The hydrogeological situation on 1 March 2025
In February 2025, the recharge was insufficient over a large part of the country and only the south-east benefited from effective surplus rainfall. The situation remained above normal for the aquifers in the western half of the country. In the eastern part of the country varying, and less positive levels were recorded in the aquifers, generally ranging from moderately low to moderately high. The levels in the aquifers in the Roussillon region and Corbières Massif remained low to very low.
Until vegetation starts to grow again, the trends and the situations of the aquifers around the country will depend mainly on rainfall. The generally positive start to the 2024-2025 recharge period means we can expect satisfactory levels across much of France at the end of winter. However, if the seasonal forecasts of Météo-France are correct, a lack of rainfall is expected at the end of winter and the beginning of spring. In this case, the state of the reactive aquifers could deteriorate rapidly.
Carte de France hexagonale de la situation des nappes d'eau souterraine au 1er mars 2025.
© BRGM
Evolution of the trends observed on piezometers from March 2024 to February 2025.
© BRGM
Trends
The recharge began in September 2024 in the rainy parts of the country with reactive aquifers and was active in all aquifers around the country in October. Overall, the recharge was extremely dynamic in October, but slowed significantly in November. It then picked up again in December and January, except in the south-east.
In February 2025, the recharge slowed and the water levels increased in only 49% of aquifers (71% in January). The trends for the month varied depending on the amount of local rainfall and how reactive the aquifers are.
In the south-east, the aquifers in the southern Massif Central, Languedoc (except Aude), Lower Rhône, Provence and Côte-d’Azur regions benefited from several recharge episodes during February. The levels generally rose sharply, particularly in eastern Languedoc and in the Cévennes foothills. In the aquifers of the Bas-Rhône, Durance rivers and in the Grands Causses area, the evolution in water levels varied according to the amount of local rainfall during the month.
Across the rest of mainland France and in Corsica, insufficient rainfall filtered deep into the ground during the month of February. Overall, the reactive aquifers had two recharge episodes: the first at the beginning of February, following the heavy rainfall at the end of January, and the second during the last ten days of February. However, the trends were variable and depended on the amount of water that filtered down into the ground. Consequently, the trends started to reverse in many reactive aquifers, which recorded stable or falling levels, since the effective rainfall no longer offset the outflows to natural outlets (watercourses, springs, sea) and abstractions. This was particularly the case in the north-eastern quarter of France and in the northern and central parts of the Massif Central, as well as in the Armorican Massif, the Aude valley, Roussillon and along the Corsican coastline, with the exception of Cap-Corse.
As regards the inertial aquifers, the general trends did not change compared with the previous month. In the Artois and Paris Basins, the Sundgau (southern Alsace) area and the Saône corridor (Dijon, Bresse and Dombes), the winter rains are slowly starting to seep through and are gradually reaching the aquifers. Consequently, the levels continued to rise: the recharge continued but slowed down in less inertial areas. In the Rhône corridor, from the Savoie foothills to the Bas-Dauphiné, the recharge remained modest. Levels in February generally remained low or stable.
Comparison between 1 March 2024 and 1 March 2025
Map of France showing the state of the aquifers on 1 March 2024 (left) and 1 March 2025 (right).
© BRGM
Evolution of the situation observed on piezometers from March 2024 to February 2025.
© BRGM
Aquifer situation
The recharge period began between September and October 2024 and reached particularly high levels. The changes in the aquifer levels then varied during the winter according to the rate of recharge inflows. Overall, the situations deteriorated slightly in November and December 2024 and then improved in January 2025. Aquifer levels remained above the monthly averages. In January, only the aquifers in Roussillon region and around certain parts of the Mediterranean coast, from Languedoc to Provence, had low to very low levels.
In February 2025, the overall state of the aquifers deteriorated again but still remained above average: the levels recorded at 19% of the observation points were below monthly norms, 21% were comparable with monthly norms and 60% were above average (compared, respectively, with 18%, 14% and 68% in January). It should be noted that 16% of the points monitored reached very high levels in February (also 16% in January).
The situation was slightly better than last year, in February 2024, when 46% of the levels observed were above monthly norms. Currently, many aquifers have higher levels than those recorded during the same period in 2024. This is particularly true for the inertial aquifers in the Paris Basin, whose situation has gradually improved over the last 12 months, and for the aquifers on the Mediterranean coast and in Corsica.
The changes observed in the reactive aquifers depended on recent rainfall totals. Consequently, the state of the aquifers started to deteriorate in February in areas that did not receive sufficient rainfall (north-eastern quarter of France, northern and central parts of the Massif Central, and the Aude valley) but improved in the south-east, which received heavy rainfall (southern part of the Massif Central, eastern Languedoc, Provence and the Côte-d’Azur).
The situation in reactive aquifers remained generally satisfactory, from moderately low to high. More specifically, the reactive aquifers in the western half of the country had surplus levels, generally moderately high. The aquifer levels recorded in areas that experienced heavy rainfall in January were high: the Jurassic limestone aquifers of the Brenne and the Vienne regions and the basement aquifers of the south-eastern Armorican Massif. Over a large north-eastern quarter of the country, the aquifers were affected by a recent lack of rainfall and the levels were moderately low to close to normal. In the south-east, the February rains were beneficial. The aquifers' levels ranged from moderately low to moderately high. Certain local situations remained vulnerable, with low levels in the downstream area of the Aude valley, which received little rain in February, and in the Astien aquifer between Valras and Agde. Levels in the aquifers of the Roussillon plain and Corbières Massif remained low to very low. The rainfall in recent months has not managed to compensate for the accumulated lack of rainfall over the last three years in the Pyrénées-Orientales département. Finally, the situation in Corsica is due to the uneven distribution of rainfall: levels were moderately high to high in the north-east of the island and close to normal to low on the west and south-east coasts.
As regards the inertial aquifers, the situations are changing extremely slowly and remained very similar to those recorded in January 2025. The levels of the aquifers of the Paris Basin and the Artois Basin were moderately high to very high. No observation point had levels below normal, except for the Cenomanian sand aquifers in the Perche and Maine regions. An increasing number of piezometers are showing very high levels, and some have reached levels not seen for 20 years, notably in the aquifers in the Brie Tardenois, Vexin and Beauce regions. The aquifers in the Sundgau (southern Alsace) and Saône corridor have remained, respectively, moderately low and comparable to normal since the summer of 2024, due to their significant inertia. Certain situations varied locally, with levels ranging from low to high. In the inertial aquifers of the Rhône corridor, the situation is deteriorating upstream and downstream, due to inconsistent rainfall in recent months. Levels were above monthly averages in the Savoie foothills and eastern Lyon area, close to average in Northern Isère and moderately low in Lower Dauphiné.
Aquifers with surplus water
Several aquifers showed surplus levels, with high to very high levels, compared to those recorded for February in previous years:
- The recharge continued in the inertial aquifers in the Artois Basin and eastern Paris Basin, which had high to very high levels;
- The reactive aquifers in the basement formations of the south-eastern Armorican Massif and in the Jurassic limestone formations of the Brenne and Vienne valleys declined from very high down to high levels after the heavy rainfall in January;
- The levels of the inertial aquifers in the Savoie foothills remained high and stable in line with the levels of January 2025.
Aquifers with low water levels
The situation was unfavourable in several aquifers with moderately low to very low levels compared to those recorded for February in previous years:
- The reactive aquifers of the north-east (the Jurassic limestone aquifers in Lorraine and the Côte-des-Bars, the basement aquifers in the east and aquifers in the volcanic formations of the Massif Central) had a lack of rainfall in February and recorded moderately low levels;
- The levels in the aquifers in karst limestone formations of the Corbières Massif remained low;
- The situation in the aquifers in the Roussillon multilayer formation remained critical, with low to very low levels.
Aquifer recharge: 3 questions to provide a better understanding of the process
How do aquifers fill up and how do they empty?
Groundwater levels vary throughout the year, from high levels in winter (when vegetation does not absorb rainwater) to low levels in summer (the traditional depletion period).
The fate of rainfall varies greatly depending on the time of year and the condition of the ground surface on which it falls. Usually, the groundwater-recharge period takes place from early autumn (September-October) to early spring (March-April), a six-month period during which vegetation is dormant (with low evapotranspiration) and rainfall is generally more abundant. If the winter is dry, groundwater recharge is very low.
From spring through summer, rising temperatures coupled with the regrowth of vegetation and thus increased evapotranspiration, limit the infiltration of rainfall into aquifers. Between May and October, unless there are exceptional rainfall episodes, aquifer depletion usually continues and levels will keep decreasing until the autumn.
Why do some aquifers recharge faster than others?
Groundwater flows at different rates depending on the porosity (percentage of gaps/cracks in the rock) and permeability (capacity to allow water to circulate, i.e. interconnectivity between these gaps/cracks) of the aquifers. The larger the gaps and the more interconnected they are, the faster the water will flow, for both refilling and depletion.
It takes a given volume of water different periods of time to travel the same distance, depending on the kind of rock formation:
- a few years in a porous formation,
- a few months in a cracked formation,
- and a few days, or even a few hours, in a karst formation.
Inertial and reactive aquifers: what are they?
The impact of the winter recharge varies according to the cyclic nature of the aquifer, i.e., its reactivity to rainfall infiltration.
We refer to aquifers that are:
- reactive (when they are composed of sand, gravel, karst limestone or weathered granite formations). These aquifers are characterised by their rapid reaction times: they can recharge during heavy summer rainfall, but are also highly sensitive to drought. Their levels can therefore vary very quickly over the course of the same season.
- inertial (when composed of chalk, non-karst limestone, sandstone formations). Their reaction times are slow. They can have multi-annual cycles, meaning that they require a long period to recharge or empty.
Cyclicity of aquifers in mainland France.
© BRGM
Forecasts
The Météo France seasonal forecasts for March, April and May (2025) predict warmer and drier weather across the whole of France.
Until the vegetation starts to grow again, the trends and therefore the evolution of the state of the aquifers will depend exclusively on the total amount of rainfall. If the Météo-France forecasts are correct, there will be a lack of water flowing into the aquifers during the latter stages of the recharge period, which will end prematurely. Indeed, if there is insufficient rainfall, the recharge episodes will not offset the outflow volumes (through natural outlets and due to abstractions). Equally, the warmer temperatures will favour the growth of vegetation as early as March. Consequently, most of the water that filters into the soil will be consumed by vegetation and will therefore not seep deep into the ground.
If this scenario proves to be true, the levels in reactive aquifer will quickly decline. In this case, the depletion period will begin early and the situation will quickly deteriorate, in just a few weeks. This means the summer forecasts will be pessimistic, even for the aquifers that are currently at high levels. The situation could deteriorate even more rapidly if demand for groundwater is strong, due to the high temperatures and a lack of rainfall.
On the contrary, if there is significant rainfall at the end of winter and beginning of spring, the aquifer levels could rise, particularly in the most reactive aquifers (basement, karst limestone, alluvial aquifers). In addition, the snow-melt could also recharge certain aquifers around the Alps and Pyrénées. If the inflows are sufficient, this will keep the recharge active and maintain or even improve the situation of the aquifers.
In conclusion, the forecasts for reactive aquifers will remain uncertain until the beginning of spring. If satisfactory levels are to be hoped for during this summer, then the recharge must remain active and last throughout the spring, thereby making it possible to maintain above-normal levels and delay the start of the depletion period.
The forecasts for the aquifers in Roussillon plain over the coming months are pessimistic, regardless of the rainfall and temperature scenario. It seems unlikely that there will be a sustainable replenishment of these aquifers before the start of the depletion period. Levels are expected to remain below normal until spring, and even low to very low for the deep Pliocene-sand aquifer.
As for the inertial aquifers, any lack of rainfall over the next three months and the early growth of vegetation will have a more long-term effect and not therefore be immediately visible. The levels will stabilise before the period of depletion gradually sets in. Indeed, the rise in water levels usually lasts for a few weeks after the rain has stopped seeping deep into the ground. The situation in the inertial aquifers will therefore remain stable for several weeks before deteriorating more or less slowly during the end of spring and through the summer, depending on the demand for groundwater through abstractions.
Given the inertia of these aquifers, relatively reliable forecasts can be made from the end of winter, even if the recharge period is not yet over. The situation in the aquifers in Artois and Paris Basins, the upper Rhône corridor and eastern Lyon area should remain close to or above normal levels during the spring and summer. It is highly unlikely that these aquifers will drop to low levels. However, less satisfactory situations could occur locally, in areas subject to heavy abstraction. The aquifers in the Sundgau and the Saône corridor (Dijonnais, Bresse and Dombes) should remain close to or just below monthly norms. Finally, the forecasts are not very optimistic for the aquifer in the Bas-Dauphiné area, since the current levels will not guarantee satisfactory levels during the summer. The levels should remain moderately low or even deteriorate over the coming months, especially if Météo-France's seasonal forecasts are correct.
The short-term risk of flooding due to rising groundwater levels in reactive aquifers would seem to be less and less likely. However, the risk cannot be discounted entirely, since it depends on recent rainfall.
In February 2025, high to very high levels were already recorded in the inertial aquifers in the Paris Basin and Artois Basin. However, flooding from an inertial aquifer is caused by exceptionally high rainfall across the entire catchment area. Consequently, such flooding lasts longer when the aquifer level is high and that aquifer covers a large area of land.
According to BRGM projections, there is a high probability that very high levels (ten-year highs) could be measured at several piezometers:
- Seno-Turonian chalk aquifer on the Picardy Plateau (Somme and Oise);
- Seno-Turonian chalk aquifer in Normandy;
- Seno-Turonian chalk aquifer in Touraine;
- Seno-Turonian chalk aquifer in Burgundy and the Gâtinais area;
- Turonian chalk marl aquifer in the southern part of Champagne;
- Lutetian limestone and Ypresian sand aquifers in the north and centre of the Paris Basin (Brie, Parisis and Vexin);
- Tertiary limestone and Seno-Turonian chalk aquifers in Beauce (Ile-de-France and western border);
- Cenomanian sand aquifers in the Perche and Maine.
Locally, 20-year highs or even historical records could be recorded at certain piezometers in the Paris Basin by the end of winter.
Therefore, there could be a risk of flooding due to rising groundwater levels at the end of winter and the beginning of spring, especially if the total rainfall over the next few weeks is excessive. However, the recharge seemed to be slowing in February in the aquifers concerned and Météo-France's forecasts predict warmer and drier conditions for the next three months.
Close monitoring is recommended in these areas over the coming weeks.
Next groundwater tables status report
Our groundwater report is now published every month, in the middle of the month.
The next issue will be published in mid-April 2025.
State of groundwater: monitoring by BRGM
Groundwater is a widely used resource: in metropolitan France, it accounts for nearly two-thirds of drinking water consumption and more than one-third of agricultural water consumption. It is also widely used in the industrial sector. Groundwater tables depend on cyclical recharges.
BRGM monitors groundwater levels and quality in mainland France. Discover the actions carried out by the French geological survey and the resources and databases available on groundwater in France.
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Carte établie le 9 mars 2025 par le BRGM, à partir de données de la banque ADES acquises jusqu’au 28 février 2025.
Source des données : banque ADES (ades.eaufrance.fr) / Hydroportail (hydro.eaufrance.fr) / Fond de carte © IGN. Producteurs de données et contribution : APRONA, BRGM, Conseil Départemental de la Vendée, Conseil Départemental des Landes, Conseil Départemental du Lot, EPTB Vistre Vistrenque, Parc Naturel Régional des Grandes Causses, Syndicat Mixte d’Etudes et de Travaux de l’Astien (SMETA), Syndicat Mixte pour la protection et la gestion des nappes souterraines de la plaine du Roussillon (SMNPR).
Cette carte présente les indicateurs globaux traduisant les fluctuations moyennes des nappes. Ils sont établis à partir des indicateurs ponctuels relevés au niveau des points de surveillance du niveau des nappes (piézomètres).
L'indicateur "Niveau des nappes" compare le mois en cours par rapport aux mêmes mois de l’ensemble de la chronique, soit au minimum 15 ans de données, et jusqu'à plus de 100 ans. Il est réparti en 7 classes, du niveau le plus bas (en rouge) au niveau le plus haut (en bleu foncé).
Les zones grises correspondent à des secteurs sans nappes libres, c'est-à-dire avec une couche imperméable ou semi-perméable au-dessus de la nappe, et/ou des secteurs comportant une très faible densité de points de suivi. Ce dernier cas concerne notamment les zones montagneuses dont les nappes sont petites et hétérogènes.
L'indicateur "Évolution des niveaux" traduit la variation du niveau d'eau du mois échu par rapport aux deux mois précédents (stable, à la hausse ou à la baisse).
Ces indicateurs globaux rendent compte de situations et de tendances générales et ne tiennent pas compte d'éventuelles disparités locales.