Another hydroelectric power station authorized on an ecologically sensitive river

On May 14, 2025, the Lyon administrative court of appeal validated the construction of a hydroelectric power plant on the Sallanche river, a tributary of the Arve (in Haute Savoie). FNE had challenged the prefectoral environmental authorization order in 2019, as the project threatened this river, classified as a biological reservoir, and diverted more than half the water flowing into the Sallanche. This ruling follows an initial decision by the Grenoble Administrative Court on December 6, 2022, which had initially annulled the project’s authorization precisely because of the risks it posed to the ecosystem.

FNE AURA (France Nature Environnement AUvergne-Rhône-Alpes), notes that this decision leads to a further artificialization of waterways, a phenomenon that is at the root of the difficulties in achieving good ecological status for rivers. Indeed, more than half the rivers in the Rhône-Méditerranée basin are in unsatisfactory condition, and many rivers already modified by artificial developments are struggling to maintain balanced biodiversity.

In legal terms, the administrative court of appeal adopted a different interpretation of current legislation, in particular article R214-109 of the French Environment Code. Unlike the Grenoble administrative court, it did not consider that the planned diversion would significantly affect the hydrology of the river, even though the latter is classified as a biological reservoir.

The court therefore overturned the Grenoble administrative court’s ruling and validated the prefectoral decree of December 26, 2019 authorizing the project.

This ruling reflects continuing legal uncertainty, particularly after a legislative attempt in 2019 to simplify the interpretation of rules on the protection of biological reservoirs. However, the Conseil d’État overturned this amendment and favors a case-by-case approach, leading to the risk of contradictory decisions and increasing legal uncertainty for the protection of biodiversity.Yet another hydroelectric plant authorized on a River with high ecological stakes.

More info :

Cour administrative d’appel de Lyon :
https://www.actu-environnement.com/media/pdf/jurisprudence/57.pdf

FNE :
https://www.fne-aura.org/communiques/region/centrale-hydroelectrique-de-sallanches-un-pas-de-plus-vers-la-degradation-de-nos-cours-deau/