Investigation of Climate Change Impacts to the Coastal Aquifer of North Germany: A 3D Modelling Study

Abstract:

Climate change is expected to induce sea level rise in the German Bight, which is part of the North Sea, Germany. Climate change may also modify discharge of the river Weser flowing into the German Bight, which will alter both water levels and salinity distributions along the coast. To study the long-term effects of sea level rise and discharge variations to the salinity distribution, a 3D seawater intrusion model was designed using the fully coupled surface-subsurface numerical model HydroGeoSphere. The model simulates the coastal aquifer as an integral system considering complexities such as variable-density groundwater flow, surface-subsurface interaction, irregular land topography and anthropogenic structures (e.g. dykes, drainage canals, water gates). Using PEST, steady state groundwater flow of year 2009 is calibrated. In addition, 3 climate change scenarios are simulated based on the calibrated model: (i) sea level rise of 1 m, (ii) the salinity of the seaside boundary increased by 25 %, and (iii) the salinity of the seaside boundary decreased by 70 %. Results demonstrate the changes of fresh groundwater resources, surface water depths and salinity distribution. The obtained results are useful for coastal engineering practices, drinking water resources management and for the development of climate change adaptation strategies.