An assessment of European water storage requirements for adaptation to climate change

The planning of water management measures for adaptation to climate change entails simulating scenarios using complex hydrological models. However, turning model simulation results into specific insights, and consistently identifying the necessary actions may not be obvious. In this study, we propose a novel and efficient method to distill the results coming from a complex model simulation (LISFLOOD) over continental Europe into two key indicators that could be represented and communicated in simple maps. Along with a commonly used indicator of trends in water availability, we define a new indicator of trends in water storage capacity requirements to compensate the phase lag between availability and demand. We use these indicators to identify regions with a need for enhanced water storage capacity, for water saving measures, or a combination of both. While trends of increasing availability in the north of Europe and decreasing availability in the south were confirmed in line with previous studies, the new indicator allows to detect patterns of increasing storage requirements due to unfavourable changes in intra-annual distribution of availability. Based on the proposed indicators, we estimate for Europe a need for 72 Mm 3 to 110 Mm 3 per year of additional water storage capacity, to adapt to evolving water availability caused by climate change. The study is a proof of concept based on available model simulations and conditional to their validity. The novel approach presented here is proposed for screening level assessment of coping strategies, before delving into more detailed planning of specific investments.