Présentations Colloques

In the early 1980's, hydrological research at the Belgian Nuclear Research Centre was initiated. Although the research was initially conducted in the framework of the Belgian nuclear waste disposal programme, currently managed by ONDRAF NIRAS, the most recent groundwater model update (2016) frames within the responsibilities of the Flemish Environment Agency with respect to groundwater management. **In the 35-year research period, most efforts have been put to characterizing the groundwater flow using piezometric measurements, collecting measurements of hydraulic properties, defining the hydrostratigraphy and integrating all information by means of groundwater flow modelling. By formulating a conceptual model, the latter method combines the measured data with general hydrogeological knowledge and hypotheses on the aquifer system. Therefore it can be used to discover knowledge gaps and gives way to new data acquisition followed by another modelling step. This iterative research cycle allowed increasing our level of knowledge while decreasing the level of uncertainty on the prediction of necessary indicators related to the aquifer systems. **In this work, the evolution of the hydrogeological knowledge - both data and modelling efforts - in the confined aquifers in N-Belgium is presented, which are being heavily influenced by groundwater (over)exploitation. **A thorough understanding of the phenomenology and the past evolution of this hydrogeological system in N-Belgium will facilitate simulating realistic future behaviour under different scenarios. In the case of deep geological disposal, this includes assessing the consequences that climate changes may have on the hydrogeological system (e.g. warming in combination with marine transgression, cold climate with permafrost). In the case of the groundwater policy, this includes assessing the consequences of historical long-term groundwater extraction on the confined aquifer systems and assessing the impact of alternative future exploitation scenarios on the quantitative status of these groundwater bodies. **