Drought: because the abundant spring rains will not be enough to recharge the aquifers

The rains of recent months raise questions… After a particularly dry winter, will the unusual spring rainfall be enough to avoid the drought already announced for this summer 2023? No, according to the Bureau of Geological and Mining Research. The latter announced on Wednesday May 17 that on May 1, 68% of French groundwater remained at worrying levels. And this despite the abundant rains that fell in some regions in the last two months, “In March and April 2023, the accumulation of precipitations was in excess over a large part of the territory” which had “a beneficial impact” on the water the two northern thirds of the territory, but “the situation remains unsatisfactory in a large part of the country”, indicated the BRGM.

“Tablecloths not yet sufficiently refilled”

“The situation in early spring is worse than last year”, when in April only 58% of groundwater levels were below normal, the organization underlines. This could therefore portend an even drier summer this year. The summer situation of 2022 had already been marked by an exceptional drought.

However, unlike last year, France was particularly rainy in the months of March and April, especially in the northern part of the country. “These rains have made it possible to generate recharge episodes and to postpone the start of the emptying period in the more humid sectors”, notes the BRGM.

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“It is the vegetation that will first use this water, then what remains will then be in the soil,” Éric Sauquet, hydrologist at INRAE ​​explained to franceinfo in particular. “There is the risk of having layers that are not yet sufficiently recharged compared to what is normally expected”.

If the groundwater situation has “significantly” improved on the groundwater of the Armorican massif, the Manche coast and the Grand-Est, it is more complicated in the south of France. The rains infiltrated in depth “were insufficient or even non-existent”. And the situation in the coming weeks will not go in the right direction, according to the BRGM. He anticipates that, in the month of May, “in the absence of sufficient rainfall, the depletion should generalize to all aquifers. The levels should then remain low and the situation should deteriorate” more or less rapidly depending on the region.

Agricultural drought and underground drought

On May 1, 17% of groundwater levels were above the monthly norm (8% in March), but 68% of levels remained at moderately low to very low levels,” including 20% ​​at very low levels (19% in March), underlines the BRGM. But according to the agrometeorologist Serge Zaka, the drought of the aquifers must be distinguished from the agricultural drought. The latter “concerns the first two meters of soil and therefore the surface water which allows plants to develop,” explains in Marianne. Groundwater drought is the one “against which the ongoing rains are powerless, while it is the most worrying”.