Climate change impacts on future snow, ice and rain runoff in a Swiss mountain catchment using multi-dataset calibration

Abstract

The hydropower reservoir of Gigerwald is located in the alpine valley Calfeisental in eastern Switzerland. The lake is fed by runo ff from rain, snow melt and ice melt from a few small glaciers, as well as by water collected in a neighbouring valley. Study focus: Water resources in the Alps are projected to undergo substantial changes in the coming decades. It is therefore essential to explore climate change impacts in catchments with hydropower facilities. We present a multi-dataset calibration (MDC) using discharge, snowcover data and glacier mass balances for an ensemble of hydrological simulations performed using the Hydrologiska Byråns Vattenbalansavdelning (HBV)-light model. The objective is to predict the future changes in hydrological processes in the catchment and to assess the bene fi ts of a MDC compared to a traditional calibration to discharge only. New hydrological insights for the region: We found that the annual runo ff dynamics will undergo signi fi cant changes with more runo ff in winter and less in summer by shifting parts of the summer melt runo ff to an earlier peak in spring. We furthermore found that the MDC reduces the uncertainty in the projections of glacial runo ff and leads to a di ff erent distribution of runo ff throughout the year than if calibrated to discharge only. We therefore argue that MDC leads to more consistent model results by representing the runo ff generation processes more realistically.