Hydrogeological situation on 1 July 2023
In June, the aquifers suffered depletion and 75% of them had lower levels than average. Precipitation enabled recharge episodes, but this only improved the state of aquifers in the southern third of France.
The situation remains unsatisfactory across much of the country: 68% of aquifer levels were still below monthly norms in June (66% in May 2023) with low to very low levels in many areas.
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. Concerning the reactive aquifers, the trends and developments will depend primarily on effective local rainfall, the degree of evapotranspiration and the demand for water. Recharging is expected to be episodic and of low intensity. The situation will need to be closely monitored in aquifers which currently have levels that are below the monthly norms, as well as in areas where abstraction is particularly high.
Map of groundwater levels in France on 1 July 2023.
Map drawn up by BRGM on 10 July 2023, based on data from the ADES database, acquired up to 30 June 2023. Data source: ADES database / Map background © IGN, BD Carthage.
This map shows the global indicators reflecting the average fluctuations of the aquifers. They are based on point indicators collected at groundwater level 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.
During the 2022-2023 recharge period the contribution was inadequate over a large part of France. Early spring rainfall led to recharge episodes, thus delaying the start of the depletion period in those areas with the highest rainfall. The depletion period began gradually between March and May.
In June, precipitation did little to replenish the aquifers. This is because rainfall from sometimes violent storms only percolates a little into the ground. In addition, high temperatures encouraged evapotranspiration and increased plants’ water requirements. Most aquifers are currently being depleted: the levels observed at 75% of measurement points had dropped in June (60% in May).
Over the northern two-thirds of the country, levels are falling. This is normal for the period. Rainfall in late spring and summer has little effect on the aquifers; water infiltrated into the ground merely moistens the soil and is immediately used by vegetation. As a result, in the areas which received rainfall, practically none of it infiltrated deep into the ground or was sufficient to compensate for the volumes discharged into the outlets or to generate recharge episodes. However, some of the most sensitive aquifers, such as the Jurassic limestone aquifer south of the Poitou threshold, had their levels sustained by the storms.
In the southern third of France, the May rains moistened the soil and were taken up by the vegetation. In June, rainfall had a contrasting impact on the aquifers, depending on their respective reactivity and the accumulation of local rainfall. As a result, occasional flood peaks were recorded in the highly reactive karst limestone aquifers (Grands Causses, Cévennes border and Provence). In the centre of the Aquitaine Basin, around the Mediterranean and in Corsica, the rate of discharge of the alluvial and Tertiary formations was slowed.
Situation in relation to the June averages
In 2022, the low-water period was severe for most of the aquifers, with recharging remaining low during the autumn and winter of 2022-2023. At the end of the winter, the situation of the aquifers was therefore unsatisfactory. Rainfall in early spring improved the condition of the most reactive aquifers in the northern two-thirds of the country.
Between the beginning of April and the end of June, the groundwater situation across France as a whole changed little, or even deteriorated slightly. Overall, the state of the aquifers remained unsatisfactory: 13% percent of observation points had levels above monthly norms (14% in May). However, 68% of the levels remained moderately low to very low (66% in May) while 19% were very low (19% in May). The situation is better than that of last year (75% of levels below normal in June 2022) but more contrasted locally.
Over a large part of northern France, the situation is hardly changing, depending on local rainfall over the last few weeks and the sensitivity of the aquifers to recharging.
As far as reactive aquifers are concerned, the situation remained stable during June in areas that received rainfall and is deteriorating slightly in areas where there is a rainfall deficit. Cumulative rainfall during spring enabled some reactive aquifers to remain at levels close to or higher than monthly norms. Reactive aquifers suffering from rainfall deficits currently have moderately low to low levels. However, situations can vary greatly locally, depending on rainfall and the volumes of water abstracted.
As for the inertial aquifers, the rains have had no effect and the situation is gradually deteriorating. Only the chalk aquifers of the Artois-Picardy coast benefited from a significantly excessive winter recharge in 2022-2023 and have high levels. The state of the inertial aquifers in the Paris Basin is not very favourable, with levels being generally moderately low to low. The situation may be more strained locally, with very low levels. Aquifer levels in the Sundgau (southern Alsace) and the Rhône-Saône corridor are a cause for concern, ranging from moderately low to very low. The very low levels are gaining ground and historic lows are being recorded in many areas.
In the southern third of the country, abundant rainfall in May and June has improved the situation. However, rainfall has been unevenly distributed and the state of the aquifers is locally heterogeneous. Some aquifers in the Aquitaine Basin and Provence are showing satisfactory levels, close to or higher than monthly norms. However, several sectors remain under pressure, with persistent low to very low levels. There has been very little rainfall to make up for the deficits of recent months in the areas that received the least rainfall or in the less reactive aquifers: the aquifers of the Roussillon plain, the Valas-Agde Astian sands aquifer and the alluvial aquifers of the Côte d'Azur.
Aquifers in good condition
The situation is good in several aquifers, with moderately high to high levels in comparison to those for June in previous years:
- The levels of the Cenomanian chalk marl aquifer on the Artois-Picardy coast are moderately high, following the excess recharge of 2022-2023;
- The aquifers of the Armorican Massif basement, from Brittany to the Vendée, benefited from excess rainfall in March and April, so levels are moderately high;
- The Adour and Gave de Pau alluvial aquifers have benefited from exceptional recharge events over the last two months and their levels are high;
- Levels in the alluvial aquifers and tertiary formations along the coast of Corsica are high, following the rains of May and June.
Aquifers in unfavourable condition
Many aquifers are in an unfavourable condition with very low levels compared to June levels for previous years, owing to an extreme rainfall deficit these last few months or years:
- The inertial Plioquaternary and Miocene aquifers in the Sundgau, Dijonnais, Bresse, Dombes, Nord Isère and Bas-Dauphiné areas are showing low to very low levels, due to several successive winter recharges of low intensity and very inertial behaviour;
- The coastal alluvial aquifers of the Côte d'Azur have very low levels due to a lack of rainfall in 2022 and 2023;
- The Valas-Agde Astian sands aquifer and the aquifers of the Roussillon multi-layer aquifer are experiencing an unprecedented situation, with low to very low levels. Limiting water abstraction seems to have a beneficial effect on the near-surface aquifer in the northern part of the coastal edge of Roussillon.
Comparison between 1 July 2022 and 1 July 2023
Map of France showing the state of the aquifers on 1 July 2022 (left) and 1 July 2023 (right).
The seasonal forecasts from Météo-France for July, August and September predict higher-than-normal temperatures across the country and wetter-than-normal conditions in the south, from the Pyrenees to the Mediterranean basin. Elsewhere, no clear scenario has emerged for rainfall.
As regards the inertial aquifers of the Artois Basin, the Paris Basin and the Rhône-Saône corridor, it is unlikely that there will be recharge episodes during the summer, barring very exceptional rainfall events. So, no improvement is likely before the autumn. The situation is expected to gradually deteriorate, more or less rapidly depending on the volumes of groundwater abstracted.
As regards reactive aquifers, the trends and developments will depend primarily on effective local rainfall and the demand for water. However, rainfall infiltration at depth should remain very limited over the next few months and the depletion process should continue. The situation is likely to deteriorate rapidly for aquifers that do not benefit from small recharge events and for those that are most affected by abstraction.
The lack of rainfall over a large part of the north of the country and the high temperatures forecast by Météo France could accentuate the downward trend. On the one hand, high temperatures could contribute to an increase in the amount of water required by vegetation and water abstraction. On the other hand, if there is not sufficient rainfall (resulting in dry ground and an increased demand on water supplies), the situation may continue to deteriorate. However, the rain that fell at the end of June and the beginning of July should reduce the need for irrigation and thus relieve the pressure on water resources, notably in areas that received the most rainfall.
From the Pyrenees to the Mediterranean basin, rainfall events may cause temporary recharging. This would help maintain groundwater levels and possibly even lead to them increasing. For levels to increase, thus improving the aquifers’ condition, significant rainfall would be needed as well as it being over ground that is already damp.
The situation needs to be closely monitored, notably in all the reactive aquifers with levels below June norms, as well as in inertial aquifers, which had low water levels in June, or in areas where abstraction is particularly intensive.
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