As you may have noticed, there's a lot of driftwood on the Serre-Ponçon reservoir. This phenomenon recurs every year. However, it's much more pronounced this time of year: why is this, and what can be done to control it?
An event linked to violent meteorological phenomena.
Although our reservoir is man-made and regulated by its concession-holder, EDF, it is nonetheless vulnerable to the vagaries of the weather. The bad weather of December 2023 and spring 2024 is testimony to the violence of these phenomena, which global warming tends to increase. Not seen since 1957, these torrential floods swept away shrubs, trees and other materials, generating ice jams in the heart of the lake estimated at a total volume of 130,000 m3.
At the heart of the lake? not quite! In the spring, the S.M.A.DE.SE.P. undertook 4 worksites, which, at a cost of almost €200,000, made it possible to remove more than 50,000 m3 of wood from areas that could be mechanized, but a large proportion of the driftwood could not be treated, as it scattered along the 92 km of shoreline inaccessible by land. In the absence of any intervention, the lake's upwelling is now returning this wood to the water, creating risks and inconveniences for water sports activities.
As you can see, water level plays a major role, but not the only one! Wind is more than an asset. Thermal breezes, which only develop in the afternoon under the effect of the heat, send the wood back to the end of the lake, concentrating it. We had to wait for the late summer temperatures to benefit from these breezes. This made it possible to set up booms, which you'll find on the Ubaye branch, the Réallon torrent and the Boscodon. More than 15 booms have been designed and positioned to block the wood in certain sectors, so that it can then be extracted in dedicated areas.
For the time being, the question of how to recycle these materials remains a real challenge for the syndicat mixte. While the French government no longer authorizes the burning of wood, the search for economic recovery of this "waste" remains fundamental in order to reduce the cost of treatment. The lake's resilience plan takes this issue fully into account, with a view to investigating ways of recycling it, particularly in terms of the feasibility of a "garden soil" sector. At any rate, this is the direction the syndicate is taking!
Whether you're a swimmer, a yachtsman or a walker, the Serre-Ponçon lake is just as beautiful as it is beautiful, but requires extra care and vigilance!
We're sure you'll come across our teams working on the daily beach sweep. Don't hesitate to come to their aid by concentrating your wood on the same area: a helping hand, however small, becomes important if, on the scale of the whole lake, we are all mobilized!