By the end of the century, the water temperature of Swiss rivers will increase up to 3.5 degrees if no climate protection measure is taken. Those of the Alps will be particularly affected, according to a study by EAWAG and the University of Basel.
sda
Climate change is already clearly noticeable in Swiss watercourses: water temperature has continued to increase in recent decades and flows have also changed, the EAWAG water research institute said on Thursday.
A team of scientists has modeled future water temperatures using data from 82 flow measurement stations managed by the Federal Environment Office (OFEV). Modeling was based on air temperature forecasts at ground level and flows, this for three different climatic scenarios.
According to these results, published in the magazine Aqua & Gas, less climate protection measures are taken, the more the temperature of rivers will increase. The evolution is not, however, continuous. While warming accelerates in the scenario without climate protection measures, it reaches a tray in the middle of this century in the scenario with climate protection measures.
Types of watercourse
In addition, the extent of water warming differs depending on the type of watercourse. It is the most important in alpine waters, which will warm up by 3.5 ° C by the end of the century if no climate protection measure is taken. This is linked to the increase in air temperatures, which is also the strongest in these regions.
Getting will be almost as important in the rivers downstream of the lakes: there, it will reach +3.4 ° C in the extreme case. As water stays longer in lakes, it can warm up more, which is felt in downstream rivers.
In the measurement stations downstream of the sources, where the watercourse is strongly influenced by groundwater, the temperature does not change hardly, only by +0.05 ° C in the near future or +0.1 ° C in the distant future.
Modification of flows
In addition to the evolution of the average temperatures of the rivers, the authors also studied the modification of the flows and extreme temperatures of the rivers during the summer months. According to their analyzes, flow rates will decrease by 10% to 40% in summer, which will further strengthen the seasonal warming of rivers and will cause long periods of drought.
On the other hand, flow rates will increase by 10% to 30% in winter. Extreme temperature events will be the most frequent by the end of the century in the rivers located downstream of the dam lakes, followed by the rivers of the plateau.
Scientists suggest using groundwater more to regulate temperature, for example by infiltrating rivers water in phreatic tablecloths in winter and injecting groundwater into rivers in summer. The flow rate is also increased during periods of summer drought.
