After a summer marked in France by a record drought, worsened by global warming, the search for solutions to preserve water has become a priority. How can we conserve this resource when it becomes abundant, so that we can still have it several months later?
Among the avenues studied, an animal, an outstanding builder, living on the banks of rivers, is of particular interest to farmers and water management specialists: the beaver. Long hunted for its fur and meat, to the point of coming close to extinction, this now protected mammal has gradually returned to certain French waterways.
“The beaver, a hydrologist who knows waterways very well”
In Ardèche, Lionel Coste, a rodent specialist, regularly observes its tracks with his team of naturalists. He has known for a long time the ecological interest of the beaver and is delighted with this awareness: "With climate change and major periods of drought, particularly in the south of France, the construction of dams makes it possible to create wetlands and above all to preserve them for a whole part of the summer. It also makes it possible, by retaining the water, to better supply the groundwater tables, so we can take an example, it costs us nothing and we know that it is very effective. And then the beaver has a few million years of experience, I think he is a hydrologist who knows the waterways very well."
In the Drôme, Cédric Cadet takes care of the rivers on behalf of the community and to try to give them back the place they have gradually lost, the project manager draws inspiration from the works of the beaver. With the “1:15 p.m. on Saturday” team, they walk a path that was once the bed of the river. "In 1965, here, there is not a tree, we are really in the bed. And 1965, on a hydrogeological scale, it is a minute ago. The river has completely incised itself, that is to say, it has sunk into the land. very quickly towards the Rhône, very quickly towards the sea. It’s a real hydraulic highway…” he laments.
Recreating buffer zones to avoid flooding downstream
Watercourses modified to favor human activity to the detriment of the balance of ecosystems and water management: "There was the drainage of landscapes, a massive extraction of wood from rivers. It was a big mistake... There was also major hydraulic work to try to control, channel the watercourses downstream. And that too, accelerated the watercourses and led to what we called regressive erosion, that is to say that the bottom is disappearing from the river And undoubtedly also the disappearance of the beaver", explains Cédric.
The territory was marked by the drought of 2022 where some villages no longer had access to drinking water. Beaver-style wooden dam construction operations then began in the spring of 2023. The goal: to slow down the water so that it infiltrates and ensures there is water all year round but also to avoid flooding in urbanized areas further down the river. “If we multiplied these operations over kilometers of waterways, we would recreate buffer zones which would be activated more quickly at the time of the flood. And therefore the flood would arrive much less quickly, much less strongly in the downstream areas,” demonstrates the site manager.
Upstream of the dams, their work over the past three years is beginning to bear fruit. The water meanders through the trees again and formerly dry land has been returned to the river.
