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Impact of a changing climate, land use, and water usage on Europe’s water resources: A model simulation study

Abstract: 
In this work, an assessment of the impacts of climate change on Europe’s water resources has been performed, focusing on the effects of 2°C warming. Climate projections from 1981-2100 were run through a distributed hydrological model assuming constant land use and water demand (year 2006). In this study, the 2°C warming period of five climate change projections was analysed. As a consequence of a 2 degree climate change, it is expected that - except for the Mediterranean region - precipitation will increase in most parts of Europe with the highest values over the Alps and Eastern Europe. These increases in precipitation are most likely linked to the increase in temperature which triggers more convective storms in the summer months. The observed consequences of a 2 degree climate change for the river flow and extreme events – floods and droughts - are: • The annual median river discharge shows an increase in most parts of Europe, except for the Mediterranean area where a decrease in flow is projected in all four seasons. • As a consequence of climate change, extreme peak discharges are projected to increase in almost every part of Europe, even the Mediterranean. The highest increases in flood hazards are found in the summer months for the inland countries whereas coastal zones and parts of Scandinavia show a decrease in floods. These increases are probably linked again to the increase in temperature which triggers more convective storms with a higher probability of floods. Especially urban areas near larger rivers might need more attention to flood risk management and planning, due to projections of growth of urban areas and increased flood hazard. • Streamflow droughts will become more severe in the summer season mainly for the Mediterranean region (Spain, Portugal, Greece). This might have an impact for cooling water intake for industrial and energy production activities, irrigation water availability, critical environmental flow conditions, as well as hydropower potential. • According the climate change projections the most extreme events are projected to occur in summer with an increase in flood risk in the eastern part of Europe (e.g. Poland) and the Baltic countries and extreme droughts in the Mediterranean region. These projected future changes in the hydrological cycle are directly reflected in the water resources indicators. Especially the southern European countries are projected to face increased water shortages: • Climate change projections lead to an increase in the number of days per year that river flows are lower than a critical minimum in the Mediterranean regions and a decrease in the northern latitudes. Especially Spain and Portugal face increased low flow conditions. • The climate change projections lead to a decrease of groundwater resources in the southern European countries and an increase for the northern countries. Further over-abstraction of groundwater in southern European countries – beyond renewable capacity – might lead to critical deep groundwater levels and increased pumping costs to extract the water for use at the surface. • Soil moisture stress conditions - which could reduce agricultural crop yields, are especially increasing under the 2oC warming scenario in the already stressed areas in the Mediterranean. Specific crop yield effects are described in the report on agriculture. - • The southern European regions with already a high current water consumption relative to water availability are projected to be most affected by a 2-degree warming due to a decrease in freshwater resources, and at the same time an increased need for irrigation water due to higher evaporative demands. • In the Mediterranean countries and especially in Spain the water resources situation will become more unsustainable. Inflowing upstream freshwater is also not sufficient to meet local water needs under a 2 degree warming. • For eastern Europe, the projections indicate that some regions will rely to a reduced extent on upstream inflow to meet their local water demands. Policy implications: • Especially in the Mediterranean part of Europe, water savings will be essential to adapt to the decreasing overall water availability; savings could take place to increasing irrigation efficiency, sub-optimal or deficit irrigation strategies, efficiency increases in cooling processes in industry and energy production, public water savings, a better intra-annual management of water resources in a basin (e.g. storing winter water in hydropower reservoirs for irrigation water use in summer. Increased synergies between the water and agricultural policies are needed. • To raise awareness for the importance of water, setting a reasonable price on water will be an essential incentive for users for water savings. As long as water is either free of charge or to cheap, users will likely not be urged for savings. • A better control on and prevention of illegal abstractions is needed to prevent over-abstraction of groundwater in a number of European regions. A better reporting of water abstractions does help the monitoring of water resources as well. • Given the expected increase in flood hazard, especially in the urbanised areas – which in many cases are expected for further grow until 2050 according to JRC’s LUISA projections – flood risk management, prevention and adaptation to floods will become an even bigger issue.