Barrage de la Bathie

Barrage de la Bathie is a major gravity dam located on the Isère River in the Savoie department of the French Alps. It forms the central storage reservoir for the vast hydroelectric complex known as the Usine hydroélectrique de la Bathie, which is a key component of the Compagnie Nationale du Rhône's energy network. The dam's primary role is to regulate water flow for power generation at downstream plants, significantly contributing to the Électricité de France's renewable energy portfolio in the Auvergne-Rhône-Alpes region.

History

The project was conceived in the early 20th century as part of a broader national effort to harness the hydroelectric potential of the Alps. Construction began in the 1930s under the direction of the Compagnie des forces motrices de la Haute-Isère, a precursor to modern French energy entities. Its development was closely tied to the industrialization of the Tarentaise Valley and the growing energy demands of nearby cities like Chambéry and Grenoble. The dam was completed and inaugurated in the years following World War II, representing a significant achievement in post-war French infrastructure and engineering.

Technical specifications

The structure is a classic straight gravity dam, constructed primarily from cyclopean concrete. It stands approximately 104 meters high and has a crest length of 240 meters. The reservoir, Lac de la Bathie, has a storage capacity of around 40 million cubic meters, covering a surface area of nearly 80 hectares. The dam's spillway is a controlled ogee crest type, designed to safely manage extreme flood events from the mountainous Isère catchment. Its foundation rests on solid gneiss and schist bedrock, typical of the geological formations in the Belledonne massif.

Construction and engineering

The build site presented formidable challenges due to the rugged terrain and harsh alpine climate of the Beaufortain region. Engineers employed innovative techniques for the era, including extensive use of cableways for transporting materials and a large workforce housed in temporary camps. The project required the diversion of the Isère River through a system of cofferdams and tunnels during construction. Key figures from the Corps des Ponts et Chaussées oversaw the design, ensuring it met rigorous safety standards for withstanding high seismic activity in the Alpine orogeny zone.

Operation and purpose

The dam's primary function is to provide seasonal water storage and flow regulation for a cascade of hydroelectric power stations downstream, most notably the underground Usine hydroélectrique de la Bathie. This plant, operated by Électricité de France, has a substantial installed capacity and plays a crucial role in meeting peak electricity demand and providing grid stability. The stored water is also used for compensating low-flow periods in the Isère, supporting other power facilities operated by the Compagnie Nationale du Rhône further downstream in the Rhône valley.

Environmental and social impact

The creation of Lac de la Bathie permanently altered the local landscape, submerging sections of the valley and affecting terrestrial ecosystems. It has influenced sediment transport and water temperature regimes in the Isère River downstream. The project required the displacement of some agricultural land and led to significant demographic changes, bringing an influx of workers and later supporting tourism related to the reservoir. While providing clean energy, it remains a point of discussion regarding the balance between renewable energy development and the preservation of alpine environments in regions like the Parc national de la Vanoise vicinity.

Category:Dams in France Category:Buildings and structures in Savoie Category:Hydroelectric power stations in Auvergne-Rhône-Alpes