Conceptual uncertainty assessment for a catchment scale model

Groundwater flow model of the Neogene aquifer system, representing an important water supply resource has been developed within the performance assessments studies of a geological disposal of radioactive waste in Belgium. In order evaluate the discrepancy between estimated parameter and a measured value of the Kasterlee Clay aquitard, uncertainty analyses were applied on three aspects of its conceptual model. These analyses included the parameterisation, geometry (thickness) of all units and the geometrical representation of the Kasterlee Clay. The results of the analyses showed that the conceptual model of the Kasterlee Clay should be reconsidered, allowing less resistance of the unit locally. To identify such places, further site investigation is recommended.