According to the Bureau of Geological and Mining Research, after a historically dry month of February, “all of France is affected”. Nearly 80% of the water tables thus show a level below normal.
Groundwater levels have never been so low. This is the observation made by the Bureau of Geological and Mining Research (BRGM), in charge of groundwater monitoring, in its latest report published on March 13, 2022. For the month of February, almost all “aquifers show levels below normal and 80% of them have a moderately low to very low level”explained Violaine Bault, BRGM hydrogeologist, at a press conference.
In comparison, in February 2022, only 47% of the water tables were below normal. “We have already experienced a similar situation” at that time, in 2012 and 2017, but what is new, “It’s that all of France is affected”, she points out. This unprecedented situation therefore accentuates the threat of a probable early drought in the coming months, according to the Bureau of Geological and Mining Research.
/2023/03/22/641afe17e3c2d_graph-nappes.png)
How to explain such a phenomenon ? “We had a rainfall deficit in 2021 and 2022”, explains Gilles Porel, hydrogeologist and lecturer at the University of Poitiers. In other words, the amount of rainwater falling on France “was too low between October and March, when water seeps into the soil to reach the water tables”.
According to Météo France, the month of February was the fourth driest month in France since 1959, with in particular a record series of 32 days without rain between January 21 and February 21 and an overall deficit of precipitation exceeding 75 %. This lack was particularly damaging, with a “sudden stop charging”deciphers Violaine Bault.
Less water and less good water
Result: the rains infiltrated during the autumn are very insufficient to compensate for the deficits accumulated during the year 2022, affected by major heat waves, and to permanently improve the fragile balance of the water tables. And after this winter period, even if it rains, it will unfortunately be too late to recharge the water tables, because “water no longer enters the soil in the summer because of the resumption of vegetation, which needs water to develop, and higher temperatures which promote evaporation”explains Gilles Porel.
This lack of water in the groundwater is likely to have significant consequences this summer, both on the environment and on human activity. Maintaining a balance between the water that penetrates the ground in winter and what humans can pump out the rest of the year is essential. Gold, “having empty tanks means that farmers and industrialists have to pump less and restrict themselves, which risks jeopardizing their production”explains Gilles Porel.
But another risk, also important, threatens human activity. A decrease in the volume of water poses problems as to the quality of the latter, because it risks being less diluted. “When there is an influx of clean water from rain in the soil, it dilutes the water already present in our natural reservoirs which can be polluted (with nitrate, for example)”describes Gilles Porel. “But if there is no water supply, the pre-existing pollution cannot be diluted, so we observe a higher concentration of undesirable elements.”