Die Gefahr vom See

"On my guided tours to the former Lüschersee, I always show people a marmot burrow. This shows particularly well that the soil material in the former lake basin is completely different from the one around it. When the lake still existed, dead aquatic plants as well as mud, lime and clay were deposited. This layer of calcareous clay is estimated to be about 80 centimeters. In the former lake basin, therefore, a completely different vegetation grows than in the surrounding landscape, which is why you can see the shoreline so well. In the lake basin, for example, there are many thistles; so be careful where you sit." Gino Romegialli, long-time holiday guest in Urmein, excursion guide and author of "The End of Lake Lüschersee"

The clay slates of the Nolla Clay weather easily, but are impermeable to water. As a result, the rainwater accumulates in the uppermost layers and causes a mushy mass. Since the layers on the Heinzenberg slope down to the valley, the entire slope slowly slides downhill. In the uppermost part of the slope, on the ridge, the mountain breaks apart; this creates a restless topography. The locally formed depressions are filled with water.

In the case of the former Lüschersee, it was feared that the water from the Lüschersee without surface runoff would accelerate the landslide process. As early as 1742, the first voices are known to suspect a connection between the Lüschersee and the landslides on the Heinzenberg.

The fears of the local population are also clear in the legend about the Lüschersee: "In the bottom of the lake, folk legend lets a dragon live, which roars when the weather changes. Every hundred years the monster rises out of the lake and rolls down the mountain, leaving a trail of devastation behind it." (Gino Romegialli: Das Ende des Lüschersees. Verlag Desertina, Chur, 2012.)

When reading the legend, one involuntarily thinks of periodic floods, a great threat to the villages and settlements on the mountain and to the Domleschg. For example, the underground runoff of water from the Lüschersee was classified by several engineers as an important reason for the landslides and the measure to empty the Lüschersee was decided by the federal government in 1906.

The lake indulgence
The plan was to build a water drainage tunnel, which would enable the gradual draining of the lake water. The construction of the tunnel proved to be a challenge for the construction company. The construction workers had several times deviations from the tunnel axis as well as too little wood on site for the carpentry of the tunnel and shortly before completion, a mistaken blasting claimed three lives and three injuries. After all, the Lüschersee had almost no water in the winter of 1910 during the construction of the tunnel and the lakeside section could be dug in the dry.

To this day, it is not clear whether the lake outlet really contributed to the slope stabilization. This would require comprehensive geological investigations. Many would like to see this beautiful mountain lake back – pure dreaming or perhaps reality?

The redamming
Extensive investigations showed that the lake had only a minor influence on this, which is why it has now been sealed again and is filling with water with the snowmelt in 2022. The project will be closely monitored during the test phase to rule out any influence on landslides. On June 23, 2022, an excursion to the former Lüschersee will take place.