Vidange du Rhône 2021
A few weeks ago, the Vidange du Rhône (or Chasses du Rhône, meaning Flushing of the Rhône) took place between Barrage de Génissiat (Genissiat Dam) in France and Barrage de Verbois (Verbois Dam) in Geneva. Both the CNR (Compagnie Nationale du Rhône), which manage the dams on the French side, and the SIG (Services Industriels de Genève) cooperate on this operation: It is performed every few years in order to purge sediments brought into the Rhône river by the Arve, which accumulate and increase the risk of floods.
For a few days, the dams in the area are opened and their reservoirs emptied, in order to increase the discharge rate with the goal of flushing the sediments from the river bed. The river then turns gray, just like the Arve. Another side effect is that the level of the Rhône is lowered, almost as low as before dams were built along the river so it becomes quite the view. One other, less happy, consequence is that it is a bit of a fish apocalypse, with many of them dying because of the increase in solids suspended in the water.
I went to see this phenomenon in the area around Bellegarde-sur-Valserine, first in Éloise near Pont de Grésin, as part of a hike. Then a few days later, I visited Bellegarde itself just for this purpose and walked along the Rhône. Because of the the Corona restrictions on border crossings, unfortunately, I couldn’t visit the area upstream of the Verbois Dam in Geneva.
