Hydrogeological situation on 1 May 2025
Depletion is continuing, with levels falling in 61% of aquifers. The groundwater situation is variable: levels are broadly close to or just below normal in the reactive aquifers in the north and above normal in inertial aquifers and the aquifers in the south. The levels in the aquifers in the Roussillon region and Corbières Massif remain low to very low.
The downward trend is expected to continue in May and through to the autumn. Recharge episodes could occur from time to time in the event of excess rainfall on reactive aquifers. The forecast for spring and summer is optimistic for the inertial aquifers in the Paris Basin and upstream Rhône corridor, and highly pessimistic for the Roussillon region. For the rest of the country, the level of uncertainty is higher. The lack of rainfall at the end of the winter recharge is likely to have an impact on the reactive aquifers in the north over the coming months.
Map of aquifer levels in mainland France on 1 May 2025.
© BRGM
Evolution of the trends observed on piezometers from May 2024 to April 2025.
© BRGM
Trends
The recharge period began between September and October 2024. Recharging was highly active in October, but slowed sharply in November, before picking up again in December and January, except in the south-east. It then diminished from February onwards over much of France, before starting again in the south-east.
Depletion started in April 2025: 61% of levels were down compared with 49% in March. Trends are variable between north and south, depending on the amount of local rainfall.
In the north, groundwater levels are falling after three months of poor rainfall. The depletion period began in February for the most reactive aquifers and in April for the inertial aquifers of the Artois Basin and the central Paris Basin. Levels are continuing to rise only in the highly inertial aquifers in the Beauce and the Sundgau region (southern Alsace). The recharge process is slowly easing off in these areas.
In the south, rainfall in April resulted in a number of recharge episodes. However, trends vary, depending on overall local rainfall, the start of abstraction and the reactivity of the aquifer. Vegetation is active and the impact of rainfall on the aquifers is decreasing.
Comparison between 1 May 2024 and 1 May 2025
Map of France showing the state of the aquifers on 1 May 2024 (left) and 1 May 2025 (right).
© BRGM
Evolution of the situation observed on piezometers from May 2024 to April 2025.
© BRGM
Aquifer situation
Low-water levels were particularly high in 2024. Changes in aquifer levels then varied over the autumn and winter depending on the intensity of recharging. Levels remained above monthly averages overall. However, the situation has gradually deteriorated since February, with an early start to the depletion period over much of northern France.
The groundwater situation remained satisfactory overall in April: 27% of observation points were below monthly averages, 23% were comparable and 50% were higher (compared with 27%, 20% and 52%, respectively, in February).
The situation was more satisfactory in April 2024, when 65% of aquifer levels were above monthly averages. Rainfall in the spring of 2024 significantly boosted the levels of reactive aquifers. The situation is worse in 2025 in the reactive aquifers of the northern two-thirds and south-west, as well as in the inertial aquifers in the Artois and the north-eastern edge of the Paris Basin. However, the situation is better in 2025 in the inertial aquifers of the Paris Basin, Sundgau (southern Alsace) and Rhône-Saône corridor, as well as in the reactive aquifers in the south-east and Corsica.
Inertial aquifers
The state of the inertial aquifers has improved very slowly since autumn 2023. The situation between March and April 2025 was stable overall, despite a slight deterioration in the aquifers of the Artois and north-eastern edge of the Paris Basin. These less inertial aquifers have been affected by an early start to the depletion period.
Aquifer levels in the Paris Basin and Artois Basin are satisfactory, close to or higher than monthly averages. Locally, levels are very high in the centre of the Paris Basin and Beauce, and less satisfactory, but close to normal, in the eastern part of the Paris Basin and in Artois.
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 better upstream than downstream, since the winter recharge has been more abundant in the northern part over the past two years. Levels are satisfactory to moderately high in the Savoie foothills and eastern Lyon area, and are close to normal in Northern Isère and Bas-Dauphiné. However, the situation has improved for the Miocene molasse aquifer in Bas-Dauphiné and no low levels can now be observed.
Reactive aquifers
The reactive aquifers in northern France have been affected by the lack of rainfall over the past three months. Levels were moderately high to very high in January but have since deteriorated. In April, levels were close to or below normal averages. Specifically, groundwater levels are low and even very low locally in the Jurassic limestone aquifers of the Boulonnais and Lorraine regions. The situation is unsatisfactory for this time of year, with levels moderately low or close to normal monthly averages in the Jurassic limestone aquifers around the Paris Basin, the Jura and the Charentes, and in the aquifers in the Armorican Massif and the north-east and centre of the Massif Central.
In the south-west, in the Adour-Garonne basin and west of the Massif Central, the wet month of April slowed the depletion of the water tables and even resulted in several recharge episodes. This support is keeping levels consistent with normal to high monthly averages. However, vigilance is still required for the alluvial aquifers in the Adour basin and upper Dordogne valley, where levels are moderately low to low locally.
Rainfall has been higher than normal overall since February in the south-east and Corsica. Cumulative rainfall has compensated for the low levels at the start of the 2024-2025 depletion period. In the south of the Massif Central, around the Mediterranean, in Provence and in the valleys south of the Alps and in Corsica, the groundwater situation continued to improve in areas that received rainfall, otherwise remaining stable between March and April. Levels were satisfactory overall, from moderately high to high. The impact of rainfall diminishes as the vegetation becomes more active, owing to the higher temperatures. Increased pressure on groundwater (irrigation and tourism) is also a factor locally. The situation is less favourable, with levels close to normal, for the Aude valley aquifer.
Last, levels remain low to very low in the aquifers of the Corbières Massif and the Roussillon plain. Rainfall in recent months, particularly in March, has significantly improved local conditions. However, total rainfall is still far from sufficient to make up for the shortfall. The situation in the Pliocene aquifer, which is less reactive to weather conditions, continues to cause great concern.
Aquifers with surplus water
Several aquifers showed a surplus, with levels high to very high compared to those recorded for April in previous years:
- Levels are high in the inertial aquifers in the west and south of the Paris Basin, which received abundant recharges in 2023-2024 and 2024-2025;
- The reactive aquifers in the south, with the karst Jurassic limestone aquifers of the Causses du Quercy and Provence and the southern Massif Central basement, were boosted by rainfall in April and are showing high levels;
- In the coastal aquifers of Corsica, the situation gradually improved between February and April to reach high levels.
Aquifers with low water levels
The situation was unfavourable in several aquifers, where levels were low to very low compared to those recorded for April in previous years:
- Levels are low in the Jurassic limestone aquifers of the Boulonnais, after three months of insufficient rainfall;
- Levels are low in the Jurassic limestone aquifers of Lorraine, which were impacted by the end of a recharge period with insufficient inflows;
- Levels are rising or stable in the aquifers in the Roussillon multilayer formation and the karst limestone of the Corbières Massif, but nevertheless remain low to very low overall.
Key figures
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61.00%of levels are falling
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50.00%of levels are above monthly averages
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27.00%of levels are below monthly averages
Forecasts
The Météo France seasonal forecasts for May, June and July 2025, higher temperatures are expected across the whole of France. No clear scenario has been established concerning rainfall.
Over the next few months, most of the water that filters down through the soil will be consumed by vegetation and will therefore not seep far down into the ground. The depletion should continue through May and until the vegetation becomes dormant – i.e. until October or late November – and/or until there is abundant rainfall. Only occasional, local recharge episodes are likely to occur during the summer. In order for the state of aquifers to improve and their levels to increase, there will need to be significant rainfall on ground that is already damp. Moreover, this will only improve the situation in reactive aquifers. The demand on water resources through abstraction may also affect the state of the aquifers.
In May, rainfall is likely to infiltrate deeply only in wet soil, i.e. mainly in the southern part of the country. In the north, any rainfall will first moisten the soil and support vegetation growth, before infiltrating more deeply into the ground. However, heavy rainfall is not expected to be effective in recharging the aquifers. It is more likely to run off rather than infiltrate into the soil, owing to its intensity. Moreover, if Météo-France forecasts are confirmed, the higher temperatures will increase the demand for water, mainly for purposes of irrigation and leisure activities. Trends in May therefore point to a fall overall. The situation is expected to change depending on local effective rainfall, abstractions, and the reactivity of the aquifer.
Seasonal forecasts for inertial aquifers
The forecast for summer is optimistic for the inertial aquifers of the Paris Basin and upper Rhône corridor (Savoie foothills and eastern Lyonnais region). The situation looks more uncertain for the inertial aquifers of the coastal area of the Artois, the eastern edge of the Paris Basin, the Sundgau, the Saône corridor, northern Isère and Bas-Dauphiné. Levels are expected to remain close to normal or moderately low. However, more unfavourable situations could develop locally this summer, and tensions could arise.
Seasonal forecasts for reactive aquifers
Summer forecasts for reactive aquifers remain uncertain. They will depend on local rainfall and on water abstraction over the coming months.
The forecast is optimistic for aquifers in the south-west, south-east and Corsica, where levels were moderately high to high in April. However, a prolonged drought could rapidly affect reactive aquifers, particularly the Massif Central basement and karst limestone aquifers in the western and southern edge of the Massif Central and Provence, resulting in unsatisfactory levels by the end of the summer. This deterioration will be made worse by increased water abstractions, particularly for irrigation purposes and tourism.
Forecasts for the summer look relatively pessimistic, but with a high degree of uncertainty for the reactive limestone aquifers of Lorraine limestone, Côte-des-Bars, Jura and Brittany basement. For these aquifers, levels were moderately low to low in April, and the dryness of the soil is unlikely to allow effective infiltration of rainfall in May.
Finally, the forecasts for the coming months remain highly pessimistic for water tables in the Roussillon plain and Corbières massif, regardless of the rainfall and temperature scenario. Levels are expected to remain below normal, and even low to very low for the deep Pliocene-sand aquifer.
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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.
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
Map drawn up by BRGM on 9 May 2025, based on data from the ADES database, acquired up to 30 April 2025.
Data source: ADES database (ades.eaufrance.fr) / Hydroportail (hydro.eaufrance.fr) / Background map © IGN. Data producers and contributors: 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).
This map shows the global indicators reflecting the average fluctuations of the aquifers. They are based on point indicators collected at groundwater monitoring points (by means of piezometers).
The "Aquifer levels" indicator compares the current month’s figures with those of the same months in the entire record, i.e. at least 15 years of data and sometimes up to as much as 100 years of data. It is divided into 7 classes, from the lowest level (in red) to the highest (in dark blue).
The grey areas correspond to areas without unconfined aquifers, i.e. with an impermeable or semi-permeable layer above the aquifer, and/or sectors with a very low density of measuring points. This last case primarily concerns mountainous areas with small, heterogeneous aquifers.
The "Evolution of levels" indicator reflects the variation of the water level of the past month compared to the two previous months (stable, increasing or decreasing).
These global indicators reflect general situations and trends and do not take into account possible local disparities.