Potential impact of climate change on groundwater recharge in the Federal State of Lower Saxony (Germany)

In Lower Saxony, natural climate variability causes varying patterns of groundwater recharge on different time-scales. Long-term changes in climate may alter these spatio-temporal patterns. Against this background, an ensemble consisting of three IPCC-SRES emission scenarios, the global climate model ECHAM5/MPI-OM, the two regional climate models REMO and WETTREG2010, and the water balance model mGROWA were linked in order to project possible future development paths of groundwater recharge in the Federal State of Lower Saxony, Germany. The usage of data from the regional climate model REMO as climatic input resulted in projected groundwater recharge levels in the range of the present groundwater recharge level or slightly above, independently of the selected emission scenarios (B1, A1B, A2). In contrast, climate data from the regional climate model WETTREG2010 projected significantly reduced groundwater recharge levels. Such diverging results are not conducive to the development and implementation of adaptation measures to counteract climate induced changes in the groundwater budget at the federal state level. Against this background we suggest the use of projected groundwater recharge levels for specific local groundwater resources planning only after the uncertainty still prevailing in climate projections has been further reduced.