Managing Freshwater Lenses in a Dutch Coastal Setting

Farmers in the coastal area of Walcheren, the Netherlands are faced with issues of saltwater intrusion and summer drought. These coastal areas are naturally brackish-saline environments due to Holocene marine transgressions. Farming in these coastal areas relies on the existence of freshwater lenses that float on top of saline groundwater. These freshwater lenses are much smaller than what is typically found in the dunes and are the product of the balance between infiltrating rainwater and saline seepage. This research provides an investigation into the hydrology of the dune area between Oostkapelle and Vrouwenpolder and the freshwater lenses found on the farmlands using geophysical methods and density dependent groundwater flow and solute transport modeling with the numerical transport code MOCDENS3D. The model is further used to test the feasibility of shallow phreatic Aquifer Storage and Recovery (ASR) scenarios. The findings of this research outline a low cost and effective way to store water for later use such as in dry summer months with ASR and has great potential to help coastal farming and irrigation practices in similar coastal settings around the world.