Hydrogeological situation on 1 September 2025
August levels are down (77%) even though the depletion is slowing. Effective rainfall this summer mitigated the depletion of groundwater reserves, but did not lead to any visible improvement in the situation. The current state of groundwater reserves is generally low to near normal for reactive aquifers and more satisfactory, near normal to high, for inertial aquifers.
In September, the recharge period could begin in those areas that benefit from rainfall and have reactive aquifers. Changes in situations will depend on the cumulative recharge. Active depletion should continue for inertial aquifers until October-November. Their situation is not expected to change significantly. The situation will need to be closely monitored in groundwater reserves whose levels are currently below the monthly averages, especially in the absence of effective rainfall.
Groundwater situation: a new map and more frequent bulletins
The BRGM groundwater status report, which is eagerly awaited by the public every month, is being revamped. It will now be published twice a month, and the map will have a new colour scheme to make it easier to read.
As of 1 July 2025, the comparative map between the current month and the same month of the previous year will also be reissued with the new colour scheme.
Map of aquifer levels in mainland France on 1 September 2025.
© BRGM
Evolution of the trends observed on piezometers from September 2024 to August 2025.
© BRGM
Trends
The depletion period began very early, starting in February, in the reactive aquifers in much of northern France. It then spread to the inertial aquifers of Artois and the Paris Basin during the spring and became established between April and May in the aquifers of southern France and Corsica. From May onwards, levels remained low, as rainfall was no longer sufficient to trigger recharge episodes. However, the depletion rate among reactive aquifers was slower in areas that benefited from rainfall.
In August 2025, depletion remained the dominant trend, with 77% of levels falling (88% in July). This is usual for this time of year. Moreover, summer rainfall rarely has an effective impact on groundwater recharge, since storms lead to run-off and any water that manages to penetrate into the ground is almost entirely absorbed by vegetation and therefore does not filter down very deeply.
Depletion is ongoing in most inertial aquifers and those areas with reactive aquifers and little rainfall. However, the depletion rate has slowed in several areas due to small, sporadic replenishments from effective rainfall or a drop in pressure linked to the abstraction of water.
Rainfall during the last ten days of August thus led to a temporary recharge of highly reactive aquifers (basement, karst limestone and alluvial deposits) in the southern two-thirds of the country. Slight increases in levels are particularly noticeable in the last few days of August. However, these replenishments were insufficient to reverse the monthly trends. The only stable levels are found in a few reactive aquifers in north-eastern France.
Abstractions for irrigation and watering were often lower in August 2025 than in previous years. Two factors could explain the early cessation or reduction of these abstractions. On the one hand, rainfall was sufficient to cover part of the plants' water requirements. On the other, crops were in advance in their development, which led to early harvests and therefore less demand for irrigation. This observation can be seen in heavily exploited aquifers such as the highly inertial Beauce aquifer, or the alluvial aquifers of the Aquitaine Basin.
Comparison between 1 September 2024 and 1 September 2025
Map of France showing the state of the aquifers on 1 September 2024 (left) and 1 September 2025 (right).
© BRGM
Evolution of the situation observed on piezometers from September 2024 to August 2025.
© BRGM
Aquifer situation
Low-water levels were particularly high in 2024 (October). They then varied during autumn and winter depending on the intensity of recharge: very slowly for inertial aquifers and more rapidly for reactive aquifers. The overall situation has gradually deteriorated since February across much of northern France and since April–May in the south.
In August 2025, the groundwater situation remained mixed: the levels recorded at 38% of the observation points were below monthly averages, 29% were comparable and 33% were above average (compared with 44%, 24% and 32%, respectively, in July).
The situation was far more satisfactory in August 2024: 70% of levels were above monthly averages, due to abundant recharge in 2023–2024 and strong support from rainfall in spring 2024. The situation is better in 2025 for the highly inertial aquifers of Beauce and Sundgau (southern Alsace) and for the reactive aquifers of Corsica, Hérault, Orb and the Roussillon plain.
In August 2025, the status of groundwater reserves was slightly better than in July thanks to effective rainfall and reduced abstraction pressure. Some aquifers are deteriorating due to persistent rainfall deficits: the Artois and Picardy Plateau chalk aquifers, the Côte-des-Bar Jurassic limestone aquifers, and the Limousin Plateau basement aquifers in the Cévennes.
Inertial aquifers
The status of inertial aquifers has remained generally satisfactory for August, with indicators close to normal or moderately high.
The situation of the Artois aquifers is worse in the west, where levels are moderately low, than in the east, where they are close to normal. The chalk aquifer is marly in the western part and therefore more sensitive to the persistent rainfall deficit since February.
In the Paris Basin, levels are moderately high to high for the most inertial aquifers in the south-west and north-west. The situation deteriorated more rapidly for the less inertial aquifers on the western and south-eastern borders. Their levels are moderately low to close to monthly averages.
Aquifer levels in the Sundgau (southern Alsace) and the Rhône-Saône corridor are generally close to average. Certain situations varied locally, with levels ranging from low to high.
Reactive aquifers
The status of reactive aquifers is mixed, but remains unsatisfactory in many areas. The groundwater situation depends on the 2024-2025 recharge, total rainfall in recent weeks and aquifer reactivity.
The early onset of depletion – as early as February or March – led to a deterioration in the situation of aquifers in the Boulonnais region and the north-eastern two-thirds of France (i.e. Grand-Est, Jura and Massif Central). The storms in June, July and August in the north-east helped to maintain levels and slowed down the depletion of groundwater reserves. The aquifers of the Massif Central basement were particularly affected by the summer rainfall deficits. In August, levels were below the norm, ranging from moderately low to low. Some of the very low points concern the Limousin basement aquifers.
Levels are more satisfactory in the Armorican Massif, the Aquitaine Basin, around the Mediterranean and in Corsica, being generally moderately low to close to the monthly average. Spring rains and, to a lesser extent, summer rainfall occasionally helped to maintain water levels. Levels are high for less reactive aquifers that have recently been recharged, i.e. upstream Garonne, Côte d’Azur and Corsica. Finally, levels remain low to very low in the aquifers of the Aude valley, the Corbières Massif and the Roussillon plain.
Aquifers with surplus water
Several aquifers showed a surplus, with moderately high to high levels compared with records for previous Augusts:
- The moderately high to high levels of the inertial aquifers in the west and south of the Paris Basin can be explained by the surplus recharges in 2023-2024 and 2024-2025;
- The levels of the alluvial aquifers of the upstream Garonne and its main tributaries remain moderately high;
- The Astian sand aquifer at Valras-Agde is moderately high, while abstractions have decreased;
- The rainfall in July and August has helped to maintain moderately high levels in the coastal aquifers of Corsica.
Aquifers with low water levels
The situation was unfavourable in several aquifers, where levels were low to very low compared with those recorded for previous Augusts:
- The levels of reactive aquifers in the Jurassic limestones of the Boulonnais region and Lorraine were low as a result of insufficient rainfall since February;
- The levels in the Massif Central basement, the alluvial deposits and tertiary basins of the Limagne region, and the volcanic formations were low to very low in some areas;
- Levels were low to very low in the aquifers in the Roussillon multilayer formation, the karst limestone of the Corbières Massif and the alluvial deposits of the Aude valley.
Key figures
-
77.00%of levels decreased
-
33.00%of levels were above monthly averages
-
38.00%of levels were below monthly averages
Forecasts
According to the Météo France seasonal forecasts for September, October and November 2025, higher temperatures are expected across the whole of France. No clear scenario has emerged for rainfall.
The irrigation campaigns and tourist season are coming to an end, and the high temperatures forecast by Météo-France are not expected to have an impact on the volumes abstracted.
Seasonal forecasts for inertial aquifers
for September, October and November 2025, higher temperatures are expected across the whole of France. No clear scenario has emerged for rainfall.
The irrigation campaigns and tourist season are coming to an end, and the high temperatures forecast by Météo-France are not expected to have an impact on the volumes abstracted.
Seasonal forecasts for reactive aquifers
Late summer to early autumn is generally a pivotal period, between the end of the summer depletion (falling levels) and the beginning of the winter recharge (rising levels). Rainfall in late August and September is likely to trigger the first recharge episodes, particularly for the most reactive aquifers (basement and karst limestone). In September, the recharge period is expected to start in areas benefiting from rainfall. However, in the absence of sufficient effective rainfall, levels should continue to deplete until the arrival of heavy rainfall.
Changes in this situation in the coming weeks will depend on the cumulative recharge. The status of reactive aquifers should remain stable or even improve in the event of rainfall. It should deteriorate in areas where there are no recharge episodes.
Low-water levels for 2025 are expected to be generally below average, while not reaching the levels recorded in 2022 and 2023. There is considerable uncertainty surrounding the date on which this low-water level will occur. It should be noted that a late and insufficient recharge could significantly impact reactive aquifers that are currently below the monthly averages. Some aquifers could therefore experience a severe, late low-water point.
The situation will need to be closely monitored in groundwater reserves whose levels are currently below average, especially in the event of late low-water levels.
Press contact
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 4 september 2025, based on data acquired up to 31 August 2025.
Data source: ADES (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.