Recent advances in the use of process-based groundwater vulnerability for risk mapping

Groundwater vulnerability and hazard maps are often combined to produce GIS-based cartographic representations of the risk of groundwater pollution in studied aquifers. Results remain however often quite subjective for two main reasons. First, identification, in the investigated catchment, of anthropogenic activities often requires a combination of heterogeneous sources of information. Their classification in terms of the potential hazard they induce for groundwater quality remains subjective. Second, most of the time, groundwater vulnerability maps that are used for this combination are often based on relatively empirical approaches, with the combination of different factors using rating and weighting methods. These factors are also often implicitly interdependent which is not so consistent for evaluation methods based on multi-factor indicators.

Here, we take advantage of the process-based groundwater vulnerability Apsû method (Popescu et al. 2019) to develop a more rigorous methodological framework for the integration of groundwater vulnerability and hazard maps into sound risk assessment maps. We show with examples that the different process-based criteria that are the basis of the Apsû method for intrinsic vulnerability mapping (travel time to groundwater) and specific vulnerability mapping (relative quantity of pollutant reaching the saturated zone or water table) can be used to elaborate efficient decision support maps for land use planning and groundwater protection. We also propose a new concept of “aquifer scale protection zone” and a screening approach that allows restricting the use of targeted hazardous substances in specific areas of the groundwater catchment zone where they show elevated risks of groundwater pollution.

The proposed concepts and methodology are illustrated using a mixed urban – agricultural catchment in the Walloon region of Belgium.

Ref : Popescu, C., Brouyère, S. and A. Dassargues, 2019. The APSÛ method for process-based groundwater vulnerability assessment. Hydrogeology Journal 27(7): 2563-2579.