Map of aquifer levels in mainland France on 15 May 2026.
© BRGM
Trends observed on piezometers on 15 May 2026.
© BRGM
Trends
On 15 May, 77% of groundwater levels were falling, indicating that the discharge period is well under way.
Most aquifers are experiencing increased discharge, as there was little rain during the second half of April. Rainfall levels recorded in early May were not high enough to ensure effective groundwater recharge.
The soils became dry due to the lack of rainfall in April. In early May, vegetation growth and the wetting of dry soils used up a lot of the rain, and stormy weather patterns with heavy and unevenly distributed rainfall prevented effective deep infiltration. Only a few piezometers, installed in highly responsive aquifers, recorded a moderate increase in groundwater levels following rainfall events.
Groundwater levels in less responsive aquifers, such as the Sundgau limestone formations, have continued to rise. Groundwater levels have started to stabilise or fall in the Artois limestone, Normandy chalk, Paris Basin and Rhône-Saône corridor formations, in the fluvio-glacial alluvia to the east of Lyon and in the Armagnac limestone formations.
Levels are falling at most responsive groundwater sites. The limestone layers of Entre-deux-Mers and Sologne, the Cévennes basement, the Roussillon Plain Eocene sands, the Massif Central volcanic formations and Corsican alluvial deposits are the only aquifers where groundwater levels have stabilised.
Groundwater levels in other aquifers are declining.
Situation observed on piezometers on 15 May 2026.
© BRGM
The groundwater situation
The status of groundwater levels in the less responsive aquifers is the same as it was on 1 May. In these aquifers, the levels are close to the norm, except in the Armagnac limestone and Beauce aquifers, where they are moderately high. Groundwater levels in the Boulonnais and Avesnois limestone aquifers are moderately low.
The status of the more responsive aquifers is slightly worse due to the lack of rainfall in April and higher water demand from growing vegetation and for human consumption.
Groundwater levels have gone from “close to the norm” to “moderately low” in basement aquifers in the west of the Armorican Massif and eastern Limousin, and in the Charentes Jurassic limestone layers.
The situation is also worse for groundwater levels in the Poitou Jurassic limestone formations, where they have fallen from “moderately high” to “close to the norm”.
Levels in the Plioquaternary aquifer of the Aquitaine Basin have risen from “close to the norm” to “moderately high”.
Levels at other groundwater sites remain close to or above the norm. Groundwater levels in the Garonne, Lower Rhône and Roussillon Plain alluvial aquifers and in the Vistrenque aquifer remain high to very high.
Forecasts
Groundwater levels are expected to follow a predominantly declining trend in the coming weeks, according to Météo-France’s forecast of relatively dry and warm conditions for the next fortnight.
The outlook for less responsive aquifers remains uncertain. If too little rain falls, plant growth will tend to absorb it all, 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. Groundwater levels in the Boulonnais and Avesnois limestone formations are already moderately low and should be monitored closely.
The outlook is good for responsive aquifers showing levels above the norm. Groundwater sites in the arch-shaped Jurassic formations along the Paris Basin’s northeastern border, in the Vosges sandstone layers and Triassic limestone formations of Lorraine, in volcanic edifices, the Armorican and Limousin basements and the Limagne tertiary basins should be monitored closely. 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 increased abstraction could have a rapid and significant impact on the highly responsive aquifers where levels are already recorded as being below the norm, as in the Brittany and Limousin basements.
