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Abstract

The German Elbe basin is characterised by low water availability and high nutrient loads in its river system. Due to low average annual rainfall and high probability of further reductions in coming decades, the basin appears to be particularly exposed to potential climate change effects. The GLOWA-Elbe project carried out various model simulations for a range of scenarios in order to examine climate change effects and to assess the vulnerability of water users in the Elbe region. Results are discussed with important stakeholders and used as a starting point to develop appropriate strategies for water resource management to mitigate or even reverse recent detrimental developments – such as high levels of diffuse nutrient emission loads from agriculture and artificially increased runoff in the many parts of the basin. For most scenarios, climate change itself would not lead to a reduction of diffuse nitrogen emissions. Therefore, further specific measures like, e.g. taxation of mineral nitrogen fertilizer are needed to decrease the nitrogen surplus of farms and, hence, reduce emissions to the river system and the North-Sea. The sensitivity of runoff to climate change was explored in detail for the Spree-Havel sub-basin. There, the flooding of 12,000 ha of abandoned open pit coal mines is creating a new artificial lake chain (with land shares in South-Brandenburg and North-Saxony), including several new water reservoirs to regulate runoff. Following the results of several simulation studies it would be favourable to accelerate the flooding of pit mines, given the possibility of further decreased precipitation in the future. Otherwise, meeting water demand downstream, which competes with the flooding of pit mines, will become an increasingly complicated endeavour in the coming decades. The consequences become apparent during summer month with insufficient Spree flows in order to remain the wetland area Spreewald – a nature reserve and national attraction for boat tourism – and to match the surface water demand of the Berlin area. Alternatively, the Spree-Havel surface water regime could be stabilised by water imports from the neighbouring Oder basin or by extending the remaining life of lignite mining activities. However, both alternatives could create substantial environmental problems elsewhere.