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The 2013-2015 drought in the Metropolitan Region of São Paulo exposed the lack of resilience of the regional water supply system, highly dependent on the Cantareira reservoirs. In this paper, inflows to each of the four main Cantareira reservoirs are tested for systematic change. Persistent trends in streamflow, rainfall, temperature and evapotranspiration are first evaluated. Streamflow was also tested for step change. Double-mass curves were employed to assess modification in the precipitation-runoff relationship. Subsequently, we used the climate elasticity method and the ABCD model to quantify the relative contribution of climate and human activities into the detected trends. Only Cachoeira and Atibainha sub-basins showed a significant downward trend in streamflow. The results for step change were also significant, and the year of occurrence coincided with breakpoints in precipitation-runoff relationship. For both Cachoeira and Atibainha, human activities had a more significant impact on streamflow reduction than climate variability. Land use and cover maps suggest that the reduction of pasture/abandoned land parallel to an increase in reforestation/silviculture is behind streamflow reduction. The results highlight the importance of coordinating land-use patterns and water management, as an important contributor beyond any considerations of a changing climate. Implications for better managing regional water resources are discussed. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]