In accordance with Swiss law, the owners of dam installations are bound to operate an alarm system within the area below such installations. Both the Punt dal Gal dam, with its capacity of 164 mio m3, and the Ova Spin dam, with its capacity of 6.3 m3, come under this law.
The water alarm system is an integral part of the safety concept, and is there to alert the population in the case of exceptionally high water or flooding.
Annual siren test
Throughout Switzerland, each year on the first Wednesday afternoon in February a siren test is carried out. On this occasion sirens are tested in two modes: "general alarm" and "water alarm".
At 1.30 the "general alarm" goes off throughout Switzerland: a regular up and down whining tone lasting one minute is heard. If necessary this siren test is carried out again at 2 o'clock.
From 2.15 to latest 3 o'clock the "water alarm" is set off in endangered areas below dams. The alarm consists of 12 long, low tones, each lasting 20 seconds at 10 second intervals.
If the "general alarm" goes off outside the above-mentioned times, it indicates that the population may be in danger. In such case people are asked to listen to the radio, follow the instructions given by the authorities, and inform their neighbours. The "water alarm" will only be heard once the "general alarm" has been sounded and implies that one must leave the danger zone immediately. Further advice and rules of conduct can be found inside the back page of the telephone directory under "alarming the population in case of danger". Within endangered areas leaflets are distributed throughout the area giving instructions to be followed in the event of the "water alarm" being sounded.Local authorities are responsible for informing local populations with regard to rules of conduct in emergency situations.