The hydrogeological situation on 1 April 2025
Following a period of insufficient recharge in February and March 2025, aquifer levels dropped across a large part of the country. Only the south-east of France benefited from effective excess rainfall, resulting in rising levels. Overall, the situations varied according to the recent weather conditions, the state of the vegetation and how quickly the aquifers react to rainfall infiltration. The levels in the aquifers in the Roussillon region and Corbières Massif remained low to very low.
From April onwards, recharge episodes will probably be occasional and not particularly intense, unless there are exceptional rainfall episodes. The forecasts for this coming spring and summer are optimistic for the inertial aquifers in the Paris Basin. However, they are more variable for the rest of the country. The low intensity of the end of the winter recharge will probably have an impact on reactive aquifers over the coming months, particularly if the weather remains dry through the spring.
Carte de France hexagonale de la situation des nappes d'eau souterraine au 1er avril 2025.
© BRGM
Evolution of the trends observed on piezometers from April 2024 to March 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. During the autumn and winter, the intensity of the recharge depended on the total amount of rainfall: the recharge was extremely active in October, then slowed sharply in November, before picking up again in December and January, except in the south-east. In February, the recharge then slowed down over a large part of the country, but actually picked up in the south-east.
In March 2025, there was confirmation that the recharge period was coming to an end: levels at 49% of observation points dropped (compared to 29% in February). 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 along the edge of the Cévennes, in Provence, around the Mediterranean coast and in Corsica benefited from several recharge episodes in February and March. The wet soil helped rainfall filter down towards aquifers, but the regrowth of vegetation limited the amount of water that filtered deep into the ground. Nonetheless, the aquifer levels rose in March, due to the very high total monthly rainfall.
In the rest of the country, the trends varied depending on the inertia of the aquifer. The lack of rainfall in February and March had an impact on the aquifers and the start of the depletion period effectively kicked in across a large part of the country. After the drop in the levels of reactive aquifers in February, the least inertial aquifers also experienced decreases. Only the highly inertial aquifers in the Artois Basin, the centre of the Paris Basin and the Sundgau region (southern Alsace) had rising levels. However, the recharge also seems to be gradually slowing in these areas.
Comparison between 1 April 2024 and 1 April 2025
Map of France showing the state of the aquifers on 1 April 2024 (left) and 1 April 2025 (right).
© BRGM
Evolution of the situation observed on piezometers from April 2024 to March 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 autumn and winter according to the rate of recharge inflows. Overall, the aquifer levels remained above monthly averages. In February, only the aquifers in Roussillon and in certain western areas along the Languedoc coast had low to very low levels.
The state of the aquifers gradually deteriorated in February and March 2025. However, the overall situation remained above average in March: the levels recorded at 27% of the observation points were below monthly norms, 20% were comparable with monthly norms and 52% were above them (compared with 19%, 21% and 60%, respectively, in February). It should be noted that 12% of the points monitored reached very high levels in March (16% in February).
The situation was slightly worse than last year, in March 2024, when 58% of the levels observed were above monthly norms. The inertial aquifers in the Paris Basin, Sundgau region (southern Alsace) and the Rhône-Saône corridor were at higher levels than at the same period last year. The levels of the inertial aquifers in the Artois Basin and in the reactive aquifers were generally lower than in 2024, except in the Languedoc and in Corsica.
The levels in the aquifers in the south of the Massif Central, around the Mediterranean coast, in Provence and in Corsica remained stable or, in some cases, improved slightly compared with last month. The impact of the very heavy rainfall in March was mitigated by the regrowth of vegetation and, in certain local areas, by increased demand on groundwater (irrigation and tourism).
In the majority of the aquifers in the south-east, the significant recharge in February and March compensated for the accumulated lack of inflows during the late autumn and early winter of 2024-2025. The aquifer levels were close to normal to moderately high in Corsica, the Côte d'Azur, Provence, on the edge of the Cévennes and in the Vistrenque, as well as in the Hérault and Orb valleys. Certain local situations remained fragile, notably in the downstream area of the Aude valley and in the Astien aquifer between Valras and Agde.
The levels remained low to very low in the aquifers of the Corbières Massif and the Roussillon plain. The situation had improved significantly in the reactive aquifers in the Corbières region and in the alluvial aquifers in Roussillon, but levels in many areas remained low to very low. The situation in the Pliocene aquifer, which is less reactive to weather conditions, has not improved significantly and continues to show very worrying levels.
In the reactive aquifers across the rest of the country, the situation deteriorated slightly compared with February. The state of these aquifers varied, ranging from moderately low to high.
The impact of the above-average recharge in autumn and early winter can still be noted in the aquifers in the western half of the country. Levels were satisfactory, ranging from close to normal to moderately high or even high in the Jurassic limestone aquifers of the Brenne and Vienne areas. Moderately low levels were observed locally: in the Jurassic limestone aquifer in the Boulonnais, the basement aquifers in the west of the Armorican Massif and the west of the Massif Central, and in the alluvial aquifers in the valleys of the Pyrénées (Adour and Gaves rivers).
In the centre-east and north-east of the country, the situations were less satisfactory, ranging from moderately low to comparable-to-normal. Locally, certain levels were low, particularly in the Jurassic limestone aquifers in the Lorraine and Jura regions, and in the volcanic aquifers of the Chaîne des Puys mountains.
The state of the inertial aquifers has improved very slowly since autumn 2023.
The levels of the aquifers in the Paris Basin and Artois Basin were moderately high to very high. None of the points observed had below-normal levels. Very high levels were recorded in the Tertiary aquifers of the central Paris Basin and Beauce.
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 has deteriorated both upstream and downstream, due to inconsistent rainfall in recent months. Levels were moderately high in the Savoie foothills and to the east of Lyon, but were close to normal in Northern Isère. Groundwater levels in the Bas-Dauphiné were generally close to average, but were less satisfactory in certain localised areas, ranging from moderately low to low in the Drôme des Collines area.
Aquifers with surplus water
Several aquifers showed surplus levels, with high to very high levels, compared to those recorded for March in previous years:
- The inertial aquifers in the Paris Basin and to the east of the Artois Basin have benefited from the abundant recharges in 2023-2024 and 2024-2025 and had high to very high levels;
- The reactive Jurassic limestone aquifers of the Brenne and Vienne areas remained at high levels, due to an above-average recharge;
- The aquifer in the tawny sands (sables fauves) and Miocene limestone formations of the Armagnac area was not particularly affected by the lack of inflows at the end of the recharge period and its levels rose, remaining high.
Aquifers with low water levels
The situation was unfavourable in several aquifers with low to very low levels compared to those recorded for March in previous years:
- Locally, the situation in the Astian sand aquifer at Valras-Agde deteriorated, with low levels recorded in March;
- Levels in the aquifers in the karst limestone formations of the Corbières Massif rose but remained low;
- The situation in the aquifers in the Roussillon multilayer formations remained critical, notably in the Pliocene aquifer, with low to very low levels recorded.
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 April, May and June 2025 predict higher temperatures across the whole of France. No clear scenario has been established concerning rainfall.
From spring onwards, the rise in temperatures, the regrowth of vegetation and therefore the increase in evapotranspiration will significantly reduce the amount of rainfall that filters through to the aquifers. The trends in April will therefore depend on these factors, but also on the volumes abstracted. During the spring, the snow-melt in the Alps and Pyrénées should maintain the levels of aquifers that are sensitive to the winter melt.
Over a large part of the country, the depletion period started a little early, due to the lack of rainfall in February and March. In April, the depletion period should begin in the most inertial aquifers in the Artois Basin and the Paris Basin, while continuing in other aquifers. Any potential rainfall will first moisten the soil and support vegetation growth, before infiltrating more deeply into the ground. The trends are therefore likely to take a downward turn, unless there are major rainfall events.
Over the next few months, recharge episodes will probably be occasional at best and only affect reactive aquifers. Moreover, if the forecasts from Météo-France are confirmed, the higher temperatures will increase the demand for water for irrigation purposes, particularly if there is a lack of rainfall.
The forecasts for this summer are optimistic for the inertial aquifers in the Paris Basin and Artois Basin. These aquifers were well above normal levels in March and they are not particularly sensitive to weather conditions during the summer. Forecasts are more uncertain for the coastal area of the Artois region, where the aquifer is less inertial and the levels were already moderately low in March.
As regards the inertial aquifers in the Sundgau (southern Alsace) and in the Rhône-Saône corridor, the forecasts are linked to the local conditions observed at the end of the recharge period. These forecasts vary for the inertial aquifers in the Sundgau (southern Alsace) and the Saône corridor, due to different local situations. Water stress could arise in certain sectors this summer. Finally, the forecasts are relatively optimistic for the eastern Lyon area and the Savoie foothills. The situation is unlikely to change much in Northern Isère and Bas-Dauphiné, and levels should be just below normal this summer.
There is a degree of uncertainty concerning the forecasts for reactive aquifers since the levels will depend on the total rainfall and volume of abstractions over the coming months. However, the forecasts seem to be fairly optimistic concerning the aquifers that had moderately high levels in March: the Jurassic limestone aquifers in the Bessin and Berry, from the Brenne to Vienne and on the edge of the Poitou area, the basement aquifers in the southern Armorican Massif and the aquifers in the centre-west part of the Aquitaine Basin. However, a prolonged drought could quickly affect these aquifers, resulting in unsatisfactory levels by the end of the summer.
In the south-east and Corsica, the trends in April will depend on the total local rainfall. If the inflows are sufficient, this will keep the recharge active and maintain or even improve the short-term situation of the aquifers. The snow-melt could also recharge some of the aquifers in the valleys and around the Alps. If there is insufficient rainfall, the depletion period will rapidly become active in all aquifers. In this case, the situations could deteriorate. This deterioration will be exacerbated by increased water abstractions, particularly for irrigation purposes and to meet the demands of tourism.
Forecasts for the summer are relatively optimistic, but with a high degree of uncertainty for aquifers that had moderately high levels in March, notably in the Côte d'Azur, Provence and the Vistrenque and in the coastal aquifers from Nîmes to Montpellier.
As regards the aquifers in the Roussillon plain and, to a lesser extent, in the Aude valley, the forecasts for the coming months are pessimistic, regardless of potential scenarios in terms of the rainfall and temperatures. Levels are expected to remain below normal, and even low to very low for the deep Pliocene-sand aquifer.
There is no longer any short-term risk of flooding due to rising groundwater levels in reactive aquifers.
However, flooding from an inertial aquifer is caused by exceptionally high rainfall across the entire catchment area. Such flooding lasts longer when the aquifer level is high and when these high levels concern a large area. In March 2025, very high water levels were recorded in the inertial aquifers of the Artois Basin and the Paris Basin. However, the depletion period should begin in April and the risk of flooding due to rising groundwater levels should diminish.
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 (eastern Pays de Caux);
- Lutetian limestone and Ypresian sand aquifers in the north and centre of the Paris Basin (Valois and southern Brie);
- Tertiary limestone and Seno-Turonian chalk aquifers in the Beauce (western border);
- Cenomanian sand aquifers in the Maine département.
Therefore, there could be a risk of flooding due to rising groundwater levels in April but this should diminish during the spring as the recharge period comes to an end.
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-May 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 10 avril 2025 par le BRGM, à partir de données de la banque ADES acquises jusqu’au 31 mars 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.