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Ressources eau souterraines

Groundwater management

Flagship project / New decision support tools for better water resource management

Introduction d'entête
In a context of global changes, intensive exploitation and pollution of groundwater is a societal as well as a health issue. How can we ensure sound management of the resource while better managing its quality?
Body
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3D geological model showing the surfaces of the different formations (Quaternary, continental and marine Pliocene) on the Perpignan plain.
© BRGM

The issue of groundwater quality is a challenge for our societies, due to pollution from agriculture (nitrates, pesticides), industrial waste (heavy metals, nanoparticles) and wastewater discharges. In coastal areas, saltwater intrusion resulting from excessive exploitation can also adversely affect aquifer quality. BRGM has a long-standing interest in this subject, to the point of making it one of its scientific priorities. The teams follow a global and multidisciplinary approach that enables them to move from research to the creation of innovative tools that can be used on different spatial and temporal scales.
The aim is to offer technical decision-support solutions (monitoring tools, integrative passive samplers, hydro-geophysical observatories, models, advanced analytical technology for detecting emerging compounds, platforms for visualising integrated data on a region, etc.) for addressing regulatory issues or societal questions. Two projects carried out in 2019 demonstrate the variety of solutions to be implemented.

POLDIF is helping to improve the quality of groundwater in the Loire-Brittany basin

In the Loire-Brittany basin, the presence of nitrates or plant protection products has a major effect on groundwater quality. For example, the inventory carried out in 2013 under the European Water Framework Directive (WFD) showed degradation in 39 of the 143 groundwater bodies recorded in the area.

The aim of the POLDIF project is to create new tools to improve knowledge and management of groundwater quality in the basin. Its multidisciplinary approach brings together hydrogeologists, geochemists, economists, modellers, geologists, geophysicists and chemists. The approach is also being applied at different scales, from the entire basin down to the catchment area, and including experimental laboratory approaches.

Three different sites were chosen for their contrasting characteristics with respect to hydrogeology and agricultural pressure. The project has achieved some significant results. The use of integrative passive samplers to monitor water quality for over two years has led to the identification of compounds that were not previously monitored, found at low concentrations. The rate of nitrate and pesticide transfer from soil to groundwater was also estimated for different geological materials, underlining the importance of taking the transfer time into account when assessing actions to be taken. Lastly, a nitrate transfer modelling tool was coupled with an economic approach to assess the environmental costs and benefits of programmes undertaken to preserve or restore water quality.

Dem’Eaux tracking saltwater intrusion in Roussillon

Another issue is that if the recharge level of a coastal aquifer falls, this can lead to saltwater intrusion from the sea. What can be done to characterise this phenomenon in a complex multilayer aquifer and exploit the water it contains on a long-term basis?

Here again the Dem’Eaux Roussillon collaborative R&D project brings together geologists, geophysicists, geochemists, hydrogeologists, hydrologists, environmental economists and computer scientists, who are tasked with describing the characteristics and behaviour of the Plio-Quaternary aquifer of the Roussillon plain, whose groundwater supplies the greater Perpignan area with drinking water. The work initially led to a detailed characterisation of the geological reservoir. The first conclusion was that this coastal aquifer’s submarine extension over more than 20 km needs to be taken into account in order to understand how the aquifer works. The researchers also documented a generalised downward trend and its influence on the vertical leakage processes occurring between the aquifer’s different layers, by analysing the piezometric history of the entire plain over a 60-year period.

In addition, thanks to high-resolution hydro-geophysical observatories on the plain (one on the coast, the other inland), scientists can now monitor the processes controlling seawater intrusion and determine the mechanisms involved. A 3D real-time data visualisation system is being developed, in collaboration with the project’s other technical partners (universities, companies and local authorities). The aim is to create a resource management tool, a demonstrator likely to interest other regions affected by the issue of saltwater intrusion.

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Extract from the geophysical results obtained as part of the POLDIF project. A and B: 2D sections showing the distribution of raw and interpreted data on electrical resistivity. C: resulting geological cross-section. © BRGM

Dem’Eaux tracking saltwater intrusion in Roussillon

Another issue is that if the recharge level of a coastal aquifer falls, this can lead to saltwater intrusion from the sea. What can be done to characterise this phenomenon in a complex multilayer aquifer and exploit the water it contains on a long-term basis?

Here again the Dem’Eaux Roussillon collaborative R&D project brings together geologists, geophysicists, geochemists, hydrogeologists, hydrologists, environmental economists and computer scientists, who are tasked with describing the characteristics and behaviour of the Plio-Quaternary aquifer of the Roussillon plain, whose groundwater supplies the greater Perpignan area with drinking water. The work initially led to a detailed characterisation of the geological reservoir. The first conclusion was that this coastal aquifer’s submarine extension over more than 20 km needs to be taken into account in order to understand how the aquifer works. The researchers also documented a generalised downward trend and its influence on the vertical leakage processes occurring between the aquifer’s different layers, by analysing the piezometric history of the entire plain over a 60-year period.

In addition, thanks to high-resolution hydro-geophysical observatories on the plain (one on the coast, the other inland), scientists can now monitor the processes controlling seawater intrusion and determine the mechanisms involved. A 3D real-time data visualisation system is being developed, in collaboration with the project’s other technical partners (universities, companies and local authorities). The aim is to create a resource management tool, a demonstrator likely to interest other regions affected by the issue of saltwater intrusion.

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Geophysical investigations (here near Saint-Brieuc) generate resistivity profiles used to determine the hydrogeological functioning of a site. This knowledge improves our understanding of the contaminant transfer mechanism.
© BRGM - A. Portal
Portrait de l'auteur
Nicole Baran — hydrogéologue au BRGM
Prénom de l'auteur
Nicole
Nom de l'auteur
Baran
Fonction de l'auteur
hydrogeologist
Portrait de l'auteur
Yvan Caballero — hydrogéologue  au BRGM
Prénom de l'auteur
Yvan
Nom de l'auteur
Caballero
Fonction de l'auteur
hydrogeologist
We follow a global approach, covering technical, regulatory and societal aspects, that extends from research through to the creation of innovative decisionsupport tools.