Climate change impact on groundwater recharge in Slovenia in the period 2011-2100

Slovenia is a water rich country. More than 90% of its drinking water supply is covered from groundwater resources. Due to the geographical positon of Slovenia on the junction of the Alps, Mediterranean, Dinaric Alps and Pannonian Basin, big interand intraannual variations occur in both, time and space. For the determination of country-wide actual groundwater recharge quantities in high spatial resolution (100m grids), the water balance model mGROWA (Herrmann et al., 2014) has been implemented in Slovenia in 2017.mGROWA is a deterministic water balance model, calculating runoff generation and runoff components including net groundwater recharge in daily time steps. On one hand mGROWA model results are used for water resources management issues. For this purpose runoff quantities determined in daily time-steps are aggregated to mean long-term averages, e.g. mean long-term groundwater recharge levels for hydrological periods or decades. For assessing the impact of climate change on Slovenian groundwater resources the high temporal resolution of mGROWA is used in order to represent inner-annual shifts of groundwater recharge appropriately. Projections of groundwater recharge under climatic change conditions were analysed by running the mGROWA model with EUROCORDEX scenario data as climate input. For this purpose three scenarios were used: RCP2.6, RCP4.5 and RCP8.5. For each climatic scenario the combinations of regional and global climate models for Slovenia were selected based on the best fit of the climate scenario results to observed climate data in the past. For the RCP2.6 scenario two regional model combinations were used and for the RCP4.5 and RCP8.5 scenarios six regional model combinations. Arried out for the Model calculations have been carried out for the period 1980-2100 using the model period 1981-2010 set as the reference period. For assessing the the climate change impact, the periods 2011-2040, 2041-2070 and 2071-2100 have been selected. For these periods (and the 3 scenarios) geographical and geostatistical analysis were carried out, e.g. with regard to the absolute change and relative deviation of groundwater recharge for minimum, maximum and median. All that was analysed on annual and seasonal (spring, summer, autumn, winter) timescale along with a confidence analysis. The results indicate impacts of climate change on groundwater resources with distinctive periodical and regional patterns that will be presented at the IAH conference.