A massive aquifer is stored just beneath volcanic rocks at the crest of the central Oregon Cascades — possibly the largest aquifer of its kind in the U.S., according to researchers at the University of Oregon.
The discovery could have implications for water users in the region as drought and extreme weather limit snowpacks, rainfall and water availability.
According to a study published earlier this week, at least 81 cubic kilometers of active groundwater is stored at the Cascade Range crest in an area near the Santiam Pass. That’s more than four times the capacity of Crater Lake, which holds approximately 18.7 cubic kilometers of water.
“It is a continental-size lake stored in the rocks at the top of the mountains, like a big water tower,” Leif Karlstrom, the University of Oregon earth scientist who led the study, said in a news release.
Karlstrom said there are similar large volcanic aquifers north of the Columbia Gorge and near Mount Shasta, but the Cascade Range aquifer appears to be the largest mapped thus far.
Though scientists have long known that the mountains in Oregon hold water, they were not sure just how much. The University of Oregon team — along with scientists from other universities, the U.S. Forest Service and the U.S. Geological Survey — initially set out to better understand how water moves through the volcanic landscape and in the process discovered the massive aquifer under the rocks.
Using deep drill holes dug in the 1980s and 1990s to explore geothermal energy resources, the scientists were able to infer how deeply groundwater was infiltrating through cracks in the volcanic rocks to map the volume of the underground reservoir.
Because the drill holes did not cover a larger area, scientists said the size of the aquifer may be more massive than they were able to measure.
While that much water is good news in the era of climate change, it’s unclear whether the discovery could help solve Oregon’s water woes. Like other groundwater aquifers, this one needs to recharge and hence is dependent on a good snowpack — which is forecast to rapidly decrease 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 said.
The findings also point to heightened volcanic hazards in the area, the scientists said, as magma interacting with lots of water often leads to explosive eruptions.
Gosia Wozniacka covers environmental justice, climate change, the clean energy transition and other environmental issues. Reach her at gwozniacka@oregonian.com or 971-421-3154.
