Switzerland: Discover the record temperatures of 70 Swiss lakes

Swiss lakes water has Roomed like never before at the end of June-early July. Is it only linked to the heat wave?

The temperatures of surface water, which are presented here, depend strongly on short -term weather conditions. But if we arrive at such high values, it is because the water of the lakes is warmer than in the past, and this throughout the year. Compared to the 1970s, air temperature increased by around 2.5 degrees in Switzerland. The temperature of the lakes follows this trend. This translates for example by the fact that the winter brewingwhich providesdeep oxygenoccurs less and less in a large lake like Lake Geneva, because it can no longer cool enough.

Do these high temperatures worry you?

They pose several problems for life in the lake. Fish are suitable for specific temperatures. In the oceans, we see them migrate towards the poles. However, lakes are closed places: migration is not really possible. Fish from here will not be able to leave elsewhere and others, which would be better suited, will not be able to come naturally. Unless they are introduced, voluntarily or accidentally, which can be problematic in relation to the balance of the entire ecosystem.

The increase in lakes temperature is linked to global warming. Secondly, does it also risk intensifying the phenomenon?

Given their low volume, the lakes have little impact on the temperature of a continent. On the other hand, on a local scale, during scorching periods, the lake refreshes air temperatures during the day. At night, he will rather maintain them a little higher. In the spring, the presence of the lake often avoids frosts, which is highly appreciated for the vine or fruit trees for example. Even warmer, the lakes will remain important for these mechanisms, which remain the same.

Does this warming water have consequences on the local weather?

The more hot the air, the more moisture it can absorb and cause intense precipitation. The temperature of the lake can play a role, but it is not as decisive for our regions as that of larger water areas like the Mediterranean or the Atlantic.

Precisely: the problem that we see in our lakes also occurs in the seas and the oceans. Is it identical?

We meet the same warming mechanisms in seas and oceans. But there, we are still witnessing another problem: the rise in waters, because the volume of the oceans increases with each additional degree, and not only with the supply of the cast iron water. The inertia is such that the level of the seas is not yet adapted to the current warming of the atmosphere, not to mention the future increases. The whole geography of the ribs will change. This will pose more and more problems to the populations who live near the coasts and to the entire world balance.

And for the lakes, what should we expect for the future?

Air temperatures will in no case be able to return to what they were before and if the world continues to burn oil, gas and coal, they will further increase. All the conditions are therefore unfortunately met so that the temperatures of our lakes also continue to record new records, and this for all seasons. Even if we happen that we lived an exceptionally fresh or cold period, it will not reverse the trend.

How far can we go? Is there a limit beyond which “it will no longer be possible”?

There are limits beyond which vegetable and animal life in lakes is doing less well and some fish will not survive. According to the center “The house of the river”, the salmonids may be the most affected because they appreciate fresh temperatures and the water rich in oxygen (Read opposite).