Explain megabasins to us

A year after the Sainte-Soline clashes, megabasins are still at the heart of the news. The government intends to facilitate and simplify their installation.

The “Uprising of the Earth” collective calls for Monday evening March 25 for rallies in front of the prefectures or gendarmeries of several departments, one after the violent clashes which broke out during a gathering banned by the Deux-Sèvres prefecture against a water reserve in Sainte-Soline. They caused numerous injuries, including two demonstrators who fell into a coma.

These megabasins are also called “substitution reserves”. These are huge water reservoirs built to supply certain agricultural operations. The megabasins are dug in the plain, plasticized and waterproof. They are surrounded by dikes several meters high, can extend over several hectares and contain hundreds of thousands of cubic meters of water. They are particularly present in the west of France, especially in the Poitevin marsh area.

The filling method

They fill most of the time, by pumping water into the groundwater when they fill in winter. Rainwater would not be sufficient to fill the megabasins, especially when it does not rain for months. The idea of ​​their promoters is to store the pumped water “in the open” to distribute it during periods of drought, in summer, to their crops or livestock meadows. For them, the survival of their farms is at stake.

These megabasins are the subject of several criticisms. The main point of discontent put forward by opponents is emptying groundwater for the benefit of a few farms, but to the detriment of other water users. Seeing part of the stored water evaporate or bacteria and algae developing in the megabasins are also among the concerns. Finally, for the opponents, with these reservations, we do not raise the question of crops that consume too much water.

The government’s position

The executive supports this type of water reserves and refutes the term megabasins. The government intends to facilitate and simplify their installation, but also to finance them with tens of millions of euros. A way of responding to the current anger of the agricultural world. Several mega-basin projects have been abandoned or suspended in recent years following appeals to administrative justice. For some, already built, it was forbidden to fill them.