The Fontestorbes fountain in Ariège

It’s in the Pyrenees, in Belesta, that you can see this incredible phenomenon. The Fontestorbes fountain is said to be… intermittent! In other words, it alternates between very strong and very weak flow, or even almost none at all, in the space of an hour. But only during a certain period! Your Les Grottes campsite, near Tarascon-sur-Ariège, takes you on a journey to the center of the earth…

The mysteries of Fontestorbes

Here we are faced with one of nature’s curiosities. An enigma even! The river that flows out of the Fontestorbes cave flows intermittently with astronomical regularity. For 36 minutes and 36 seconds, the river cascades, then stops for 32 minutes and 30 seconds. The flow is around 1,600 liters per second, and can reach 3,000 liters per second after a storm, for example! What is this intriguing phenomenon of communicating underground basins? Many specialists and speleologists have tried to find a tangible explanation for this very rare phenomenon of intermittent flow. Erosion would have placed the ends of the two conduits (upstream and downstream of the fountain) side by side and at roughly the same level. This would explain why, during periods of low water (summer), an air-intake phenomenon would produce a high head loss to the point of almost completely interrupting the flow.

Why is this phenomenon only visible in summer?

The underground pulsations responsible for this intermittence only occur from July to October. In some drought years, the phenomenon can last until January! The rest of the year, the fountain flows continuously. The Fontestorbes f ountain is fed by an 85 km2 basin. In the absence of rain and therefore of infiltration water, the spring is fed by large underground reserves estimated at 30 million m3. When the spring is dry, the discharge rate is higher than the filling rate. So the reservoir empties faster than it fills. Air enters and the siphon opens. The drain then stops until the reservoir fills up again.

Taste Fontestorbes lemonade

A curiosity of nature, this spring is also renowned for the quality of its water. The Fontestorbes fountain is used to create a traditional lemonade: Fontestorbes lemonade. Once you’ve finished your visit, come and dip your lips in it and feel the fine natural bubbles tickle your gullet. We hope you enjoy your visit to this captivating and unusual listed tourist site.