Impact of an extreme dry and hot summer on water supply security in an alpine region.

Climate change will induce an increasing drought risk in western and southern Europe and a resulting increase in water stress. This paper investigates the impact of both the extreme hot and dry summer of 2003 and the PRUDENCE CHRM climate change scenario summer for 2071-2100 on the monthly water balance (available water resources versus water demand) within the Kitzbueheler Region in the Austrian Alps. As a baseline period the climate normal period from 1961 to 1990 was chosen. In both summer scenarios total flow and ground water recharge decrease substantially, due to the decrease in precipitation and increase in evapotranspiration However, regional water availability is still sufficient to serve all water demand stakeholders. As a result of decreased snow cover duration, flow seasonality changes within the CHRM scenario. Especially springs are very vulnerable to these climatological conditions; average local groundwater recharge is reduced by 20% up to 70% within both scenarios. Due to the hydrogeological characteristics of the case study area and the typical small structured alpine water supply infrastructure, local deficits can occur. But also groundwater aquifers in the valleys show a decrease in water availability. These results are supported by observations made in 2003 throughout Austria and Switzerland.