The rigole de la montagne (English: trickle of the mountain) was an important facet of the Canal du Midi, engineered by Pierre-Paul Riquet in southern France. The canal itself was built during 1666-1681. A critical aspect of the Canal du Midi was the supply of sufficient water to feed the canal. Each boat traversing its length would require a large quantity of water in the locks in order to climb or descend.
The original plan was to take water from the Sor River at Revel via the rigole de la plaine and transport it to the Bassin de Naurouze to provide a source of water for the canal. In order to placate mill owners fearful that they would lose too much water from the Sor, the rigole de la montagne would supplement the Sor upstream from the rigole de la plaine at Conquet. It was to collect water from the Alzau stream, as well as others, and divert them to the River Sor at Conquet.[1][2]
In 1664, Louis Nicolas de Clerville had the idea for a single large dam of the Laudot valley near Saint Ferreol, which became the Bassin de Saint-Ferréol. He also had the idea of digging a tunnel through the Cammazes ridge to connect the rigole de la montagne to the reservoir in the valley without utilizing the Sor river at all.[2] In 1686, the engineer, Marshal Sebastien Vauban, extended the rigole de la montagne 4.5 miles from Conquet to connect it to the Bassin de St. Ferréol. The path included a 132-yard, 9-foot-diameter (2.7 m) tunnel at the village of Les Cammazes.[1]
In order to reduce leakage in some locations, the trench is lined with bricks.[3] Beautiful walking paths accompany the waters flow.
The following is translated from the French Wikipedia article of this same name: