Ruisseau des Planches (Planches stream) is a fragile water source for several municipalities in western Lyon, in France, which lack groundwater reserves. In 2024, the Lyon Metropolis commissioned setec to carry out a study to better assess the water resource and the volumes available for various uses.
“The first step was to assess the stream’s minimum natural flow and the needs of aquatic ecosystems: the difference gives us the quantities available for human use,” explains Céline Truffier, project manager at setec hydratec.
The study then looked at the various water management tools in the region. “The aim is to build consensus around the resource. Local stakeholders agree, for example, on maintaining water reservoirs for market gardening activities that supply the city: the challenge is to ensure that the necessary volumes are drawn from the stream in winter, to maintain sufficient flow for natural habitats in summer,” explains Céline Truffier.
In an urbanised environment, the challenge is also to reduce soil sealing. “Our study recommends separating the networks dedicated to wastewater and stormwater management, so that the latter can return to the natural environment or be used for domestic watering instead of being collected and sent to a treatment plant.”
Decision-making support
Finally, by modifying the morphology of the watercourse, it is possible to create safe havens for species during periods of drought and create a more resilient environment. “These proposals serve as decision-making tools for the local authority and provide a basis for consultation with local stakeholders,” concludes Céline Truffier.
