Projections on the future of water resources related to climate change appear to indicate a probable decline in groundwater resources in France, due to local decreases in the natural recharge of groundwater. As a result, measures to preserve resources need to be taken. Artificial groundwater recharge could be considered as a means of sustainably managing these resources. Surface water (in particular water courses) could be used for the artificial recharge of groundwater. The use of treated wastewater, subject to a change in the regulations (which do not currently allow their use in this framework), could also be considered.
This practice is particularly developed in countries under high water stress. In mainland France, it can be used occasionally, where it mostly has a quantitative objective to seasonally increase the resources used for the production of water intended for human consumption or for crop irrigation, and/or a qualitative objective to preserve these resources against pollution or saltwater intrusion.
Before considering the development of this practice, it is essential to identify the health hazards and risks that could result. Indeed, the water whose use could be considered may carry various types of microbiological and chemical contaminants. For this reason, ANSES issued an internal request, specifically within the framework of the French National Climate Change Adaptation Plan, to formulate recommendations in order to control the health risks associated with artificial recharge of groundwater, based in particular on experience of artificial recharge carried out in France and abroad.
The Agency’s recommendations
In light of the data currently available on the health hazards associated with artificial groundwater recharge from surface water and treated wastewater, ANSES considers that this practice could be used to counter the decrease in groundwater resources, under certain conditions:
- artificial recharge of groundwater must not degrade the quality of groundwater nor require additional water treatments after abstraction for the same use relative to a non-recharged resource;
- all recharged groundwater resources must be compatible with their current or future use to produce water intended for human consumption, in order to avoid undermining these resources for the future;
- the quality of the recharge water must be better than or at least equivalent to the quality of the groundwater.
Moreover, it must be possible to use the artificial recharge system in a sustainable manner, which in particular requires good management of the recharge site, monitoring of contaminants that may be present, etc.
The Agency reiterates that the artificial recharge of groundwater must not impact the achievement of the environmental objectives ensuing from the Water Framework Directive for the body of groundwater. It also emphasises the importance of preserving the quality of groundwater resources in the long term, specifically to guarantee quality compatible with production of water intended for human consumption, without needing to use additional treatments that would have to be paid for by local authorities and consumers.
In addition, projects for artificial recharge must be based on a specific need related to the target water resource (periodic shortage, balance between demand and the resource available).
Lastly, ANSES recommends improving knowledge on sites of artificial groundwater recharge in France, on the one hand to ensure sustained quality of recharged groundwater, and on the other to better characterise the hazards to humans.