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Can the recent storms end the drought?

2022-08-17T17:11:45.104Z

French soils are experiencing unprecedented drought with a rainfall deficit of 20% since winter 2021.



After several waves of unprecedented heat waves, violent storms have been hitting France since Sunday.

According to

La Chaîne Météo*

, the Channel coasts and the eastern half of the country are concerned, including seven departments in the South-East placed on orange storm alert this Wednesday, August 17.

The return of rain and cooler temperatures were eagerly awaited after an exceptionally dry period.

During the month of July, considered the driest month on record since 1959, soils and waterways dried up, putting the lives of wildlife at risk.

As of July 1, 2022, "

88% of groundwater tables were below average

", according to

La Chaîne Météo

.

Rains not “sustainable” enough

This drying of the soil is due to a rainfall deficit since winter 2021 of 20%.

An alarming situation because "

the water tables could not be recharged

" explains Pascal Scaviner, head of the forecast service at

La Chaîne Météo

.

To curb the phenomenon,

“the rains should be more durable

,” he adds.

Too violent and too short, these localized storms will not solve the drought problems.

The rhythm of these precipitations "

only for one to two hours

", does not make it possible to supply the soil with water, he continues.

Read alsoWhere does the "smell of rain" come from?

Water infiltration problems

Some soils in drought conditions have hardened and "

will refuse infiltration

", observes Yves Tramblay, hydrologist at the Research Institute for Development (IRD).

"

It is first the ground on the surface that dries up, then over time, that in depth

".

An experiment carried out by researcher Rob Thompson, published by the British University of Reading, confirms this hypothesis.

However, for Yves Tramblay, this video is not completely accurate because it tests the infiltration of water on a ground in the presence of grass, "

the water can very well flow on the sides without we can see it

”.

Moreover, if certain areas refuse water, this is not the case for all of France, wishes to correct the scientist.

All soils do not react in the same way

”: “

clayey

” soil, for example, will let water run off less than “

sandy

” soil.

An analysis approved by Pascal Scaviner of

La Chaîne Météo

, who claims that this week's thunderstorms can stop the dryness of soils "

already moistened

" by the first showers, but only in a "

punctual

" way.

Flood risks

The problems of non-infiltration of rainwater in the ground lead to the risk of flooding.

"

The excess

" will "

run off

" to join waterways such as "

rivers

" or the sea, deciphers Yves Tramblay.

This phenomenon represents a high risk because the accumulated rain can flood “

urban areas

” and “

reliefs

”, warns Lieutenant-Colonel Jean-Frédéric Biscay, vice-president of the national union of firefighters Avenir Secours.

"

When we face runoff in the city, where the tarmac ground is tight, the speed of flow can lead to the creation of dangerous and destructive waves

", he testifies.

Faced with the dangers of significant flooding, the firefighters "

are aware of the issues

" and are ready to intervene, reassures Jean-Frédéric Biscay.

However, the lieutenant-colonel confided to

Le Figaro

the complexity of this type of operation: “

Weather information does not yet allow us to predict the intensity and exact location of a stormy episode

”.

Despite the difficulties “

to determine the landing zones

” of bad weather, the emergency services work a lot by “

anticipation

”.

Read alsoParis: return to normal in transport after “very intense” storms and floods

Since Sunday, firefighters have already carried out multiple interventions in France, particularly in the "

Gard

" where "

the prefecture had wanted the campsites to be evacuated

".

A "

good decision of anticipation

", for Jean-Frédéric Biscay.

The vice-president of the Avenir Secours union urges the authorities to carry out preventive missions with the population, in order to facilitate the rapid safety of the French.

A possible solution while the forecasts of Pascal Scaviner of

La Chaîne Météo

envisage “

a persistence of the drought in the coming months

”.

*The Weather Channel is a property of the Figaro group.

Source: lefigaro

All tech articles on 2022-08-17

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