Simulation of the groundwater balance in selected recharge areas on the German Baltic Sea coast

Climate change will have a strong influence on coastal lowland areas. Besides changing climate conditions in the future, the expected sea level rise (MSA) will probably have an impact on the water balance in those areas. Nevertheless, a regional analysis of climate change impacts on German coasts is still pending. Within the interdisciplinary project COMTESS (Sustainable coastal land management:Trade-offs in ecosystem services) supported by the Federal Ministry of Education and Research, the impacts of climate change on the groundwater level are analysed for two lowland areas on the German Baltic Sea coast. The changing salt concentrations in the groundwater are additionally taken into consideration. The finite element system FEFLOW serves as a tool for the analyses. Steady groundwater flow models are generated and calibrated to a long-term average current state with FEFLOW. Afterwards, a transient validation is performed. The simulation of future conditions is enabled by changing the climatic and hydrological conditions in the validated model such as the groundwater recharge and the MSA. WETTREG-scenarios, provided by the Potsdam-Institute for Climate Impact Research, deliver the meteorological data basis in this project. This paper presents the simulation results from both research areas. Local characteristics and differences between the areas lead to different developments. Especially the drainage measures of the areas via pumping stations turned out to be a decisive factor influencing the water balance and the salt concentration.