Photo : Zairon / Wikimedia Commons (CC BY-SA 4.0)
La Source du Lison
The source of the Lison gushes out at Nans-sous-Sainte-Anne, in the Doubs, at the bottom of a reculée. It is an exsurgence: the water comes out of Middle Jurassic limestone after circulating through a network of underground cavities. It drains a basin of about 114 km², covering the Champagnole limestone plateau. The mean flow at the source is about 5.35 m³/s.
The Lison is a river of about 25 kilometres, a tributary of the Loue, which it joins at Châtillon-sur-Lison. Upstream it crosses the picturesque gorges of the Haut Lison, in a typical karst landscape.
During heavy rain, the underground network fills and the overflow escapes through the Sarrazine cave, creating a temporary stream, the bief Sarrazin. The Creux Billard, a deep rocky cirque, lies about 200 metres upstream of the source and makes this underground circulation visible. The site is developed near the edge-tool works of Nans-sous-Sainte-Anne. The look of the place varies greatly with the season and rainfall, the source being most spectacular after heavy precipitation.
