Hydrographic areas — Metropolitan 2016 — BD Carthage

Circular No 91-50 of 12 February 1991 on hydrographic coding and spatial identification of surface aquatic environments in metropolitan France defines the hydrographic zone as follows: ‘The entire French territory is divided into elementary zones known as hydrographic areas. Their boundaries are based on those of the topographical catchment areas (in whole or in part).’ An area is a division of a subsector which may comprise up to 10. It is entirely within a river basin limit and serves, together with other elements, to delimit various programming or regulatory areas such as the Water Planning and Management Plans, sensitive areas and water bodies referred to in the European Framework Directive of 23 October 2000. A water catchment area covers, in part or in full, the territory of one or more municipalities. Conversely, the territory of a municipality is either fully included within a water catchment area or split into several zones. Different scenarios in the hydrographic zone may exist: a — The main watercourse of the hydrographic zone takes its source within the zone: It is an upstream area whose contour corresponds to that of the topographical catchment area of the main watercourse at the exit point of the area. b — The water catchment area is crossed by the main watercourse and the pk of the downstream point is not 1000: It is an intermediate water catchment area. c — The water catchment area is crossed by the main watercourse, the downstream point of which corresponds to pk 1000: This is the area downstream of the water catchment area, d — The hydrographic area is bordering the coastline. Three scenarios: * or is a main watercourse which has its source in the area: This is the case (a); * or this downstream zone is the last intermediate basin before the mouth of the main river: This is then the case (c); * or the area includes a linear line of the coastline with the mouth of the coastal river and areas drained by ‘rus’ flowing directly into the sea, e — The area does not have superficial run-off but is nevertheless a recipient of asleep watercourses located upstream. The list of hydrographic areas shows two special cases: — In order to avoid the creation of border river regions, five hydrographic zones on the border with Italy or Spain (codes Y670 and Y680 corresponding to two upstream ends of the Po basin, S910, S911 and S912) have been attached to the coastal river regions (S and Y codes) of the catchment areas on which they depend, Although the hydrographic logic is that zone U204 (Jougnena sub-basin belonging to the Rhine basin) should be attached to the Rhine-Meuse basin district, it is nevertheless attached to the Rhône-Médean-Corsica basin (Saône) given the small size of this area and its remoteness from the Rhine-Meuse basin, — Although the hydrographic logic would require the areas of sector D0 (the Sambre basin in France) to be assigned to Region B (Meuse basin), they are administratively linked to the Artois Picardie basin, given the remoteness of the Meuse and Sambre basins in France and the confluence of these two rivers which takes place abroad.