont-sur-Sambre, not to generate electricity. The reservoir holds 4.5 million cubic metres.