• La Vilaine has turned neon green in recent days due to an episode of heat conducive to the proliferation of cyanobacteria.

  • In Rennes, the city has however developed new beaches, with the hope of reopening swimming in its river.

  • The destruction of hedges, wetlands and the use of pesticides have polluted the rivers of the department.

They all burst out laughing when we asked them if they wanted to go swimming. Installed on the grass of Baud-Chardonnet Park, these students play cards, in the shade, a few meters from the water. In recent days, the heat has been intense in Rennes and the desire to cool off is there. However, no member of this small group plans to take a dip in the river next to it. "The Vilaine, she is gross, we never bathe in it", they slip, laughing. A "beach" has however been set up in this brand new park. The ambition had even been displayed by the mayor of Rennes Nathalie Appéré to find a good ecological level in the river, in order to consider swimming. Here, but also in the ponds of Apigné. Is it really possible? One can doubt it as the site is vast.But hope remains.

With the thermometer climbing, some residents have dared to take to the water in the Vilaine in recent days, while cyanobacteria pollution has made the water fluorescent green. “I have bathed in it before but that was when I was 18. I will not do it again today, ”slips Julien, barely 30 years old, between two strength training exercises. “My boyfriend has already done it. He had gone to shower right after but he still had red patches all over his body, ”says Lisa, a student who lives in Baud-Chardonnet. A few years ago, a friend of hers even contracted leptospirosis, also called “rat disease”, after swimming in the Rennes river. The young woman would dream of being able to take a dip in the stream, which almost passes under her window.She is probably not close to being able to do so.

Like the vast majority of rivers in the department, the Vilaine is a victim of the ravages of human activity and its flow is reduced considerably, allowing the proliferation of cyanobacteria. These small algae attack the skin and can be potentially dangerous if ingested. Dogs have already died elsewhere in France. “It's a land erosion problem. For sixty years, we have torn up the embankments, drained the plots, extended our urban areas, removed the wetlands. All this favors the drying up of our waterways ”, explains Pascal Hervé, vice-president of Rennes Métropole in charge of the file.Add to that higher and higher phosphorus concentrations due to global warming and water pollution (thank you pesticides and slurry) and you have cyano bingo.

Canoeing enthusiasts must adapt

Beyond swimming, these concentrations pollute aquatic life and that of many inhabitants.

At the departmental canoe-kayak committee, sessions with children are regularly modified to adapt to this scourge which affects all of France.

“At the paddle school, we often offer water and balance games for the youngest.

It's essential, ”explains Gaëlle Régnier, technical manager.

When the water is polluted, these activities do not take place and instructions are given not to touch the water.

Impossible to manage with children.

However, something will have to be done.

In 2027, a European directive will require Ille-et-Vilaine to present 60% of its surface water "in good ecological condition".

Guess how many we are today?

Be careful, it will hurt ... In 2021, only 3% of surface water is considered "in good ecological condition".

In this context, can we seriously consider a return to swimming in the Breton capital?

“I hope so, but it will take time.

We took sixty years to destroy the grove.

Now we need to recreate it.

The site is vast, but the will is there, ”explains elected Pascal Hervé, a farmer based in Laillé.

More hedges, less pesticides

To achieve this, the Rennes metropolitan area has doubled its budget for owners of plots located in the watersheds of the Vilaine.

The objective is to encourage farmers to recreate bocage hedges and reduce or even eliminate the use of pesticides.

Communities want to recreate wetlands that filter pollution and limit water warming.

And must absolutely modernize the sewage treatment plants located along the rivers.

Only then can we dream of diving from the pretty wooden pontoons that line the stream.

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  • Agriculture

  • Algae

  • Planet

  • Pollution

  • Reindeer

  • Bathing

  • Water

  • Pesticides