- At the beginning of July, Météo-France had indicated that, over the last three months, the soils had “clearly dried up over a large northern and eastern half of the country”.
- The soils were then qualified as “extremely dry” from Haute-Normandie to Hauts-de-France and to the Grand Est.
- For climatologist Jean-Michel Soubeyroux, although we have not yet reached the level of drought in 2019, the current situation requires the greatest attention.
"July 2020 will probably be the first among the driest months of July," Météo-France warned on July 29. In a few weeks, more than 60 departments were forced to put in place measures to restrict water supply. In the process, farmers in 47 departments directly affected by the drought were authorized - by decision of their ministry - to use fallow areas to graze their herds or mow to produce fodder.
If the situation is particularly critical in the Grand-Est and in the Loire Valley, the whole country is now faced with significant soil drought. How to explain this phenomenon ? Where do we stand compared to previous years and what levers for action exist? Jean-Michel Soubeyroux, climatologist for Météo-France, answers the questions of 20 Minutes.
Is the level of precipitation in France more critical this summer than in previous years?
We must distinguish between meteorological drought and agricultural drought. Meteorological drought corresponds to the deficit of precipitation. It can be calculated over a month, over a season or over a longer period. Since the start of 2020, the rainfall deficit across the country is estimated at -10% compared to the average. However, the situation is better than last year since at the same time we measured a deficit of -20%.
But this lack of rain comes after several years of drought, it is a phenomenon which is repeated and which affects more or less the same regions. In 2020 we find a drought that at first glance looks furiously like the 2019 drought or even that of 2018. This repetition has the effect of alerting public opinion but it also creates confusion because we do not always know what drought we are talking about.
What are the most severely affected areas?
Four regions are particularly affected by this rain deficit. These are the Hauts-de-France (-13%), Grand-Est (-13%), Auvergne-Rhône-Alpes (-20%) and Bourgogne Franche-Comté (-21%) regions %).
What about agricultural drought?
For agricultural drought, we measure it at a time T. At this moment, practically all of France is in deficit, that is to say in "dry soil anomaly" with the exception of two places: Brittany and some areas around the Mediterranean which have recently benefited from severe thunderstorms. In these areas, soil moisture is considered correct.
Faced with #drought, decision taken to authorize mowing or grazing fallow land.
It is a decision with immediate effect in the face of the difficulties encountered by breeders. https://t.co/cKYP8sCyQn
On the other hand, the entire area located to the north of a line going from Cherbourg to Grenoble is at a “ten-year dry” level, that is to say at a level of drought that is only encountered every ten years. years. One region is still more particularly affected, it is the Grand-Est region with an exceptional drought character for Alsace which had not been measured for 50 years. The situation in this department is particularly serious since we are at the same level of drought as that which occurred in 1976 and which serves as a “reference” in the matter.
How do you explain this phenomenon?
Even if there is a repetitive nature, the drought we are experiencing is totally different from that of 2019. Last year, we observed a very marked winter drought with poor filling of the water tables and then a very high humidity in spring followed by a scorching summer and a brutal drought of the soil.
This year, at the beginning of March, we had broken soil moisture records. The winter was very wet with rain records in the Grand-Est in particular. But since March 10, there has been a very significant rainfall deficit throughout France which is the cause of the current drought in the soil.
For the moment, the summer has not been exceptionally hot, we are a little above the seasonal normal, but as there has been a prolonged deficit in precipitation, we end up with a more marked drought. To give you an idea, since the beginning of April, we have had a very marked rainfall deficit (-40%) in the Grand-Est. And in Hauts-de-France, it is even stronger with -49% precipitation. In this region, it is the 2nd driest period recorded by Météo-France over this period.
Should this finding alarm us?
Even if the current situation seems more favorable than that of last year, it requires great attention. As it rained a lot this winter, the water level remains correct. But the situation can still evolve since the level of drought and the temperature levels are closely linked. For now, we are moving towards a second heat wave at the end of this week. The trends that we are observing are rather in favor of a worsening of the situation and therefore call for vigilance.
Are the restrictive water supply measures put in place in more than 60 departments sufficient? Are there other levers of action?
The levers of action are very different depending on the types of activities that use water resources. Some agricultural activities are totally dependent on climatic resources. The drought will therefore affect them more strongly. Other activities, on the other hand, can compensate for this lack of rain by drawing water from underground or from water reservoirs. Then of course, it is possible to reduce the consumption of resources. This is what is being put in place in many territories and these measures are likely to increase. But in the long term, the question of reducing our water consumption or adapting our consumption may arise.
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