Irrigation water storage pits farmers against communities over shrinking groundwater

Background

In basins where summer withdrawals are no longer sustainable, one response is to pump and store water in winter for summer irrigation (substitution reservoirs, known in the French debate as megabassines). The approach concentrates benefit on connected irrigating farms while the pumped resource, shallow groundwater, is a common good, which makes allocation fairness the heart of the conflict.

Observable evidence

• Deux-Sevres, France: a program of 16 substitution reservoirs led by the Coop de l'eau 79, roughly 70 percent publicly financed, became the national symbol of the conflict. The Sainte-Soline reservoir (627,868 cubic metres) drew a demonstration on 25 March 2023 with about 200 injured protesters per organizers (40 serious) and 47 injured gendarmes.
• Courts split the program: the Bordeaux administrative court of appeal ruled 4 of the 16 reservoirs illegal in December 2024 for lack of a protected-species derogation (the little bustard), while the Conseil d'Etat confirmed the other 12 in October 2025.
• The Loi Duplomb (August 2025) created a presumption of major public interest for agricultural water storage, upheld with reservations by the Conseil constitutionnel, keeping the legal ground contested.
• Scientific disagreement persists: BRGM modelling projects limited aquifer impact under substitution rules, while hydrologists and NGOs point to evaporation losses, maladaptation lock-in of irrigated maize, and biodiversity harm.

Who is affected

Irrigating and non-irrigating farmers, downstream communes and drinking-water syndicates, wetland ecosystems, and taxpayers financing the works.

Impact if unaddressed

Escalating territorial conflict over every storage project, legal uncertainty for agriculture, and continued aquifer decline while the fight absorbs the attention needed for demand-side transition.