Evaluating the risk of groundwater pollution through the combination of hazards and groundwater vulnerability maps

The objective of the MSc thesis is to develop a systematic framework for groundwater pollution risk evaluation starting from the groundwater vulnerability maps of Wallonia developed through a GIS-based interface. The aim is rather to conduct a first assessment, that could trace the path for further application and be integrated in the existent Apsû methodology for vulnerability assessment. The first phase of the study consisted in undertaking a literature review on regional risk assessment procedures in the other countries and regions of the world, in order to identify the best approach to apply in Wallonia: the “European Approach” is selected. The probability that, following the occurrence of a hazardous event on the surface of the soil, the contamination could reach the water table and have a serious impact on the groundwater status is evaluated. To do so, data on potential pressures on soil is collected, to create an Hazard map. The risk assessment is carried out on a regional scale for groundwater body RWM040, combining the created Hazard Map, Intrinsic Vulnerability map and Consequences. The selected groundwater body has been subject of several studies, due to the peculiar features of the chalks aquifer (e.g. double porosity and dry valleys), that enhance the risk of groundwater pollution. Furthermore, the area, harshly affected by nitrates and pesticides pollution linked to the extensive agricultural practices, is a perfect site to test the strength of the developed method.