Alarming? Yes, confirms Aurore Degree (photo) to whom we asked to decipher this study. But the agronomist engineer of Gembloux Agro-Bio Tech, specialist in hydrology and soil physics, also wants to see positive: that of an alert which must force us to set up now, both internationally and that of Wallonia (see below), reasoned management policies of freshwater reserves.
Emptying of continental stocks
“Overall, the quantity of water on earth does not decrease, explains Aurore Dégré. What the study demonstrates is that the water of the continents, those of ice on earth, glaciers, lakes, soil or even water tables decreases. It is a phenomenon of emptying continental stocks in the oceans.”
At such a point, underlines the American study that all this “terrestrial” water is today the main factor in the increase in ocean level.
Another key point underlined by researchers: 68 % of freshwater losses observed in continental areas result from pumping underground tablecloths.
Because if, in Belgium, we are lucky that they recharge (still) during the winter, this is not the case everywhere. “In the United States, we pump in very deep but also very little supplied tablecloths,” said Aurore Dergé. These are non-renewable tablecloths which, for some, will be exhausted in ten years. “
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Less water for 75 % of the population
The study identified four “mega drying” areas in the northern hemisphere. In recent years, their area has increased by more than 830,000 km² each year – almost 300 times the surface of Belgium.
These four areas are northern Eurasia, northern Canada and Alaska, Central and South America, North Russia and an area encompassing the Middle East and North Africa. Consequence: in 101 countries, 75 % of the world’s population lives in areas that experience massive decreases in their freshwater reserve …
Solutions? Put in place global a concerted management of water management at the scale of travelers, says Aurore DEGRÉ. We are far from it when we see, for example, that the deviation of the Jordan by Israel has reduced resources for other countries such as Jordan or Chinese dams on the Mekong, reduce water resources in Cambodia.
Another major response to this shortage: to improve the efficiency of irrigation worldwide. “Today it is only 50 %. The techniques are not sufficiently controlled because it is always impression that the resource is infinite.” A myth that is smashed on the results of this study.
“In Wallonia, the challenge is to make the floors less waterproof”
Talking about drying in Wallonia will undoubtedly smile those who only analyze the climate situation through the whims of the weekly weather bulletin. However, the decrease in freshwater reserves is a serious issue, including here.
“Today, we are in the balance between what we take from the groundwater and recharge, explains Aurore Degree. But with the effects of climate change, it might not last.”
If successive droughts led to directly threaten the reserves, one of the main dangers would reside elsewhere: in the increasing waterproofing of the soil. Because the water tables are essentially recharged by infiltration. “With us, the challenge is therefore to make the floors less impermeable, she says. In urban areas by reducing concrete spaces, but also in the countryside.”
Because in agricultural circles, the settlement of land and the loss of organic matter also aggravate the waterproofing phenomenon. While climate change, by intensifying the episodes of violent rains, strengthens runoff. Dermeter cocktail for tablecloths which, rather than seeing the water infiltrate slowly to them, see it spinning towards the rivers.
In this context, certain measures taken to prevent floods, such as the multiplication of storm basins, dredging of rivers or concrete of the banks, may seem logical in the short term. But they prove to be counterproductive in the long term. “Because it is equivalent to sending water immediately to the sea, says Aurore DEGRÉ. What needs is to try to infiltrate the water where it falls.”
Solutions exist to achieve this: plant hedges, arrange ditches to slow down flows, recreate meanders of rivers, shorten agricultural plots in the direction of the slope or accept that water stagnates longer on the fields. The engineer also warns against another danger: if today agriculture is not the main consumer of water reserves (it is industry and household consumption), the error would be to embark on massive irrigation to cope with droughts that will multiply. Preserving the resource will also go through reasoned use and adaptation to the level of cultural practices.
Beyond this crucial issue for Wallonia to keep the water falling on its territory, the American study strengthens the conviction of scientists that we are not safe, within 15 to 20 years, of forest fires similar to those who currently ravage the south of France.
At the beginning of the year, an assessment but also of the Center for the Risk Analysis of Climate Change pointed out that this risk will only increase in the coming years. And that, like the insufficiency of our policies to promote the resilience of its groundwater, Wallonia is not ready to deal with it today. AW