Modelling runoff from highly glacierized alpine drainage basins in a changing climate

The future runoff from three highly glacierized alpine catchments is assessed for the period 2007-2100 using a glacio-hydrological model including the change in glacier coverage. We apply scenarios for the seasonal change in temperature and precipitation derived from regional climate models. Glacier surface mass balance and runoff are calculated in daily time-steps using a distributed temperature-index melt and accumulation model. Model components account for changes in glacier extent and surface elevation, evaporation and runoff routing. The model is calibrated and validated using decadal ice volume changes derived from four digital elevation models (DEMs) between 1962 and 2006, and monthly runoff measured at a gauging station (1979-2006). Annual runoff from the drainage basins shows an initial increase which is due to the release of water from glacial storage. After some decades, depending on catchment characteristics and the applied climate change scenario, runoff stabilizes and then drops below the current level. In all climate projections, the glacier area shrinks dramatically. There is an increase in runoff during spring and early summer, whereas the runoff in July and August decreases significantly. This study highlights the impact of glaciers and their future changes on runoff from high alpine drainage basins. Copyright (c) 2008 John Wiley & Sons, Ltd.