How did reservoirs and locks improve navigation between Lyon and the Mediterranean Sea?

To improve navigation between Lyon and the Mediterranean Sea, the Rhône River underwent extensive engineering modifications to overcome its natural gradient and shoals. These improvements replaced the river's original slope with a series of level reaches and locks, which allow vessels to transition safely between different water levels.1

Additionally, dams were constructed to create reservoirs that submerged hazardous shoals, providing a deeper and more consistent channel for transport. These locks are often integrated with hydroelectric dams, such as the one at Donzère-Mondragon, which features a significant depth of 24 meters (80 feet) to accommodate modern shipping requirements. By bypassing difficult sections with canals and regulating the flow through these structures, the river has been transformed into a reliable transportation funnel between northern and southern France.12