Delineation of groundwater protection zones based on tracer tests and transport modelling in alluvial sediments

Regulations aiming to protect exploitable groundwater resources were edicted in Belgium a few years ago. Therefore, prevention and protection zones are defined by law and must be determined practically around each pumping well or spring, based on local hydrogeological conditions. The determination of hydrodynamic and hydrodispersive parameters, characterizing the local flow and transport properties of the aquifer, requires pumping and tracing tests. The interpretation of these field experiments, considering the heterogeneity of the geological layers, is performed through the use of numerical FEM simulations of the groundwater flow and pollutant transport conditions in a deterministic framework. After calibration of the model on experimental measurements, multiple simulations with contaminant injections at various points of the modeled domain allow the determination of the transfer time of the pollutant in the studied aquifer whilst taking the updated heterogeneity into account. On the basis of the computed transfer times in the saturated zone, the various prevention and protection areas can be assessed based on provisions of the law.