Research shows that climate change is altering the water regime

Bern, 16.03.2021 - There will be no general shortage, but water may be scarce depending on the region and time of year – conversely, heavier rainfall will lead to more local flooding. These are the findings of the Hydro-CH2018 project published today, Hydrological Principles of Climate Change. The extensive study was carried out under the lead of the Federal Office for the Environment (FOEN) in conjunction with the National Centre for Climate Services (NCCS). Climate change means that our use of water will have to change in future.

How will climate change affect the water regime in Switzerland, the 'reservoir' of Europe? This was the key question addressed by the NCCS Hydro-CH2018 research project. The impact is much greater than previously thought: without climate protection measures, by the end of the century there will be around 30 per cent more water in the rivers in winter, and 40 per cent less in summer. In summer, the temperature in rivers and streams will rise by around 5.5 degrees Celsius. With climate protection measures, such as those provided for in the revised CO2 Act, the changes are more moderate, but still have significant consequences. The findings of the Hydro-CH2018 project (see box), in which various research institutions and federal agencies collaborated under the lead of the Federal Office for the Environment FOEN, were published on 16 March. These are its key messages:

Water regime changes: Less meltwater

The hydrological scenarios in Hydro-CH2018 build on the Swiss CH2018 climate scenarios. In winter there will be greater precipitation; the snowline will rise, meaning more rain will fall than snow. Summers will be drier and warmer. The glaciers will continue to recede, and less snow and glacier ice mean lower water reserves for the summer. The water regime will change. The findings of Hydro-CH2018 suggest that significantly less meltwater will flow into streams, rivers and lakes in summer - and water temperatures will rise.

These changes also affect power plants and electricity production. In winter, when electricity demand is high, more power can be produced using the greater volumes of water available. In summer, however, when less water is available, power plants will be able to generate less electricity. The shortfall can be met by electricity from solar energy. All those sectors that rely on water use will have to deal with these changes: power plants and electricity suppliers, drinking water suppliers, agriculture, shipping and industry.

Water shortages in summer

Summers will become drier and hotter. The hydrological scenarios show that too little water will be available in summer, especially in agriculture. In intensively farmed areas, water may become scarce during the summer growth period, when plants require large amounts of water. At the same time, there will be less water in the soil and in the water bodies during this period. The solution may be to plant crops and plant varieties that require little water and tolerate heat well, and to install more efficient irrigation systems. Groundwater is less sensitive to drought than rivers and lakes, but may also become scarce in some regions.

Natural hazards are on the increase

The Hydro-CH2018 research findings further show that natural hazards such as floods and landslides are occurring with greater frequency. Rainfall will be heavier and so flood events will be more likely. In the high mountains, the glaciers are melting and the permafrost is thawing. As a result, steep mountainsides are less stable, and the situation for infrastructure is increasingly precarious. More needs to be done to mitigate these changes in natural hazards, for example by constructing flood defences.

Biodiversity in and around water is under threat

As the climate changes, our lakes and rivers are getting warmer. Their biodiversity is under threat. As the water temperature rises and small bodies of water dry out more often, this causes harm to many of the creatures living in and around the water. Cold-loving fish such as brown trout and grayling need to be able to find colder water. As the water in a lake warms, there is less mixing of the different water layers, causing a lack of oxygen. The more natural a body of water is, the better it can respond to the warming climate and provide a healthy habitat. Water bodies therefore need to be protected from pollution and excessive use and to be kept close to their natural state.

The results of the 'Hydrological principles of climate change' project show that the water regime is changing markedly and that there are various ways we can adapt to these changes. This is in line with the 2012 federal strategy for adaptation to climate change, whose aim is to ensure that the environment, economy and society are able to cope with the effects of global warming. The Federal Council adopted the action plan for this strategy in August 2020. The measures contained in the action plan are to be implemented by 2025. For example, urban green spaces and areas of water can help to make cities less hot. New and better connected conservation areas will help animals and plants to adapt to climate change.

In addition to adaptation, Switzerland must take further measures to reduce greenhouse gas emissions in order to slow the rate of global warming.

The Hydro-CH2018 project
As the leading federal agency for hydrology and water, the Federal Office for the Environment FOEN was commissioned by the Federal Council to investigate the impact of climate change on water. It did this in collaboration with 15 renowned Swiss research institutions. Scenarios were developed for various areas, and these provide a basis for decision-making and planning on climate change issues related to water. The scenarios are freely available to all interested parties.
The National Centre for Climate Services NCCS is the federal government's climate services network that develops and provides knowledge bases for climate change adaptation and mitigation. These include the newly created Hydro-CH2018 scenarios for water and other climate services (e.g. the Swiss climate scenarios published in 2018).

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