Modeling of water balance response to an extreme future scenario in the Ötztal catchment, Austria

Abstract. The aim of the study was to investigate the impact of climate change on the water balance of the Ötztaler Ache catchment in Tyrol, Austria. For this purpose the conceptual hydrological model HBV-D REG was applied. First, the model was calibrated and validated using current observed climate and discharge data. Second, the calibrated model was applied with reanalysis data. Third, downscaled climate scenarios from 2010 to 2099 served as input data to the HBV-D REG. Thereby two extreme land cover scenarios were considered: for water balance modeling a constant glacier coverage from today and additionally for runoff simulations a complete loss of glaciered area. The downscaled climate data were generated with the expanded downscaling method. Scenario simulations indicated an increase in annual areal temperature by 3.4 °C and a slight decrease in annual areal precipitation by 89 mm in the next one hundred years. According to the hydrological modeling, these climate changes caused an increase in evapotranspiration and a decrease in snow coverage. Furthermore model simulations showed an increase in winter and spring runoff, whereas summer runoff was highly sensitive to glacier coverage and decreased with complete loss of glacier coverage.