Bild: KEYSTONE
Four of Europe’s largest rivers also have their source or entirely in Switzerland, and it shares three of Europe’s largest lakes with its neighbors: old agreements on water use are now being put to the test.
Switzerland is the moated castle of Europe. The Rhine and Rhone rise in the Swiss Alps, as does the Ticino, which feeds the Po, and the Inn, which flows into the Danube: the major Swiss rivers actually flow in all four directions – through the four major neighboring countries.
In Italy, the extreme drought is entering its second year. The question arises as to whether Switzerland is contributing to the fact that the Po, the lifeline of northern Italian agriculture, is drying up.
At the request of blue News, the Federal Office for the Environment provided a simple comparison that shows how much water flows down the Po from Switzerland: “The discharge from Switzerland, the outflow from Lake Maggiore at Sesto Calende, is around ten percent of the discharge volume of the Po into the Adriatic.”
90 percent of the water in the Po does not come from Switzerland
This means that 90 percent of the water that flows from the Po into the sea comes from other tributaries and precipitation. However, a scientist from the snow and avalanche research institute SLF recently calculated that the amount of snow in winter accounts for up to 40 percent of the water volume of the rivers that rise in the Alps.
After all, the Rhone carries 20 percent of the water volume on the Swiss-French border, which it releases several hundred kilometers further into the Mediterranean. The Inn, which flows into the Danube, accounts for just one percent of the flow at its estuary into the Black Sea. All these values refer to the long-term average.
The low-precipitation winter and the thin snow cover in the Alps currently indicate that the drought in southern Europe will become even more severe.
The lakes near the border are more important than the amount of water in the rivers, explains Carlo Scapozza, head of the hydrology department at the Federal Office for the Environment (FOEN). Lake Maggiore, 80 percent of whose water surface lies on Italian soil, is an important water reservoir for northern Italy.
Lake Maggiore is a reservoir of northern Italy
How much water leaves Lake Maggiore is regulated at the weir near Sesto Calende in Italy. The concession specifies the range in which the level of Lake Maggiore may fluctuate.
According to Bafu, there has been an attempt to keep the level of Lake Langen high in spring since 2015 as a reserve for July and August. “For this adjusted regulation to work, however, sufficient snow reserves must be built up in winter and precipitation must fall in spring. This was not the case last year, »continued the Bafu representative.
In the summer of 2022, the Secretary General of the Po River Basin Authority held a Interview with the SRF appealed to Switzerland to supply Italy with water from its reservoirs. Here, the needs of Italian agriculture collide with the Swiss electricity reserve, which requires reservoirs that are as full as possible.
One thing is clear: Switzerland can help Italy to save part of the water reserve in midsummer. But only if enough rain and snow has fallen beforehand.
Switzerland still regulates the discharge volume of Lake Geneva
The level of Lake Geneva is even completely under Swiss control. After the Rhone has left Lac Léman in Geneva, it widens into the river, which in France is mostly used for agriculture and as a transport route, but also for electricity production.
According to the Bafu, France had refrained from participating in the regulation of Lake Geneva in 1984. In the meantime, however, the country is negotiating an agreement with Switzerland that regulates the use of the Rhone in both countries. Part of this should concern the regulation of low and high water.