GQ10: Groundwater Quality Management in a Rapidly Changing World (Proc. 7th International Groundwater Quality Conference held in Zurich, Switzerland, 13–18 June 2010). 50 A regional flux-based risk assessment approach of contaminated sites on groundwater bodies S. BROUYERE 1 , P. JAMIN 1 , F. DOLLE 1 , B. CHISALA 1,2 , PH. ORBAN 1 , I.-C. POPESCU 3 , C. HÉRIVAUX 4 & A.DASSARGUES 1 1 Université de Liège, Fac. Applied Sciences, Dpt ArGEnCo, Geo³-Hydrogeology and Aquapôle Research Centre, Building B52, 4000 Sart Tilman, Belgium Serge.Brouyere@ulg.ac.be 2 University of Sheffield, Groundwater Protection and Restoration Group, Kroto Research Institute, University of Sheffield, Broad Lane, Sheffield S3 7HQ, UK 3 Service publique de Wallonie, DGARNE-DGO3, Division de l'Eau, Direction des Eaux Souterraines 4 BRGM (French Geological Survey), Water department, 1039 rue de Pinville, 34000 Montpellier, France. Abstract In the context of the Water Framework Directive, management plans have to be set up about water quality issues in surface and ground water bodies in the EU. In heavily industrialised and urbanised areas, the cumulative effect of multiple contaminant sources is likely to present a risk which has to be evaluated. In order to propose adequate measures, the calculated risk should be based on criteria reflecting the risk of water quality deterioration, in a cumulative way and at the scale of the whole surface water or groundwater body. An integrated GIS- and flux-based risk assessment approach for groundwater and surface water bodies is described with a regional scale indicator for the evaluation of the quality status of the groundwater body. It is based on the SEQ-ESO currently used in the Walloon Region of Belgium which defines, for different water uses and for a detailed list of groundwater contaminants, a set of threshold values reflecting the levels of water quality and degradation with respect to each contaminant. The methodology is illustrated with a first real scale application on a groundwater body corresponding to a contaminated alluvial aquifer which has been classified at risk of not reaching a good quality status by 2015. Key words regional risk assessment, groundwater body, industrial contaminants, Water Framework Directive, megasite INTRODUCTION The EU Water Framework Directive requires management plans about quality of surface and groundwater bodies. These plans can not be defined without considering contaminated industrial sites potentially harmful for water resources. Each single site does not necessary constitute a threat for the whole aquifer or the groundwater body. However, in heavily industrialised and urbanised areas, because of the spatial extent of groundwater bodies, many contaminant sources are likely to be considered with complex groundwater vectors for contaminant dispersion. In such a context, a meaningful regional risk assessment approach has to be developed (e.g. Critto & Sutter 2009), considering the cumulative effect of multiple contaminant sources. At the same time, all the spatially distributed data require GIS databases and decision tools.