in search of alternatives against drought

In a hundred French municipalities, the pipes are empty and the water does not flow when the taps are opened. The exceptional drought that the country has been going through since the end of July, the hardest since 1959, has emptied the rivers and the water tables. To deal with it, the Government, associations and the population must resort to strong restrictions, transport of water in tanker trucks and distribution of bottles.

In parallel, several voices ask that new ways of accessing water be found. Some of the techniques suggested are reusing used water, desalination of seawater or general use of rainwater… Measures that have already been implemented in several countries but that do not prosper in France, usually due to strict regulations or of environmental concerns.

Reuse used water

“France and the European Union must catch up on their delay in recycling used water,” says Julie Mendret, a researcher at the Membrane Institute of the University of Montpellier. “Today, less than 1% of the treated water in France is reused. In Italy it is 8% and 14% in Spain”, she details. “We are very far from the levels of several countries where these methods are widespread, such as the Gulf countries, Kuwait and Qatar. In Israel, pioneers in the field, they reach 80%.”

Normally, the water that we find in our taps is extracted from the water table and then made drinkable in specialized plants. Once consumed, it is treated in purification plants before being discharged back into the water cycle. If it were recycled, it would not be dumped again, but would be put back into the pipes.

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Specifically, France recycles every day 19,000 cubic meters of used water that allows the fields and golf courses to be irrigated. “We could expand these uses to clean roads or irrigate green spaces,” recalls Julie Mendret. “And why not go further and re-create drinking water from recycled water?” she says.

In Vendée, the Jourdain project will experiment with this solution in the near future. Instead of being thrown back into the sea, part of the water coming from the Sables-d’Olonne treatment plant will be recovered and treated before being reintroduced into the drinking water circuits. “It would be the first time it has been done in Europe, but this method is already used in Singapore or Namibia, for example,” says the specialist.

According to Mendret, France is held back by “overly demanding regulations” and many difficulties in getting projects accepted locally. In March, the Government expanded the permitted uses for recycled water, to recharge water tables or fight fires. At the European level, the member countries asked on August 3 to “step on the accelerator”.

“Be that as it may, we will not be able to recycle all the water. Perhaps it is essential to reject part of it to maintain the levels of water bodies and preserve biodiversity. It is not necessary to solve one problem by creating another,” the researcher clarifies. “But it is a very interesting option, especially for coastal areas where used water is normally released back into the water. It is fresh water lost.”

Popularize the use of rainwater

For her part, Fabienne Trolard, director of research at the National Research Institute for Agriculture and the Environment (Inrae, for its acronym in French), calls for generalizing the use of rainwater, which is not drinkable, in particular houses. “In France, all the water we consume is drinkable. We don’t have the option of using rainwater to water the plants,” she laments. “In Belgium or Germany, buildings have been working with double-circuit systems for a long time: drinking water only reaches 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’ more than once. Some of our neighbors recycle it three or four times. In Israel, five or six.”

Desalinate sea water

In Haute-Corse and Brittany, in the small towns of Rogliano and l’Île de Groix, the mayors wanted to experiment with another solution to the drought: desalinate seawater.

Like the recycling of used water, this technique is already widespread abroad. The International Association for Desalination, which brings together scientists, industrialists and NGOs, counts more than 17,000 installations of this type throughout the world. In total, more than 300 million people depend on them for their water needs. “The ones that use it the most are Saudi Arabia and Israel. In recent years, the Maghreb countries have also invested massively in these systems,” explains Fabienne Trolard. “The reason is simple: in these arid countries where fresh water is scarce, it is one of the only solutions.” In Jordan, one of these desalination plants will be installed on the shore of the Red Sea in 2026 and, if all goes well, it will produce between 250 and 300 million cubic meters of drinking water per year, that is, 750 million liters of water per day.

But this technique has several drawbacks. “Desalination plants consume a lot of energy and are uneconomical for municipalities,” explains Trolard. “But above all, they produce waste, brines that nobody knows what to do with.” On average, according to a UN report, for every liter of fresh water generated, 1.5 liters of this salt water are also discarded, usually into the ocean itself, unbalancing ecosystems.

Catch mist and dew

In other parts of the world, a myriad of small-scale solutions exist. Chile, for example, collects more liters of water each year from fog. This technique has existed since the pre-Columbian era and is simple: nets with a very dense mesh are installed on foggy days. Small droplets get trapped and run off into containers. This procedure is economical, ecological and natural, but it only works in very specific weather conditions.

Along the same lines, Laurent Royon, a researcher at the Interdisciplinary Laboratory of Future Energies in Paris, is studying the possibility of recovering dew drops. “This technique could be used anywhere, even in deserts, where it is cold at night,” says the scientist, citing ongoing research in India, Benin and Morocco. But its use is equally limited, since barely half a liter per cubic meter is collected.

Displace icebergs, make it rain… some controversial “miracles”

Until now, the measures described are used on a medium or large scale in various parts of the world. But there are scientists who want to go even further and seek to extract water from reserves that have not yet been exploited. In a study published in May entitled ‘Unconventional water resources’, researchers from the United Nations University gave a dozen ideas.

However, some of these paths seem to be, in the end, counterproductive. For example, “seeding” clouds would allow rain to be triggered at the desired time. Studied since the sixties, especially in China, this idea seeks to exploit the water that is present in the atmosphere in a gaseous state, in the clouds. Only between 10 and 15% of the water contained in the clouds ends up precipitating as rain. By sending aerosols using small rockets, the researchers believe they could increase the amount of rain. The first problem is that the effectiveness of this technique is in doubt, but the second is more serious: modifying the weather in this way could cause chain reactions that are difficult to anticipate.

Just as surprising is another proposal: there are scientists studying the possibility of displacing icebergs, which are composed of fresh water. For almost forty years, the French engineer George Mougin has been dedicated to this idea. Mougin has even tried 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 proposal that seems plagued by technological, ecological and financial problems.

*Article adapted from its original in French