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The must-read article to understand the exceptional drought that has hit mainland France – franceinfo

This summer, mainland France is hot. Its soil is also increasingly thirsty. While the country experienced, in the first week of August, the third heat wave since June, droughts of varying degrees hit across the region. In the face of what she described as ‘Exceptional drought’ and in “The historical situation that many regions are going through”Prime Minister Elizabeth Bourne activated the Ministerial Crisis Unit on Friday, 5 August. “This drought is the worst ever in our country” and others “The situation could continue for the next 15 days, or it could become more worrying.”Matignon confirms.

More than 100 municipalities are deprived of drinking water, increased restrictions on water use, vegetation death, farmers worry … this episode, which can go on, It has dire consequences for both the environment and the economy. The Franceinfo channel gives you the keys to understanding this unusual phenomenon.

How did we get here?

To understand the origin of the drought we experience at the beginning of August, we have to go back several months. It happened in several stages.Jerome Nicholas, a hydrologist with the Bureau of Geological Research and Mining (BRGM), explains. first of all, “We met Very low groundwater recharge during the winter, and a deficit even in a large part of the aquifers”In other words Underground rock layers through which water flows. “Shipping was interrupted very quickly, due to late winter with little rain,” continue. Sentences The arrival of good weather marks the end “refill” start “evacuation” from this groundwater.

“After April, rainwater is mostly absorbed by growing plants or evaporated by heat” Before reaching the depths, he explains Propluvia website. Thus, June rains allowed “To reduce the demand for groundwater – when it rains we need less irrigation, we take in less water – but we have not contributed to groundwater recharge,” Jerome Nicholas explains.

But in July, France experienced very high temperatures, along with a significant rainfall deficit (about 84%, with variations by region). Jerome Nicolas summarizes: “At the surface level, there is a shortage of water. At ground level, levels are low, or very low, depending on the region. These two combined effects mean the resource may be running out locally.”

Finally, while conditions vary from district to district – sometimes even within the same district – the almost generalized heat of July has exerted a strong pressure on water resources throughout the territory. Because the higher its temperature, the greater the demand for it. And this, ironically, is when the resource is less available.

Why is this drought exceptional?

According to Météo France, July 2022 is the driest month of July during the period 1959-2022 on a national scale. It is the second driest month after March 1961. “We have been in a record drought for soil moisture since July 17 nationally”Jean-Michel Sobero, a climate scientist at Météo France, said on Wednesday. floors “drier than it was on the same date in 1976 and 2003”The agency that fears confirms it “The absolute record for topsoil dryness, dating back to 2003, has been beaten” this year.

This phenomenon is unprecedented in its scope: 93 departments in French territory out of 96 are now concerned with the “drought plan” and 62, or two-thirds of the country, are in “crisis”. So drought is particularly visible on vegetation that loses its leaves prematurely and is more susceptible to fires or even on the flow of waterways.

A tree lost its leaves in a field in Portel de Corbiere (Aude), August 2, 2022 (IDRISS BIGOU-GILLES/HANS LUCAS/AFP)

According to the French Biodiversity Office, citing West of FranceAnd the 27% of them are dry. At L’Orleans-sur-Droms (Droms), the river disappeared for nearly two kilometers. The flow of the Loire dropped to 129 m3/s on 20 July (versus 475 m3 at the beginning of the month) and reveals, with a water level two meters below its usual level, unrecognizable landscapes. In Vienna, almost a thousand kilometers of rivers and streams dried up, More than 4,400 km in section, with severe consequences for animals and plants, depending on these environments.

Is it caused by global warming?

“We are in a critical situation, it is a new sign that global warming is not a fad but a fact in the process of asserting itself,” Monday said in franceinfo Christophe PicchuMinister of Environmental Transformation and Regional Cohesion. For Jerome Nicholas, “It is always difficult to understand the share of responsibility for global warming, but we observe an average rise in temperatures leading to an increase in extremes, in their frequency and intensity”he explains. “lamClimate change is intensifying the water cycle.” We can read in Part two of the latest IPCC report (in English). “This brings more heavy rains, accompanied by flooding, and more severe droughts in many areas.”

“What we are going through this year is no surprise, One of its authors, Gonéri Le Cozannet, a researcher at BRGM, explains. We face three of the four risks we have identified for Europe this summer. They are: high temperatures that pose a threat to ecosystems – particularly through fires – and to human health; loss of agricultural productivity associated with drought; Finally, a shortage of watersummarizes. As the climate continues to warm, the likelihood of these events will increase.

Who consumes the most water in France?

In France, out of the annual volume of water consumed estimated at 5.3 billion cubic meters annually, agriculture is the main consuming activity (that is, it is withdrawn and not returned to aquatic environments), with 45% of the total water being consumed, before cooling power plants (31% ), drinking water (21%) and industrial uses (3%), according to the Ministry of Agriculture. Once the department takes care of the “alert” threshold, the fee for cultivation is limited, then reduced by at least 50% In departments on the “booster alert”. At the “crisis” threshold, only priority withdrawals are allowed, such as drinking water supply, sanitation, health and safety operations: toFarmers are prohibited from irrigating their crops including a Localized irrigation system (drip, micro sprinkler …).

For Gonéri Le Cozannet, this crisis is an additional argument in favor of adapting to global warming. “For agriculture, the challenge is to prepare for upriver. For example, in certain areas, artificial recharge of groundwater, changing crops in favor of crops that use less water, etc. We are also talking, in the report of Group 2 of the government body International Climate Change, agroforestry, but we see that this is not what is mainly practiced today,” continued.

A cornfield in Montaijo in Vendee on August 3, 2022 (MATHIEU THOMASSET / HANS LUCAS / AFP)

If drinking water accounts for 21% of the water used in France, then this resource, which comes mainly from groundwater, remains the priority at the highest level of alert. And when they run out, despite these efforts, tank trucks are tasked with supplying the communes. Dobbs, Drôme, Finistère, Haute-Saône, Dordogne, Vosges, Var, … A shortage of drinking water is observed in many areas. “More than a hundred municipalities in France” Already deprived of drinking water and being supplied by trucks, Christophe Picchu, Minister of Environmental Transformation, said Friday.

Will the drought ever end?

“Draining of the water table has begun and will continue until this fall, when there will be less evaporation and less stress on vegetation.Jerome Nicholas explains. There we will be able to actively monitor the precipitation, that is, what will make it possible to raise the levels of the groundwater table. But before the end of the discharge, in the fall, is there a way out?

If potential summer rains can limit drainage, don’t wait for short-term forecasters in Météo France “There is no significant rainfall over France extensive enough to alter the state of the drought”explain Jean-Michel Sobero, from Meteo France. Add : “I tend to think it will take a month of extra precipitation before we get back to normal, and we don’t have forecasts in that direction.

Moreover, if strong storms can certainly quench the thirst of vegetation, then you will not succeed in raising the level of the groundwater table: on dry land, water flows and does not penetrate deep.

I was too lazy to read everything, can you give me a summary?

Winters were particularly dry in mainland France and Corsica. Under these conditions, when good weather came, the water level was often low, even very low, in certain areas. This summer, the country experienced an abnormally hot month in May and then experienced several extreme heat waves. Events reinforced by global warming that led to a higher demand for water from plants and crops. However, in July, it rained hardly – if any – in many areas, putting more pressure on already deficient groundwater levels: it is a drought, and the government is no longer hiding its concerns..

The situation can stabilize when the rains return. In the short term, showering will reduce the need to tap groundwater. But only in the fall will the conditions for filling the groundwater table be met.

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