Red alert on groundwater. Suffering for several months, these natural water reserves continue to suffer from the unusual autumn heat and insufficient rainfall. Their charging period, which traditionally starts in September, is delayed and still remains "very uncertain" for October, already raising concerns for 2024.
On 1 October, 66% of metropolitan aquifers were still below normal, a slightly worse situation than at the end of August (62% below normal), the Bureau of Geological and Mining Research (BRGM), which is responsible for monitoring the main drinking water reserves in mainland France, announced on Thursday.
Read alsoDrought: why the groundwater situation "continues to slowly deteriorate"
"The storms in mid-September were not very effective for the recharge of the aquifers" and consequently "the situation deteriorates between August and September", says the public body, noting that 18% of its observation points remain at very low levels. Nevertheless, "the situation is generally more favourable than that observed last year, in September 2022, when 74% of levels were measured below normal," BRGM points out in its monthly bulletin.
Contrasting situation
However, the situation is more mixed. The rains that fell in places in the spring and summer have helped to partially recharge some of the aquifers. This is the case on certain parts of the coast, from Seine-Maritime to Pas-de-Calais or the Atlantic coast.
In Charente, in the Massif Central and in the south-east, the rains that occurred in mid-September did not have a visible impact on the aquifers, due to low infiltration and still very active vegetation that absorbed most of the water flowed.
However, most of the country is still facing worrying groundwater levels, particularly around the Mediterranean, in the Rhône-Saône corridor and in southern Alsace. According to the Propluvia website, about two-thirds of metropolitan departments remain at least partially at the crisis red level for drought, leading to significant restrictions on access to water.
Pivotal period
The situation is all the more worrisome as autumn is a "pivotal period". September usually marks the beginning of the resumption of charging, with the occurrence of the first significant rainfall and the drop in temperatures. But this year, "the share of rainfall infiltrated deep remains low due to insufficient rainfall and localized and intense thunderstorms favoring runoff. In addition, the vegetation is still active, due to high temperatures, and consumes some of the infiltrated water," BRGM points out.
According to Météo France, this first month of meteorological autumn was the hottest September ever measured in France, continuing a series of almost two years above normal for the season.
Read alsoWeather: 20 "abnormally hot" months in a row... A record-breaking streak that may not be over
"The mild temperatures are likely to postpone the dormancy of vegetation" and consequently the recharge of the aquifers, according to the BRGM. "The start of the charging period therefore remains very uncertain for the month of October," the organization concludes.