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When to speak of drought?


FOCUS - How is drought defined? Are there different levels? What are the causes ? Our answers.

Drought is no longer reserved only for summer periods.

The lack of rain is worrying, especially in certain regions of France.

February 2023 was the fourth driest month recorded since 1959.

Le Figaro

takes stock of the drought phenomenon.

What is drought?

Drought is a natural phenomenon characterized by a lack of water over a period long enough to affect soils and vegetation.

This phenomenon can be cyclical or exceptional and can affect a localized area such as an entire subcontinent.

While some areas are more vulnerable, droughts can strike almost anywhere on the globe.

Drought should not be confused with aridity.

Indeed, an arid region can experience episodes of drought.

Lack of rain will be a permanent feature of the arid zone climate.

These are generally regions where rain is rare and temperatures are high.

Drought will therefore be a one-off phenomenon in an area.

Read alsoDrought: “The situation is worse than last year on the same date”, warns Christophe Béchu

According to the regions of the world and their water resources, the definition of the state of drought varies, according to the Water Information Center.

In France, absolute drought is considered when no drop of rain (i.e. less than 0.2 mm/day) has fallen for 15 consecutive days.

In the United States, drought is established if a large area receives 30% or less precipitation than normal over a period of 21 consecutive days.

In Australia, if an area receives less than 10% rainfall compared to the annual average, then it is considered to be in a state of drought.

Finally in India, drought is established if rainfall drops by 75% compared to seasonal norms.

What are the types of drought?

There are three types of drought depending on the situation:

Meteorological or atmospheric drought


“it is not raining”.

A prolonged rainfall deficit affects a territory.

Edaphic drought


that is to say of the soil, also known as

agricultural drought

 : "the soils are dry".

Lack of water affects the development of vegetation.

It depends on the moisture content of the soil at a depth of one meter.

This drought depends on rainfall, but also on the nature of the soil, farming practices and the type of plant.

Hydrological drought


 “there is no more water in the rivers”.

Groundwater levels and river flow are decreasing;

aquatic environments are impacted and their natural functioning is disrupted.

This may be due to a particularly long and intense meteorological drought, but also to an overexploitation of water resources.

What are the causes of drought?

Natural (weather) causes

At the origin of the drought, there is the lack of water and high temperatures.

In the event of insufficient precipitation during the winter and spring (between September and March), the water reserves cannot be recharged as they should to maintain a hydrological balance.

Since August 2021, all months have had a rain deficit, except December 2021, June 2022 and September 2022. An episode that is all the more worrying as it occurs right in the groundwater "recharge period", from September to March .

For February, "

all the groundwater shows levels below normal and 80% of the levels are moderately low to very low, against 60% a month earlier and 50% on March 1, 2022", indicates the Bureau of Geological Research

and mining companies (BRGM).

The areas of the Rhône corridor, Limousin, Causses and the Roussillon plain are particularly affected, displaying “ red

” levels and “

very low

” water tables


We have already experienced a situation with many more red dots

“At that time, in 2012 and 2017, “

but what is unprecedented

is that all of France is affected

”, underlines Violaine Bault, hydrogeologist at BRGM.

The meteorology is an interesting indicator: in the event of a prolonged anticyclonic period, the risk of drought increases.

Just like high temperatures that favor the evapotranspiration of plants

human causes

Excessive water consumption for human activities can lead to worsening drought.

When water reserves decrease due to unfavorable meteorology (persistent anticyclone), they are not always managed efficiently by man in the context of his agricultural, industrial and domestic operations.

Overexploitation of water resources can lead to groundwater drying up and threaten their sustainability.

What are the consequences of drought?

Since the 1970s, the areas affected by drought have doubled to the point that droughts claim more victims and cause more population displacements than cyclones, floods and earthquakes combined.

It is often women, children and the elderly who pay the heaviest price.

The main consequences of drought are


On the population:

the health of children and the elderly is very fragile and sensitive to high heat because they do not have the reflex, nor the desire to drink to fight against their dehydration which can kill.

On wildlife:

a lack of water affects fish living in the water, but also animals that drink from water points;

On forests:

drought will make trees drier and dehydrated, which can cause their death.

In addition, very dry vegetation will be conducive to the start of fires which will emit harmful gases which will pollute the atmosphere and accentuate the greenhouse effect.

On agriculture:

the irrigation of crops (such as wheat in France) is affected by drought because water reserves are low.

On soils:

in autumn, dry soils, which nevertheless need to be recharged with water, will no longer be able to absorb precipitation, creating floods and landslides.

On the drinking water reserves:

the supply and evacuation of household water is not done correctly, because the level of the rivers, streams and groundwater is very low.

In some rural areas, water is rationed or cut off.

On electricity production:

water is used to cool some nuclear power plants, so they are shut down during droughts and periods of heat wave when the demand for electricity increases: air conditioning, fan, refrigerator which require a lot of 'electricity.

Who are the main water users?

In France, the annual volume of water consumed (ie the part of the water withdrawn that is not returned to aquatic environments) is estimated at 5.3 billion m3, which represents 82 m3/inhabitant.

Domestic water consumption now accounts for 10% of global water consumption, with strong variations depending on the country's level and way of life.

Moreover, the presence of an abundant water resource of good quality is often a factor in the establishment of industries near watercourses.

Water can thus be used to carry out many operations.

Are there alert levels?

There are four levels of drought, justifying, depending on their degree, the taking of appropriate measures:

1 /

Level of vigilance

in which users are informed of the situation and encouraged to save water resources.

2 /

Level of alert

in which the use of water for agricultural purposes may be restricted or even prohibited on certain days of the week, and certain nautical activities, the watering of gardens at certain times of the day, car washing, etc. prohibited.


Heightened alert level

under which the above restrictions are further tightened.

Up to 50% water savings may be required.


Level of crisis

within the framework of which a total ban on non-priority withdrawals can be prescribed, including withdrawals for agricultural purposes, authorizing the use of water only for health, civil security, supply of drinking water or for purposes of maintaining sanitation.

Is drought considered a “natural disaster”?

The natural disaster guarantee has been compulsorily included in all damage insurance contracts (except for boats) since the law of July 13, 1982, indicates the website of the Ministry of Ecological Transition.

It is financed by part of the premium paid by the insured and makes it possible to cover damage that could not normally be covered by other damage insurance guarantees.

For an insurer to be able to cover your claim under this cover, the state of natural disaster must be declared in your municipality by the public authorities in an interministerial order published in the Official



You have a period of 10 days from the publication of the interministerial order noting the state of natural disaster to notify your insurer.

The insurer has one month from receipt of the estimated statement of losses suffered or the expert report to send you a proposal for compensation.

Source: lefigaro

All tech articles on 2023-03-30

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