The construction of the water alarm system and the preparation for a rapid evacuation of the population was created during World War 2 and even before the safety-related legislation. A federal decree in September 1943 had determined that the following measures were necessary.

• Active and passive protection of the dams against the effects of war
• Lowering of reservoirs
• Establishment of water alarm facilities

This was decided in May 1943 after the bombing of three dams in the Ruhr area, as it was feared that this could also happen in Switzerland. After the bombing in the Ruhr, Switzerland reacted quickly. Only a few months later, the federal decree was implemented and the installation of sirens was ordered. The first water alarms were installed in 1945 at the Bannalp and Klöntal dams. The decision at that time helped the further development of the safety and warning concept in Switzerland. On 9 July 1957, the Dams Ordinance came into force, which is still anchored in law today. In the same year, a critical review revealed that the remote control had to be technically adapted and that the sirens, due to their lack of autonomy, were not suitable for war. In 1961, Kockum Sonics AG (at that time under Ericsson AG) delivered the first sirens, pneumatic air siren TYFON) with an operating autonomy of 30 days.

To this day, Kockum Sonics AG supplies water alarm systems and siren systems for dams in Switzerland and worldwide. After the Vajont disaster in 1963, when a landslide into the Italian reservoir triggered a flood wave and killed more than 2000 people, it was realised that the water alarm should not only be used for military attacks but also for other threat scenarios. On 10 February 1971, as a result of the disaster in Italy, the dam regulations were revised and it was stipulated that water alarm systems must also function in peacetime.

In the past, sirens were used separately for the “water alarm” and the “general alarm”. Today, so-called “combination sirens” are used in the flooded area, which is reached by the flood wave within 2 hours. Combination sirens are equipped with the general and water alarms. In Switzerland, there are currently around 630 combination sirens in use, which are maintained by the cantonal authorities.

What should I do when the water alarm sounds?

When the water alarm sounds (twelve continuous low-pitched tones lasting 20 seconds each, at intervals of ten seconds), the population must

• leave the endangered area immediately
• observe the local information leaflets and follow the instructions of the authorities.

Sources Information:

Bundesamt für Bevölkerungsschutz Schweiz – Geschichtliches zum Wasseralarm. (2004). Was bedeutet Wasseralarm? https://blog.alertswiss.ch/de/rubriken/news-babs/was-bedeutet-wasseralarm