Hydrogeological situation on 1 December 2025
The recharge was under way in November, with 57% of levels rising (37% in October). However, the recharge episodes were unevenly distributed over the month and only enabled the situation to remain stable in relation to October. The overall state of the aquifers remained satisfactory, ranging from moderately low to moderately high. The situation remained poor in the Roussillon area, where the aquifers continued to show low levels.
Over the winter, the trends and any changes in the situations will essentially depend on the effects of recent rainfall in the case of reactive aquifers and the total, cumulative rainfall over the recharge period in the case of inertial groundwater. The trends and situations could change over the course of a few weeks in reactive aquifers but more slowly in inertial aquifers.
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 December 2025.
© BRGM
Evolution of the trends observed on piezometers from December 2024 to November 2025.
© BRGM
Trends
The recharge period began between the end of August and September in many reactive aquifers (except in the Armorican Massif). It then paused at the beginning of October before resuming at the end of October. In the case of inertial aquifers, the recharge period began in October.
In November, the recharge was well under way, with 57% of levels rising and just 30% decreasing (compared with 37% and 42% respectively in September).
Inertial aquifers
The recharge period is struggling to establish itself in the inertial aquifers in the Artois region and Paris Basin. Levels rose in the less inertial aquifers to the west of the Artois region, in Sologne and Sancerre. As regards the other inertial aquifers, the rate of depletion slowed from October onwards at many observation points. However, the rainfall that managed to filter deep into the ground was still not enough to compensate for the outflows (rivers, sea, abstractions) and thus allow the recharge period to set in.
The recharge started in either October or November in the inertial aquifers in the Rhône-Saône corridor, since there was a greater amount of rainfall between September and November.
Reactive aquifers
The recharge was under way in the majority of reactive aquifers in November, with levels rising. While effective rainfall was unevenly distributed over the month, the quantities were nevertheless sufficient to enable recharge episodes to occur. In fact, the majority of the observation points recorded a drop in levels at the beginning of the month, since the recharge episode at the end of October was followed by a lack of rainfall at the beginning of November, which was then followed by a (sometimes significant) rise in levels at the end of the month.
The rainfall at the end of the month, which was often quite heavy, did not always compensate for the lack of rainfall at the beginning of the month. The levels were stable in the reactive aquifers in eastern Lorraine and in the aquifers on the edge and to the south of the Armorican Massif.
The trends varied along the Mediterranean coast and in Corsica, where monthly rainfall was below average during the autumn. The aquifer recharge was struggling to get under way. Consequently, levels in the aquifers in the Vistrenque, Bas-Rhône and Durance regions were all down in November. However, a number of rainy episodes allowed recharges to occur in certain aquifers, particularly on the western coast of the Languedoc region, where levels were up.
Comparison between 1 December 2024 and 1 December 2025
Map of France showing the state of the aquifers on 1 December 2024 (left) and 1 December 2025 (right).
© BRGM
Evolution of the situation observed on piezometers from December 2024 to November 2025.
© BRGM
Aquifer situation
At the end of this summer, the aquifer situation was generally satisfactory in the inertial aquifers and most of the reactive aquifers. The situation then improved in reactive aquifers in September, and remained stable in October.
In November, the levels were satisfactory, ranging from moderately low to moderately high. The situation was virtually the same as in October: the levels recorded at 35% of the observation points were below monthly averages, 22% were comparable with monthly norms and 43% were above average (same as in October).
The situation was far more satisfactory in November 2024, following an extremely active start to the recharge period and despite the month of November itself being dry: 65% of levels were above monthly norms. However, the situation in 2025 was actually better than in 2024 in the aquifers in the Roussillon plain and the Corbières Massif.
Inertial aquifers
As regards the Artois region and Paris Basin, the inertial aquifers continued to benefit from the abundant recharges in 2023-2024 and 2024-2025. However, the 2025-2026 recharge period has been slow to get under way and this year's extended depletion period has had an impact on the state of the aquifers. The levels recorded in the less inertial aquifers in the Artois, Champagne, Burgundy, Gâtinais, Perche and Maine regions were close to monthly norms or moderately low. The aquifers with greater inertia in the centre of the Paris Basin remained at moderately high levels.
The levels in the aquifers in the Sundgau region (southern Alsace) and the Rhône-Saône corridor ranged from close to normal to moderately low. Levels at the beginning of 2025 in these areas were lower than in the Paris Basin, but the depletion period did not last as long.
Reactive aquifers
Between September and November, there was little change in the situation in the reactive aquifers. The inflows were generally sufficient to maintain the levels in the aquifers but not enough to bring about any notable improvement in the situation. The state of the aquifers improved slightly in the area stretching from southern Alsace to the northern Alps and in the west of the Massif Central, due to the abundant rainfall in these sectors. The situation deteriorated in areas that had little rainfall, such as the southern part of the Armorican Massif, the Cévennes, Provence and the Côte d'Azur.
Satisfactory levels – ranging from moderately high to close to normal – were recorded in reactive aquifers that benefited from significant recharge episodes between September and November. This essentially concerns the aquifers located across a central strip of the country, from the Jura to Charentes.
The moderately low levels observed in certain aquifers can be explained by the dry autumn, resulting in a late or weak start to the recharge period. The aquifers in the Armorican Massif and Avesnois region only began to recharge at the end of October. As regards the Adour basin, the Mediterranean coast and Corsica, the rainfall during autumn was poorly distributed in space and time and only a small amount of water managed to filter deep into the ground.
The levels were slowly improving in the aquifers in the Roussillon plain, the Corbières massif and the Aude valley, but remained low.
Aquifers with surplus water
Several aquifers had very high levels, when compared with those recorded for November in previous years:
- The limestone aquifers in the Jura benefited from a strong start to the recharge period (September to November);
- The limestone aquifers in the Causses du Quercy had excess recharge episodes in November;
- The situation in the alluvial aquifers of the lower Rhône and its main tributaries improved due to the inflows that occurred in September and then in November.
Aquifers with low water levels
The situation was less favourable in certain aquifers, whose levels were moderately low to low compared to those recorded for November in previous years:
- The bedrock aquifers in the Armorican Massif, in which the recharge period started late (end of October);
- The aquifers around the Mediterranean coast and in Corsica have been affected by the autumn drought;
- The levels in the alluvial aquifers in the Aude valley, in the multilayer aquifer in the Roussillon and in the karst limestone aquifers in the Corbières Massif remained low.
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 December 2025, January and February 2026 predict higher temperatures than usual across the whole of France. No clear scenario has been established concerning rainfall in mainland France.
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 Sundgau (southern Alsace) and the Rhône-Saône corridor, the recharge period is expected to continue in December and until spring 2026.
As regards the inertial aquifers in the Artois area, the lack of rainfall in November does not allow for optimism regarding the imminent start of the recharge period for the most inertial aquifers.
Over the longer term, situations are expected to evolve only slowly during the winter and into spring, either improving if there is excess effective rainfall or deteriorating if there is a deficit. Forecasts are confident that there will be no winter drought for the inertial aquifers of the Paris Basin, which are currently at above-normal monthly levels. However, given the very late start to the recharge period in this area, there is uncertainty surrounding the forecasts for spring 2026.
Reactive aquifers
In the case of normal to above-average rainfall in December, the recharge of reactive aquifers should continue actively. The situation should therefore remain stable or improve. If rainfall is insufficient, infiltration will not be able to compensate for the volume of outflow (natural outlets and withdrawals). Depletion could then resume. The situation will deteriorate more rapidly if the deficit is significant and the aquifer is reactive.
As regards to reactive aquifers showing current levels above normal, this early winter recharge gives hope for satisfying levels over the coming weeks. However, forecasts for early spring 2026 remain uncertain. Indeed, the situation could also deteriorate rapidly in the event of insufficient rainfall. Levels in summer 2026 will depend on abundant recharge during the winter and continuing into the spring, in order to delay the start of the discharge period.
Particular attention should be paid over the coming weeks to aquifers that are showing signs of a deficit in recharge and that are at moderately low levels in November (Armorican Massif, Adour, south-east and Corsica).
Finally, it remains highly uncertain whether groundwater levels in the Roussillon plain, which were low in November, will return to normal levels by spring 2026.
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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 5 December 2025, based on data acquired up to 30 November 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.