The role of deep groundwater management strategies in ensuring sustainable resource management and preserving dependent ecosystems Case study of the Gironde department, France

In the Gironde department (France), which relies on deep aquifers for 97% of its drinking water supply, groundwater management is critical to meet human needs while preserving ecosystems dependent on these resources. With a population of 1.7 million, including Bordeaux Métropole, and a history of overexploited aquifers identified as early as the 1990s, local stakeholders have adopted innovative approaches to ensure long-term resource sustainability.

Groundwater management in Gironde combines global and local strategies. At the global level, the SMEGREG (a public entity dedicated to deep aquifers) developed a trial-and-error methodology to determine extractable volumes, incorporating extraction scenarios, regional flow model simulations, and expert validation. A panel of hydrogeological experts - currently unique in France - examines variations in groundwater reserves and evaluates their acceptability. Adherence to these extractable volumes is now central to the region’s water management strategy.

However, meeting human water needs is not the only concern of local stakeholders. Locally, the focus shifts to preserving groundwater-dependent systems (wetlands, rivers, springs, etc.) by identifying these areas and maintaining critical piezometric levels. An atlas of groundwater-dependent systems is currently being developed. This atlas is designed to facilitate the management of interface environments and to provide a shared foundation for establishing operational management rules.

Additionally, a strong emphasis on public awareness and demand management has been pivotal. Programs such as "Espaces Info Économie d'Eau" (information booths on water resources and consumption management) and "L'eau un enjeu majeur" (school-based awareness programs) engage the public and students, while technical guides and communication campaigns encourage water-saving behaviors. These efforts have allowed the region to accommodate 300,000 new residents without increasing water extractions, demonstrating the effectiveness of managing demand to complement supply-side strategies.

By adopting this dual-scale approach, combined with a water-saving strategy, the Gironde department exemplifies how sustainable groundwater management can effectively balance the needs of human populations and fragile ecosystems. However, with the increasing population driving higher water demand despite the ongoing conservation efforts, and the significant influence of recharge modifications on these inertial hydrosystems, the ongoing revision of the Water Management Plan (SAGE) will provide an opportunity to collectively adapt our water management strategy to ensure long-term sustainability.