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The Rhine River Basin is increasingly vulnerable to extreme drought events, driven by climate change and evolving socio-economic pressures. These developments pose significant challenges to existing low-flow and drought management practices across national borders.
In response, the International Commission for the Hydrology of the Rhine Basin (CHR), in collaboration with the Central Commission for the Navigation of the Rhine (CCNR), the International Commission for the Protection of the Rhine (ICPR), and the EU Horizon-funded STARS4Water project, launched the Socio-Economic Scenarios (SES) Project (2023–2025). This two-year initiative aimed to provide information for policy and planning on transboundary water resources management by delivering science-based insights into future surface water availability, demand, and allocation under plausible future scenarios, while fostering transboundary cooperation and raising awareness of potential water shortages.
Key activities included collection of socio-economic data, co-designing shared socio economic narratives, improving the IWRM Rhine Modelling Framework and simulating and assessing scenarios on future water resources availability and water use.
The project was co-designed with input from the three Rhine Commissions and STARS4Water partners, ensuring that stakeholder perspectives were central to the development of scenario narratives and the identification of key questions related to future water stress. Three socio-economic scenarios were developed:
1. Rhine Sustainable Community – centred on sustainability and collaborative governance
2. Rhine Middle of the Road – reflecting moderate socio-economic growth and policy continuity,
3. Rhine Economic Growth – prioritizing economic expansion with higher resource demands.
These scenario narratives were paired with regional climate projections to explore combined biophysical and socio-economic futures.
To support the scenario development and robust modelling, the project compiled a comprehensive dataset from global, EU, national, and local sources. This included environmental data (precipitation, temperature), water infrastructure data (reservoirs) and socio-economic data (population growth, urbanisation, GDP). A selection of these datasets were used to update and parameterize the Rhine IWRM Modelling Framework capable to simulate water balances and low-flow conditions across the Rhine Basin.
The scenario narratives were translated into quantitative model inputs, defining key parameters for water demand, water use, infrastructure, and allocation rules. Climate change projections were integrated, and simulations were run to assess future surface water availability, sectoral shortages, and low-flow discharges at key locations in the basin. The IWRM Rhine Modelling Framework addresses key stakeholder concerns, such as sector specific shortages and seasonal water stress.
Key findings of the IWRM Rhine model simulations of the KNMI'23 climate scenarios in combination with the novel co-designed socio-economic scenarios for the situation 2050 in the transboundary Rhine basin are:
• The climate change indicated that changes in glacier and snow melt alternate discharge regimes. Dry summers that are currently considered exceptional, are likely to become more frequent causing a higher risk of low flows.
• Socio-economic developments in the basin will lead to change in water demand and use: while irrigated agricultural water use is expected to increase, domestic and industrial water use can rise or decline, depending on sector specific developments and climate change impact. Largest water demand for irrigation is in the Upper Rhine subbasin area, while industrial water demand is major in the Lower Rhine subbasin. In the Delta Rhine subbasin flushing for preventing saltwater intrusion is the major water user and will further growth due to sea level rise.
• Rising water demand accelerates water stress: combined climate change and socio economic scenarios show increasing water shortages, especially under pathways like the one in the Economic Growth scenario combined with severe climate change scenario Hd2050, intensifying competition among water use sectors.
These results highlights the growing influence of water demand and use in shaping future sustainable water management and dealing with low-flow conditions from source to sea —not only nationally but also across borders. Water allocation rules and prioritization of water among sectors or across countries as well as re-use (including return flow to the river) require more attention and dialogue: clear rules for prioritizing water among sectors and countries at the river basin level are currently absent, but essential towards the future to ensure equitable distribution during scarcity, considering seasonal variability and sectoral specific needs.
The findings of the SES project underscore the importance of transboundary coordination and adaptive governance in managing future droughts and water scarcity in the Rhine Basin. It contributes in raising awareness among stakeholders on water allocation, prioritization, and the risks of future water shortages. The project provides valuable information for fostering policy dialogue and basin-wide planning efforts such as the updating the Rhine River Basin Climate Adaptation Strategy of the ICPR.
In light of the above, recommendations are made for continued scenario-based planning to anticipate diverse futures, strengthened data sharing and joint modelling efforts, and deeper stakeholder engagement in SES research on enhanced preparedness for droughts and freshwater availability to support river basin planning and informed decision making on necessary actions