Outstanding result / Nature-based solutions: a toolbox for sustainable groundwater management

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GPS referencing of a piezometer (instrumentation for monitoring and analysing water quality) located in the infiltration basin of the controlled aquifer-recharge system. © BRGM - G. Picot

BRGM is developing a catalogue of nature-based solutions for sustainable groundwater management through two projects, JPI Water EVIBAN and SFNGest'ESO. 

Whether new or already known (but re-adapted, or used in an original way), nature-based solutions are, by definition and above all, "natural". They can be applied in both rural and urban environments and are in line with key objectives in the fight against climate change, notably as regards addressing the increasing scarcity and deterioration of water resources, and the need to protect biodiversity in aquatic environments.

The use of NBSs in the fight against climate change

Nature-based solutions bypass the limits of conventional means used until now. Indeed, over the last few decades, conventional civil engineering solutions have shown their limits in mitigating the effects of climate change. Episodes of extreme rainfall or drought have challenged conventional management methods. For example, storm-water basins, which retain excess rainwater produced during a storm, were designed to deal with known rainfall patterns. But in the face of accelerating climate change, these basins are no longer suitable. 

The artificialisation of land combined with increasingly dense urban development (housing) has also increased the risk of flooding due to soil sealing. In this context, heavy rainfall can cause drainage and sewerage networks to flood, and affect the operation of treatment plants, resulting in the risk of environmental pollution due to the discharges from waste-water treatment plants (affecting rivers, lakes, sea, subsurface and groundwater). BRGM is therefore working on all these different issues.

JPI Water EVIBAN: an experimental site for controlled aquifer recharge which eliminates micro-pollutants

This European programme, which ended in 2023, concerned a French pilot site located in Normandy. The programme confirmed that a system involving the collection and treatment of waste water in a traditional treatment plant combined with infiltration through the soil and through the coastal dune aquifer (already in use for 30 years) can provide additional water treatment to eliminate micro-pollutants, which are not yet monitored within the regulatory framework of this controlled aquifer-recharge system.

The dune aquifer acts as a natural filter. BRGM, which worked with the municipal council and the water-management operator Saur on this programme, analysed the water and was able to model and reproduce the behaviour of flows and certain micro-pollutants. While such practices go back a long way, reed beds were added to the infiltration basins on this pilot project to make the system more sustainable and adapted to the natural site of this coastal area. 

The JPI Water EVIBAN programme carried out on this site had a significant impact; notably, it raised the awareness of the local population about these systems and changed the way they are perceived, since local people realised that the waste-water treatment plant could pollute the coastal waters.

Thanks to the experimental monitoring and the model developed for this pilot project, local stakeholders are now interested in deploying these solutions to reduce the environmental risk at other coastal waste-water treatment plants in Normandy.

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Proportions of treated waste water (TWW) in the coastal dune groundwater at Agon-Coutainville and main behavioural patterns of recharged TWW in the aquifer (direction, flow velocity and TWW proportion) simulated by the hydrodynamic model. © Guillemoto et al. 2023

SFN-Gest’ESO: studying the effects of NBSs at aquifer level

Managed by BRGM in partnership with AERMC (Rhône-Mediterranean-Corsica Water Agency), this programme aims to examine the direct effect of NBSs on groundwater. While the solutions concerned are often well known, using them as a means to achieve sustainable groundwater management is a new approach. 

Three areas, each being representative of a different environment, were studied using a multidisciplinary approach combining hydrogeological tools, interviews with local stakeholders and surveys among the general public. 

In the Drugeon catchment basin (Doubs), the rewilding of the watercourse and the rehabilitation of peat bogs – implemented to restore aquatic biodiversity –have helped to mitigate the effects of climate change on aquifers while reducing greenhouse gas emissions.

In the Vistrenque-Costières area (Gard), an ecological compensation programme based on semi-natural grasslands has helped to restore the quality of the aquifer used to supply drinking water. In eastern Lyon, alternative storm-water management solutions based on "soil unsealing" can be used to increase aquifer recharge and improve the catchment basin's capacity to mitigate the effects of climate change.

Based on these promising results, greater consideration needs to be given to groundwater when designing NBSs, in order to strengthen the coherence between public policies and enable local regions to improve their resilience to global change. 

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Hydrogeological processes associated with the use of NBSs in agro-forestry environments. © BRGM