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29.06.2021 | Study: Climate change is altering Switzerland's water balance

High electricity production during the winter

Ueli Walther




Climate change will have an impact on future electricity production in Switzerland. There is more precipitation in the winter. It rains more often than it snows, and the snow line is rising. Summers are drier and warmer. Glaciers continue to recede. In concrete terms this means: When electricity demand in the winter is high, more water results in higher power production. In turn, power plants produce less electricity during the summer because there is not as much water.

With an annual precipitation of 1400 mm, Switzerland has one of the most water-rich countries in Europe. In addition, it has large water storage capacities in the form of natural and artificial lakes, glaciers, the snow cover, the ground and ground water. The Rhine and Rhone Rivers, as well as other important tributaries to the Po and Danube Rivers, come from the Swiss Alps.

How is climate change impacting the water situation in Switzerland, Europe's water reservoir? The NCCS research project Hydro-CH2018 focused on this question. The study (see PDF below) comes to the conclusion that: The impacts are greater than previously assumed. Without climate protection measures, rivers will carry an average of 30 per cent more water in winter and 40 per cent less in summer by the end of this century. The temperatures in rivers and streams will rise by about 5.5 degrees centigrade during the summer. With climate protection measures, such as those that were foreseen in the rejected CO2 Act, the changes would be more moderate, but still have significant consequences. 

Increasing pressure on water management

The results of the Hydro-CH2018 project indicate that climate change is putting more pressure on Swiss water management. All three areas of water management – water use, flood protection and water protection ­– are strongly affected by climate change. Measures that are already in place are helping to align water management with the climate of the future. Additional adaptations to climate change must follow.

The changes also affect hydropower plants that produce climate-friendly electricity covering nearly 60 per cent of Switzerland's power needs. Hydropower is still benefiting from the melting glaciers over the entire year. In the long term, these melt water inflows will decrease. The role of hydropower as a means of storage for solar and wind power and for power grid stabilisation will grow.

Differences in storage plants and run-of-river power plants

Whilst power production from storage power plants can be adjusted to demand and price to a certain extent, run-of-river power plant production is dependent on the water supply. In the future, rivers and streams will carry more water in the winter, making it possible to produce more electricity from hydropower. The expected decrease of summer outflows will result in lower power production during this season. Storage power plants can partially compensate these seasonal changes by retaining water. 

Expected changes in the production of run-of-river power plants
Positive and negative impacts for run-of-river power plants

The Swiss Competence Center for Energy Research SCCER investigated how climate change impacts power production in eleven Swiss run-of-river power plants. Nearly all the plants indicate an increase in winter production in the future as compared to the reference time period from 1981-2010. By mid-century this corresponds to an  average increase of about 5 % independent of whether the scenario is seen with or without consistent climate protection measures. By the end of the century, this value will increase to 10 % without climate protection measures, but would remain stable if these were instituted. Annual production stays the same or drops only slightly with climate protection measures. With no climate protection measures, a drop of 3 % by mid-century, and of 7 % by the end of the century is expected.

High-altitude alpine power plants are the exception, and show an increase in production. This is mainly due to glacial melting. Currently all of Swiss hydropower is benefiting from glacial melting. In the time period from 1980 to 2010, 3 to  4 % of Swiss hydropower production was attributed to glacial melting, which corresponds to about 1.0 to 1.4 TWh per year. However, the contribution from glacial melting will decrease by 0.56 TWh per year by mid-century and by 1 TWh per year by the end of the century.

Challenges and opportunities for storage power plants

Storage power plants are strongly exposed to natural hazards owing to their alpine locations. In particular, glacial melting, permafrost thawing and more frequent, heavy precipitation intensify the natural hazard situation for hydropower plants in the Alps. Depending on the storage volume, they can hold back large water volumes or floods and make a contribution to flood protection. In the future, the demands for the multi-purpose use of reservoirs, such as for flood retention or as a water resource during water shortages, could increase. It is also expected that alpine reservoirs will silt up more quickly owing to additional sedimentation. There is also some potential for expanding the storage lakes in Switzerland. You can read about where and how here: Higher dams for more winter electricity

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