The study prior to the establishment of a water resources management plan (2021-2025) for the Monts du Devès groundwater body aims to acquire new knowledge to prepare the management of Devès groundwater. This underground resource is present in the basaltic flows of the Devès volcanic massif located mainly in Haute-Loire and Ardèche and serves more than 100,000 people in drinking water in Haute-Loire, Ardèche and Lozère, agricultural uses (livestock watering, ...), geothermal and natural, for watercourses and wetlands. This resource is currently unknown, but several indicators already show its fragility (lowering of one of the slicks of the massif since 2015, difficulties of drinking water supply for several communes of the massif during the drought of 2022). And climate change scenarios predict a 20% reduction in the recharge of Devès aquifers by 2050, knowing that the areas served by the resource could at the same time increase. Hence the need to set up a management of this resource.