www.scaldit.org Characterisation of groundwater bodies in the Scheldt pilot river basin district Ph. Meus* ICS-SCALDIT, P08 « Groundwater » * Ministère de la Région wallonne, Direction générale des Ressources naturelles et de l’Environnement, Division de l’Eau, Direction des Eaux souterraines 8/1/2019

Pilot river basins Scheldt PRB 8/1/2019

Scheldt river basin and district 8/1/2019

Initial characterisation of GWB delineation of groundwater bodies inventory of pressures (-> impress group) general character of the overlying strata in the catchment area from which the groundwater body receives its recharge those groundwater bodies for which there are directly dependent surface water or terrestrial ecosystems GWBs at risk... 8/1/2019

French approach Criteria main aquifers, eventually aggregated hydrological/hydrogeological basins 8/1/2019

1st step delineation of systems Flemish approach 1st step delineation of systems main aquitards geographical Criteria Central flemish system Basement system Ypresian aquitard Basement + central systems 8/1/2019

2nd step: delineation of groundwater bodies Flemish approach 2nd step: delineation of groundwater bodies aquifers (high resolution) piezometric depressions Criteria GWBs Central system 8/1/2019

Wallonian approach Criteria main aquifers eventually aggregated, and productivity based! hydrological/hydrogeological basins 8/1/2019

Groundwater body delineation for whole district Scheldt district France Wallonia Flanders Carboniferous limestones GWBs Cretaceous chalk GWBs Eocene sands GWBs 8/1/2019

Delineation of groundwater bodies: an example of capture ? Jeker Fontijbeek Mombeek Demer Scheldt basin Meuse basin Wallonia Flanders -200 -100 100 200 5000 10000 15000 20000 25000 30000 35000 40000 afstand (m) hoogte mTAW 8/1/2019

Groundwater bodies characterisation: typology Country/Region Geological unit GWB name Identity Aquifer setting Aggregation? Aquifer type Lithologies Flow type 8/1/2019

Step by step, the impact assessment within the WFD Vulnerability mapping (2nd type map) Ex. higher concentration of NO3 -, reduced spring discharge Ex. charges of NO3-, high pumping rate Pressures Diffuse sources pollution Point sources pollution Abstraction Artificial recharge Source Target 1 Target 2 Groundwater body surface Groundwater body s.s. Pressures transfer through the unsaturated zone Recharge areas (1st type map) Pressures transfer through the saturated zone Changing state of GWB - trends By reference to thresholds, maybe an impact Pathway 1 Pathway 2 Ex. NO3- > 25 mg/l, insufficient discharge in surface water 8/1/2019

GWB vulnerability assessment 8/1/2019

Conclusion delineation of GWDs now fully achieved at the district scale this work has allowed criteria for characterisation of recharge zones evaluation of GWBs at risk characterisation of GW-SW interactions, as well as dependent ecosystems further characterisation will follow the new groundwater directive and appropriate guidelines 8/1/2019