Lake of Gruyère

Longest reservoir of Switzerland

The Lake of Gruyere or Lac de la Gruyere is a Swiss reservoir. It is located in the canton of Fribourg between cities Bulle and Fribourg. With a length of the lake of 13.5 km it is the longest reservoir in Switzerland. In the lake the island of Ile d' Ogoz is.


The arch dam Rossens was completed in 1948. The preparatory work for the construction of the wall began in 1944. In 1945 the site was established. In the years 1946 to 1947 up to 1000 workers were employed on the site. The construction cost amounted at the end of 72 million SFr. ( estimated were 60 million SFr. ). Planners of the dam was the Freiburg engineer Henri Gicot.

Origin of the name

The Freiburg newspaper La Liberté led to this end, through a survey. There were sent in 1447 responses;

  • 535 Lac de Thusy
  • 478 Greyerzersee
  • 434 Lac d' Ogoz

The most frequently mentioned proposal was referring to the name of the stone arch bridge of 1544 over the Sarine (Pont de Thusy ), which was flooded by the lake. By decision of the State Council of 6 July 1948, the name Lac de la Gruyère has been set.

On May 15, 1948 we were started with the waters of the lake, which was filled on September 20. The inauguration ceremony took place on 14 October 1948.


  • Lakes in Switzerland: Natural and reservoirs, Federal Office for the Environment FOEN, 2007 → lakes in Switzerland ( PDF)