Hydrological response of the Otztal glacierized catchments to climate change

This paper investigates the hydrological response of glacierized headwater catchments to future climate change in the Otztal Alps, Austria. To this end, two conceptual hydrological models, HBV (Hydrologiska Byrans Vattenbalansavdelning) and HQsim, are applied for the simulation of future daily discharge in three (nested) catchments with varying degrees of glaciation. The models are forced with downscaled climate change projections, and outputs from an empirical glacier model, which is able to simulate future glacial evolution. Under the future conditions, the outcomes show initially that runoff increases for all catchments without changes in the runoff regimes. In the long term, summer runoff is expected to decrease and winter/spring runoff is expected to increase in all catchments. These runoff changes are accompanied with regime shifts from glacial/glacio-nival runoff regimes to runoff regimes with a higher nival component. Changing runoff conditions might also lead to changes in the seasonality of annual flood peaks with an earlier appearance of flood peaks, and an increasing appearance of low flow conditions during summer months. The outcomes of the two hydrological models show minor differences. The results of this study provide improved understanding of the future impact of climate change on the water cycle of glacierized Alpine catchments.