Hydrographic sub-sectors — Metropolitan 2016 — BD Carthage

The hydrographic breakdown is the four hierarchical partitions of the French territory carried out according to decreasing hydrographic areas:
— hydrographic region (1st order),
— hydrographic sector (2nd order),
— hydrographic sub-sector (3nd order),
— hydrographic area (4nd order).
One sector is cut into a maximum of 10 sub-sectors and one subsector is divided into a maximum of 10 hydrographic areas.

The definition of sub-sectors and their boundaries is the responsibility of the Water Agencies.