Published in "Water Resources Research doi: 10.1002/2014WR015549, 2014" which should be cited to refer to this work. Robust changes and sources of uncertainty in the projected hydrological regimes of Swiss catchments Nans Addor (1), Ole Rössler (2), Nina Köplin (2,*), Matthias Huss (3), Rolf Weingartner (2) and Jan Seibert (1,4) (1) Department of Geography, University of Zurich, CH-8057 Zurich, Switzerland (2) Oeschger Centre for Climate Change Research & Department of Geography, University of Bern, CH-3012 Bern, Switzerland (3) Department of Geosciences, University of Fribourg, CH-1700 Fribourg, Switzerland (4) Department of Earth Sciences, Uppsala University, SE-752 36 Uppsala, Sweden (*) now at: Swedish Meteorological and Hydrological Institute, SE-601 76 Norrköping, Sweden Corresponding author:
[email protected] Abstract Projections of discharge are key for future water resources management. These projections are subject to uncertainties, which are difficult to handle in the decision process on adaptation strategies. Uncertainties arise from different sources such as the emission scenarios, the climate models and their post-processing, the hydrological models and natural variability. Here we present a detailed and quantitative uncertainty assessment, based on recent climate scenarios for Switzerland (CH2011 data set) and covering catchments representative for mid-latitude alpine areas. This study relies on a particularly wide range of discharge projections resulting from the factorial combination of 3 emission scenarios, 10 to 20 regional climate models, 2 post- processing methods and 3 hydrological models of different complexity. This enabled us to decompose the uncertainty in the ensemble of projections using analyses of variance (ANOVA). We applied the same modeling setup to 6 catchments to assess the influence of catchment characteristics on the projected streamflow and focused on changes in the annual discharge cycle.