In the western United States, the issue of water shortage is increasingly being raised. In a burning way, with the fires that ravaged Los Angeles.
The truth behind the California wildfires: What early reports of the disaster reveal
Global warming, in fact, reduces the coatcoat snowy on the Cascade Range. It also intensifies droughts. All of which puts a strain on already limited resources in the region. But researchers from the University of Oregon (United States) have just made a discovery that could ease the situation.
A huge water reserve – at least 81 cubic kilometers – hidden beneath the volcanic rocks at the top of the state’s central Cascades. A reserve of almost three times the maximum capacity of Lake Mead, the reservoir currently in great difficulty along the Colorado River, supposed to supply water to California, Arizona and Nevada.
Unexpected quantities of water under volcanic mountains
If researchers were interested in the region, it is because they hoped to understand, precisely, how water moves in this landscape shaped over millions of years by volcanic activity. In the Proceedings of the National Academy of Sciencesthey say that they relied on work carried out in the 1980s and 1990s. Colleagues then drilled the ground in search of geothermal resources. But they discovered that rocks a kilometer deep – which should have been warmer – kept the same temperature as the surface rocks. An effect of water infiltration.
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-The discovery of this immense aquifer beneath Oregon could also be important to scientists’ understanding of the landscapes of this volcanic region. Because geologists note that when magma erupts in dry conditions, it usually turns into surface lava. But when groundwater comes into play, gas and ash explosions can occur.
By analyzing where the temperature begins to rise in these deep boreholes, the University of Oregon researchers were able to infer how deep groundwater was seeping through cracks in the volcanic rocks. Enough to finally map the volumevolume of the aquifer – understand, the underground water reservoir. Or at least, its minimal volume. Because the drilling – not originally intended for the evaluation of water resources – does not cover the entire area.
Doubts about the longevity of the water tank
But researchers remain cautious. “It is a large active groundwater reservoir at present, but its longevity and resilienceresilience to change are determined by the availability of recharge water”underlines Leif Karlstrom, geologistgeologistin a press release from the University of Oregon. The example of the Great Artesian Basin of Australia is striking. It contains almost 1,000 times more water, but does not recharge on a human scale.
And the aquifer beneath the Cascades is mostly recharged by snow. Snow which should become increasingly rare with global warming. Precipitation in the form of rain could help maintain it. But “a series of bad winterswinterswithout rain » could also put him in difficulty. Additional studies will be needed to learn more about this dynamic.
