The Jaun waterfall, considered one of the most beautiful in Switzerland by Switzerland Tourism, is the most important spring in the Fribourg Pre-Alps. For a long time, its hydrology was a mystery to scientists.

They wondered where the water that gushes out of the rock and feeds this imposing waterfall came from. In 1928, geologists attempted to solve this enigma. 12 km from the waterfall, in the Morteys valley, they coloured the water of a stream at the point where it gradually disappeared into the ground. Eleven days later, the dye reappeared at the Jaun waterfall. Part of the mystery had been solved!

Since then, numerous studies have outlined the extent of this typical karst watershed (see map). In so-called karst areas, rainwater and snowmelt, rather than flowing over the surface following the topography of the land, infiltrate into a network of underground galleries. These tunnels are created and enlarged over time by a chemical dissolution process that limestone undergoes when it comes into contact with water. During its journey underground, the water eventually comes up against a less permeable geological layer, which causes it to emerge at the surface to form a spring, like the one at Jaun.

Since the 1970s, speleologists and divers (see image) have been exploring the gallery leading to the waterfall (up to 300 m), which represents a tiny part of this vast aquatic subterranean world.

The Jaun waterfall is a spectacular example of the underground flow of water in the limestone regions of the Pre-Alps. This is why it is included in the Fribourg inventory of geotopes of cantonal importance.

In collaboration with the municipality of Jaun