The process of siltation occurs when fine particles, such as silt and clay, accumulate in the gaps of a riverbed or ground, blocking the natural flow of water and air. This phenomenon has been ongoing in the Durance River for nearly 70 years, since the construction of the Serre-Ponçon dam in 1957. This siltation is threatening the survival of the brown trout, a native fish species that traditionally lays its eggs in gravel nests. Over time, the accumulation of fine material has turned parts of the riverbed into what experts call "aquatic deserts," where the necessary conditions for trout reproduction are no longer met. The fine sediments clog the gravel, blocking the flow of oxygen that the eggs need to survive, often leading to their suffocation before they hatch. The Serre-Ponçon dam, completed in 1957, was a remarkable feat of engineering at the time, standing 123.5 meters high and capable of storing over 1.2 billion cubic meters of water. It was built to provide water and electricity to the region, and it remains one of France’s largest hydroelectric structures. However, the dam has also drastically altered the natural flow of the Durance River and its tributary, the Verdon. By capturing most of the river’s flow and redirecting it through canals and hydroelectric plants, EDF (the French electricity company) has significantly reduced the water volume and hydraulic force downstream of the dam. This change has disrupted the river’s natural ability to transport and redistribute sediments, which are vital for maintaining the riverbed’s structure and supporting aquatic life. In response to this ecological challenge, EDF has implemented targeted water releases, intended to mimic the cleansing effects of natural floods by flushing out accumulated silt. However, the Durance River presents unique difficulties due to its geology. The river’s tributaries drain areas rich in marl, a type of soft rock that easily breaks down and releases a large amount of fine sediment. This high sediment load makes it difficult to control siltation, and in some cases, the water releases may actually deposit more fine material than they remove. As a result, the riverbed continues to degrade over time, with the fine particles blocking the tiny channels through which water and oxygen once flowed freely. The impact on the brown trout is particularly concerning, as the species relies on clean gravel for reproduction. Female trout dig nests in the riverbed, laying their eggs in these basins before covering them. For the eggs to develop, a continuous flow of water must pass through the gravel, delivering dissolved oxygen. When silt clogs the gravel, this flow is blocked, and the eggs suffocate. To monitor this issue, scientists have installed measuring stations along the river, conducting topographic surveys before and after water releases to assess their impact on the riverbed’s quality. These efforts are part of a broader challenge faced by river managers across France, who must balance the need for hydroelectric energy with the preservation of aquatic ecosystems. The Durance River has become a case study in this complex relationship, highlighting the need for sustainable solutions that support both human needs and the natural environment.