Water temperature is one of the key physical parameters that determines chemical and biological processes in a watercourse. The FOEN’s measurements are the basis for monitoring temperature changes and understanding their causes.
A clear trend toward warmer temperatures can be seen when looking at long-term changes in water temperatures in Swiss bodies of water. In the section of the Rhine River at Basel, the temperature has risen by more than 2°C since the 1960s. Similar temperature increases can also be observed in other bodies of water in the Central Plateau. Climate change and heated water discharged from sources such as cooling systems (e.g. for nuclear power plants or industry) or even wastewater treatment installations are contributing to these changes.
Water temperature is a key factor in the state of surface water. The temperature of water influences all metabolic processes, the duration, course and speed of growth as well as the composition of the biotic communities that live in it. The viability and activity of aquatic organisms are dependent on certain temperature limits and optima. That is why knowledge of temperature dynamics is an extremely valuable interpretative tool.
Due to climate change, the temperature of surface waters is expected to rise further in the coming decades. This will put more pressure on sensitive aquatic organisms in specific stretches of watercourses and progressively destroy the conditions they require for survival. These changes will also increase the risk of diseases in aquatic organisms. The FOEN is currently conducting a preliminary study on the problem of rising temperatures in the context of climate change and anthropogenic influences. The findings of this study will be used to identify the priority areas where action needs to be taken. Less tolerance may need to be shown to the additional heat discharged by human activities.
In accordance with the ecological goals of the Waters Protection Ordinance, the temperature conditions of surface waters must be as near natural as possible.
The FOEN's temperature monitoring network provides the basis for monitoring the effectiveness of Swiss environment protection legislation (Water Protection Act and Ordinance). It also helps us to understand the factors affecting temperature (e.g. thermal power plants, anthropogenic heat input and withdrawal, water management interventions, climate trends). In cooperation with cantonal and national agencies and research institutes, the FOEN is studying the impacts on organisms such as fish.
The FOEN has been operating a temperature monitoring network in watercourses since the 1970s. Care is taken to ensure that the measurements take on one bank of the river yield representative results for the entire river cross-section. The monitoring network comprises around 80 stations.
Up-to-date data can be viewed on the internet and on various apps or received via SMS. The data and statistical values over the entire measurement period are published in tabular form on the internet. Temperature data evaluations are also published in the Hydrological Yearbook of Switzerland.
