Understand everything about the "worrying" situation of groundwater

• French groundwater levels are particularly low at the start of the year and significantly lower than the previous year. 

• In France, groundwater provides around two-thirds of drinking water and one-third of agricultural irrigation.

• 20 Minutes

  looks for you at these water reserves at “worrying” levels. 

French groundwater is thirsty.

Our underground water reserves were at the end of December at "worrying" levels over a large part of the country, the Bureau of Geological and Mining Research (BRGM) warned on Friday.

What is going on ?

When to expect an improvement?

takes stock for you.

What's going on with our groundwater?

“The groundwater levels for the month of December are unsatisfactory,” writes the public body in a situation bulletin on January 1.

“More than three-quarters of the groundwater levels remain below the monthly normals with many sectors showing low to very low levels”, he notes, stressing that “the levels are significantly lower than those of December of last year”.

The BRGM thus notes “worrying” levels over a large part of the territory, with however a few local exceptions such as Brittany or Alsace.

In detail, the BRGM shows that only eight groundwater tables have levels "around the average", the others displaying a "moderately low", "low" or even "very low" level.

None are at “moderately high”, “high” or “very high” levels at the start of the year.

A worrying situation.

In France, groundwater provides around two-thirds of drinking water and one-third of agricultural irrigation.

Why are they empty?

According to Météo-France, 2022 was the hottest year ever recorded in France with 14.5 degrees of average annual temperature but also one of the driest, with a rainfall deficit of some 25%.

However, to fill up, groundwater tables need precipitation.

"The rains infiltrated during the fall are very insufficient to compensate for the deficits accumulated during the year 2022 and to improve the state of the groundwater in the long term", explains the Bureau of Geological and Mining Research.

And when it rains, soils that have been thirsty over time become partially impermeable.

The autumn rains, on very dry soils, therefore first benefited the surface soils and the vegetation before recharging the water tables at depth.

In this experiment Dr Rob Thompson of @UniRdg_Met shows just how long it takes water to soak into parched ground, illustrating why heavy rainfall after a #drought can be dangerous and might lead to flashfloods.

@R0b1et @UniRdg_water pic.twitter.com/zbb3xLTXdK

— Uni of Reading (@UniofReading) August 10, 2022

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Will the next few months bring enough rain to reverse the trend?

In its bulletin of major climate trends over three months for the period January March 2023, Météo-France did not advance at the end of December “no precise scenario” in terms of precipitation for France.

However, it is the rains that will be decisive.

"Trends and changes in the state of groundwater in the winter period depend exclusively on infiltrated rain, and therefore on rainfall accumulations, and the inertia of the groundwater [response time to infiltrated rain]", underlines the BRGM.

But the situation is alarming, especially in the Southwest.

“Today, we know that it will be practically impossible to fill them”, in the region, explains Guillaume Choisy, director general of the Water Agency of this area which extends over 25 departments of Charente-Maritime. in Ariege.

If rain is so rare in 2023, "we will arrive at a much worse situation than the one we experienced at the end of summer 2022", when almost all metropolitan departments experienced water restrictions, he said. added.

Orders are still in force in a dozen of them.

Can snow be a game-changer?

Snow is announced in the Pyrenees on Sunday.

“A period of cold weather with snow in the mountains can make it possible to regularly fill the dams during the melting”, explains Guillaume Choisy.

“But normally these dams are more than half full during this period.

There, they only oscillate between 17% in Ariège and 25% in the Hautes-Pyrénées and Pyrénées-Atlantiques, ”he warns.

The snow will allow the layers to fill up, but without it and without regular rainfall, the situation will be "extreme" in summer.

"Even for an average year, we will have difficulty providing for all uses," warns the director general of the Adour-Garonne Water Agency.

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• Environment

• Planet

• Drought

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• Potable water

• Heat

• Global warming