Changes in runoff

The contribution of meltwater from snow and ice to runoff will continue to decrease, leading to changes in the seasonal distribution of runoff. In the future, Swiss watercourses will carry more water in winter and less in summer, although the total annual runoff will only decrease slightly.

Climate change will affect the water balance in two ways: by altering the seasonal distribution of precipitation and by increasing the air temperature. The climate scenarios show that precipitation will increase in winter and decrease in summer, with evaporation increasing in all seasons.

In winter, warming means that more precipitation will fall as rain, even at higher altitudes, and therefore run off more quickly. A smaller area of Switzerland will be snow-covered. In addition, the snowpack will form later in the year and melt earlier. As a result, runoff and groundwater recharge will increase in the winter months, whereas there will be less meltwater in spring and summer.

Annual cycle of the Rhine

Annual cycle of the Rhine
The arrows show how the mean monthly runoff of the Rhine at Basel will change by the end of this century if no climate change mitigation takes place. The lighter areas represent the simulation range.

In summer, higher temperatures will cause the glaciers to melt faster, meaning that the watercourses supplied by these glaciers will carry more water. However, this will only be a temporary phenomenon: meltwater from small glaciers is already starting to decrease again, with large glaciers expected to follow suit by 2050 at the latest.

Water in the Kander

Water in the Kander
The graph shows how the proportions of rainwater and meltwater from snow and glaciers in the runoff at Kandersteg will change if no climate change mitigation takes place. The proportion of rainwater increases significantly from 54 to 74%.

More water in winter

The combined effect of all these developments is that, in the future, almost all watercourses will carry more water in winter. In the absence of climate change mitigation measures, winter runoff will increase by between 10 and 50% by the end of the century, while in summer and autumn it will decline by 30 to 50% compared with today.

The change in seasonal inflows will also affect water levels in lakes. However, total annual runoff will probably only decline by around 10%.

The seasonal dynamics of groundwater levels and spring discharge rates will also change, with high and low phases becoming more pronounced. Water levels and discharge rates will become higher in winter, and lower in summer. Water management practices must adapt to these changed conditions.

Expected changes in runoff

Expected changes in runoff
The maps show the expected changes in seasonal runoff for various catchments by the end of the century (2070–99) compared with the reference period (1981–2010) if no climate change mitigation takes place.

Expected changes

  With climate change mitigation
end of the century
Without climate change mitigation
end of the century
Runoff from snowmelt –0 to –30 %  –30 to –60 % 
Winter runoff –0 to +20 %  +10 to +50 %
Annual runoff –5 to +5 %  –0 to –20 %
Possible range of changes in 2070 to 2099 in comparison to 1981 to 2010 (simulation range). 30-year averages across Switzerland rounded to 5%.

The key messages can also be found in the Hydro-CH2018 brochure, which is available in printed form or electronically as a download.  

Further information

Documents

cover_broschüre_en.PNG

Brochure Hydro-CH2018

This brochure explains how Switzerland's water balance works and what changes can be expected. It is aimed at users in the field.

Effects of climate change on Swiss waters

The report ‘Effects of climate change on Swiss waters’ gives a concise overview of the results and is a gateway to further technical information and data.

Last modification 13.03.2021

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Contact

Federal Office for the Environment FOEN

Hydrology Division
Papiermühlestr. 172
3063 Ittigen

hydrologie@bafu.admin.ch
www.bafu.admin.ch

Print contact

 

“Almost 60% of Switzerland’s electricity comes from hydropower plants. In the future, run-of-river power plants on major rivers may be able to generate less electricity in summer, but more in winter. This is a good thing as energy consumption is particularly high in the winter. However, as the glaciers disappear and annual
runoff decreases slightly, there will be less water overall for electricity generation.”

Maja, power plant engineer

https://www.nccs.admin.ch/content/nccs/en/home/climate-change-and-impacts/schweizer-hydroszenarien/kernaussagen/abfluesse-im-wandel.html