Gualbert Oude Essink (Civil Engineering, Delft University of Technology, The Netherlands) is specialist at Deltares, Unit Subsurface and Groundwater Systems, and associate professor at Utrecht University. His expertise is on modelling of variable-density groundwater flow and solute transport under palaeo, flooding, drought and global & climate change conditions. Gu combines innovative monitoring techniques with state-of-the-art modelling leading to new tools for better assessing freshwater availability. He has been involved in European water projects such as Crystechsalin, CliWat and Climate Proof Areas. Gu participates in research projects on vulnerable freshwater resources in the Netherlands (NatureCoast), Egypt (GERD, Nile delta), Singapore, Bangladesh (SWIBANGLA) and Vietnam (UDW Rise and Fall). He leads a Dutch Aquifer Storage & Recovery consortium on promising solutions for local freshwater supply to reduce drought and salinity stresses (www.GO-FRESH.info). Gu participates in the programs FRESHEM Zeeland and Flanders Belgium (Helicopter Electromagnetic survey for fresh-salt groundwater distribution), NWO-STW Water Nexus (project Resource analysis and regional water management), COASTAR consortium, NWO New Delta research "Fresh groundwater reserves in 40 major deltas under global change" and Wetsus project 'groundwater velocity monitoring techniques'. He gives courses and lectures, teaches at UNESCO-IHE Delft, publishes in journals and supervises seven PhD-candidates.