French police have fired tear gas at protesters at a large demonstration in the west of the country.
Thousands of people had gathered in Sainte-Soline to protest against plans for a new water reservoir.
Several police cars were set on fire after clashes broke out at the construction site.
The unrest follows weeks of anti-government demonstrations in Paris and other cities over President Emmanuel Macron's pension reforms.
Though unrelated to the protests over plans to raise the state pension age, the latest demonstration adds to the growing sense of public anger within France.
Opponents of the irrigation project in Sainte-Soline, near Poitiers, marched in large numbers on Saturday despite a ban on gatherings in the district.
The procession set off late morning, with at least 6,000 people taking part, according to local authorities, although organisers claim the group numbered 25,000.
They are protesting against one of the reservoirs being built in the Deux-Sèvres department - developed by a group of 400 farmers to reduce mains water usage in the summer.
France's worst drought on record last year intensified discussions over water resources. Supporters of artificial reservoirs say they could provide the solution to shortages during future dry spells.