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The American West is hungry for water, and scientists just found a previously unmapped aquifer three times the size of Lake Mead.
The discovery came when researchers, studying drill holes left behind by previous geothermal experiments, found that rock remained wet further down that previously imagined.
Although a boon for the parched West, the aquifer is fed by snowpack, and scientists estimate dramatic reductions in snow in the Cascades in the coming decades.
As the world warms, water in the American West is becoming more and more vital. Lake Mead and Lake Powell, two of the largest reservoirs out west, were at their lowest levels in 2023, and severe drought in some places is leading to ever-encroaching desertification where fertile grasslands slowly turn arid as the well, metaphorically speaking, dries up.
While this is a concerning scenario for those living in the southwestern U.S., the Pacific Northwest, while extremely dry in the summer months, receives a lot more rain as prevailing winds off the Pacific Ocean and mountain ranges, such as the Cascades, unleash months of moisture on the region. Now, a new study from the University of Oregon says that the Cascades may have squirreled away a lot of that water deep undergound.
A team of researchers led by earth scientists at the University of Oregon (UO) analyzed drill holes created decades ago by scientists surveying for geothermal energy, and after finding evidence of water as the holes went deeper, the researchers found that the Cascades could contain 81 cubic kilometers of water—that’s three times the size of Lake Mead at its maximum capacity. The results of the study were published in the journal Proceedings of the National Academy of Sciences (PNAS).
“It is a continental-size lake stored in the rocks at the top of the mountains, like a big water tower,” UO’s Leif Karlstrom, a co-author of the study, said in a press statement. “That there are similar large volcanic aquifers north of the Columbia Gorge and near Mount Shasta likely make the Cascade Range the largest aquifer of its kind in the world.”
Finding this body of water came as a complete surprise. Initially, the team set out to better understand how the Cascades evolved over time, specifically how water flowed through the region. To do this, they analyzed rocks where two zones of the Cascades collide at Santiam Pass in central Oregon. Usually rocks get warmer as you dig deeper, but while analyzing these long-abandoned drill holes, the scientists noticed that the rocks’ typical temperature gradient was disrupted—a tell-tale sign of water permeating the rock. The scientists measured where rock temps increased again and estimated that the Cascades were hiding one big aquatic secret.
Because the scientists were working with holes drilled for geothermal purposes and not for mapping groundwater, the scientists’ 81-cubic-meter estimate is likely on the lower end of how big this hidden cache of water could actually be. While a possible untapped source of freshwater is cause for celebration, the researchers also urge caution. The groundwater in the Cascades is fed by snow, and snowpack is expected to decline significantly in the Cascades in the coming decades.
“It is a big, active groundwater reservoir up there right now, but its longevity and resilience to change is set by the availability of recharging waters,” Karlstrom says.
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