In a hundred French municipalities, the pipes are empty and the water no longer flows through the taps.

The exceptional drought which has affected the country since the end of July, the most severe since 1959, has emptied the rivers and groundwater.

To cope, the government, local communities and the population have recourse to the D system, between severe restrictions, transport of water in tank trucks and distribution of bottles.

At the same time, many voices are being raised to seek new ways of exploiting water.

Among the techniques mentioned: reusing wastewater, desalinating seawater or even democratizing the use of rainwater... Measures already widely practiced in certain countries, but which are struggling to impose themselves in France, often in due to strict regulations and environmental concerns.

Reuse wastewater 

"France and the European Union must catch up on the recycling of wastewater," says Julie Mendret, researcher at the Membranes Institute of the University of Montpellier.

"Today, less than 1% of treated water in France is reused. It's 8% in Italy and 14% in Spain," she explains.

"We are far from certain countries where this is completely democratized, especially in the Gulf countries such as the United Arab Emirates, Kuwait and Qatar. In Israel, a pioneer in this area, we reach 80%."

As a reminder, traditionally, the water that ends up in our taps has been extracted from groundwater and then purified in drinking water treatment plants.

Once consumed, it is treated in treatment plants before being discharged into waterways.

If it is recycled, it will not be rejected but reintroduced into the pipes. 

In concrete terms, France recycles 19,000 m3 of wastewater daily, which is used to irrigate agricultural crops and water golf courses.

"We could completely expand these uses to clean roads or water green spaces," says Julie Mendret.

"And why not go further and reproduce drinking water from this recycled water?"

In Vendée, the Jourdain project will soon be experimenting with this solution.

Instead of being discharged into the sea, part of the water from the Sables-d'Olonne wastewater treatment plant will be recovered and treated before being reinjected into the drinking water circuits.

"It would be a European first but it is already in place in Singapore or Namibia, for example," notes the specialist.

According to her, France is hampered by "overly demanding regulations" and difficulties in getting these projects accepted at the local level.

In March, however, the government extended the uses for recycled water, to recharge groundwater or fight fires.

At the European level, the member countries called, on August 3, "to speed things up". 

"In any case, we will not be able to recycle all the water. Sometimes, it is essential to reject it to maintain the flow of nearby rivers and preserve biodiversity. You should not solve a problem by creating another", she nuances.

"But this option remains very interesting, especially for coastal areas where wastewater is often discharged into the sea. It is lost fresh water."

Democratize the use of rainwater

For her part, Fabienne Trolard, director of research at the National Research Institute for Agriculture and the Environment (Inrae), calls for the generalization of the use of rainwater, which is not drinkable, especially among individuals.

"In France, all the water we consume is drinkable. We only have the right to use rainwater to water our plants," she laments.

"In Belgium or Germany, homes have long been operating with dual-circuit systems: drinking water only arrives at the taps for drinking and showering. The rest is supplied with rainwater, stored in individual tanks," she explains. 

With this system, "we could even reuse this 'grey water' [undrinkable water] several times. Some of our neighbors recycle it three or four times. In Israel, it's five or six."

desalinate sea water

In Haute-Corse and Brittany, in the small towns of Rogliano and the island of Groix, the mayors wanted to experiment with another solution to the drought: the desalination of seawater. 

👷 Installation of a temporary #sea water #desalination unit

📍 On the Port-Melin site in #Groix

💧 To guarantee the continuity of the production of #drinking water to the population

☀️ In a context of crisis # exceptional drought

+ info 👉

— Lorient Agglo (@LorientAgglo) August 5, 2022

Like wastewater recycling, this technique is already widely used abroad.

The International Association for Desalination, which brings together scientists, industrialists and NGOs, counts more than 17,000 plants of this type in the world.

In total, more than 300 million people depend on it for their water needs.

"The first users are Saudi Arabia and Israel. In recent years, the Maghreb countries have also invested massively", explains Fabienne Trolard.

"The reason is simple: in these arid countries where fresh water is sorely lacking, it is one of the rare solutions."

In Jordan, a plant is to be set up on the shores of the Red Sea in 2026, it should produce between 250 and 300 million cubic meters of drinking water per year, according to the authorities,

But this technique has its share of drawbacks.

"These factories are very energy-intensive, and therefore not very economical for the municipalities", notes Fabienne Trolard.

"But above all, it produces waste, brines, which we don't know what to do with."

On average, according to a UN report, for every liter of fresh water generated, 1.5 liters of this saline mud is released, usually into the ocean, upsetting ecosystems.

Capture the fog and dew 

Elsewhere in the world, a myriad of small-scale solutions exist.

In Latin America, Chile, for example, harvests several liters of water from fog each year.

This technique, which has existed since the pre-Columbian era, is very simple: very tightly meshed nets are installed on foggy days.

The droplets come to cling to it and then run off towards containers.

A cheap, ecological, natural process, but which however only works in very specific weather conditions. 

In the same vein, Laurent Royon, researcher at the Interdisciplinary Energy of Tomorrow Laboratory in Paris, is studying the possibility of recovering dewdrops.

"This technique could be used everywhere, even in the deserts, where it is cold at night," he says, listing ongoing experiments in India, Benin and Morocco.

But use remains limited with barely 0.5 liters per cubic meter harvested approximately per night. 

Moving icebergs, making rain fall...controversial "miracles"

If all the measures mentioned are already used on a more or less large scale in the world, other scientists want to go further and seek to tap into still untapped reservoirs of water.

In a study released in May and entitled "Unconventional water resources", researchers from the United Nations University list a dozen of them.

But some of these leads ultimately turn out to be counterproductive.

For example, cloud seeding, which would trigger rain on command.

Studied since the 1960s, particularly in China, the idea is to exploit the water present in the Earth's atmosphere in the vapor state, in the clouds.

Indeed, only 10 to 15% of the water contained in these clouds ends up falling as rain.

By sending aerosols through small rockets or fireworks, for example, researchers are trying to increase the amount of precipitation.

Problem: not only is the effectiveness of the technique debated, but changing the weather could cause chain reactions elsewhere on the planet that would be difficult to anticipate.  

Equally surprising, scientists are studying the possibility of moving icebergs, which are made up of fresh water.

For almost forty years, this track occupied the French engineer Georges Mougin, who sought to move these huge blocks of ice to countries subject to drought.

In 2010, his experiments led to the conclusion that it would take five months and 4,000 tons of oil to transport an iceberg from Canada to the Canary Islands.

A track that therefore seems to pose as many technological, ecological and financial problems.

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