President Emmanuel Macron announced new water-saving measures for France on Thursday as he sought to brush aside weeks of political turmoil after he imposed a deeply unpopular pensions reform.

Protesters calling for him to resign had gathered in the Alpine town of Savines-le-Lac ahead of his announcement, as he faces the biggest challenge of his second term in office.

Two people were arrested before he even arrived on the shores of western Europe's largest fresh-water reservoir.

"There is contestation over a reform, but it doesn't mean everything else should grind to a halt... We need to continue working," Macron told reporters to the backdrop of snow-capped mountains.

After a devastating heatwave last summer and record low rainfall this winter, Macron said he wanted to reuse 10 percent of all water in France by 2030.

"We have decided to launch 1,000 projects in five years to recycle and reuse water," he said.

"We want to reuse 300 million cubic metres, or... 3,500 bottles of water per French person per year," he said.

Last summer was Europe's hottest on record.

Winter has also been particularly dry in France, with a record dry spell of 32 days without significant rainfall earlier this year.

The country's groundwater levels were 80 percent lower than average on March 1.

People around France are still outraged over Macron's pensions plan, which includes raising the retirement age from 62 to 64.

"Manu, we have a lot to worry about if you're going to manage water like you did pensions," read one protester's poster in Savines-le-Lac on Thursday, addressing the president with an informal nickname.

- 'Unacceptable violence' -

Macron's government on March 16 triggered widespread anger when it invoked a controversial executive power to ram through the bill without a parliamentary vote.

After two months of largely peaceful mass protests, spontaneous demonstrations erupted on a daily basis, with some angry protesters clashing with security forces.

The authorities have blamed the unrest on violent "troublemakers" bent on damaging public property, but rights groups have criticised the police's disproportionate use of force in dealing with the crowds.

The unrest has also trickled into protests not directly related to the pensions reform.

Two men are fighting for their lives in hospital after clashes on Saturday at a rally against giant water "basins" in the southwestern village of Sainte-Soline.

Campaigners there were trying to stop the construction of the pools to irrigate crops, which they say will distort access to water amid drought conditions.

"There have been scenes of unacceptable violence these last few weeks," Macron said.

There were peaceful protesters in Sainte-Soline, the president said, but also "you had thousands of people who simply came to wage war".

France's highest constitutional authority will rule on the pensions reform on April 14.