Water and climate change: Four key messages

How does climate change affect the water situation in Switzerland, the water castle of Europe? This question was the focus of the NCCS research project Hydro-CH2018. The effects are much greater than previously assumed: Without climate protection measures, there will be on average 30 percent more water in rivers in winter towards the end of the century, but 40 percent less in summer than before. The temperature in rivers and streams will rise by around 5.5 degrees Celsius in summer. With climate protection measures, such as those envisaged by the revised CO2 Act, the changes will be more moderate, but will still have significant consequences. The results of the Hydro-CH2018 project (see box), in which various research institutions and federal agencies collaborated under the leadership of the Federal Office for the Environment (Bafu), were published on March 16, 2021 (cf. study here). These are the Core statements:

Water regime changes: less meltwater

The hydrological scenarios Hydro-CH2018 are based on the Swiss climate scenarios CH2018. There is more precipitation in winter. It rains more than it snows, because the snow line rises. In summer, it is drier and warmer. Glaciers continue to recede. Less snow and glacier ice lead to lower water reserves for summer. The water balance changes. According to the results of Hydro-CH2018, significantly less meltwater flows into streams, rivers and lakes in summer - and the water becomes warmer.

These changes also affect power plants and electricity production. More water in winter, when electricity demand is high, allows for higher electricity production. In summer, on the other hand, power plants with less water generate less electricity. An alternative is electricity from solar power. Everyone who uses water has to deal with these changes in water: Power plants and electricity suppliers, drinking water suppliers, agriculture, shipping and industry.

Water can be scarce in summer

The summers of the future will be drier and hotter. The hydrological scenarios show that there is too little water in summer, especially in agriculture. In areas heavily used for agriculture, water may become scarce during the growing season in summer because the plants then need a lot of water. At the same time, there is less water in the soil and water bodies in the future during this period. Crops and plant varieties that require little water and tolerate the heat well, as well as sparing, targeted irrigation, can be a solution. Groundwater is less sensitive to drought than rivers and lakes, but may also become scarce regionally.

Natural hazards on the rise

The research results of Hydro-CH2018 further show that natural hazards such as floods and landslides are increasing. It rains more heavily and floods can therefore occur more frequently. In the high mountains, glaciers are melting and permafrost is thawing. As a result, steep mountain slopes are less stable, as are buildings in the high mountains. Here, it is important to take precautions and prepare even better for the changing natural hazard situation, for example with protective measures such as flood barriers.

Biodiversity in and around water in danger

With climate change, waters continue to warm. Biodiversity is threatened. The increasingly warmer water and the more frequent drying out of small bodies of water are harming various creatures in and around the water. Cold-loving fish such as brown trout or grayling must be able to move to colder water. Water layers in lakes can only mix poorly, oxygen is missing. The more natural a body of water is, the better it can respond to global warming and serve as a habitat. It is therefore important to protect water bodies from pollution and excessive use and to keep them close to nature.

The results of the project "Hydrological basis for climate change" show that the water balance is changing markedly and that there are various ways to adapt. This is in line with the federal government's climate change adaptation strategy of 2012, which aims to ensure that the environment, economy and society in Switzerland can cope with the effects of global warming. The Federal Council adopted the action plan for this strategy in August 2020. The diverse measures in it are to be implemented by 2025. For example, green spaces and water areas in cities can help them become less hot. New and better-connected protected areas will help animals and plants adapt better to climate change.

In addition to adaptation, it remains central that Switzerland takes further measures today to reduce greenhouse gas emissions and thus slow down global warming.

Source: Bafu

The Hydro-CH2018 project

As the leading federal agency on hydrology and water, the Federal Office for the Environment has worked with 15 renowned Swiss research institutions on behalf of the Federal Council to investigate how climate change will affect water. From this, scenarios for various areas were developed. They serve as a basis for decision-making and planning on climate change issues related to water. The bases are freely available to users from administration, politics and industry as well as other interested parties.
The National Centre for Climate Services NCCS is the federal government's network for climate services that develops and provides knowledge bases for climate change adaptation and mitigation. This includes the newly produced scenarios on water "Hydro-CH2018" as well as other climate services (e.g. the Swiss climate scenarios published in 2018).