INFOGRAPHICS. Faced with the very worrying level of groundwater, the risk of drought increases further for this summer

The rains of March were not enough to fill the basement. No less than 75% of the water tables in France were below normal last month, announced the Geological and Mining Research Bureau (BRGM) during a press briefing on Thursday 13 April. This is a slight improvement compared to the month of February, when 80% of the water tables showed a level lower than normal. But it is much worse than last year at the same period (only 56% in March 2022).

In detail, the distribution of this lack of water is very heterogeneous on the territory. While the level of water contained in the basements is rising in the west and south-west of France, that of the water tables in the Paris basin, in the east and in the south continues to decrease. The BRGM considers that many sectors are of concern.

To explain this, experts point to the low level of precipitation since last fall. France even experienced, in the heart of winter, 32 consecutive days without rain, which brought a sudden halt to groundwater recharge. Since then, the soils have been very dry and the vegetation absorbs most of the rain, limiting its infiltration into the soil. “From April, the recharge episodes should remain punctual and not very intense, except for exceptional rainfall events.notes the public body.

All groundwater is at risk

As a result of the lack of rain over the past six months, the risk of drought for the coming summer is already very high in certain areas, as shown by the map published Thursday by BRGM, which highlights the territories most at risk. . France is notably crossed there by a wide bright red band marking a “very high risk” of drought.

The Paris basin, part of central France and the Saône and Rhône basin are concerned. These are areas in high demand for our water consumption, where groundwater recharge has been insufficient or non-existent, and where experts still anticipate deterioration. In the other regions, the risk is more limited but very real, due to great uncertainty related to rainfall. “No aquifer presents a very low risk of drought”warns the BRGM.

At the same period a year ago, the drought risk map for the summer of 2022, which was nevertheless that of all records, was less worrying. In addition to the observation of rain forecasts, the BRGM evokes the weight of irrigation. “If, like last year, it does not rain much and the temperatures are high, the irrigation campaigns will start very early”warns Violaine Bault, hydrogeologist at the BRGM.