Aquifers: the situation remains difficult
Groundwater levels remain mostly low, due to the shortfall in effective rainfall in August and the continued high demand for water for various purposes.
As in the previous month, the draining of aquifers continued throughout France, due to the lack of effective rainfall in August and the summer increase in groundwater abstraction.
With water levels below monthly norms at 61% of monitoring points, the overall groundwater situation is still problematic. The most responsive aquifers, or those which had benefited from only a moderate recharge, were well below normal monthly norms. The situation was worse than on 1 September 2025 (when the levels at 44% of monitoring points were below monthly norms).
There were contrasting aquifer levels across the country. They were very low for the aquifers of the Limousin basement and the Jura limestone formations and the northern plain of Alsace, but still high for the aquifers of the Vistrenque formations.
The responsive aquifers whose levels remained above monthly norms can expect to maintain satisfactory levels over the next three months. However, there are uncertainties regarding the distribution and effectiveness of autumn rainfall, which would help to re-moisten the soil. Reducing the amount of water abstracted from aquifers to meet the needs of various summer uses (irrigation, drinking water supply) will help to reduce the strain on groundwater resources. The outlook for the longer term remains uncertain.
Map of aquifer levels in mainland France on 1 September 2026. Map drawn up by BRGM on 4 September 2026, based on data acquired up to 31 August 2026.
© BRGM
Evolution of the trends observed on piezometers from August 2025 to August 2026.
© BRGM
Groundwater trends
The groundwater draining continued in August. Piezometer readings showed a general downward trend across the country. This can be explained by the lack of effective rainfall throughout France since May, with a particularly marked period of drought and high temperatures since June.
Data collected in August 2026 show that groundwater is draining at 90% of the monitoring points. Levels were stable at 8% of the monitoring points and only 2% showed rising levels. The degree of drainage appears to be greater than in August 2025.
Aquifers with slow response times
In August 2026, the water levels in aquifers with slow response times continued to fall. This is the case for the Beauce, Artois, Normandy and Lutetian limestone aquifers, and the aquifers of the Ypresian sands, the Paris Basin, the Vosges sandstone and the Triassic limestone formations of Lorraine, the Bresse and Dombes formations, and the fluvio-glacial formations of eastern Lyon and the Dauphiné.
Only the level of the Sundgau gravel bed aquifer remained stable.
Aquifers with quick response times
Levels decreased in almost all the aquifers. Only the aquifers in the karst limestones of Quercy, the Limagne basins, the Cévennes and Montagne Noire basement, the alluvial deposits of the Hérault, and the Tertiary formations of the Lower Rhône and the Durance have water levels that are stabilising.
This is normal for the period, since very little of the rain that falls during storms (which are often violent) filters into the ground. In addition, the high temperatures encouraged evapotranspiration and increased plant water requirements. Water abstractions for irrigation and tourism may have accelerated the fall in levels in certain areas. It should be noted, however, that there have been slight rises in the readings of a few piezometers following the rain over the last few days, although this does not, for the time being, indicate that these aquifers are beginning to recharge.
Comparison of the situation between September 1, 2025, and September 1, 2026
Map of France showing the state of the aquifers on 1 September 2025 (left) and 1 September 2026 (right).
© BRGM
Evolution of the situation observed on piezometers from August 2025 to August 2026.
© BRGM
Overall groundwater situation
The situation deteriorated during August 2026, due to a lack of rainfall, high temperatures and ongoing groundwater abstraction.
At the end of August, only 39% of the monitoring points showed satisfactory groundwater levels, which were slightly above or around monthly norms. The levels at 61% of monitoring points were below normal. More specifically, the levels at 19% of the monitoring points were above normal, 20% were comparable with monthly norms and 61% were below normal (compared with 16%, 21% and 63% respectively at the end of July).
The current situation appears worse than that observed at the end of August 2025, when 30% of levels were above monthly norms, 26% were comparable with monthly norms and 44% were below.
Aquifers with slow response times
There were contrasting levels across the country in aquifers with extremely slow response times.
Certain aquifers had moderately high levels in relation to monthly norms, namely the aquifers in the limestone formations of the Beauce and Armagnac regions.
The Sundgau aquifer had levels close to the average.
The aquifers of the Lutetian limestone and Ypresian sand formations in the north of the Paris Basin, those of the Artois and Normandy chalk formations, the Dijon, Bresse and Dombes formations, and the fluvio-glacial alluvial aquifer of the Dauphiné and the Savoy foreland had moderately low levels for the season.
Levels were low in the Vosgian sandstone and Triassic limestone aquifer of Lorraine.
It should be noted that significant localised differences were observed within these aquifer systems.
Aquifers with quick response times
The situation in highly responsive aquifers also varied across the country.
Water levels remained moderately high in the Valras-Agde sand aquifer and the alluvial aquifer of the Roussillon plain. Levels remained very high in the aquifer in the Vistrenque formations.
Some aquifers have deteriorated since 15 August; these are the aquifers of the Armorican basement and the Aquitaine Basin, where water levels are now low.
The situation of certain aquifers has improved since 15 August; these include the Périgord and Angoumois limestone aquifer, where the level has risen from low to around average, and the Côte des Bars limestone aquifer, where the level has risen from very low to low. Water levels in the alluvial aquifers of the Hérault and the lower Rhône are now moderately high for the season.
The levels of the Touraine chalk aquifers, the Jurassic limestones of the Brenne and the Vienne, the Entre-deux-Mers limestones, the alluvial deposits of the upper Garonne, the Corbières limestones, the sands of the Roussillon plain, the Jurassic limestone formations of the Grands-Causses, the limestone formations of Provence and the fluvio-glacial formations of eastern Lyon are approximately normal.
Some of their levels remained low. This is the case for the basement aquifers of the Morvan and the eastern Massif Central, the Jurassic limestone formations of the Charentes, the limestone formations of Lorraine and the Jura, and the Champagne chalk aquifer.
The aquifers in the Limousin basement, the Jura limestone formations and the northern Alsace plain had very low levels.
The other aquifers with a rapid response time still had moderately low levels.
It should be noted that significant localised differences may be observed within these aquifer systems.
Changes in the groundwater situation from September 2022 to September 2026
The groundwater situation from 1 September 2022 to 1 September 2026.
The situation in 2026 is significantly less worrying than in 2022 (except in the Massif Central, the Jura, the Vosges and northern Alsace). However, it is also less favourable than in 2023 (except in the south), 2024 (which stands out as an exceptional year with a wet summer) and 2025 (particularly in the North, North-West, Grand Est and Limousin).
© BRGM
Key figures
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90.00%of levels are declining
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19.00%of the levels are above monthly averages
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61.00%of the levels are below monthly averages
Forecasts
Météo-France’s seasonal forecasts for the period from September to November 2026 indicate a likelihood of above-average temperatures across the whole of the country. With regard to rainfall patterns, Météo France states that there is a likelihood of above-average rainfall along the Atlantic coast, but that no particular scenario is favoured for the rest of the country.
Water is still needed for vegetation and human activities both of which are linked to the persistently high temperatures. The latter will exacerbate the drainage from almost all aquifers, at least for the month of September. Nevertheless, with water demand falling and the irrigation season coming to an end, the draining of aquifers is expected to slow.
Aquifers with slow response times
The levels in less-responsive aquifers depend on the levels reached during the previous low-water period and on the total amount of effective rainfall during the entire recharge period.
Only the level of the Sundgau aquifer is stabilising. In the other aquifers, whose levels are already falling, the downward trend will continue until the autumn.
However, the outlook for the autumn of 2026 remains uncertain. Piezometric levels will inevitably be lower than those observed in 2025, due to more moderate recharge during 2025–2026 but, above all, because of the lack of effective rainfall observed since May.
Aquifers with quick response times
The lack of effective rainfall in August resulted in the continued draining of responsive aquifers. Nevertheless, as regards aquifers with water levels ranging from above normal to moderately high to high, the seasonal forecasts remain favourable.
For the other aquifers, whose levels are around or below normal, there are uncertainties, and the outcome will depend on autumn rainfall.
Highly responsive aquifers are sensitive to prolonged and intense droughts. This is the case for the aquifers of the Limousin basement and the limestone formations of the Jura and the northern Alsace plain, where the situation is already a cause for concern.
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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
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). These global indicators reflect general situations and trends and do not take into account possible local disparities.
The "Aquifer levels" indicator (colours) 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-shaded areas are areas where there are no extensive unconfined aquifers and/or no monitoring points. 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).
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).