Future climate change is likely to have an impact on the occurrence of hydrological extremes in Europe. While many studies have looked at changes in climatic variables such as temperatures and precipitation, most of the impacts of extreme droughts and floods are related to hydrological variables such as river flows. In this paper we look at changes in river discharge in Europe under various scenarios of climate change by using simulations of a hydrological model driven by high-resolution regional climate simulations. We use extreme value analysis to derive high- and low-flow characteristics from the simulated streamflow time series. More specifically, for analysing changes in river droughts we employed the methods of block maxima and partial duration series to obtain minimum flows and flow deficits and fitted extreme value distributions by the maximum likelihood method. For floods we fitted generalised extreme value and Gumbel distributions to the annual maximum river discharges. By comparing return levels under current and future climate conditions we obtain an estimate of the change in the probability of flooding and drought occurrence due to climate change. To account for uncertainty in the simulated future climate change we analysed results of a number of different climate models and emission scenarios. Results suggest that in many European rivers extreme discharge levels may increase in magnitude and frequency, except in northeastern Europe where a reduction in snowmelt floods dominates the signal. Changes in flood hazard are subject to considerable uncertainty due to effects of climate model formulation on the simulation of extreme precipitation. Predictions of changes in streamflow drought are more robust and show an increase in severity and persistency of droughts in most parts of Europe, except in the most northern and northeastern regions.
Keywords: Climate change; Hydrological extremes; Extreme value analysis; Droughts
Biography: Rutger is a climate impacts scientist at the Met Office Hadley Centre. His work focuses on the consequences of climate change for hydrology and terrestrial ecosystems. Before joining the Met Office in 2009 he worked at the Joint Research Centre of the European Commission in Italy on flood and drought hazards in Europe under scenarios of future climate change. Rutger obtained his PhD from the University of Utrecht, the Netherlands, in 2002 with a study on climate impacts on sub-arctic hydrology.