The hydrogeological situation on 1 July 2024
The depletion period began and developed gradually during the spring. In June, most levels had dropped.
The state of the aquifers in June was very satisfactory, following a 2023-2024 recharge surplus and contribution from spring rainfall. Only highly inertial aquifers (Sundgau, Bresse and Dombes) or areas in which the recharge was insufficient (Roussillon, Aude, Hérault and Corsica) recorded below-normal levels.
In July and until the end of summer, aquifer levels are expected to continue to fall. The situation in inertial aquifers is not expected to change much in the next few weeks, except in areas with particularly intensive abstractions. As regards the reactive aquifers, the trends and developments will depend primarily on effective local rainfall, the degree of evapotranspiration and the demand for water. Recharge episodes are expected to be occasional, and of low intensity. However, the situation needs to be closely monitored in aquifers that have moderately low to very low water levels at the moment, as well as in areas where abstraction demand is particularly high.
Map of aquifer levels in mainland France on 1 July 2024.
© BRGM
Evolution of the trends observed on piezometers from November 2023 to June 2024.
© BRGM
Groundwater trends
The 2023-2024 aquifer recharge was far greater than normal across a large part of the country, except for the Pyrenees, Roussillon, along the western coast of Languedoc and in Corsica. The depletion period began developing gradually in April 2024. However, there was sufficient accumulated rainfall in the spring to keep the soil moist and meet the needs of vegetation. Consequently, rain was able to filter deep into the ground and maintain levels or even recharge certain aquifers up to May.
In June 2024, depletion was under way and most of the aquifer levels had dropped. Levels had risen at 20% of observation points and had fallen at 62% (compared to 38% for higher levels and 39% for lower levels respectively in May).
The depletion period for the inertial aquifers began slowly in April for the Artois aquifers and between May and June for those in the Paris Basin and the Rhône-Saône corridor. In June, depletion was well under way, with aquifer levels falling in the Artois Basin and the north-east and south-west of the Paris Basin. Trends reversed in June for the most inertial aquifers: they were stable or rising slightly for the Normandy, Touraine and Sologne chalk aquifers and for the aquifers in the Rhône-Saône corridor. Finally, recharge was still occurring in the Beauce and Sundgau aquifers (southern Alsace). In fact, some sectors of these aquifers began to recharge between February and March, three to four months after the first autumn rains had infiltrated. The rising levels in June were due to the slow infiltration of late winter and spring rainfall. However, the observation points for the Beauce aquifer show different recharge rates depending on the sector, with some stabilising and others continuing to recharge.
Reactive aquifers are sensitive to local rainfall and meteorological droughts. Depletion was occurring in June in almost all the aquifers, with levels falling. The rain was largely absorbed by the dry ground and vegetation. However, the rate of depletion is often reduced by small amounts of rainfall generating a momentary recharge episode. There was enough rainfall infiltration to compensate for outflows (from rivers and streams, springs, the sea and water abstraction) and levels were rising or stable in Alsace, Lorraine and Berry. The melting snow and rain also had an impact on the aquifers in the Alpine valleys, where levels had risen.
Comparison between 1 July 2023 and 1 July 2024
Map of France showing the state of the aquifers on 1 July 2023 (left) and 1 July 2024 (right).
© BRGM
Evolution of the situation observed on piezometers from November 2023 to June 2024.
© BRGM
The groundwater situation
The aquifer situation during the low-water period in 2023 was unsatisfactory, with levels being generally below monthly norms. The situation was reversed in November 2023 with the onset of heavy rainfall. Rainfall continued throughout late autumn and winter, resulting in a 2023-2024 recharge surplus for almost all aquifers, with the exception of those in the Pyrénées-Orientales, Aude and Corsica. Spring rainfall helped to keep levels up and maintain a very satisfactory overall situation.
In June 2024, the situation was close to that of the previous month. Aquifer levels were generally above monthly norms: the levels recorded at 17% of the observation points were below monthly norms, 13% were comparable with monthly norms and 70% were above them (compared with 19%, 11% and 70%, respectively, in May). The varying state of the different aquifers is mainly due to the intensity of the 2023 winter and 2024 spring recharges and the respective speed with which aquifers react to infiltrated rainfall.
The situation was more favourable than that observed for the previous year, in June 2023, when 68% of the levels recorded were below monthly norms. Only aquifers in the Pyrénées-Orientales and Corsica had levels that were lower than in June 2023. June 2024 was the third wettest June for aquifers over the last 30 years (after June 2001 and June 2013).
As for the inertial aquifers in the Artois area, Paris Basin, Sundgau (southern Alsace) and Rhône-Saône corridor, their states did not change between May and June. The state of the inertial aquifers was generally satisfactory, with moderately-high to high levels. Only the state of the Beauce aquifer improved, due to persistent recharge, and approached that of monthly norms. The highly inertial aquifers in the Bresse and Dombes regions and in the Sundgau (southern Alsace) still had moderately low levels, varying from low to very low locally.
Locally, less-satisfactory levels – from moderately low to low – were recorded on several piezometers in the south and south-west of the Paris Basin (Normandy chalk aquifer south of the Seine and Cenomanian sand aquifers of Perche and Maine and north of the Beauce aquifer) and in the hilly region of the Drôme (northern part of the Miocene molasse aquifer of the Bas-Dauphiné).
In the case of reactive aquifers, changes in their state between May and June depend on local accumulated rainfall. The situation changed very little between May and June: it improved slightly in a few areas where there was significant rainfall (e.g. north-west of the Massif Central) and deteriorated slightly in those that received little rain (e.g. Brittany).
The situation remains very satisfactory for many reactive aquifers, with moderately high to very high levels being recorded. This can be explained by a surplus recharge in 2023-2024 and by the contribution of spring rainfall. Some of the Jurassic and Cretaceous limestone aquifers in the centre-west (Brenne, Poitou watershed, Périgord and Angoumois basin) and the basement aquifers in the south of the Armorican Massif (from the Vilaine to the Vendée bocage) had the highest levels recorded in June for 20 years.
The rainfall deficits in June are affecting the most vulnerable aquifers, which received less recharge in 2023-2024. The state of aquifers in the Limagne plain and the volcanic formations of the Massif Central has deteriorated slightly and is now approaching monthly norms. The state of the aquifers was close to or locally below normal for the Adour and Gave de Pau alluvial aquifers, as well as locally in the upper Garonne valley. The aquifer levels in Provence and the Côte d'Azur were generally close to monthly norms, but the levels varied, ranging from low to high, depending on local rainfall totals over the last few weeks.
The situation remains unsatisfactory along the western coast of Languedoc and in Roussillon. The Valras-Agde Astian sands aquifer had levels in line with monthly norms due to a low abstraction rate (for drinking water, tourism and irrigation), but situations may vary from place to place. The levels of the Hérault and Orb alluvial aquifers were moderately low and those of the Aude low. Aquifer levels in Roussillon remained very worrying, from low to very low. Rainfall in the spring led to recharges of the reactive near-surface aquifers of the Corbières massif and the alluvial aquifers of the Roussillon plain. However, the infiltrated volumes remain insufficient to compensate for the deficits recorded over the last two years. Rainfall has had no impact on the more inertial Pliocene sands aquifer. Finally In Corsica, there were strong contrasts in the state of aquifers, with low to very low levels in the Cap Corse area and the eastern plains, and close to normal to moderately high monthly levels along the western coast.
Aquifers that are in a very good state
Several aquifers were found to be in a very good state, with levels being very high in relation to the levels recorded for June in previous years:
- The carboniferous limestone aquifers of the Avesnois benefited from a very high recharge surplus in 2023-2024;
- The basement aquifers of the Vilaine basin in the Vendée bocage region benefitted from significant effective rainfall during the winter and spring;
- Levels in the reactive Jurassic and Cretaceous limestone aquifers in the centre-west (Brenne, Poitou threshold, Périgord and Angoulême basin) were strongly boosted by spring rainfall.
Aquifers that are in a poor state
Several aquifers were in a poor state, with low to very low levels compared to those recorded in June of previous years, due to an extreme lack of rainfall over the last few months or years:
- The aquifers of Cap Corse and the eastern plains of Corsica have deteriorated;
- The Aude alluvial aquifer continued to have low levels, with a lower than normal recharge in 2023-2024;
- The state of the multi-layer aquifer in Roussillon and the karst limestone aquifers in the Corbières massif remained poor, with low to very-low levels, due to a lack of rainfall over the last two years.
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
Forecasts
The Météo-France seasonal forecasts for July, August and September predict higher-than-normal temperatures across the country and drier-than-normal conditions in the south. Elsewhere, no clear scenario has emerged for rainfall. The lack of rainfall and high temperatures could lead to agricultural drought and could increase the water requirements of vegetation and abstractions. As a result, the situation is likely to deteriorate, all the more rapidly to the extent that demands are made on aquifers. The rainfall in late June and early July and the relatively low temperatures should, however, reduce the need for water, particularly for irrigation in the most heavily irrigated areas.
For the inertial aquifers in the Artois Basin, the Paris Basin and the Rhône-Saône corridor, levels should continue to fall over the summer. Depletion is expected to spread to the Beauce and Sundgau aquifers (southern Alsace) during the early summer. It is unlikely that there will be recharge episodes until vegetation becomes dormant and significant rainfall occurs, i.e. until mid-autumn or early winter, barring very exceptional rainfall events. In fact, inertial aquifers are not very sensitive to weather conditions during the summer period.
No improvement is expected before the autumn, and the situation is likely to stabilise or gradually deteriorate, as is usual at this time of year. The rate of depletion will depend mainly on the volumes abstracted from the groundwater.
Most of the inertial aquifers will enter their depletion period in a good state. Seasonal forecasts are therefore optimistic for aquifers whose June levels were above monthly norms. The highly inertial aquifers in the Sundgau, Bresse and Dombes regions were in a less favourable condition in June and will need to be particularly closely monitored. In addition, local tensions could arise in areas where water levels are currently below normal, or in areas where there is a lot of abstraction (e.g. in the Normandy chalk aquifer, south of the Seine, the Cenomanian sands aquifer in the eastern part of the Pays de la Loire and Centre-Val de Loire, in northern Beauce, and in the Miocene molasse aquifer in northern Drôme).
Reactive aquifers are very sensitive to weather conditions. Trends and changes in the situation over the next few weeks will mainly depend on effective local rainfall and demands for water. However, rainfall infiltration at depth is likely to remain localised and not very intense during the summer.
Consequently, levels will probably decrease if there is a lack of effective rainfall or if there are significant abstractions. However, they could remain stable or rise if there is enough total rainfall to compensate for outflows through natural outlets (rivers and streams, springs, sea) and abstractions.
The situation is likely to deteriorate rapidly for aquifers that do not benefit from small recharge events and for those that are strongly affected by abstraction. The situation in June was favourable for most of the reactive aquifers which suggests that levels will be close to or above normal in July and even August. The summer period will certainly be less complicated than last year. This being said, the most reactive aquifers (basement aquifers in the Massif Central and Armorican Massif, the karst limestone aquifers in Provence, the Jura and around the Massif Central) could empty in just a few weeks, if there is a long, intense drought. Consequently, changes in the levels of these highly reactive aquifers need to be closely monitored, in relation to local rainfall and water abstraction. Finally, certain other areas will also need to be closely monitored, since current levels are not sufficient to guarantee satisfactory levels over the summer: Roussillon, Aude, Hérault and Corsica (north and east).
Next groundwater tables status report
Our groundwater report is now published every month, in the middle of the month.
The next issue will be published in mid-August 2024.
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.
Press contact
Map drawn up by BRGM on 9 July 2024, based on data from the ADES database, acquired up to 30 June 2024. Data source: ADES database (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.