Increasing challenges in solving hydrogeological problems require advanced modelling tools to provide insight into process understanding and system behavior. Applications include water supply and groundwater protection, contaminant transport and remediation, cryo-hydrogeology, waste storage and resource extraction, including mining and geothermal energy. These systems are often complex, involving multiple coupled processes in heterogeneous porous or fractured porous media. Modelling challenges include process representation, domain characterisation and parameterisation, balancing simplicity and complexity in conceptual models, and computational effort. This session targets innovative development and applications of numerical models to such challenging hydrogeological systems. We welcome contributions at the laboratory, field or basin scales, and from daily to seasonal to geological time scales. Contributions which address current societal and environmental challenges in hydrogeology including climate change are particularly welcome.