Pauline Drzewiecki, BRGM’s Regional Director, and Delphine Alexandre, Vice-President of the Regional Brittany Council, signing the MétéEAU Nappes Agreement on 22 January 2025 in Rennes.
© BRGM - Pierre Vassal
Implementing the MétéEAU Nappes tool throughout Brittany
Water supply issues were particularly acute in Brittany in 2022–2023, highlighting the need to better anticipate and manage the region’s groundwater resources at times when they are under pressure during the low-water period. Groundwater accounts for more than a quarter of the region’s water resources and is used to supply drinking water. Groundwater resources also contribute to supporting Brittany’s river flows, particularly during the low-water period. Given their role, the decision was taken to roll out the MétéEAU Nappes tool throughout Brittany. BRGM is working towards this with the support of the Brittany Region.
As well as real-time monitoring of groundwater levels, MétéEAU Nappes can be used to produce seasonal forecasts based on various weather prediction scenarios up to 6 months ahead. To achieve this, the monitoring points used for the platform must have a sufficiently long history of measurements to allow for robust statistical predictions. The dynamics of aquifers (water-filled rock layers) vary considerably depending on local geological conditions, and modelling is required for all the observation points to be included in MétéEAU Nappes.
Groundwater level predictions will be translated into maps and diagrams. Featuring a dynamic, easy-to-use web interface, the tool will inform users of likely groundwater levels for a range of 6-month weather scenarios and of any water usage restrictions applied locally if drought conditions are expected. The tool could also be useful to anticipate intense rainfall events and the risk of groundwater flooding.
This €270,000 project involves modelling 25 groundwater observation points across Brittany by the end of 2026.
How BRGM monitors groundwater in Brittany
In Brittany, groundwater levels are monitored continuously and in real time by BRGM using 52 piezometers (boreholes that are used to determine water table depth at that point). They are distributed throughout the region to cover the main geological and hydrogeological formations and variations in climate from west to east and inland from the coast. The nature and geometry of rock layers vary greatly on a local and regional level, meaning that the aquifers are highly diverse depending on many hydrogeological factors, such as geology, porosity, permeability, depth, weathering and responsiveness to precipitation; which all need to be evaluated.
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