Ain. Why is the level of the Rhône lowered in Bugey?

Ducks and swans on dry land are quite common. But ducks and swans on dry land in the middle of what is now the bed of the Rhône, much less so. Since May 15, the water level has been lowered voluntarily for the needs of an operation by the Compagnie Nationale du Rhône (CNR), the Société des Forces Motives de Chancy-Pougny (SFMCP), and the Services Industriels de Genève (SIG). They are coordinating a vast sediment management program.

The objective: to gradually transfer up to 1.5 million ^m3 of sediment, the equivalent of the volume of 600 Olympic swimming pools, stored in the Swiss Verbois dam reservoir.

Carried out every three to four years under the supervision of the Franco-Swiss authorities, this operation aims to prevent the risk of flooding in certain districts of Geneva, but also to promote the sedimentary continuity necessary for the life of the most powerful river in France.

The operation involves gradually and simultaneously lowering the level of the reservoirs at the Verbois (SIG), Chancy-Pougny in Switzerland (SFMCP) and Génissiat dams in Ain (CNR). At the same time, the CNR is carrying out specific operations on its five hydroelectric facilities located downstream, between Seyssel and Sault-Brénaz.

Until May 27, more than 400 people spread across the Geneva Rhône and the French Upper Rhône will take turns to manage and monitor the smooth running of the operation, carry out numerous environmental monitoring operations, and take samples to check the quality of the water and its sediment concentration.