The situation of groundwater tables in France did not change significantly in October compared to September, and two thirds of them remain below seasonal norms, announced Thursday, November 16, the Bureau of Geological and Mining Research (BRGM ).
As of November 1, France had 65% of its groundwater, the main reserves of drinking water, below normal, including 18% at very low levels, BRGM said in a press release.
This situation remains close to that of September, when 66% of the water tables were at insufficient levels, but turns out to be more favorable than in October 2022, when 75% of them were below the monthly averages, after a scorching summer .
A “relatively warm” September
If the rains of spring and summer made it possible to maintain or even improve the state of the water tables, the rains that fell in mid-October were on the other hand insufficient, notes the BRGM, describing an “unsatisfactory” situation. .
“Like last year, we had a relatively warm month of September and the beginning of October, vegetation which remained active until November and therefore with difficulty for the rains to infiltrate,” declared Violaine Bault , hydrogeologist at BRGM. The month of September was the hottest ever measured in France. But this report does not take into account the record rainfall totals recorded at the beginning of November.
With the October rains, “the recharge period begins,” notes the BRGM. However, the rains were very disparate in mainland France, and their impact was less strong on inertial layers – those which take the longest to recharge – than on so-called reactive layers.
“Satisfactory levels” in the West
Thus, if “the levels are satisfactory” in the West, going from Hauts-de-France to New Aquitaine, the situation is “more unfavorable” in the south of Alsace. The levels of the inertial layers of the Rhône-Saône corridor remain “worrying, from low to very low”, notes the BRGM.
Increased vigilance remains required during the fall, winter and early spring – a period conducive to the infiltration of water into the water tables thanks to less abundant vegetation –, more particularly for the water tables continuing to display low to very low levels. “The rains this fall will have an impact in November-December, and the levels at the end of winter will in fact be the accumulation of everything that will take place throughout the winter,” warns Ms. Bault.