2023-06-14 20:16:58
The Minister for Ecological Transition, Christophe Béchu, announced on Wednesday June 14 of its “very serious concerns” about the droughtparticularly in the Rhône valley and around the Mediterranean, while Météo-France and the Bureau of Geological and Mining Research (BRGM) published their bulletins on the hydrogeological situation of surface soils and reactive and inertial groundwater present in the subsurfaces. -soils.
The two documents, finalized on 1is June, draw a mixed picture. While the condition of surface soils improved in the southern half, they quickly dried up in May in the northern half. The state of the tablecloths remains “unsatisfactory over a large part of the country”.
Surface soils dried up in the north, re-humidified in the south
May 2023 didn’t quite follow the trend of previous months, according to Meteo Francesince soil humidification was observed in the southern half of the country and relatively rapid drying in the northern half.
In the South, soils received rainfall “frequent and abundant” thanks to the many storms that broke out during the month of May. After a rainfall deficit during the previous months, especially in Provence-Alpes-Côte d’Azur, the southern half of France has regained some color – with the exception of Languedoc-Roussillon, which did not benefit from the stormy rains and remains at July-like drought levels. “In the Pyrénées-Orientales, the surface soil moisture index has been posting almost uninterrupted low records since December 22, 2022”notes Météo-France, in the continuity of its previous bulletins.
The northern half of France, on the other hand, experienced the opposite situation: after relatively rainy months in March and April, the installation of a persistent anticyclone from mid-May caused the level of precipitation to drop, which show a marked deficit, particularly in Brittany, along the Normandy coast of the Channel, in Burgundy-Franche-Comté and in Alsace. This situation, made worse by a persistent north-easterly wind, very quickly dried out the soil, causing the benefit of the rainy spring to be lost.
The month of May ends with a 20% deficit in precipitation and an average temperature 0.77% higher than that of the years 1991-2020.
Since the end of May, the situation has worsened further in the northern half, due to temperatures well above seasonal norms which persist in many regions and which accentuate evapotranspiration, and therefore water loss from the soil. The national thermal indicator, which assesses the average temperature on French territory every day, has not fallen below 18°C since May 26. This uninterrupted series of twenty days is remarkable for its precocity and its duration.
The air humidity rate has also declined since the beginning of June, sometimes reaching unusually low values, as in Lorraine (barely 20%). Which has also earned certain departments to go into “high fire danger” on the new Météo-France forest weather map. Starts of forest fires have been observed in the Vosges – an extremely rare phenomenon for this region.
As for snowpacks, Météo-France mentions that on 1is june mantle water equivalent “has a deficit of more than 50% over a large part of the Alps”. The situation is relatively in line with standards in the Northern Alps, with a level close to normal for the period 1991-2020, but which remains very low for the south of the massif, below seasonal norms since the beginning of January. The situation is even worse in the Pyrenees, which have a snow cover deficit of more than 75%.
Groundwater: 66% of groundwater remains below monthly normals
May rains are “remained insufficient to generate recharge episodes and improve the state of the aquifers”analyzes the BRGM in its last update (published on June 14, it does not take into account the last two weeks). “During May, the groundwater situation changed only slightly and remained generally unsatisfactory”notes the body responsible for monitoring soil and subsoil resources.
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At the beginning of spring, the rains had partially remedied the low level of the water tables, linked to a very dry summer of 2022 and a winter recharge “deficit over a large part of the territory”. But they had not been enough to fill them, the vegetation having captured a large part of the precipitation. The rains of May, in the around the Mediterranean and in Corsica, have not brought groundwater levels back to normal either; they moistened the soil, nourished the vegetation and “rarely succeeded in infiltrating in depth”.
The result is a drop in groundwater levels in 60% of observation points (compared to 38% the previous month).
The situation is however “more contrasted” than in 2022, in the opinion of the BRGM. In the north of France, the most reactive aquifers, that is to say the most sensitive to precipitation, show satisfactory levels, better than last year, with variations depending on the sector (“moderately high to high in Brittany, “moderately low” in Lorraine and Berry, for example). In the southern third of the territory, the situation is quite different: “the rains of May were very insufficient to make up for the deficits of recent months”. In Roussillon, for example, certain observation points “show historically low levels”.
Groundwater levels should “remain on the downside for the next few weeks”, predicts the BRGM, even in the event of precipitation. Especially since the high temperatures anticipated by Météo-France “could contribute to increasing vegetation water requirements and water withdrawals” related to human activities.
New prefectural decrees have been published in recent days in an attempt to reduce these activities, by switching several areas, such as the Vendée et the Sartheat the “crisis” level, which prohibits the watering of green spaces and irrigation.
The Minister for Ecological Transition, Christophe Béchu, interviewed on CNewsasked to save water, by preventing leaks and fighting against waste, while climate change linked to human activities contributes to the degradation of water resources: ” We lived a bit like spoiled children, convinced that we would never run out of water. »
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