Map of aquifer levels in mainland France on 15 August 2026.
© BRGM
Trends observed on piezometers on 15 August 2026.
© BRGM
Groundwater trends
Groundwater levels are still falling at 92% of observation sites as of mid-August.
Almost all aquifers show a fall in groundwater levels, due to a severe lack of rain during the second half of July and the first half of August. Soils continue to be very dry and the little rain that actually fell – often during storms – was barely enough to meet the needs of vegetation. Moreover, increased abstraction due to the high temperatures worsened the natural decline in groundwater levels typical at this time of year.
Aquifers with slow response times
Of groundwater levels in less-responsive aquifers, only those in the Sundgau and Armagnac limestone formations remain stable. Levels have dropped in the chalk aquifers of Artois and Normandy, the Paris Basin formations, the Vosgian sandstone formations and the Triassic limestone aquifers of Lorraine, as well as in the formations of the Rhône-Saône corridor and the glaciofluvial deposits of the eastern Lyon area and Savoie foreland.
Aquifers with quick response times
In the more-responsive aquifers, all the groundwater levels have fallen, except in the alluvial aquifer of the Limagne plain, the alluvial deposits of the Hérault River and the basement aquifers of the Cévennes and Montagne Noire, which remain stable.
Situation observed on piezometers on 15 August 2026.
© BRGM
The state of aquifers
Aquifers with slow response times
Generally, groundwater levels in less-responsive aquifers have changed very little since the 1st of August.
Groundwater levels in the Beauce and Armagnac limestone aquifers remain moderately high. Levels in the chalk aquifers of the Artois and Normandy regions, in the Paris Basin formations and Rhône-Saône corridor formations, and in the glaciofluvial deposits of the eastern Lyon area and Savoie foreland are close to monthly norms or moderately low. Levels are low in the Vosgian sandstones and Triassic limestone aquifers of Lorraine.
Aquifers with quick response times
Regarding the more responsive aquifers, the situation has worsened due to a lack of rainfall since mid-June and the increasing demand on water resources, caused by the needs of vegetation and human activities.
Groundwater levels have changed from “close to average” to “moderately low” for groundwater levels in the limestone formations of the Angoulême area.
Similarly, groundwater levels have dropped from “moderately low” to “low” in the Albian sand aquifers of the Paris Basin and the Cotentin basement aquifer system.
Groundwater levels have fallen from “low” to “very low” in the Tertiary formations of the Armorican Massif, the karst limestone formations of Jura, and the alluvial deposits of the northern Alsace plain.
The levels in the alluvial aquifers of the Roussillon plain, the Astian sand formations in Agde as well as in the Vistrenque alluvial formations, remain moderately high to high.
Groundwater levels in the basement aquifers of the Cévennes and Montagne Noire and alluvial deposits and Tertiary formations of the Durance and Bas-Rhône basins are declining less rapidly, remaining close to the monthly average.
Forecasts
The trend over the coming weeks is likely to continue on a downward trajectory, despite Météo France forecasting rain and storms over the next fortnight. Reduced abstraction for the supply of drinking water and for irrigation due to lower temperatures will also help ease the pressure on groundwater resources.
The forecast for less-responsive aquifers remains uncertain. If too little rain falls, it will only be enough to meet the needs of vegetation, leaving no water to recharge the aquifers. Groundwater levels are expected to reach normal or moderately low levels in these aquifers in the coming weeks. The limestone aquifers in the Boulonnais and Avesnois regions, the Vosgian sandstone formations and the Triassic limestone formations of Lorraine – whose levels are already low – will need to be monitored.
Regarding responsive aquifers whose levels are currently above average, the forecast for the next few weeks is quite positive. For the others, the long-term forecast is much less certain, and whether levels remain satisfactory will depend on rainfall in the coming weeks. Low cumulative rainfall combined with the needs of vegetation and abstraction levels that remain relatively high could lead to a worsening of the status of aquifers with very quick response times, where groundwater levels are already very low, such as in the Limousin basement aquifer system and the karst limestone formations of Jura and Côte des Bars.
Map drawn up by BRGM on 19 August 2026, based on data acquired up to 15 August 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.