Swiss rivers and lakes at record lows after weeks of drought

Rivers, streams and brooks across Switzerland are suffering from weeks of drought and show extremely low levels. Among the measuring stations distributed along watercourses, eleven reached their lowest ever recorded value in July.

Between 1 April and 31 July, around one fifth of Swiss stations recorded exceptionally low discharge for the period. The figure comes from the Federal Office for the Environment, which confirmed information published by the Tages-Anzeiger.

North of the Alps, discharge in most watercourses has rarely been this low. According to the office these are low-flow conditions that occur every two to ten years, every thirty to a hundred years, or at even longer intervals, depending on the station. South of the Alps the situation is less dramatic, mainly because glacier melt continues to feed the watercourses.

The Plateau and the Jura worst affected

The two regions most affected are the Plateau and the Jura. The phenomenon is clear on the Doubs near Ocourt, in the Jura, and on the Rhine at Basel, where the river's discharge has stayed below long-term averages since the start of the year, with February the only exception.

The thunderstorms in the first half of last week did not significantly improve discharge levels. Only torrents strongly influenced by glacier melt escape this picture.

Many lakes also show exceptionally low levels. The office cites Lake Constance, Lake Zurich, Lake Zug, the Walensee and Lake Maggiore, along with smaller bodies of water such as Lake Sempach and Lake Hallwil.

Despite this situation, the federal office maintains that Switzerland still has abundant water resources. Climate change will nonetheless alter their availability in space and time. The contribution from snow and glacier melt is set to decline.

With more frequent and longer droughts, above all in summer, watercourses will tend to carry more water in winter and less in summer. Total annual availability, the office estimates, should decline only slightly.

Neighbouring countries are experiencing similar effects across western Europe. The office notes that it does not have sufficiently detailed information for a comparison, and points out that Switzerland's geographical and hydrological characteristics are distinctive.