Impact of rainfall variability on sedimentary and hydropower dynamics in a dam reservoir of southern France (1950-2023 )

Hydropower is the leading renewable energy technology, yet its vulnerability to combined environmental factors, particularly in the context of climate change, remains understudied. While the effects of climate change on hydropower are well-documented, research addressing the interplay between precipitation variability, sediment dynamics, and their effects on hydropower operations is lacking. This study investigates these interactions in the French Mediterranean region, with a focus on the Mont d’Orb dam reservoir.

An integrated approach was adopted and consisted of three main steps: (1) a sediment core analysis, relying on the establishment of an age model based on fallout radionuclide measurements, was conducted to reconstruct the influence of extreme rainfall events on sediment yield; (2) precipitation data from weather stations were statistically analyzed to identify temporal trends and shifts; and (3) dam water level and hydropower data, supplied by the operator, were analyzed to assess the combined effects of sediment accumulation, precipitation variability, and water level changes on hydropower generation.

The results show that extreme rainfall events contributed 20–60% of the annual sediment yield. While annual precipitation trends since 1950 showed no statistically significant changes, a seasonal shift in precipitation patterns was detected. Although sediment accumulation is currently not a primary constraint to hydropower generation due to reservoir management strategies, it may pose a long-term risk to storage capacity and turbine operation as it approaches critical levels. These findings highlight a critical gap in sediment management practices and emphasize the need for developing strategies to adapt to the currently changing climatic and hydrological conditions. This study highlights the necessity of integrating sediment and precipitation variability into hydropower planning to ensure its long-term sustainability in a context with an increasing frequency of droughts and extreme rainfall events exacerbated by climate change, particularly in the Mediterranean region.