Lake Annecy gradually turned green as a result of urban development in the aftermath of the Second World War. Algae multiplied, noble fish became scarce and divers, fishermen and scientists warned of the lake’s acceleratedeutrophication, i.e. its indigestion with sewage… The alarm was taken seriously by local councillors and an action plan was put in place. In 1957, the Syndicat intercommunal du lac d’Annecy (Sila) was born and sewerage work was launched to divert sewage away from the lake. Nearly forty years later, Lake Annecy is officially out of the woods and has been awarded the medal of purest lake in Europe.
