Despite heavy rains at the moment, the aquifers have dried up

ENVIRONMENT – Dry rivers, water no longer flowing from taps, waterless crops: images of the summer drought of 2022 caught the attention of the French. This winter, episodes of torrential rain from storms Gerard and Fien from late December and early in the week should reassure us about water supplies for the summer. And yet…

Unfortunately, this bad weather seems insufficient to raise the groundwater table, which is currently very low. “The same scenario applies in the summer of 2023 as in 2022,” wait with HuffPost David Labat, research professor at Paul Sabatier University in Toulouse.

Water restrictions in the middle of winter

Remember: the great mildness of late 2022 caused floods in France. For example, from December 31 to January 2, Brittany had a month of rain. In the Alps, incessant rains melted the little snow left on the slopes. The start of 2023 on January 10th, in just 24 hours, the equivalent of three weeks of rain in the Pyrenees massif, was not overlooked.

However, water levels are at levels “ worried » In most regions of France, as warned, the Bureau of Geological and Mining Surveys (BRGM) in its last monthly bulletin published on January 13.

” In December, the groundwater level is not satisfactory. “Indeed, autumn rains are too little to offset the accumulated deficit through 2022 and improve groundwater conditions in the long term.” BRGM continues « table air “. A public institution that also calls itself “fairly pessimistic” About water availability in 2023.

Neither Gerard nor Fien will allow the aquifers to be recharged

As of January 16, four departments are still on drought alert (Ille-et-Villan, Jura, Loser and Savoie) and eight are under water restrictions (Oise, Deux-Sèvres) or heightened preparedness. , Ain, Isère, Lot, Tarn-et-Garonne, Haute-Garonne and Pyrénées-Orientales), according to the government website Propluvia.

But can’t Gerard and Fien storms, which occurred in France in recent days with their share of precipitation, change the situation? Unfortunately not, answers David Labat. “When there are storms, the soil will be saturated. It is exactly like a sponge: when it is saturated, it cannot absorb more water. »

” Therefore, there is no vertical flow of water to allow recharge of aquifers “, continues researcher Paul Sabatier University. “It’s the same principle as summer storms: you can have 300 millimeters of water in a few hours without affecting the level of water tables,” later supports the professor of hydrology.

Obviously, when such bad weather occurs, the water runs off instead of seeping in, causing flooding. On Wednesday 18 January, Landes and Pyrénées-Atlantiques were also still under orange alert by Météo-France, where heavy rain was expected. “flood of rain”.

Two more months to reverse the trend

In addition to these adverse weather conditions, which had counterproductive effects, the extreme mildness of late December and early January did not allow for sufficient snow reserves. “This stock usually fills dams that regulate downstream flows (seasonal declines in rivers, editor’s note) in summer, Expect very dry lands and very low flows for July-August 2023, the researcher says.

The same alarming observation was made by Pierre Pannet, deputy director of BRGM, during a press briefing held in mid-January. If rain continues to be this rare in 2023, “ By the end of the summer of 2022, we will be in a worse situation than what we are living in.” while almost all metropolitan authorities are experiencing water restrictions.

If the groundwater situation in France is less favorable today than at the end of winter 2021-2022, there are still two months to reverse the trend. There is no miracle recipe for this: regular rains are necessary. “We need 20-30 millimeters of rain every two weeks in February and March.” still supports David Labat. After April, it will be too late, because the rains that mark the tip of the spring nose will soak into the budding vegetation and not drip into the groundwater.

“Water” action plan developed by the government

As for crops, the water situation is also very worrying in the Aude and Pyrenees-Orientales. soil moisture index is close to 0. Yes, zero, in January “, as noted by agroclimatologist Serge Zakan, in a message published on his Twitter account. The rains since January 15 and 16 are not “not enough to fill the gap, but it will relieve the fauna and flora in the first centimeters of the earth”makes the researcher somewhat relativistic.

Faced with 2022, the hottest year on record in France, with a rainfall deficit approaching 25%, the government is now drawing up an action plan. “water” For 2023 “Reducing water consumption and optimizing withdrawals, better reuse of wastewater and accelerating the reduction of leakages in water networks”. Details of the measures will be announced at a meeting of local water authorities in Rennes on January 26.

“ The government no longer has a choice: we must enter a period of water vigilance.”, there is still a lot of David Labat. The hydrologist reminds that record droughts will continue to increase with climate change. “The odds of a major deficit year like 2022 occurring in the 1980s were 20 in 10, today that chance rises to one in five. »

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