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Scientists found that an aquifer at the Oregon-California border contains nearly three times the maximum capacity of Lake Mead — much more than previously thought.

The study, published in January, reports that the aquifer contains some 21 trillion gallons of the wet stuff.

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The researchers were studying the volcanic landscape of the Cascade Range when the discovery was made.

“It is a continental-size lake stored in the rocks at the top of the mountains, like a big water tower,” Leif Karlstrom, a University of Oregon earth scientist who led the study, said in a news release. “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.”

Most Oregonians rely on water from the Cascades, but shrinking snowpack due to climate change has been exacerbating drought across the western U.S. from year to year. According to The Nature Conservancy, water security is at risk in every snowpack-dependent western U.S. basin.

Lake Mead and Lake Powell, two of the largest reservoirs in the West, recorded their lowest water levels in 2022. Both reservoirs are snowpack-fed.

(​MORE: Why Droughts Are Getting Worse in Western U.S.)

An aquifer the size of the one found in the Cascades “has implications for the way scientists and policymakers think about water in the region,” the University of Oregon news release stated, but the same issues of decreasing snowpack apply to even this large water source.

Scientists are expecting dramatic snowpack reduction in the coming decades as the planet continues to warm, so it’s not certain how long the giant water source might help Oregonians, and what other locations stand to benefit from its discovery. The researchers are pushing for more research on how drought and climate change could affect the aquifer.

(​MORE: West's Megadrought Is Worst in 12 Centuries)

“This region has been handed a geological gift, but we really are only beginning to understand it,” the study co-author, Gordon Grant, geologist with the U.S. Forest Service, stated in the release. “If we don’t have any snow, or if we have a run of bad winters where we don’t get any rain, what’s that going to mean? Those are the key questions we’re now having to focus on.”