Past and future changes of streamflow in the European Alps

Short instrumental streamflow records in the European Alps limit our understanding of the full range and long-term variability in river discharge, which could greatly impact the management of freshwater resources for the densely populated area downstream. Enhancing the understanding of past climatological and hydrological information is also essential to improve the accuracy of future scenarios for rare extreme events, such as multi-year droughts and unprecedented floods, which recently impacted severely important water resource systems and communities at the global level. Tree-ring data have proven to be a viable opportunity for reconstructing various climatic parameters, including streamflow. By using a novel climate-informed framework, the station-based streamflow records of several rivers originating from the European Alps are reconstructed dating back to the year 1100 AD. To further investigate the characteristics of streamflow and extreme events in both the past and future, this study also relies on state-of-the-art paleo simulations from the Paleoclimate Modeling Intercomparison Project phase 4 (PMIP4) and future projections from Coupled Model Intercomparison Project phase 6 (CMIP6). By integrating proxy-based reconstructions, climate model simulations and projections, and observation, the changes in streamflow and rare extreme events in the European Alps are put into a longer perspective covering both the past nine centuries and one century into the future, thus providing a unique opportunity to assess the risk of extreme events and to inform more effective water management strategies for climate change adaptation.