The groundwater situation has deteriorated
The groundwater situation deteriorated due to the lack of effective rainfall in July and the increased demand on water resources for various purposes.
As in the previous month, groundwater levels continued to fall across the whole of France, due to the lack of effective rainfall in July and the increase in groundwater abstraction.
Only 37% of observation points showed levels above or in line with monthly norms. Groundwater levels were lower than on 1 August 2025 (when 56% of observation sites were either in line with or above monthly norms).
There were contrasting levels across the country. Very low levels were recorded in the Limousin basement and Côte des Bars limestone aquifers and in the Vistrenque alluvial formations.
The responsive aquifers whose levels remained above monthly averages can expect to maintain satisfactory levels over the next three months. However, it is difficult to know how the summer rainfall will be distributed across France and whether it will be sufficient to soak into the soil and thus reduce the amount of groundwater that needs to be abstracted for various uses, particularly agriculture. The outlook for the longer term therefore remains uncertain.
Map of aquifer levels in mainland France on 1 August 2026.
© BRGM
Evolution of the trends observed on piezometers from July 2025 to July 2026.
© BRGM
Groundwater trends
The decline of groundwater levels continued throughout July. Across the country, most aquifer piezometric levels fell. This can be explained by the lack of effective rainfall over the whole of France since May, with warmer and markedly drier conditions in June and July.
The data collected in July 2026 showed that groundwater levels were decreasing at 94% of observation points. Levels were stable at 4% of the observation points, and only 2% showed rising levels. Groundwater levels appeared to be dropping faster than in July 2025.
Aquifers with slow response times
Groundwater levels in the least-responsive aquifers continued to drop during July 2026. This was notably the case for the Beauce, Artois and Normandy limestone aquifers, the Lutetian limestone and Ypresian sand aquifers of the Paris Basin, for the Vosgian sandstone, Lorraine Triassic limestone, Bresse and Dombes aquifers, and for the glaciofluvial formations of eastern Lyon and the Dauphiné.
The only levels to remain stable were those in the Sundgau gravel aquifer.
Aquifers with quick response times
Levels decreased in almost all the aquifers. The only levels to remain stable were those in the Quercy karst limestone formations and the deposits of the Limagne basins.
This is considered normal for the period. Very little of the rain that fell during storms that were often violent filtered down into the ground. In addition, the season’s high temperatures encouraged evapotranspiration and increased plant water requirements. Water abstraction for irrigation and tourism further increased the rate of decline in certain areas.
Comparison of the situation between August 1, 2025, and August 1, 2026
Map of France showing the state of the aquifers on 1 August 2025 (left) and 1 August 2026 (right).
© BRGM
Evolution of the situation observed on piezometers from July 2025 to July 2026.
© BRGM
Overall groundwater situation
The situation deteriorated during July 2026, due to a lack of rainfall, high temperatures and increased groundwater abstraction.
At the end of July, only 37% of observation points had satisfactory groundwater levels, which were slightly above or around monthly norms. A total of 63% of observation points were below normal. More specifically, 16% of observation points were above normal, 21% were comparable with monthly norms and 63% were below normal (compared with 22%, 24% and 54% respectively at the end of June).
The current situation appears worse than that observed at the end of July 2025, when 30% of levels were above monthly norms, 26% were comparable with monthly averages 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 Beauce and Armagnac limestone aquifers.
Levels in the Sundgau aquifer were close to monthly averages.
Levels in the Lutetian limestone and Ypresian sand aquifers in the north of the Paris Basin, the Artois and Normandy chalk aquifers, the Dijonnais, Bresse and Dombes formations, and those in the glaciofluvial deposits of Dauphiné were moderately low for the season.
Levels were low in the Vosgian sandstone and Lorraine Triassic limestone aquifers.
It should be noted that significant local differences were observed within these aquifer systems.
Aquifers with quick response times
The situation in highly responsive aquifers also varied across the country.
Levels remained moderately high in the Valras-Agde sand aquifer and alluvial aquifer of the Roussillon Plain. Groundwater levels remained high in the Vistrenque alluvial formations.
Groundwater levels were close to normal levels in the basement aquifer of the Vilaine River basin and Vendée bocage area, in the Touraine chalk aquifer, the Jurassic limestone formations of Brenne and Vienne, the limestone formations of Angoulême and Périgord, and of Entre-Deux-Mers, the alluvial deposits of the Upper Garonne River, the Corbières limestone aquifer, the sand aquifer of the Roussillon plain, Jurassic limestone aquifers of the Grands-Causses, the alluvial aquifer of the Hérault River, the limestone aquifers of Provence, and the glaciofluvial deposits in the eastern Lyon area.
Groundwater levels were low in other areas, such as in the basement aquifer of the Morvan and eastern Massif Central, the Jurassic limestone aquifers of Charentes, the volcanic formations of the Massif Central, the alluvial deposits of the northern Alsace Plain, Lorraine limestone aquifers and Champagne chalk.
Groundwater levels in the Limousin basement aquifer and Côte des Bars limestone formations were very low.
They were moderately low in other responsive aquifers.
However, the groundwater status of the Limagne plain basins, alluvial formations of the Adour, Gave de Pau and Lower Garonne Rivers improved, with low levels becoming moderately low.
It should be noted that significant local differences were observed within these aquifer systems.
Key figures
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94.00%of levels are declining
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16.00%of the levels are above monthly averages
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63.00%of the levels are below monthly averages
Forecasts
Météo-France’s seasonal forecasts for the period from August to October 2026 indicate an increased likelihood of above-normal temperatures across the country. With regard to rainfall patterns, Météo France states that the outlook is uncertain, except in the south of France, which could see rainfall above the seasonal average.
The water required by plants, together with higher temperatures and increased abstraction, will accelerate the decline of groundwater levels in almost all aquifers at least during the month of August. In September, with water needs decreasing and the irrigation season coming to an end, groundwater levels are expected to drop at a slower pace.
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.
The Sundgau aquifer is the only aquifer with groundwater levels becoming stable. In the other aquifers, whose groundwater levels are already falling, the downward trend will continue until the autumn.
However, the outlook for the summer of 2026 remains uncertain. Piezometric levels will certainly be lower than those observed in 2025, due to a less abundant recharge in 2025-2026.
Aquifers with quick response times
The lack of effective rainfall in July resulted in the continued decline of groundwater levels in responsive aquifers. Nevertheless, the seasonal forecast remains positive for the responsive aquifers that currently have moderately high to high levels.
For aquifers with levels close to or below normal, the outlook is uncertain and will depend on summer rainfall.
Highly responsive aquifers are sensitive to prolonged and intense droughts. For instance, the basement aquifer of the Limousin and the limestone aquifers of Côte des Bars are 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
Map drawn up by BRGM on 6 August 2026, based on data acquired up to 31 July 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.