The Ain River hydropower chain is one of France’s most strategically important systems for energy production and water resource management. It stretches approximately 60 km along the Ain River and includes six main installations. Among them are the Saut-Mortier reservoir and Vouglans dam.
Even before ReHydro, EDF has been working to modernize this hydropower system and enhance its flexibility. The focus is on transforming the Saut-Mortier reservoir into a pumped-storage hydropower facility capable of storing and releasing energy on demand. Additionally, the 40 km stretch of the downstream river is included in the impact assessment.
Now, the project team has begun the first phase of studies to support this transformation. Retrofitting the site with variable-speed reversible generating and pumping units will allow for better use of water, improved response to grid needs, and reduced environmental impacts, including lower hydropeaking intensity, better temperature regulation, and more controlled algae growth through managed water releases.
To support this work, EDF has been improving and testing detailed 1D and 3D models of the reservoir system. These models simulate how temperature and water flow interact under different operational scenarios. By consolidating them into a fully 3D digital twin, we now have a more accurate representation of spatial thermal processes and vertical stratification.
With the groundwork done, the follow-up goal is to qualify the “environmental sensitivity” of each reservoir, which describes their response to changes in weather, flow, and temperature. To support this, a semi-automated simulation tool has been created to test large sets of operational scenarios and connect multiple reservoirs within the system. The first flow-temperature scenario series for the entire reservoir chain is already in development.
These early studies lay the foundation for a smarter, more climate-resilient hydropower network. By linking ecological knowledge with flexible infrastructure, the Ain River system is becoming a model for modern river basin management under changing climate conditions.
You can read more about EDF’s long-term work on the Ain River in the publicly available paper “Initial studies for retrofitting pumped storage”.