The dam of Les Cammazes
known as "Gravette dam"
It was built on the site of a watermill called La Gravette, now engulfed by the waters of the reservoir.
The Canal du Midi...
... and its water supply
Built by Pierre-Paul Riquet towards the end of the 17th century, the canal was able to function thanks to the supply of water brought all the way from the Montagne Noire to its highest point at Naurouze by two water channels: the Rigole de la Montagne and the Rigole de la Plaine.
To deal with seasonal variations in the volume of water he could draw from the rivers in the mountain, Riquet decided to build artificial reservoirs. During the centuries that have followed, more dams and reservoirs have been built, not only to meet the needs of the canal, but also to supply water for drinking and irrigation purposes.
A protected environnement
A protection perimeter has been put in place around the site to reduce the risk of polluting the water. Public access for activities such as swimming or other water sports is forbidden.
A growing demand for water
In 1953, work started on a new dam on the Sor, on a site that included land in the communes of Les Cammazes, Sorèze, Arfons and Saissac. It was completed in 1958 and entered service in 1959.
Its purpose is to:
- supply drinking water to the local population;
- supply farmers with water for irrigation;
- regulate the flow of the Sor
The reservoir at Les Cammazes supplies the Picotalen water purification plant, irrigation systems serving Revel and Couffinal, and it maintains the level of the Sor so that the river can also be used for irrigation purposes.
The dam in figures:
- Date of construction: 1953-58.
- Height of the dam: 70 metres (arch dam).
- Surface of the reservoir: 90 hectares (225 acres).
- Water catchment area: 30 square kilometres.
- Storage capacity: 18.8 million cubic metres.
- Radius of the arch: 198.50 metres.
- Length of the dam at its crest: 300 metres.
- Thickness of the dam at its crest: 3 metres.
- Thickness of the dam at its base; 15 metres
- Volume of concrete used in its construction: 100,000 cubic metres.
- Altitude of the dam crest: 570 metres.
The institution of the Montagne Noire Waters (IEMN) is an interdepartmental agreement born of the common desire of the departments of Aude, Haute-Garonne and Tarn to create a system designed to improve living conditions in the Lauragais.
Its mission is to:
♦ Produce sufficient quantities (about 10.5 million m³/year) of high-quality drinking water in nearly 200 municipalities with more than 166,000 inhabitants,
♦ Ensure that agriculture meets its water needs, i.e. nearly 10 million m³ per year.
Since 1958, adapted infrastructures have been created to guarantee a resource that meets the growing needs of the population.
IEMN is pursuing a rigorous monitoring policy for the Cammazes dam through the implementation of a complete system that includes 145 monitoring measures that are continuously monitored or surveyed once a week and interpreted to verify the dam's proper performance.
A technical visit of the structure is organized annually. It is followed by an annual inspection organised by the State services in charge of the control of the dam. At the same time, a technical examination and a hazard study are carried out every ten years. They are used to examine the usually flooded parts of the structure.