Physics-based simulation of long-term hydrological changes in the high-alpine environments in central Europe

The European high-alpine landscapes are particularly sensitive to climate change, with accelerating glacier retreat, reduced snow cover, and altered precipitation patterns. Glacier and snowmelt play a crucial role in determining the water availability in such environments. Quantifying long-term historic streamflow variations under the impact of climate change in high-alpine landscapes has, however, rarely been studied due to limited long-term hydroclimatic observations, complex topography, and modeling challenges. Here, we develop a cascading hydroclimatic coupling framework (Reanalysis-WRF-WaSiM) to simulate streamflow changes in three high-alpine catchments (55-77 km²) with varying glacier coverages (3% to 31%) in the central European Alps from 1850 to 2015 in an hourly time step and a spatial resolution of 25m × 25m. We first build a physics-based and fully-distributed hydrological model, WaSiM, for each site, and the model performances of the snow, glacier, and river discharge modules are evaluated in detail. The models are then forced with the dynamically downscaled and bias-corrected reanalysis climate data from the Weather Research and Forecasting Model (WRF). By performing such detailed long-term hydrological simulations with high temporal and spatial resolutions for the first time, our study provides new insights into the evolution of extreme hydrological events and changes in water availability via internal flux partitioning in high-alpine environments with accelerating glacier retreats under climate change.