Climate change is altering the water regime in Switzerland

The hydrological future of Switzerland

Summers will become drier and more of the precipitation in winter will fall as rain rather than snow. This is roughly how Switzerland's hydrological future looks.

• With his team, WSL hydrologist Massimiliano Zappa has made model calculations on future water scarcity and extreme events such as drought or floods.
• It is very likely that local water shortages will occur in summer in the future, especially if no climate protection measures are taken.
• As heavy rainfall increases in summer, some regions are also at risk of more frequent flooding.

(Contact: Massimiliano Zappa)

https://www.wsl.ch/de/projekte/hydro-ch2018-forhycs-ice.html

Melting glaciers

• Due to climate change, Swiss glaciers are anticipated to lose between 59% and 93% of their 2018 ice volume by 2100.
• This has an impact on the environment, human needs and natural hazards.
• With the melting, first more, then less water flows into the water bodies, with a maximum in the first half of the 21st century.
• Continuous and long-term monitoring of Alpine glaciers with modern techniques will be a necessity, as will cooperation between natural and social sciences.

(contact: Daniel Farinotti)

https://doi.org/10.3929/ethz-b-000398099
 

Decreasing amounts of snow

• Due to global warming, the proportion of precipitation that falls as snow will decrease measurably.
• of precipitation falling as snow is measurably decreasing.
• Since 1961, the days with snowfall below 500 m a.s.l. have already decreased by about 40% and the water temporarily stored in the snow below 1000 m a.s.l. in spring by about 75%.
• Winter runoff is increasing overall, summer runoff is decreasing. By the end of the century, the share of available water from snowmelt will decrease significantly throughout Switzerland, although less strongly than the share from glacier melt.

 (contact: Christoph Marty)

https://doi.org/10.16904/SLF.2

Water storage against summer drought?

WSL researchers have assessed the potential of natural and artificial water reservoirs to mitigate future water shortages, especially for the summer months.

• A multi-purpose use of natural and artificial water reservoirs (dams) can represent a sensible climate adaptation measure. However, only a small proportion of the storage volume (3.5% on average) can actually be used.
• In the Alps there is usually more than enough water. In the future, however, water shortages will mainly occur in agriculturally used regions on the Central Plateau, where the potential of the reservoirs is only small.
• For the planning of multi-purpose storage projects, the legal framework conditions, questions of economic efficiency (high costs for rare events) and impacts on ecology and landscape must be taken into account.

(Contacts: Astrid Björnsen, Manfred Stähli)

Phase I https://www.wsl.ch/en/projects/hydro-ch2018-multiple-use-of-reservoirs.html

Phase II https://www.wsl.ch/de/projekte/mehrzweckspeicher-als-zukunftsmodell.html  (German)

Groundwater and snowmelt

Together with the Universities of Neuchâtel and Lausanne, the SLF's Snow Hydrology team used model calculations to investigate the relationship between groundwater storage and the timing of snowmelt. They found that the summer discharge of rivers that receive more water from groundwater decreases less rapidly despite earlier snowmelt. Groundwater reservoirs thus assume a buffer function.

(contact: Tobias Jonas)

https://www.nccs.admin.ch/nccs/en/home/the-nccs/priority-themes/hydro-ch2018/hydro-ch2018-forschungsprojekte.html