The overall scientific objective of the Hydrogeology Group (GHS) (“mission”) is to contribute to the good status of groundwater through increased understanding of aquifer processes, the development of tools and concepts for characterization and management, and the application of these tools and understanding to the solution of groundwater related societal problems. This overall goal is achieved through four basic research lines that address the hottest issues in groundwater hydrology and feed tools and concepts to applied lines. These lines are: Stochastics and heterogeneity; Transport; Modeling.The applied research lines are: NatureBased solutions for wastewater treatment; seawater intrusion and submarine groundwater discharge; hydrobiogeochemical tools; Groundwater resources management; porescale processes; circular economy, social considerations and Sustainable Development Goals.