Change in mean groundwater formation in the winter half year of 2021-2050 compared to 1971-2000 (projection)

The map shows the changes in the mean groundwater regeneration rate in mm/wi in mm/wi for the 30-year period 2021-2050 compared to the reference period 1971-2000 based on projected climate data. Positive values indicate higher groundwater formation in the future, negative a lower. Groundwater is a raw material that can regenerate and renew itself. The main supplier for the groundwater supply is leaking precipitation water. It ensures that the groundwater deposits of the storage rocks are replenished in the underground. The groundwater formation is particularly high in winter, as at this time a large part of the rainfall in the soil is leaking. In the warmer seasons, on the other hand, much of the precipitation already evaporates on the surface or is absorbed by plants. The rainfall and distribution as well as evaporation are influenced by climate change, which also changes groundwater formation. For the sustainable use of groundwater, it is therefore necessary to identify the possible influences of climate change on the formation of groundwater and to assess its effects. The assessment of groundwater regeneration under climate change conditions is carried out using the water balance model mGROWA18, which uses data from different climate models instead of measured climate data from past periods (i.e. 30 years). The study focuses on three periods of time: 1971-2000 as reference time, 2021-2050 as near future and 2071-2100 as a distant future. The basis for climate data is the assumption of the IPPC’s “further-how-as-to-date” scenario RCP8.5 from the Fifth Assessment Report (AR5). This is a scenario that describes a continuous increase in global greenhouse gas emissions, resulting in an additional radiative propulsion of 8.5 watts per m² compared to pre-industrial levels by the end of the 21st century. For scenario RCP8.5, a variety of climate projections are available, resulting from different combinations of global and regional climate models (or regionalisation methods). From a maximum available total ensemble of 37 climate projections, a reduced ensemble with 10 climate projections was created at the LBEG using a selection method of the DWD. The hydrologically relevant climate model data (temperature and precipitation) were subjected to monthly BIAS adjustment (through linear scaling). In addition, the climatic input parameters precipitation and potential evaporation with bilinear interpolation were transferred to a 500 x 500 m grid for mGROWA18 (downscaling). The average of the simulated changes in the annual mean groundwater renewal rate of the considered 30-year period as well as the minimum and maximum value of the range are shown.