Climate change: study shows how much rivers and lakes warm up

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Aare, 29 degrees! Study shows how much rivers and lakes warm up due to climate change 🥵

Whether Aare, Limmat or Reuss: Swiss rivers could reach almost tropical temperatures in summer by the end of the century. This is shown by the research project Hydro-CH2018 of the Federal Office for the Environment (Bafu), which was published on Tuesday.

This graphic shows how much the waters warm up. picture: bafu

The temperature in rivers and streams will rise by an average of around 5.5 degrees Celsius in summer, according to the study. In 2018, the Aare in Bern reached the previous record temperature of 23.7 degrees.

Thus the river would reach 29 degrees by the end of the century. The surface temperature of the Seen without climate protection would rise by 3 to 4 degrees in the same period, the researchers calculated.

40 percent less water in summer

Because of the heat, the riverbed of the Töss dried up in 2018. PICTURED: KEYSTONE

The reason for the sharp rise in temperature is that the water levels of the rivers will drop significantly. “Without climate protection measures, there will be an average of 30 percent more water in the rivers in winter towards the end of the century, but 40 percent less in summer than before,” the report continues.

Due to climate change, water may become scarce in Switzerland in the future, depending on the region and time of year. On the other hand, more rain locally leads to more flooding, as the results of a research project published by the Federal Office for the Environment (Bafu) show.

In winter there is more precipitation. It rains more than it snows because the snow line is rising. Less snow and glacier ice resulted in lower water reserves for the summer. The water balance is changing. According to the results of Hydro-CH2018, significantly less meltwater flows into streams, rivers and lakes in summer. That’s why the water is getting warmer.

With climate protection measures, such as those provided for in the revised CO2 Act, the changes are more moderate according to the study, but still have significant consequences. The study was carried out under the direction of the Bafu as part of the National Center for Climate Services of the Federal Government (NCCS).

Dry summers

Because of the drought, more fields have to be irrigated. Bild: TI-PRESS/ KEYSTONE

The summers would be drier and hotter in the future. In heavily used agricultural areas, water could become scarce because the plants would then need a lot of water. At the same time, there will be less water in the soil and in the waterways in the future.

According to the authors, crops and plant varieties that require little water and can withstand the heat well, as well as economical, targeted irrigation, can be a solution for adaptation. The groundwater is less sensitive to drought than rivers and lakes, but it could also become scarce regionally, it said.

Unstable mountains

Natural hazards such as floods and landslides would increase. It will rain heavier, so there could be more floods.

In the high mountains, “the glaciers are melting and the permafrost is thawing due to the rising temperatures,” says Massimiliano Zappa of the Swiss Federal Research Institute for Forests, Snow and Landscape (WSL).

This reduces the slope stability in the mountains. “Landslides, rockfalls and debris flows accumulate and the amount of loose rock increases.” In addition to steep mountain slopes, buildings in the high mountains would also be less stable.

Threatened biodiversity

Since the waters would continue to warm as a result of climate change, biodiversity is threatened. Cold-loving fish such as brown trout or grayling should be able to move into colder water. Water layers in lakes can only mix poorly due to the warming, as Martin Schmid from the Eawag water research institute explained. There will therefore be a lack of oxygen.

“In order for the water bodies to be able to adapt to climate change, their natural functions must be strengthened,” says Schmid. In addition to protecting against water pollution, this included restoring a natural river bed and removing obstacles to the migration of fish. The shading of the riparian strips by trees contributes to the cooling of the waters.

The Bafu pointed out that the Federal Council adopted the action plan for the adaptation strategy to climate change last August. The various measures contained therein are to be implemented by 2025. For example, green spaces and water areas in cities could help make it less hot there. New and better interconnected protected areas would help animals and plants to better adapt to climate change. (amü / sda)

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Climate change study shows rivers lakes warm

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