|Location:||Bellegarde sur Valserine. A40 exit Bellegarde, follow RN84 towards Nantua, park on the car park at the foot of the rail viaduct. 30 minutes walk.|
JUL, AUG French speaking guide available.
Eugène Renevier, François Jules Pictet de la Rive (1854):
Fossiles du terrain aptien de la Perte-du-Rhône
|Address:||The Tourist Office, Bellegarde-sur-Valserine, Tel: +33-4504868, Fax: +33-450486508. E-mail:|
|As far as we know this information was accurate when it was published (see years in brackets), but may have changed since then.
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The Pertes de la Valserine (Losses of Valserine) are a series of ponors or swallow holes where the river vanishes completely into a cave. The sinking river is located at the lower end of a 300m long narrow gorge, the reason why this place is also called Gorges de la Valserine (Gorges of the Valserine). Once the gorge was covered by a natural bridge named Pont des Oulles (Bridge of the Dolly Tubs), a 300m long cave were the water was flowing underground. This place was used by travellers and merchants to cross the river. Its importance was the location close to the border between France and Switzerland, and it was the only bridge in the area. So it was also popular with smugglers. In the early 20th century a border post was erected here, although it is actually more than a kilometer from the border. Today some concrete slabs allow walkers to cross the river.
The Valserine river is a tributary to the Rhone, which has its spring at the Col de la Faucille, at the border between the Ain and the Jura. It is 48km long from the spring to its discharge into the Rhone at Bellegarde-sur-Valserine. It has several tributaries, the biggest one is called Semide and has even a higher production than the Valserine. The production of the river depends very much on the season, during May the production is about 29m³ per second, in October only 8m³ per second. During a flood in January 1982 a production of 262m³ per second was recorded.
The gorge was cut into the limestone since the glaciers on top of the Jura were melting about 15.000 years ago. At this time the coldest part of the Würm Ice Age ended and some of the "lowland" glaciers started to melt. So the gorge with its impressive dolly tubs is a rather young geologic sight.
Bellegarde was the first city in France with electric light. Not far from the ponors, the first hydroelectric power plant of France was built at the river. Today only the walls remain of the impressive building.
There is a fine trail on bridges along the river, which allows a good view into the gorge and the sink. The visit is free and there are no restrictions, but obviously it has no sense to visit at night or bad weather. Also the visit includes some hiking and appropriate shoes are recommended.
The geologic situation in this area, with karstified limestone crossed by big rivers, caused another similar site called Perte du Rhône (Loss of the Rhone). In this case the Rhone went underground for a length of about 60m. This place is now destroyed, after the Génissiat Dam was built in 1948 by the architects Albert Laprade and Léon Bazin south of Bellegard. Today the river Rhone forms a 23km long lake, between the dam and the Swiss border.