Active role
The composition of river flow varies extremely between rivers worldwide. River runoff, for example, may consist mainly of recent rainfall, but also of water that had been in groundwater for many years. Research, published in Nature Geoscience, shows that groundwater has a much more active role for rivers than previous estimates suggested. ‘’Together with the research team we mapped the role of groundwater for river flow worldwide, and the implications this gives. For instance, the global computer models used to describe water cycles should be revised’’, Berghuijs explains.
Coupled systems
Such models, used for example in Intergovernmental Panel on Climate Change (IPCC) climate reports, often have disconnected groundwater and river water systems, but these will need to be explicitly linked. The study also highlights how groundwater and surface water are actually the same world. Often water management (legislation) considers these as separate entities, but this appears to be an outdated view.
Influence of groundwater
Groundwater use can directly have strong influences on river flow. For example, in river basins where groundwater is extracted, this sometimes leads to river discharges that are too low to keep their freshwater ecosystem healthy. At a smaller level, regional groundwater policies can have clear effects on the quality and quantity of river flow. These connections need to be recognised in jointly coordinating groundwater and surface water policies. Otherwise, both science and water management will be stuck with outdated policies and essential linkages between these two worlds will bring significant changes and challenges.
Groundwater research
The study, conducted by an international research team and led by a researcher from the Max-Planck Institute for Biogeochemistry in Jena, builds on previous groundwater research by VU Amsterdam earth scientist Wouter Berghuijs. As a hydrologist, Berghuijs works on aspects such as linking groundwater to climate change and flooding. The link between groundwater and surface water are the focus of two new projects. One supported by a Starter Grant from the Ministry of Education, Culture and Science and through the RESHAPE project funded by NWO-KIC.