The contrast is striking. A year ago, at the end of winter, the map of the state of water tables in mainland France was mainly covered in orange and yellow. A sign that the water reserves were too low. This year, the situation detailed this Thursday March 14 by the Geological and Mining Research Bureau (BRGM) is much more favorable. Largely tinted with blue, from Brittany to the Basque Country, via Lille and Strasbourg, the map for 2024 shows excess recharge over a large part of the territory.
Ultimately, at the beginning of March, according to the public body responsible for their monitoring, 46% of aquifers showed levels above monthly normals, compared to 5% at the same period last year. And those located in the Paris Basin, Normandy, the Massif Central and Provence-Alpes-Côte d’Azur were close to normal, barring local exceptions. Overall, the winter in the country was marked by a 10% excess rain, according to Météo France, even if these were unevenly distributed in France. Since December, charging “was very satisfactory so that [rend] optimistic”, echoed Violaine Bault, hydrogeologist at BRGM.
Only a third of the water tables remain below normal, compared to 80% last year. But these figures do not take into account the recent Mediterranean episodes and their procession of precipitation, in particular those which affected the Gard last weekend.
Contrasted situation
Among the underground reserves still in deficit, “places worry us: part of the Mediterranean rim, a small part of the Rhône valley and especially this territory of the Pyrénées-Orientales which is in an atypical and terrible situation”, highlighted this Thursday morning on France Info the Minister of Ecological Transition, Christophe Béchu. In mainland France, 9% of water tables even display “very low” levels, including those in Roussillon, which cross the Pyrénées-Orientales. Resources are historically low in this department, the driest in France due to an abysmal lack of precipitation for three years. “There has been no recharge for a year and a half,” enlightens Violaine Bault, including this winter. The few recent rains “were insufficient to penetrate deeply. They were only used to moisten very dry soils. adds the expert. Due to the shortage of blue gold in underground stocks, the BRGM is warning of a “high risk” of seawater intrusion into coastal water tables and specifies that all drinking water withdrawals have been prohibited on the coast of the Pyrénées-Orientales.
More broadly, in Occitania and as far south as the Massif Central, the state of the water tables has deteriorated in one month: a large area has gone from orange to red due to the lack of rain. Further north, in the Saône corridor, from Dijon to the north of Lyon, as well as in the south of Alsace, low levels are also considered “concerning” by the BRGM.
“You have places today where there is too much water, places where there is not enough,” summarized Christophe Béchu. The month of February was particularly mixed in terms of precipitation, with downpours in many departments and almost summer-like weather across the Mediterranean arc. A typical phenomenon of climate change, which accentuates the extremes: while the Pyrénées-Orientales remain thirsty, the Pas-de-Calais, saturated with water, has seen certain water tables overflow, which has prolonged the flooding of the rivers.
Restrictions in five departments
Currently, the majority of the city’s water tables continue to fill. “Trends are still on the rise even if charging slows down,” said Violaine Bault. And to add that the phenomenon “should continue in March and April, until vegetation resumes [qui capte l’humidité pour pousser, ndlr] provided there is enough rain.
However, Météo France predicts that next three months will be warmer than normal, which could quickly dry out the soil and increase water demand. From spring, stocks will start to decline again as they will naturally feed the rivers and be pumped for human activities.
Vigilance therefore remains essential. The BRM warns of an even greater risk of drought “severe in 2024” in Languedoc-Roussillon if it does not rain in the next two months. Tensions on the resource will also be “probable” in the Saône corridor. To anticipate, some territories have already taken measures to save resources in view of a potentially complicated summer. According to VigiEau website, five departments are subject to restrictions on use at the end of winter. A large part of the Pyrénées-Orientales, where restrictions have been in place for almost two years, remains classified in a state of “crisis” (the highest level), as does a portion of Aude and Hérault. The Lozère department is placed on “alert”, and further north, part of Ain is on “heightened alert”. Despite being in the red, Aveyron has not yet implemented any saving measures.