Hydrogeological situation on 1 January 2026
Recharging was active in December, with 63% of levels up (compared to 57% in November). There is a groundwater deficit in the north-east of the Armorican Massif, the Paris Basin, the east of Artois and the Grand-Est.
The state of the aquifers is generally satisfactory, ranging from moderately low to moderately high. The more deficient situations can be explained by recharge episodes that have been unevenly distributed over time and space since September 2025.
Over the winter and into the spring, changes in trends and situations will depend on recharge episodes. Forecasts are optimistic for January but remain uncertain in the longer term. The situation will need to be monitored closely, particularly in aquifers whose levels are currently below normal and in those where recharge has not yet become evident (particularly in the Artois region and the Paris Basin).
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 January 2026.
© BRGM
Evolution of the trends observed on piezometers from December 2024 to December 2025.
© BRGM
Trends
The recharge period began between the end of August and September for many reactive aquifers (except for those in the Armorican Massif), paused at the beginning of October, then resumed at the end of October and continued into November. As far as the inertial aquifers are concerned, the recharge period began in October.
In December, recharging was active, with 63% of levels up and 25% down (compared with 57% and 30% respectively in November).
Inertial aquifers
Recharge has still not become evident in the inertial aquifers of the Paris Basin and the Artois Basin. It has only started in areas that have received more rain since the autumn and that often have less inert aquifers. December levels were thus slightly up for the Artois coastal chalk, Champagne, Burgundy and Gâtinais aquifers, for the north-east of the Beauce aquifer and for the Perche and Maine Cenomanian sands aquifers. They are falling in all the other inertial aquifers.
Cumulative rainfall was sufficient to activate recharging of the inertial aquifers in the Rhône-Saône corridor in October or November. Levels continued to rise in December.
Reactive aquifers
The reactive aquifers were being recharged in December, with most levels rising. Recharge episodes were generally in line with December norms in the western half of the country.
The second half of December saw significant recharge episodes in the Roussillon, Languedoc and southern Massif Central regions. The aquifers of the Brittany basement and north-east Corsica also benefited from excess rainfall throughout December. Groundwater levels in these areas are rising sharply.
As a result of the rainfall shortfalls in November and December, groundwater recharge in aquifers in the Rhine-Meuse basin is hesitant. The recharge period began very late, in December, for the basement aquifers in the north-east of the Armorican Massif. Levels are rising slightly or are stable in these aquifers.
Lastly, snowfall was not very effective in recharging the alluvial aquifers in the Alps, with downward trends.
Comparison between 1 January 2025 and 1 January 2026
Map of France showing the state of the aquifers on 1 January 2025 (left) and 1 January 2026 (right).
© BRGM
Evolution of the situation observed on piezometers from December 2024 to December 2025.
© BRGM
Aquifer situation
At the end of the summer of 2025, the levels were generally satisfactory for the inertial aquifers and for most of the reactive aquifers. It then improved in September and stabilised in October and November.
In December, levels were satisfactory, ranging from moderately low to moderately high. The situation has improved slightly, but remains very similar to that in November: the levels recorded at 30% of the observation points were below monthly norms, 24% were comparable with monthly norms and 46% were above average (compared with 35%, 22% and 43%, respectively, in November).
The situation was much more satisfactory in December 2024: 61% of levels were above monthly norms. The situation is better in 2025 for reactive aquifers that have seen the beginnings of a surplus due to recharge: in the Boulonnais, Brittany and the south-east.
Inertial aquifers
The inertial aquifers of the Paris Basin and Artois still benefit from the two previous surplus winter recharges. The 2025-2026 recharge period is taking time to get under way, but groundwater levels are dropping only very slowly and remain generally satisfactory. Groundwater levels in the centre of the Paris Basin remain moderately high to close to normal. Moderately reactive aquifers around the Paris Basin and Artois are more sensitive to a lack of autumnal recharge, with levels ranging from close to normal to moderately low. Low levels have been recorded at a few points in the Champagne chalk marl aquifer.
The beginning of the recharge period was more generous for the Sundgau aquifers (southern Alsace) and those in the Rhône-Saône corridor. Their levels are expected to remain close to normal or moderately low.
Reactive aquifers
The heterogeneous situations of the reactive aquifers can be explained by recharge episodes that have been unevenly distributed in time and space since September 2025, when the recharge period began. The succession of wet and dry spells did not always allow rainfall to infiltrate effectively nor to recharge aquifers optimally.
The lack of rainfall in the autumn is affecting the aquifers in the Rhine-Meuse basin and the north-eastern Armorican Massif. Levels are deteriorating and are gradually falling below monthly norms. The most deficient situations, with moderately low to low levels, are in the northern part of the Lorraine aquifers.
The state of the aquifers in the western half of the country, from the Boulonnais to the Aquitaine Basin, and in the centre-west, from Jura to the north-east of the Massif Central, changed little between November and December. Inflows were generally sufficient to maintain satisfactory levels, from close to normal to moderately high. Some slight improvements can be seen in the aquifers that benefited from more abundant and effective rainfall in December: in the Boulonnais, Berry and the west and south of the Armorican Massif.
The situations of the Provence, Côte d'Azur and Corsica aquifers are heterogeneous, as they depend on the accumulated rainfall and the reactivity of the aquifers concerned. Recharge episodes thus affected the alluvial and karst aquifers in north-east Corsica, the Var and the Vaucluse. Levels are moderately high to very high in these areas, but below normal elsewhere.
Excess rainfall in December led to a resumption of recharging of aquifers in Roussillon, Languedoc and the southern Massif Central. Their condition has improved considerably, particularly for the most reactive aquifers in the basement and karst limestone formations. However, below-normal water levels are still being observed in the less reactive coastal aquifers. In addition, the aquifers in the Roussillon plain and the Corbières massif are slowly improving, but still have locally low levels.
Aquifers with surplus water
Several aquifers had very high levels, when compared with those recorded for December in previous years:
- The Jura limestone aquifers benefited from an early surplus recharge period (September to December);
- Significant recharge episodes during the second half of December mean that high levels have been observed for the karst limestone aquifers of the Grands Causses, the edge of the Cévennes and the Corbières massif and for the alluvial aquifers of the Hérault and Orb.
Aquifers with low water levels
The condition of several aquifers was less favourable with moderately low to very low levels compared to those recorded for December in previous years:
- The Champagne and Lorraine aquifers are showing a deficit at the start of the recharge period with moderately low levels observed;
- Some aquifers around the Mediterranean and in western Corsica are still affected by the autumn drought;
- Levels of the Roussillon aquifers are improving with recent recharge episodes, but remain low, with significant accumulated deficits.
Key figures
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63.00%of levels increased
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46.00%of levels were above monthly averages
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30.00%of levels were below monthly averages
Forecasts
The Météo-France seasonal forecasts for January, February and March 2026 predict higher temperatures across the whole country. No clear scenario has emerged regarding rainfall.
The trends and changes in termes of groundwater levels over the next few weeks will depend exclusively on degreerainfall, and therefore on cumulative rainfall, and on the response time of the groundwater table (reactivity/inertia).
Inertial aquifers
Over the next quarter, trends in the inertial aquifers of Sundgau (southern Alsace) and the Rhône-Saône corridor are expected to remain on an upward trend, with slow infiltration of rainfall in late autumn and early winter. The state of the aquifers should therefore continue to improve slowly. The forecasts for the end of winter are fairly favourable, although uncertainties remain regarding the end of the recharge period.
Recharge is not expected to be very active in January for most of the inertial aquifers in the Paris Basin and eastern Artois, due to persistent meteorological drought in December. Given their slow response to recharge deficits, these aquifers are not expected to experience winter drought. However, the outlook is less optimistic for spring and summer 2026, particularly if recharge remains deficient. Increased monitoring of these aquifers is recommended over the coming months.
Reactive aquifers
As for reactive aquifers, forecasts for the next quarter remain uncertain as they depend on rainfall totals. Forecasts are more optimistic for aquifers with above-normal levels in December than for those with below-normal levels. However, the situation may change rapidly depending on recharge events and aquifer reactivity. Levels in the summer of 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 to areas showing below-normal levels in December 2025. A return to above-normal levels by the end of winter will only be possible if there is sufficient rainfall, evenly distributed over the coming months.
The situation regarding groundwater levels in Roussillon remains fragile and forecasts uncertain. If the rains continue, groundwater levels will probably be sufficient to meet various needs during spring and summer 2026. However, areas of deep Pliocene aquifers will most likely remain in deficit. Indeed, it seems difficult to envisage a sustainable replenishment of the reserves of these slow-reacting aquifers. However, if the meteorological drought resumes during the winter and early spring, the condition of all aquifers will deteriorate again and levels will remain below normal.
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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 9 January 2026, based on data acquired up to 31 December 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.