As a result of climate change, the water temperature of many lakes has risen in recent decades. A further increase is expected. The warming affects the mixing dynamics and thus the oxygen content in the deeper layers of the lakes. In order to monitor the water temperature of selected lakes at national level over the long term, a pilot project is running until 2024.
Lake temperatures have risen in recent years due to climate change. Since 1980, the surface water in most lakes has warmed by about 0.4 °C per decade. The warming of the deep water is more variable and mostly ranges between 0.0 and 0.2 °C per decade in the deep lakes.
Temperature rise continues
Researchers have modelled the future development of temperature and stratification regimes for 30 lakes in the project Hydro-CH2018. A further increase in the temperature of the surface water layer (down to 1 m deep) is expected in all the lakes: for a scenario without climate change mitigation of between 3 and 4°C in most lakes towards the end of the century.
Effects on aquatic life
Warming has a direct effect on mixing dynamics and thus on the oxygen content in the deeper layers of the lakes. The warmer water causes the stable stratification of the lakes to begin earlier in spring and to dissipate later in autumn. Accordingly, more time is available for the oxygen in the deep water to dissipate. In addition, due to the decreasing intensity or frequency of mixing in some lakes, less oxygen is supplied to the deep water. The changed mixing dynamics also influence the nutrient cycle. As a result, the habitat for fish is restricted and potentially toxic algal blooms can occur more frequently.
Monitoring water temperature
In order to monitor the water temperature of selected lakes at national level over the long term, a pilot project will run until 2024. Further measurements are carried out by research institutions and cantonal specialist agencies.
Water temperature of selected lakes
Water temperature of Lake Murten
Measurements since July 2022 as part of the FOEN pilot project on lake water temperature, in cooperation with Eawag and the cantonal offices.
Eawag: Temperature Monitoring Lake Murten
Water temperature of Lake Hallwil
Measurements since September 2022 as part of the FOEN pilot project on lake water temperature, in cooperation with Eawag and the cantonal offices.
Eawag: Temperature monitoring Lake Hallwil
Water temperature of Lake Aegeri
Measurements since November 2022 as part of the FOEN pilot project on lake water temperature, in cooperation with Eawag and the cantonal offices.
Eawag: Temperature monitoring Lake Aegeri
Water temperature Lac de Joux
Eawag measurements since 2014.
Eawag: Temperature Monitoring Lac de Joux
Water temperature of Lake Geneva
Measurements of the LéXPLORE platform since 2020.
Eawag: Temperature Monitoring Lake Geneva (LéXPLORE Temperature Chain)
The indicated base temperature for Lake Geneva is the temperature at 90 m depth at the point where the LéXPLORE platform is located. This is not the deepest point in the lake.
Water temperature Geistsee
Eawag measurements since April 2021, as part of the FOEN pilot project Temperature Monitoring in Small Lakes.
Eawag: Temperature monitoring Geistsee
Last modification 14.11.2022