The rain returned to France on Sunday August 14 and Monday August 15. More than welcome water after months of drought at the end of a very dry winter. In several regions of the country, the water tables are at very low levels. This is the case in Provence, on the Côte d’Azur or in Poitou. Sunday, all the departments of mainland France were on drought alert, including 22 in “enhanced alert” and 68 in “crisis” – the highest level of alert. In July, less than a centimeter of water fell in mainland France, thunderstorms, followed by precipitation were therefore particularly expected.
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“We have flows from some of our springs which are halved this season compared to flows which are already not very high in July-August“, observes Laurent Lucaud, elected communist, and vice-president of Greater Poitiers in charge of water and sanitation. Sunday and Monday, it rained in all and for all less than 15 millimeters, “just a little thunderstorm“, comments the elected official. The level of the water tables in Poitou is low, even locally very low. “It should, he continues, that there is a relatively fine rain abundant, for several weeks, even several months, to be able to fill the water deficit“. Because the deficit is counted in “hundreds of thousands or even millions of cubic meters” throughout the Poitevin territory.
Especially since it is not the summer rains that recharge the water tables but rather the rains of autumn and winter. “The rains solve the problem of soils and plants. The soil is in first position against the rain, it is he who uses it first. This will allow a restart of plant lifee, explain Vazken Andreassian, hydrologist. But on the other hand, groundwater must wait: they are used last“.
“The water tables are rather reconstituted during the winter, when the soils are already almost saturated. If the recent rains make it possible to solve the problem of the rivers on the surface, the water tables, they still have to wait.”
Vazken Andreassian, hydrologistat franceinfo
Another problem, points out the hydrologist: the extreme dryness of the soil. The upcoming rain episodes promise to be short but violent. Gold, udry land does not absorb the abundant water from storms. “Very intense rains do not benefit the ground or the water tables, because there is a runoff phenomenon, which can create floods.“, alert Vazken Andreasian
All eyes are therefore on autumn and the beginning of winter with significant rainfall expected to ensure the supply of drinking water. The breaking point is not very far around Poitiers, assures Laurent Lucaud: “Our reserves are diminishing every day. If in addition, we add to this existing crisis a lack of water, the deficit will increase. We are already on the reservation of the reservation“. According to vice-president of Greater Poitiers, of “breaks in the drinking water supply over a period from November to December, this is unheard of“.
The situation is better in other regions of France. In the North, the Paris basin or the Pyrenees, the water tables have a normal level, being around the average.