Creugenat

Creugenat Estavelle - Creux-Genat


Useful Information

Location:
Open: no resrictions.
[2020]
Fee: free.
[2020]
Classification: ExplainEstavelle
Light: n/a
Dimension: Cave: A=451m asl, L=2,125m, VR=20m.
Guided tours: n/a
Photography: allowed.
Accessibility:
Bibliography: Marc Hessenauer, Pierre Xavier Meury (2002): Estavelle from Creugenat, Jura, Stalactite N° 2 December 2002.
Jonathan Vouillamoz (2013): Mapping Flood-related Hazards in Karst Using the KARSYS Approach: Application to the Beuchire-Creugenat Karst System (Ju, Switzerland), 13th Sinkhole Conference NCKRI Symposium 2, DOI: 10.5038/9780979542275.1144. online online
Address:
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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History

1933 first speleologic exploration.
1934 first diving attempt by Spengler and Scherrer.
1973 exploration by Gérard Domon and the Groupe Spéléo de Porrentruy (GSP).
2000 spring pumped and cave explored by Club Spéléo de Porrentruy.

Description

The Creux-Genat or Creugenat (Witches Hole) is a karst spring located at the border to France in the Swiss Jura. However, despite looking like a karst spring it is actually an estavelle, which means there are times when water flows out, times when water flows in, and even times when nothing happens. As an intermittent spring it is dry most of the year, but about four to five times every year after heavy rains or during snow melt the spring has a production of typically 20m³/s. At this time it is comparable to a spring of Vaucluse type. There are years with up to 10 times of production, but also years without (eg 2011). The water flows across the Courtedoux plain and finally into the Allaine at Porrentruy.

When the spring is dry the water cave below can be visited by cave divers and it has been explored for 2,125m by now. Many parts are water filled, but there are also some air filled passages behind the entrance sump. Several attempt were accompanied by pumping the entrance sump, because this makes the diving much easier.

The Courtedoux plain is quite flat and the outflow often forms a temporary lake. When the production ends the karst groundwater level may fall faster than the level of the temporary lake and so the water flows back into the cave. This is what the term estavelle means.

The catchment area of the Ajoulote underground river is the Doubs basin between pleated Jura and Milandrine basin. It has a size of 48km². The main drainage is through the La Beuchire spring, the most important karst spring in Ajoie with flow rates between 60-80 l/s and 2,900 l/s, in average 800 l/s. The Creugenat is 4.25km away and is a higher overflow, so it is activated only when the water level in the karst body raises high enough, because the main spring is not able to drain it fast enough. Normally it starts production when the outflow at Beuchire reaches 1,450 l/s.