Restore ecological continuity
Almost 60 000 obstacles, including dams, locks, weirs and mills no longer in operation block rivers in France. They are the cause of major transformations in the morphology and hydrology of aquatic environments and have a negative impact on aquatic life and sediment transport in rivers. They constitute insurmountable obstacles for aquatic organisms that must however be capable of moving freely to access the zones required for their reproduction, growth and feeding. For migratory fish, those zones range from the oceans to far up rivers. Approximately 2 000 obstacles are used for electrical generation, but the vast majority serve no clear purpose.
Reductions in the ecological continuity of rivers compromise efforts to achieve good ecological status of aquatic environments, the goal set by the WFD. That is why French and EU regulations (WFD, Water law, national eel-management plan, Grenelle environmental law, national restoration plan) now make it mandatory to restore the ecological continuity of aquatic environments. They collectively require that water stakeholders increase their efforts and projects in favour of restoration.
Today, the priority is to inventory all existing obstacles, identify the most serious, encourage the creation of public management systems to eliminate abandoned installations and ensure enforcement of regulations in protected rivers. This is a vast project in which Onema has a major role to play, in conjunction with the Water agencies and State services (DREAL, DDT) and interfacing with local stakeholders.