Lac de Chalain

Lac de Chalain is a glacial lake in the Jura department of France. It lies wholly within the commune of Fontenu, near Marigny and Doucier, in the region of Bourgogne-Franche-Comté.
Pre-historic pile-dwelling settlements found at its western end—and at nearby Grand Lac de Clairvaux—have been classified as French historical monuments since 1911 and were added to the UNESCO World Heritage List in 2011.

Geography

The lake is the largest natural lake in the department. Its 60- high limestone cliffs frame a roughly rectangular body of water long, wide and in places more than deep.
It occupies an east-west oriented reculée that opens into the Combe d'Ain. The natural spillway forms the Bief de l'Œuf, which drives a small hydro-electric turbine before joining the river Ain.
Karstic springs feed the lake from the higher plateaus and from the lakes of Narlay and Vernois.

History

Systematic archaeological excavations began in 1904 and resumed in the 2000s, reveal a continuous human presence from 4000 BC to 750 BC. A large collection of artefacts are held at the Musée d'Archéologie du Jura in Lons-le-Saunier. The most notable is a long dugout canoe dated by dendrochronology to 959 BC.
Lowering water levels in 1904 exposed the site but destroyed perhaps two-thirds of the Neolithic layers. Subsequent agriculture, drainage and tourism have further damaged the remains. The archaeological zones were protected in 1992 and given UNESCO recognition in 2011.
A hunting lodge was built in the 13th century, remodelled in the 16th and 18th centuries, and abandoned after a fire in August 1945. In the 1960s, the ruins and estate passed to the Jura department.

Ecology

The central shores expose marl sediment which supports rare calcicole plants that are strictly protected. Access is prohibited to prevent trampling.
In 2022, the departmental council closed the lakeside campsite and stopped the annual artificial draw-down to address eutrophication.