A worrying drought with no sign of improvement

La Berre ran dry in Portel-des-Corbières, in Aude, on August 2. IDRISS BIGOU-GILLES/Hans Lucas via AFP

INFOGRAPHIC – This month of July is the second driest on record since 1959.

Withered flowers, bare and browned trees, dead leaves crunching underfoot… Were it not for the stifling heat, you could imagine yourself in autumn. Since the beginning of the summer, France has been suffocating. The sky is dry, the soil cracked and the water reserves are dwindling. According to the bulletin published by the Ministry of Ecological Transition on August 4, no less than 93 departments are beyond the threshold of vigilance. In detail, 4 departments are at the first level of alert, 27 on heightened alert and 62 are deemed to be in a crisis situation.

“A combination of two factors makes the situation particularly worryingexplains Cyrille Duchesne, meteorologist at La Chaîne Météo (chain of the Figaro group). We had a particularly dry winter and spring, so we started the summer with low levels in most water tables. Added to this is a scorching summer season with a lack of lasting rain. The whole country is affected. In this sense, this drought will perhaps be even more difficult than that of 1976, which mainly concerned the north-east of France.

Last winter saw a rainfall deficit of around 20% on average across the territory, which did not allow the groundwater to fill sufficiently. “Spring made things worseadds Cyrille Duchesne, since it is the third driest spring since 1959. With the exception of the south-west of the country, which experienced a rainy episode in March, the groundwater level was already very worrying at the beginning of June in most of the territory. Since then, we have had a particularly hot summer with little rain, which has only made the situation worse.

July 2022 is thus ranked second among the driest months of all months combined in France since the start of measurements, in 1958-1959, with an accumulation of precipitation of 9.7 millimeters, according to Météo-France. “We do not yet have all the data for August to establish the precise level of the water tables at the start of the month of, but we already know that the emptying is continuing everywhere, explains Jérôme Nicolas, head of the national network for monitoring the quantitative state of groundwater at the Bureau of Geological and Mining Research (BRGM). We therefore remain on the trends of last month, with reserves which are decreasing and which are already at very low levels over most of the country. The absence of rain forces us to draw from the water tables which cannot be recovered. Many decrees limiting water consumption have however been taken in the country. They should make it possible to slow down the emptying of the reserves a little.

“Few stormy situations”

According to the July BRGM bulletin, the situation is particularly worrying in the Poitou-Charentes region, but also in Bourgogne-Franche-Comté. “We also have a very significant rainfall deficit since last winter in the south-east of the country, adds Cyrille Duchesne. We are on the way to breaking all the records there.”

And for the next few weeks, the outlook may not be exciting. “France has already experienced three heat waves, and a fourth episode of high heat is looming, continue the meteorologist. Despite some sporadic rain, we do not expect any improvement before the second half of August. This lack of rain aggravates the surface dryness of the soil, with humidity levels again historically low, especially in the north-west of the country, in the Pays-de-la-Loire and around the Mediterranean. These dry soils do not bring up moisture and maintain the hydraulic deficit. Episodes of high heat are not systematically followed by intense stormy episodes, as is generally the case. “To fuel thunderstorms, you need moisture and heat.Cyrille Duchesne explains. We only had heat, so we had very few stormy situations this summer. The conditions will a priori be more favorable after August 15.

These summer rains would in any case not be able to reverse the trend. “Water would fall on dry soils and would not penetrate deep, explains Jérôme Nicolas. Moreover, as long as the vegetation is still present, it mobilizes most of the hydraulic flow. However, the rains could, locally, slow down the emptying of the water tables by watering the crops. The groundwater filling period does not begin until October and lasts five to six months. The only thing we can hope for is rains that limit the drought on the superficial levels, which allow watering without having to draw on the reserves. The danger is that the depletion of groundwater leads to the drying up of lakes and rivers and thus degrades ecosystems.

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