In France, the drought system cuts across two different administrative structures: 

• The water management structure, which follows the geographical limits of the watersheds, a homogeneous unit from the point of view of water,
• The alert structure, which follows the administrative boundaries of the state organization: the Departments.

When a water shortage is felt in a watershed, each concerned Department issues a decree to restrict water uses. This decree is issued by the Prefecture, and sent to all the mayors concerned.

Example of an overlap map between the Watershed and the Department

(source: https://www.eau-poitou-charentes.org)