Responsive aquifers were starting to empty, although levels remained satisfactory
After the exceptional recharge episode in February 2026 followed by a lack of rain in March, the levels in more than half of the aquifers were falling. Across the country, the lack of effective rainfall in March meant that aquifers with quick response times began to empty. Despite this, the recharge remained active in a third of the aquifers, which were still benefiting from the positive effects of February's rainfall.
The levels remained satisfactory in the majority of aquifers, ranging from around normal to moderately high or even very high. Sixty-two percent of observation points were above monthly norms. The situation was better than in March 2025 (when only 52% of observation points were above monthly norms).
Aquifers in only three areas continued to show moderately low levels: the aquifers in the volcanic formations of the Massif Central, the sandstone aquifer in the Vosges and those in the Triassic limestone and carboniferous limestone formations of the Avesnois region.
The positive provisional assessment of the 2025-2026 winter recharge period means that we can expect satisfactory levels across most of the responsive aquifers over the next three months. However, it remains uncertain whether any potential rainfall in April will have a positive effect on the levels, since vegetation is starting to grow again and the demand for water to satisfy various uses – particularly agricultural – is increasing. The outlook for the longer term therefore remains uncertain.
Map of aquifer levels in mainland France on 1 April 2026.
© BRGM
Evolution of the trends observed on piezometers from March 2025 to March 2026.
© BRGM
Trends
After an exceptional recharge episode in February, the trends in March were more mixed. There was a lack of rain in March, well below the monthly norms, across the whole of France, apart from on the Mediterranean coast and in the area to the north east of the Paris Basin, where the rainfall was above average.
As a result, the vast majority of aquifers began to deplete.
In March 2026, levels were dropping at 54% of the observation points. The recharge in March was comparable to that in 2025.
Inertial aquifers
In March 2026, due to the excess rainfall in February, the recharge was generally active in the aquifers with very slow response times in Normandy, the centre of the Paris Basin, the Artois area, the Rhône-Saône corridor and in the limestone aquifers of the Armagnac region; these aquifers continued on an upwards trend. Only the levels in the aquifers in the Beauce and Brie regions began to drop.
Reactive aquifers
After the exceptional recharge episode in February, depletion commenced in the most responsive aquifers, which had high to very high levels at the end of February, due to the lack of rainfall in March. This was the case in the basement aquifers in the Armorican and Limousin regions, the Jurassic limestone aquifers in the south and south-west of the country and in alluvial aquifers (including on the Corsican coast), with the exception of the alluvial aquifer in the eastern area of Lyon and the alluvial aquifer in the southern Rhine.
As regards the aquifers along the Mediterranean coast, the substantial rainfall in March enabled the recharge to continue, or to stabilise in the case of the aquifers in the Eastern Pyrenees, the alluvial aquifers of the Aude, Rhône and coastal rivers of the Côte d'Azur, as well as in the Vistrenque basin and in the karst limestone aquifers of Provence. The alluvial aquifers of the Hérault river and the limestone aquifer of the Grands Causses started to deplete.
Comparison between 1 April 2025 and 1 April 2026
Map of France showing the state of the aquifers on 1 April 2025 (left) and 1 April 2026 (right).
© BRGM
Evolution of the situation observed on piezometers from March 2025 to March 2026.
© BRGM
Aquifer situation
Due to the exceptionally high levels recorded on 1 March, current levels remain satisfactory.
At the end of March 2026, groundwater levels were satisfactory and often above monthly norms: only 16% of the observation points were below monthly norms, 22% were comparable with monthly norms and 62% were above them (compared with 18%, 15% and 67%, respectively, in February).
The current situation is better than that recorded in March 2025, when just 52% of levels were above monthly norms. At the end of March 2026, in comparison to last year, the situation was better in all the responsive aquifers, but worse in aquifers with slower response times.
Inertial aquifers
February's rainfall enabled the recharge to continue in aquifers with slower response times. Rainwater filters slowly down through the ground to reach this type of aquifer. The levels were around average across all the chalk aquifers in Normandy, the Artois region, the Paris Basin, the Rhône-Saône corridor and the Sundgau region. The limestone aquifers in the Beauce and Armagnac regions were moderately high.
It should be noted that slight local variations were recorded in some of these aquifers.
Reactive aquifers
The situation in the responsive aquifers was satisfactory throughout the country. The exceptional recharge episode in February meant that water levels were well above normal for the month. Despite the fact that depletion had started in some of these aquifers, they remained at around-average or above-average levels.
Very high levels continued to be observed in the alluvial aquifers of the Garonne, Aude, Rhône and Hérault rivers, in the Roussillon plain and Vistrenque basin.
High levels were observed in the limestone aquifers to the west of the Massif Central and in the limestone aquifer of the Grands Causses.
In north-eastern France, the recharge was less significant. In the highly responsive limestone aquifers located in western Lorraine, the Jura and the plains of Alsace, the levels recorded ranged from close to normal to moderately high. The sandstone aquifer in eastern Lorraine is less responsive to rainfall and remained moderately low.
Key figures
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54.00%of levels decreased
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62.00%of levels were above monthly averages
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16.00%of levels were below monthly averages
Forecasts
The Météo-France seasonal forecasts for April, May and June 2026 predict higher temperatures across the whole of France. There is no clear scenario concerning rainfall.
Groundwater trends and level changes over the next few weeks will depend exclusively on rainwater infiltration, which in turn depends on rainfall totals, the response times typically associated with individual groundwater bodies, and the water needs of the vegetation coming out of winter dormancy.
The fact that plants have come out of dormancy, due to higher temperatures, could reduce the amount of rainfall that seeps deep into the ground. Consequently, the recharge could come to an end as early as April and all responsive aquifers could start depletion.
Inertial aquifers
The situation in aquifers with slow response times (the Artois area, Paris Basin, Sundgau and Rhône-Saône corridor) will depend on the levels they had at the end of the previous low-water period and on the total amount of effective rainfall received over this year's recharge period.
The recharge is expected to continue or to stabilise in April in the less-responsive aquifers in the Sundgau area (southern Alsace), and along the Rhône-Saône corridor, due to the slow infiltration of the February rains. The situation may then improve or remain stable, depending on the total amount of rain that manages to filter deep into the ground.
There continues to be a degree of uncertainty as to when the recharge period will end and how effective the spring rainfall will be in filling the aquifers. The outlook for the summer of 2026 is uncertain. Levels will undoubtedly be lower than in 2025, due to the more moderate recharge in 2025–2026.
Reactive aquifers
The positive provisional assessment of the 2025-2026 winter recharge period means that we can expect satisfactory levels across most of the responsive aquifers over the next three months. The seasonal forecasts are positive for the responsive aquifers that currently have high to very high levels.
At the end of March, the levels of responsive aquifers began to fall, but many remained moderately high to very high, particularly in the south, south-west and west of the country.
However, as vegetation starts to regrow, it is difficult to predict how effective the spring rainfall will be in filling the aquifers and what the demand on resources will be. The spring rainfall will play an essential role in maintaining the levels above normal for as long as possible. In the event of a prolonged and intense drought, the responsive aquifers could empty in a matter of weeks. Consequently, the outlook for the longer term, notably for the end of summer 2026 and the low-water period, remains uncertain.
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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 8 April 2026, based on data acquired up to 31 March 2026.
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.