Abstract
Assessing the impact of anthropogenic warming on river high flows is essential for adaptation planning. This study provides novel insights into the potential impacts of climate change on high flows in five river basins in Germany: the Rhine, Danube, Weser, Elbe and Oder using the largest ensemble available for Europe. A multimodel ensemble of 70 bias-adjusted Global Climate Models (GCM) that were downscaled using high-resolution Regional Climate Models (RCM) were used as inputs into the mesoscale Hydrologic Model (mHM). The discharge generated by mHM at a 1.2 km $$^2$$ spatial resolution was used to estimate the 90th percentile and annual maxima. These indices were averaged for historical climate periods and different amounts of global warming (i.e., 1.5 K, 2.0 K, and 3.0 K). Seasonal variations in streamflow were also evaluated by separating summer and winter half-years. We identified an overall increase in high-flow (15–30% for the northern Elbe and western Oder basins for the 1.5 K warming and $$\ge$$ 30% for the 3.0 K warming in the summer half-year) and annual maximum flow for most river basins. An exception to this is the robust reduction in the annual maximum and high-flow ( $$\le$$ 30% for the 3.0 K warming level) in the Alpine headwaters region. Significant uncertainty exists in the projections, with GCM selection contributing more to this uncertainty than RCM choice, particularly during the summer and at 3.0 K global warming. The provision of this large bias-adjusted climate model ensemble representing a fine river network can further facilitate the provision of reliable local information for planning local adaptation measures