PROPOSAL FOR THE DELIMITATION OF SURFACE WATER BODIES IN THE FRENCH PART OF THE SCHELDT DISTRICT Dans la Directive Cadre, la qualité écologique est le concept le plus important pour les cours d ’eau. On y parle de : physicochimie : SEQ EAU biologie : SEQ BIO hydrobiologie : SEQ physique Les couleurs sont au nombre de 5, comme dans le SEQ avec le vert en objectif La Directive Cadre impose une mesure de l ’écart à une référence On verra comment le SEQ EAU y répond

Methodology used for inland surface water bodies delimitation Main principles Analysis of system A: incoherences (same references for Northern and Southern France) Choice: system B CEMAGREF’s work on French hydroecoregions Voici en quelques lignes les grands traits de la Directive Cadre Sur les cours d ’eau on l ’a vu, on va se rapprocher du SEQ cours d ’eau Plans d ’eau et littoral : il existe 2 SEQ en cours d ’élaboration Eaux souterraines : il existe un SEQ réalisé.

Methodology used for inland surface water bodies delimitation Main principles Classification of streams according to Strahler ordination rather than the basin size (Strahler ordination is more pertinent for macroinvertebrates populations than basin size) Integration of fish contexts (areas inside which characteristical species (trout for salmonicol basins, pike for cyprinicol basins, barbel and dace for intermediates basins) achieve their whole biological cycle) Principle: a water body belongs to one single type

Methodology used for inland surface water bodies Practical application Work on main drains of hydrographical zones The small tributaries (Strahler ordination < 2 ) are included in the water body (It is considered than the main drain will be of good status if the small tributaries are of good status too) Nine hydroecoregions at level 2 in Artois-Picardie water basin Voici en quelques lignes les grands traits de la Directive Cadre Sur les cours d ’eau on l ’a vu, on va se rapprocher du SEQ cours d ’eau Plans d ’eau et littoral : il existe 2 SEQ en cours d ’élaboration Eaux souterraines : il existe un SEQ réalisé.

Methodology used for inland surface water bodies HYDROECOREGIONS DEFINED ACCORDING TO: Geology: - geological maps (calcareous, silicious substrata) - Lithology (permeability, resistance to erosion….) Climate: - annual precipitation - seasonal precipitation - phytoecological regions of Dupias and Rey Voici en quelques lignes les grands traits de la Directive Cadre Sur les cours d ’eau on l ’a vu, on va se rapprocher du SEQ cours d ’eau Plans d ’eau et littoral : il existe 2 SEQ en cours d ’élaboration Eaux souterraines : il existe un SEQ réalisé. Relief: - altitude - slope - density of river basin network

French hydroecoregions at first level At this level, only 3 hydroecoregions (HER) are identified in the French part of the Scheldt district. The second level has been adopted for more precizion (9 HER)

Artois-Picardie French Hydroecoregion at level 2

2 classes for the Strahler ordination (small streams for 2 and 3 orders; medium streams for 4 and 5 orders) have been created for simplification.

FISH CONTEXTS

63 INLAND SURFACE WATER BODIES for 20,000 km2

TYPOLOGY OF INLAND SURFACE WATER BODIES 13 types are identified

Water types and invertebrates : an example - Values have been proposed for IBGN (French macroinvertebrate index only for 2 HER (Calcareous substrata and Ardennes) : References concerning the IBGN index, Limits for very good/good status and good/medium status, - A cooperation with Belgium is needed for other ecoregions (polders, sands and argilous deposits), - No reference values can be proposed for level 2 HER (no sufficient data !)