The Rivers are Warming at the Same Rate as the Atmosphere

Swiss experts have found that temperatures in local rivers are constantly rising, writes Phys.org and BTA.

This strains ecosystems and may limit the use of cooling water in nuclear power plants.

The melting water of snow and glaciers limited the warming of the rivers in Switzerland for a long time, and they maintained a relatively low temperature in the summer. However, since the beginning of the century, high summer air temperatures have threatened the delicate balance. In 2018, Swiss conservationists had to move fish populations to higher altitude streams to prevent their death from overheating, water scarcity and disease.

"We were surprised to find that Swiss rivers are warming at 95% of the rate of the surrounding air," says Adrien Michel, a doctoral assistant at the CRYOS lab and the paper's lead author. "The conventional wisdom was that the melting of snow and glaciers and the fact that this water then flowed into lakes were counteracting the effect of warmer air on the Swiss plateau. That's no longer the case.", he added, Phys.org reported.

Scientists at the Federal Polytechnic School in Lausanne and the Federal Institute for Forest, Snow and Environment have analyzed river temperature and discharge trends throughout Switzerland, using two data sets—post-1979 records from 33 measurement sites, and post-1999 records from 52 sites. They observed that river waters had warmed by an average of 0.33°C per decade since 1980, and by 0.37°C per decade in the last 20 years.

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