Regional groundwater flow and ecohydrology

The development of the theory, concepts and applications of groundwater flow systems, has had a tremendous influence on hydrogeologists' understanding of spatial and three dimensional groundwater flow relationships. The recognition of how groundwater connects locations across the subsurface, horizontally and vertically over longer and shorter distances, grew steadily over several hundreds of years but had a clear culmination with the landmark papers of Joe Toth. Toth also realised and indicated the importance of groundwater flow systems for different physical, chemical, geomechanical and ecological processes at the landsurface. As hydrogeologists are focused on subsurface phenomena, this link between groundwater flow systems and the landsurface has often been neglected or simplified as a result of our mostly mono-disciplinary approaches and research capacities. Increasing attention for interdisciplinarity, as e.g. in the research on groundwater-surface water interaction andecohydrology, offers new opportunities to use groundwater flow systems for improving our understanding of phenomena like occurrence of vegetation and their dependence on groundwater, but also how the vegetation influences the groundwater system. Connecting groundwater and landsurface processes, especially at groundwater dependent wetlands, might therefore be an eye-opener for both hydrogeologists and ecologists. In this presentation we will review from where we came with respect to groundwater systems and the groundwater dependent wetlands as well as what are open issues in research and how hydrogeologists can contribute to the relatively new field of ecohydrology. We will present examples, groundwater and vegetation modelling methodologies, results and lessons learnt from case studies in Belgium and Australia in which vegetation and groundwater flow and systems analysis go hand in hand. Scenario studies on the change of landuse, climate or drainage and their impact via groundwater systems on wetlands are evaluated.