Coupled Distributed-Groundwater Modelling for Climate Change Impact on Groundwater Dependent Ecosystems.

Human-induced greenhouse gas emissions are changing the climate worldwide. Freshwater resources, such as groundwater, are particularly vulnerable to changes in the climate. To ensure drinking water availability and protect Groundwater Dependent Terrestrial Ecosystems (GWDTEs) in the future our aim is to assess the impact of climate changes on the groundwater resources. In this study we apply a coupled WetSpa-MODFLOW approach to simulate the impact of changes in potential evapotranspiration and precipitation on the groundwater recharge, flow and head. Twenty-eight different climate change scenarios were chosen from the PRUDENCE database to incorporate to a certain extent the uncertainty regarding the climate change predictions. The results show a decrease in groundwater recharge during summer, which is partly compensated by an increase in recharge during winter. The average basin groundwater level will decrease, the strongest decrease is found on the interfluves, smaller decreases are found in the valleys. Focusing on yearly extreme groundwater levels we find a decrease in both mean highest and lowest groundwater levels (respectively MHGL, MLGL). The MLGL decreases most, followed by the MHGL. The mean spring groundwater level (MSGL) stays almost constant. The average groundwater discharge in the basin drops about 4.1%. Because GWDTE's are sensitive to decreases in MHGL, MLGL and groundwater discharge we advice to closely monitor groundwater levels near ecological important areas and to take adaptive measures to increase groundwater recharge, especially in summer, to prevent ecological loss.