|Data on the structure|
|Lock type:||Gravity dam|
|Height of the barrier structure :||24 m|
|Building volume:||34 000 m³|
|Crown length:||195 m|
|Operator:||Groupe E , Friborg|
|Data on the reservoir|
|Altitude (at congestion destination )|
|Water surface||35 ha|
|Reservoir length||2.3 km|
|Storage space||300 000 m³|
|Total storage space :||400 000 m³|
|Catchment area||1 250 km²|
|Design flood :||850 m³ / s|
oldest weight wall in Europe
The Pérolles lake ( French Lac de Pérolles ) is a Swiss reservoir in the canton of Friborg at the foot of the city of Friborg . The construction work on the weight wall of Lake Pérolles was completed in 1872, making it the oldest concrete dam in Europe.
The engineer Guillaume Ritter had a vision in his day: he wanted to dam the Saane with a wall in order to supply the city of Freiburg with drinking water and to generate teledynamic energy with the artificial slope. Turbines should the water in the reservoirs to pump the city from where hydrants were supplied and apartment buildings with water. The pumps and drives for the teledynamic cable were housed in the “Magere Au” plant.
Furthermore, kinetic energy was to be fed to the Pérolles Plateau via a teledynamic cable in order to generate energy for the sawmills there. The teledynamic cable system is like a transmission belt that is guided over a large distance on pillars - similar to a modern cable car . Ritter was convinced that this system would bring industrial progress to Freiburg.
Contrary to the plans, the reservoir only supplied the sawmills with energy in the spring of 1874, which was, however, very expensive. Even later - in autumn 1874 - the houses got their water, although the quality left a lot to be desired.
In 1890 the electrification of the “Magere Au” plant began, and in 1895 the teledynamic system was replaced by conventional generation of electrical energy.
When the dam wall was raised in 1910, the new «Oelberg» power station was also put into operation. Lake Pérolles was connected to the new “Oelberg” plant through a tunnel in the Saane loop under the Bürgeln Hügel .
Today the lake is heavily filled with sediment , as the Saane has deposited a lot of material on the dam over the last 130 years. These deposits have partly led to the formation of small islands. In the picture with the view from the dam wall, on the lake, this island formation is visible, in the form of a «green strip» consisting of bushes.
Technical data of the dam
The Maigrauge / Magere Au dam was raised by 2.5 meters in 1910; it measures 18 meters at the base and 4.5 meters at the top. Of the storage volume of 0.4 million m³, 0.3 million m³ are effectively used.
Guillaume Ritter's idea was visionary for the time: the operation of a large sawmill and a wagon factory that get their power from afar. With the turbines in the “Mageren Au”, the hydropower was brought up to the Pérolles plain by means of a cable. To do this, a distance of approx. 1 km and an altitude difference of approx. 70 m had to be overcome. The cable was led through a small tunnel on pillars to the Pérolles plain and distributed.
The city of Freiburg hoped for an upswing from the new industrialization that it urgently needed. But the electricity and the electric motors soon made the teledynamic system obsolete.
The Pérolles Lake area is characterized by a rich flora and fauna . It was declared a bird sanctuary in 1961. The area from Creux-du-Loup to the dam has been a nature reserve since 1983 . Information boards explain the fauna, flora, geology, hydrology and history of the lake on an 8 km long circular route.
- Lakes in Switzerland: Natural and storage lakes, Federal Office for the Environment FOEN, 2007 ( Memento from October 5, 2008 in the Internet Archive ) → Lakes in Switzerland (PDF)