France is going through a “historic” drought period, in the words of Prime Minister Elisabeth Borne, and the month of July was the second driest since the start of Météo-France measurements.
In more than a hundred municipalities in France today, the pipes are empty and the water no longer flows from the tap.
In many cities, it is organized between pumping natural lakes, ballets of tank trucks and desalination of seawater.
Will these methods of combating this episode of drought be sufficient for the decades to come, which will be increasingly hot and dry?
France is facing an "exceptional drought" according to Prime Minister Elisabeth Borne.
On Thursday, 93 departments are subject to water restrictions, 62 of which are considered "in crisis", the highest level of alert.
And, according to Météo-France, France had not experienced such a dry month of July since 1959. But how do cities organize themselves in the face of the lack of water?
Desalination units, tank trucks, drawing water from natural lakes… Many initiatives are being put in place while more than 100 towns are deprived of drinking water in France.
Harvesting, purifying and distributing water from lakes
When communities affected by drought and whose water tables have dried up are lucky enough to have fresh water, they turn to their natural lakes.
In the Vosges, the town of Gérardmer has decided to tap into its eponymous lake.
The water from the public network was declared undrinkable for 48 hours.
"The water goes through purification stations because there is a chemical control of the water which is done before distribution", explains Fabienne Trolard, research director at the National Institute of Research for Agriculture (Inrae).
The situation is not new for Gérardmer who has already had to draw from his lake for "a few days" in 2015 and 2020, and "more importantly in 2003" even if these are now "extreme situations".
And more and more frequent.
We must therefore remain cautious because “we endanger the aquatic ecosystem that the lake contains if we draw too much and dry it out,” says Fabienne Trolard.
These sources of fresh water are already in high demand to cool our nuclear power plants.
And this method obviously requires a source of fresh water on the territory of the municipality.
Desalinate seawater despite environmental risks
Orphaned by a lake but surrounded by seawater, the village of Rogliano, in Corsica, has opted for the acquisition of a desalination unit, a first on the Isle of Beauty.
The unit cost 1 million and 50,000 euros and will produce 500 cubic meters of drinking water per day.
The island of Groix, in Brittany, has also invested in such a device.
The perfect futuristic solution to drought?
"It's very expensive and, above all, we end up with brines, that is to say extremely salty water that we don't know what to do with", tempers Fabienne Trolard, doctor in geoscience and expert in water resource management.
“We are starting to have a few sea desalination plants in the Mediterranean but, behind that, we have a real environmental problem because we don't know what to do with the waste,” she illustrates.
On average, for every liter of fresh water generated, 1.5 liters of saline sludge is released, usually into the ocean, disrupting ecosystems.
The “final solution”
Sometimes cities have neither fresh nor salt water on their land.
They then rely on their neighbors and are forced to supply themselves with tank trucks.
"In general, it's the last solution because we just move the water", underlines Fabienne Trolard who evokes an "emergency solution".
An analysis shared by the Minister of Ecological Transition, Christophe Béchu, who asks the municipalities to “anticipate”.
"If you have to go and provide water, you shouldn't worry about it in the morning when there is no more water in the pipes", he said on Thursday, during a visit to the Alpes de Haute Provence.
To avoid shortages and moderate the ballet of water on the roads of the Ile-de-France – already in great demand by holidaymakers, the departments are pulling out their most classic weapon: restrictions.
The drier the weather, the more limited the use of water.
For departments in "crisis", the highest level of alert, only priority direct debits are authorized.
No question of watering his lawn or cleaning his car.
Pre-dug reservoirs
But "it is difficult to constrain the inhabitants and to monitor them", underlines Fabienne Trolard, who insists on the work of pedagogy so that "everyone understands that these resources are limited and that they must be managed as well as possible".
In addition, "it's only when you have your nose above it that you say to yourself that we should take care of it when it requires investments for years or even decades in advance", underlines the doctor in geoscience.
In Ile-de-France, four artificial lakes were dug in the 1960s to regulate the course of the Seine.
At the time, the objective was to protect Paris from flooding in the event of torrential rains.
With global warming, these lakes also act as reservoirs and make it possible to adjust the level of the river when there is not enough or too much precipitation.
"Creating reservoirs is important, but it is absolutely necessary to restructure the distribution of water", reacts Fabienne Trolard who insists all the same on the other necessary investments such as "rainwater reservoirs" in private homes with systems for recovering rainwater from the roofs of dwellings or “double circuits”.
Take (finally) “the turn”
“It consists of a drinking water circuit and a so-called gray water circuit, that is to say the water from the dishwasher or the shower, not the toilets, which is recycled on site and reused” , explains the research director.
With this system, some of our European neighbors manage to recycle “grey” water three or four times, “which is not at all the case in France”.
In Israel, it is even “five to six times”.
Rainwater can also be collected for use in our toilets (which are now supplied with drinking water).
These dwellings make it possible to recycle “20 to 50% of water”.
"The reuse of wastewater has lagged behind in France, in particular because we have a certain number of water lobbies who absolutely did not want public research to work on these subjects",
Our dossier on the 2022 drought
As droughts are set to increase in the coming years, the overhaul of our water management is becoming urgent.
“You have to invest for the long term,” says Fabienne Trolard.
Some measures will show their effectiveness ten or even twenty years after their implementation.
A very slow delay when you know that “as long as you are not facing the wall, it is difficult to turn the corner”.
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