An assessment of the impact of climate change on evapotranspiration, groundwater recharge, and low-flow conditions in a mesoscale catchment in Northeast Germany

Future climate changes might have some impacts on the discharge regime of rivers in Germany regarding, e.g., longer low-flow periods in summer months due to a decreased precipitation and increased evapotranspiration. During such low-flow periods, water temperature increases leading to a reduced oxygen concentration and a decrease in water quality. An assessment of such impacts is required to derive adaptation strategies for future water-resources management. The main objective of our study was to obtain an estimation of the impact of projected future climate change on evapotranspiration, groundwater recharge, and low-flow conditions. For that purpose, we applied a hydrological catchment model in the Ucker catchment with an area of 2415 km(2) located in the lowlands of NE Germany using meteorological time series from 1951 to 2055. These time series were generated by the Potsdam Institute of Climate Impact Research based on the At B-Scenario with an increase of 1.4 degrees C of the mean annual temperature and a mean decrease of 8% in annual rates of precipitation. After model calibration, the comparison of simulated and observed daily discharge rates from 1989 to 2003 led to a Nash-Sutcliffe-Index NS = 0.63. The results of this simulation study indicated that the amount of days with low-flow conditions in the Ucker river will increase and groundwater recharge especially at forested areas will decrease in an order of magnitude of 1%-94%.