Lake Vioreau will be emptied of its water in October to carry out requalification work on its dam.
The structure, built in 1835, no longer guarantees a sufficient water level to circulate on the Nantes-Brest canal.
Part of the canal will therefore be closed to navigation for a year and a half, from next fall until spring 2024.
We will have to say goodbye to canoeing and boat trips... From September 20, for individuals, and October 3, for professionals, it will no longer be possible to navigate on the Nantes-Brest canal, in the Loire- Atlantic, for a year and a half.
The dam of the large Vioreau reservoir, the main water supply for the canal, is due to undergo major requalification work from next autumn.
The lake, located at Joué-sur-Erdre north of Nantes, and 4 kilometers long, will then be completely emptied from October of its 8 million cubic meters of water spread over 180 hectares.
The last time such an operation was carried out on the large Vioreau reservoir dates back to 2003.
“We found weaknesses and leaks in the dam, which led to the water level of the lake being lowered from 9 meters to 7 meters to reduce the pressure”, says Jean-Luc Séchet, the vice-president of agriculture. , sea and coastline, waterways and port in the Loire-Atlantique department.
The fish will be saved
By decreasing the amount of water in the Vioreau reservoir, the department was forced to close navigation on the canal earlier, last season.
To avoid this situation, the work is aimed at sealing the dam, raising it by one meter and also automating "all the instruments needed to control the water level, the pressure and the opening valves”.
As the reservoir is emptied, a "safeguard fishing" will be carried out with the department's fishing federation.
“It's often spectacular since we're going to take all the fish out of the lake and then dispatch them to different ponds,” says Jean-Luc Séchet.
A project worth 13 million euros, including one million to clean out the eastern part of the lake and thus obtain better water quality.
"This is where there is the most silt and problems related to phosphorus", underlines the vice-president.
The stage is considered delicate because it will be necessary to clean the banks “while preserving the ecosystem”.
An educational event
The department would like to make this work an educational event.
Users will also always have access to the ten kilometers of marked trails around Lake Vioreau.
"On this occasion, we will do an important action so that everyone can see the rescue fishing, the dry pond and understand the history of this dam", exclaims Jean-Luc Séchet.
The lake and its dam were built in 1835, at the request of Napoleon I, with the aim of guaranteeing continuous navigation on the Nantes-Brest canal.
Its primary function is still essential, especially in times of drought.
It is also the largest water reservoir in Loire-Atlantique.
It now hosts a leisure center with various water activities.
The lake will be replenished "naturally, thanks to the rain" during the winter of 2023 to allow navigation from the spring of 2024. A next public meeting is scheduled for Tuesday, at the municipal hall of Joué-sur-Erdre , to "represent the entire calendar and answer the questions that will be asked".
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To safeguard
A fault ?
To print