Hydrogeological situation on 1 November 2025
There was confirmation that the aquifers were entering into their recharge period in October, with 37% of levels up (29% in September). However, the recharge episodes were not particularly intense and the state of the aquifers deteriorated slightly compared with September. Nonetheless, the situation remained satisfactory overall, with levels ranging from moderately low to moderately high. The situation remained poor in Roussillon, Aude and Southern Corsica, where levels were low to very low.
In November and through the winter period, the situation and trends in reactive aquifers will depend on the total rainfall. As regards the inertial aquifers, the recharge should commence in November. The situation in these aquifers should start to improve gradually in November, as the rain that fell in September and October filters deeper into the ground.
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 November 2025.
© BRGM
Evolution of the trends observed on piezometers from November 2024 to October 2025.
© BRGM
Trends
The recharge period commenced between the end of August and September in many reactive aquifers in the southern two-thirds and north-eastern part of France. However, the levels continued to drop in September in the reactive aquifers in the Armorican Massif and in certain aquifers in the centre and western part of the Aquitaine Basin. Most of the inertial aquifers had not yet entered their recharge period in September. Rising levels were only observed locally in the south-western part of the Paris Basin and in the eastern Lyon area, due to heavy rainfall and lower abstraction rates.
In October, the trends varied, depending on the amount of rain that fell across different parts of the country, and how rapidly the aquifers in different areas react to rainfall: 37% of levels were up and 42% were down (compared with 29% and 54% respectively in September).
Inertial aquifers
The general downward trend continued in the inertial aquifers in the Artois region, Paris Basin, Sundgau (southern Alsace) and Saône-Rhône corridor. Effective rainfall can take several weeks to filter deep into the ground, reach the aquifers and reverse the trends.
That being said, the recharge continued to progress in the eastern Lyon region during October, and seems to have commenced locally in other areas, notably in the Artois coastal area, the centre-north part of the Paris Basin and in the north of the Bas Dauphiné. Stable or rising levels were observed in a few areas, due to the aquifers' slightly faster reaction times and/or particularly heavy amounts of rainfall in September and October.
Reactive aquifers
The trends in reactive aquifers also varied in October. The recharge period, which began in September, was interrupted at the beginning of October and then resumed towards the end of the month. Most observation points recorded decreasing levels at the start of the month, followed by rising levels (sometimes quite significant) at the end of the month. The monthly trends in the aquifers therefore depended on the balance between the in-flows that occurred at the end of the month and the losses due to natural outflows. If the rainfall at the end of October was enough to offset the outflows, the overall trends were either stable or rising. This was the case in the majority of reactive aquifers. On the other hand, a downwards trend was observed in aquifers where the rainfall was insufficient to compensate for the outflows.
The aquifers in the Avesnois area, the Armorican Massif and the central and western parts of the Aquitaine Basin have not yet entered their recharge phase; in these areas, most levels were down in September and remained so in October. The rainfall at the end of October was not enough to recharge the aquifers effectively, either because their levels were particularly low or because the rain initially served to moisten the dry soils and did not therefore seep directly down to the aquifers.
In the far south, from the valleys of the Pyrénées to the Mediterranean coast, the recharge period has struggled to get started. Here, the overall situation remained stable but the trends varied locally, due to rainfall being unevenly distributed across the area.
Comparison between 1 November 2024 and 1 November 2025
Map of France showing the state of the aquifers on 1 November 2024 (left) and 1 November 2025 (right).
© BRGM
Evolution of the situation observed on piezometers from November 2024 to October 2025.
© BRGM
Aquifer situation
At the end of the summer, the aquifer situation was generally satisfactory for the inertial aquifers and most of the reactive aquifers. Levels were moderately low in some reactive aquifers, in which the recharge had not yet set in. The situation in the aquifers in the Roussillon, Corbières Massif, Aude and southern Corsica remained very poor, with low to very low levels.
In October 2025, the levels were generally satisfactory, ranging from moderately low to moderately high. The situation was slightly worse than in September: the levels recorded at 35% of the observation points were below monthly averages, 22% were comparable with monthly norms and 43% were above average (compared with 31%, 23% and 46% in September, respectively).
The situation was far more satisfactory in October 2024, following an extremely active start to the recharge period: 79% of levels were above monthly norms. In 2025, the situation had only improved in the highly inertial aquifers of the Beauce and Sundgau areas (southern Alsace) and in the aquifers in the Roussillon plain and the Corbières massif.
Inertial aquifers
In the Artois basin and Paris Basin, the depletion period began early this year and the recharge period has not yet started. This long depletion period has particularly affected the less inertial aquifers. As a result, the levels in the marl chalk aquifers in the Artois and Champagne regions were moderately low in October. Generally speaking, the levels are higher in aquifers that function with a higher degree of inertia.
The depletion period was short and not particularly intense in the aquifers in the Sundgau area (southern Alsace) and the Rhône-Saône corridor. The levels in October were generally comparable to monthly norms. However, the situations varied locally, with low levels in Northern Isère and Bas-Dauphiné but high levels in the eastern part of the Lyon region, for example.
Reactive aquifers
Between September and October 2025, there was little change in the situation in the reactive aquifers, whose levels depended on the recent amount of local rainfall. For example, they deteriorated very slightly in the extreme southern part of the country and in the north-east of the Massif Central, while improving in the western part of the Massif Central. The overall state of the aquifers remained satisfactory in October, ranging from close to monthly norms to moderately high.
The levels in the aquifers in the northern half and centre of the country had suffered from a particularly long depletion period this year. The heavy rainfall at the end of August, in September and at the end of October generally compensated for this. However, some reactive aquifers still had moderately low to low levels, since the recharge period set in later than usual and/or the rainfall in these areas was less abundant than in the rest of the country: Boulonnais and Avesnois regions, northern and western parts of the Armorican Massif, Berry and Limagne. Consequently, the recharge was relatively non-existent in the aquifers in the north and west of the Armorican Massif in recent weeks. The aquifer recharge in the Jurassic limestone formations of the Berry region began quite late this year, at the end of October.
The situation in the aquifers in the far south of the country varied locally, due to uneven amounts of rainfall in September and October. The levels were generally more satisfactory inland, in the Languedoc region (south of the Massif Central and edge of Cévennes) and in Provence, with lower levels observed towards the Mediterranean coast and in the valleys of the Pyrénées. The levels were low in the aquifers in the Roussillon plain, the Corbières massif and the Aude valley. Finally, the aquifers in the extreme southern region of Corsica (Alta Rocca, Balagne and Fium'Orbu) were also in a very poor state in terms of their levels.
Aquifers with surplus water
Several aquifers had very high levels, when compared with those recorded for October in previous years:
- The Beauce aquifer continues to benefit from the significant recharges that occurred between 2023 and 2025, due to its highly inertial nature;
- The situation in the alluvial aquifers of the lower Rhône and its main tributaries improved due to the substantial inflows at the start of the recharge period.
Aquifers with low water levels
The situation was unsatisfactory in several aquifers, where levels were low compared to those recorded for October in previous years:
- The aquifer in the Jurassic limestone formation of the Boulonnais region has been affected by a particularly long depletion period this year;
- The levels in the alluvial aquifers in the Aude region, in the multilayer aquifer in Roussillon and in the karst limestone aquifers in the Corbières Massif remained low;
- The aquifers in the far south of Corsica continue to be affected by the lack of rainfall over the last few months.
Key figures
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37.00%of levels increased
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43.00%of levels were above monthly averages
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35.00%of levels were below monthly averages
Forecasts
The Météo-France seasonal forecasts for November and December 2025 and January 2026 predict higher temperatures than usual across the whole of France, and higher-than-average rainfall in Corsica. No clear scenario has been established concerning rainfall in mainland France.
The effect of reduced water abstraction, from the end of the summer onwards, will ease the pressure on groundwater. The vegetation went dormant during the month of October. The trends in terms of groundwater levels over the next few weeks will therefore depend exclusively on the degree of rainfall infiltration (and therefore total rainfall) as well as the reactivity of the aquifers.
Inertial aquifers
As regards the inertial aquifers in the Artois area, Paris Basin, the Sundgau (southern Alsace) and the Rhône-Saône corridor, the depletion phase had slowed or even ceased at the end of October. The recharge period has begun in some of the less inertial aquifers or in areas that received more rainfall. This suggests that inertial aquifers around the country will soon be entering their winter recharge period.
The state of the aquifers should start to improve in November, as the rain that fell in September and October filters deeper into the ground. However, over the longer term, the situation is expected to evolve slowly during autumn and winter, and through to the spring. It will either improve, if there is a surplus of effective rainfall, or deteriorate, if there is a lack of rain and the amount of rainfall does not compensate for the amount of water that flows out naturally through springs, rivers and into the sea, or that is consumed by human withdrawals. The forecasts continue to suggest that no winter drought will affect the inertial aquifers in the Paris basin, whose levels are currently above monthly norms.
Reactive aquifers
The conditions forecast should enable the reactive aquifers to continue recharging in November. The rain that fell at the end of October is filtering deep into the ground and this process should continue at the beginning of November, and thus have a positive impact on the aquifers in areas that received plenty of rainfall. If there is sufficient rain in November, this should result in recharge episodes. In this case, the rainfall should quickly have a noticeable effect on the aquifers. If not, the levels in the aquifers could start to drop and the situation could deteriorate.
During the autumn and winter, the trends and developments will depend exclusively on the amount of rainfall infiltration. The current situation does not allow us to predict what will happen in the coming months and say whether there will be either a period of drought or flooding due to rising groundwater. The levels in reactive aquifers at the start of next spring (2026) will depend on the overall recharge that occurs during the autumn and winter. It should also be noted that the amount of rainfall during next spring will also play a crucial role in maintaining high groundwater levels and in delaying the start of the depletion period.
The aquifers in which low to very-low levels were observed in October (Boulonnais, Roussillon, Aude and southern Corsica) need to be monitored closely. Since the situation is currently unfavourable in these areas, a significant amount of rainfall will be required across all of these regions in the coming months to replenish the groundwater resources in the long term. Consequently, the situation must continue to be closely monitored during the 2025-2026 recharge period.
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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 7 November 2025, based on data acquired up to 31 October 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.