Increased emissions of greenhouse gases such as carbon dioxide means that more radiant energy from the sun is stored in the atmosphere. This leads to global warming of the Earth and causes changes in atmospheric circulation patterns. At our latitudes, the consequences are higher average temperatures and changes in the snow and ice cover. Extreme weather events such as dry spells, storms and heavy rainfall are also on the increase. The latter are facilitated by the fact that the air can absorb more water vapour.
The results of a study carried out by the Swiss Federal Institute for Forest, Snow and Landscape Research WSL on the impact of climate change on runoff water in the ewz concession areas are as follows.
Compared to the reference scenario of recent years, snowmelt in mountain areas occurs earlier in the year. Overall, it is decreasing because precipitation is falling more in the form of rain instead of snow. This is also the reason why winter runoff is likely to increase. In addition, the atmosphere is wetter in winter. Summer runoff, on the other hand, is decreasing significantly. In all scenarios, glacier runoff declines sharply in the first half of the century and then disappears altogether.
Runoff change with climate protection
In a climate change scenario with effective climate protection measures, annual runoff will remain constant on average until the end of the century. It is true that there will continue to be years with high runoff and years with low runoff.
Runoff change without climate protection
In a climate change scenario without or with only limited climate protection measures, the effects on water runoff are more accentuated. The snow melts even earlier in the year and is less frequent. Glacier melt will cease towards the end of the century. Compared to the reference scenario, precipitation decreases significantly in summer and increases in autumn and winter. The result is peak runoff in spring and lower runoff in autumn, as was previously observed in water bodies in the canton of Ticino.
The effects of the changed runoff scenarios on power production are complex. In general, the increasing fluctuations within a given year complicate seasonal production planning and increase the challenges in the planning and management of hydropower plants.
Longer dry periods lead to lower power production from run-of-river hydropower plants. In the mountains, they also influence the level of reservoirs. Already today, faster glacial melting and more intense rains are depositing larger amounts of sediments such as gravel, sand and silt in the reservoirs. The lakes therefore need to be dredged more frequently than in previous decades.
Studies show that, in addition to power production, other business activities of ewz are likely to be affected by the effects of climate change. In particular, the expected increase in extreme weather and heat and dry spells will require adjustments to processes and may require additional measures.
Stronger storms that blow objects around and produce larger hailstones can damage PV systems (solar power). Storm Bernd in Zurich in 2021, for example, caused such damage. Increasing heat also reduces the efficiency of PV systems. However, the number of sunny days is also likely to increase significantly in the future, which in turn will have a positive impact on power production from PV systems.
The transmission and distribution of electricity must take account of the fact that the transmission lines expand as the heat increases in summer. The maximum temperature of components must also not be exceeded. At higher temperatures, the resistance of the transmission lines increases, increasing transmission and distribution losses.
We are well positioned in the climate-neutral contracting business with the heating and cooling supply. In future, we should also benefit from the net-zero targets set by the city of Zurich and the private sector. An increase in demand for cooled rooms during summer should also have a positive impact on our business activities. Cooling systems based on renewable energies, such as those of ewz, have an advantage here. In turn, warmer winters and better insulation of buildings reduce the demand for heating.
