To run a water mill in France to generate electricity you need a water right (droit d’eau) and an autorisation for exploitation (autorisation d’exploiter). Both are issued by the DDT (Direction Départementale du Territoire) in the department in which the mill is situated. The waterright tells you, the mill is entiteled to use water from the river to generate power. The autorisation for exploitation will tell you under which supplemantary requirements. The water right is both a recognition of the right itself as the voume, head and the amount of water that should run though the original river bed (débit réservé) When you want to sell the electricity to the grid, ENDIS will ask for these documents. Even without delivering to the grid, these documents are compulsary and they detemine a part of the value of your mill.

The water right is part of an object (i.e. a water mill), not bound to a person and not tranferrable without the mill. You as an owner should be able to prove your water right to the authoroties. There is a difference in the water rights from before the French revolution (1789) and after the French revolution. Before the French revolution water rights were issued by the crown. When you want tot prove your mill had a water right before the French revolution, you can use the Cassini map. When your mill is on that map, it is convincing evidence. Beside that, the mill should be still there. A ruin has less chance to get the water right confirmed than a mill with a roof. Other proof can be found in the departeental archives. Usually you can find information about the type of mill and what it was used for. This is important for the specification of the water right.

To specify your water right you need to indicate head and volume. Beside that you need to propose the volume that has to flow in the orginial river bed. Sometimes the DDT has these figures, or a part of it. When not, you can use the information from the archives to prove what the function was, how made wheels were there, etc. With these figures and the fysical situation, you can determine what the head and the power should haven been. Based on that and an estimation of the efficiency, you can prove the volume. To propose the volume that has to flow in the orginial river bed you can use the hydrological data that is published on www.vigicrues.gouv.fr.

When the water right, including head, volume and the water flow through the orignal river bed is acknowledged, you can ask the DDT for an "autorisation d’exploitation".