The article to read to understand the exceptional drought that is affecting mainland France


This summer, mainland France is hot. Their soils are also increasingly thirsty. While the country experienced, in the first week of August, its third heat wave since June, the drought affected, to varying degrees, the entire territory. Faced with what she described as an “exceptional drought” and the “historic situation that many territories are going through”, Prime Minister Elisabeth Borne activated the interministerial crisis unit on Friday, August 5. “This drought is the worst that has ever been recorded in our country” and “the situation could continue for the next 15 days, or even become more worrying”, underlines Matignon. More than 100 municipalities deprived of drinking water, increasing restrictions on water use, dying vegetation, worried farmers… This episode, which could last, has serious consequences, both in the environment and in the economy. Franceinfo gives you the keys to understanding this extraordinary phenomenon. How did we get here? To understand the origin of the drought we are experiencing at the beginning of August, we need to go back a few months. “It happened in several stages,” explains Jérôme Nicolas, hydrogeologist at the Geological and Mining Research Office (BRGM). First of all, “we experienced a very low recharge of underground water during the winter, deficit even in a large part of the aquifers”, that is to say, the underground layers of rocks through which the water circulates. “The recharge was interrupted very quickly, due to a late winter with little rain,” he continues. Because the arrival of good weather marks the end of the “recharge” and the beginning of the “drainage” of these underground waters. “Beyond April, the rainwater is essentially absorbed by the plants, in full growth, or evaporates due to the heat” before reaching the depths, explains the Propluvia site. Thus, the rains in June made it possible to “limit the request for underground water – when it rains, we need to irrigate less, we take less – but they did not contribute to the recharge of the aquifers”, explains Jérôme Nicolas. . But in July, France experienced very high temperatures, along with a significant rainfall deficit (around 84%, with regional disparities). Jérôme Nicolas summarizes: “At the surface level, there is a lack of water. At the underground level, the levels are low, or very low, depending on the region. It is these two combined effects that mean that the resource can be depleted. locally “. Drought alert thresholds in France on August 2, 2022 according to the government site Propluvia, which lists orders restricting water use. (SCREEN CAPTURE / PROPLUVIA / FRANÇA TELEVISIONS) Finally, while the situations differ from one department to another – sometimes even within the same department -, the heat of July, almost generalized, exercised over the whole territory a strong pressure on water resources. Because the hotter it is, the more the demand explodes. And this, ironically, when the resource is least available. Why is this drought exceptional? According to Météo France, July 2022 is the driest July in the period 1959-2022 on a national scale. It ranks second among the driest months, behind March 1961. “We are in a record drought situation for soil moisture since July 17 nationally,” said Jean-Michel Soubeyroux on Wednesday, climatologist at Météo France. . The soils are “even drier than they were on the same date in 1976 and 2003”, underlines the agency, which fears that “the absolute record for surface soil drought, which dates back to 2003, will be surpassed” this year. This phenomenon is also unprecedented in its magnitude: 93 departments of the French territory out of 96 are now affected by the “drought plan” and 62, or two thirds of the country, are in “crisis”. Drought is therefore particularly visible in vegetation that loses its leaves prematurely and is much more vulnerable to fire, or even in the flow of waterways. A tree lost its leaves, in a field in Portel-des-Corbières (Aude), on August 2, 2022. (IDRISS BIGOU-GILLES / HANS LUCAS / AFP) According to the French Office for Biodiversity, cited for Ouest-France, 27% of them are dry. In Loriol-sur-Drôme (Drôme), the river has disappeared for almost 2 km. The flow of the Loire dropped to 129 cubic meters/second on July 20 (against 475 at the beginning of the month) and reveals, with a water level two meters below its usual level, unrecognizable landscapes. In Vienne, nearly a thousand kilometers of rivers and streams, out of the 4,400 km that make up the department, have dried up, with serious consequences for the fauna and flora that depend on these environments. Is it caused by global warming? “We are in a critical situation, it is a new indication that global warming is not a fad, but a reality that is in the process of imposing itself,” Christophe Béchu, Minister of Ecological Transition and Cohesion, told franceinfo on Monday territorial . For Jérôme Nicolas, “it is always difficult to understand the part of responsibility for global warming, but we observe an average warming of temperatures that leads to an increase in extreme events, in frequency and intensity”, he explains. “Climate change is intensifying the water cycle,” says the second part of the latest IPCC report. “This leads to more intense rains, with accompanying floods, and more intense droughts in many areas.” “What we are experiencing this year is not a surprise, explains one of its authors, Gonéri Le Cozannet, researcher at the BRGM. This summer we are experiencing three of the four risks that we had identified for Europe. That is: extreme heat that means a risk to ecosystems – especially from fires – and to human health, a loss of agricultural productivity linked to drought and, finally, a shortage of water, he summarizes. As the climate continues to warm, these events will become increasingly more likely.” Who consumes the most water in France? In France, of an annual volume of water consumed estimated at 5.3 billion cubic meters per year, agriculture is the main consuming activity (that is, withdrawn and not returned to the aquatic environment), with 45% of total water consumed, before the cooling plants. (31%), drinking water (21%) and industrial uses (3%), according to the Ministry of Agriculture. As soon as a department is hit by the “alert” threshold, therefore, rates for agriculture are capped, and then reduced by at least 50% in departments on “raised alert”. At the “crisis” threshold, only priority withdrawals are authorized, such as drinking water supply, sanitation, health and safety: farmers are prohibited from watering their crops, even through 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 upstream. For example with, in certain areas, the artificial recharge of groundwater, a change of crops in favor of crops that consume less water, etc. We are also talking, in the report of the group. 2 of the IPCC, agroforestry, but we see that this is not what is mainly practiced today”, he continues. A field of corn, in Montaigu, in the Vendée, on the 3 ‘August 2022. (MATHIEU THOMASSET / HANS LUCAS / AFP) If drinking water represents 21% of the water used in France, this resource that comes mainly from underground water remains a priority at the highest level of alert . And when, despite these efforts, it runs out, the tankers are responsible for supplying the municipalities. Doubs, Drôme, Finisterre, Haute-Saône, Dordogne, Vosges, Var,… There is a shortage of drinking water in many regions. “More than a hundred municipalities in France” are already deprived of drinking water and supplied by trucks, he said Friday Christophe Béchu, Minister of Ecological Transition. Will the drought ever end? “The drainage of underground water has started and will continue until this autumn, when there will be less evaporation and less stress on the part of the vegetation, explains Jérôme Nicolas. It is here that we can observe effective rains, that is to say, which will allow to raise the level of the water tables. But before the emptying ends, in the autumn, is there a way out? If the possible summer rains could limit the emptying, Météo France meteorologists, in the short term, do not expect “any significant precipitation sufficiently widespread in France to change the drought situation”, explains Jean-Michel Soubeyroux, of Meteo France. He adds: “I would tend to think that it would take a month of excess rain before it returns to a normal situation, and no we have no forecast in that direction.” Moreover, if heavy storms could quench the thirst of vegetation, they would not succeed in raising the level of water tables: in dry land, water runs off and does not penetrate deeply. I I was lazy to read -everything, can you give me a summary? The winter was particularly dry in mainland France and Corsica. Under these conditions, when good weather arrived, water tables were often low, even very low, in certain regions. This summer, the country experienced an abnormally hot May and was then exposed to several intense heat waves. Events driven by global warming that cause a large demand for water from vegetation and crops. However, in July there was almost no rain – if any – in many regions, which put more pressure on the already deficient water table: it’s a drought, and the government is no longer hiding its concern. The situation could stabilize when the rains return. In the short term, the showers would reduce the need to tap groundwater. But only in autumn will the conditions be met to fill the water table.
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