A massive freshwater reservoir is hiding under the Great Salt Lake
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A massive freshwater reservoir is hiding under the Great Salt Lake
A massive hidden freshwater reservoir beneath the Great Salt Lake could reshape both science—and solutions to its growing dust crisis.
Date:
March 21, 2026
Source:
University of Utah
Summary:
A hidden freshwater system deep beneath the Great Salt Lake has been revealed using airborne electromagnetic surveys. Scientists found that freshwater extends much farther under the lake than expected, reaching depths of up to 4 kilometers. The discovery began with mysterious reed-covered mounds formed by pressurized groundwater pushing upward. Researchers are now investigating whether this underground water could help control hazardous dust from the drying lakebed.
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A pragmities-covered mound that has formed on the dry playa of Farmington Bay. It was formed in recent years by freshwater getting pushed to the surface of the exposed lakebed. Credit: Brian Maffly, University of Utah
A newly identified underground freshwater system beneath the Great Salt Lake is becoming clearer thanks to a study that used airborne electromagnetic (AEM) surveys to map geologic formations below Farmington Bay and Antelope Island along the lake's southeastern edge.
Researchers from the University of Utah analyzed the data and found that freshwater fills sediments beneath the lake's highly salty surface, reaching depths of 3 to 4 kilometers, or about 10,000 to 13,000 feet. The helicopter-based survey was carried out last year after scientists observed freshwater emerging under pressure in parts of the exposed lakebed in Farmington Bay, forming unusual mounds covered in dense phragmites reeds.
According to lead author Michael Zhdanov, the study marks the first time AEM technology has successfully detected freshwater beneath the thin layer of conductive saltwater at the surface of the Great Salt Lake. The team also mapped how far the freshwater extends beneath Farmington Bay and estimated how deep the water-saturated sediments go by identifying the underlying basement structure.
"We were able to answer the question of how deep is this potential reservoir, and what is its spatial extent beneath the eastern lake margin. If you know how deep, you know how wide, you know the porous space, you can calculate the potential freshwater volume," said Zhdanov, a distinguished professor of geology & geophysics and director of the Consortium for Electromagnetic Modeling and Inversion, or CEMI.
State-Funded Research on a Newly Discovered Aquifer
The findings were published in the Nature-affiliated journal Scientific Reports. This work is part of a broader research initiative led by the University of Utah's Department of Geology & Geophysics and funded by the Utah Department of Natural Resources. The goal is to better understand groundwater beneath the Great Salt Lake, the largest terminal lake in the Western Hemisphere.
Senior faculty and graduate students have contributed to this ongoing effort, which has already produced two additional studies, with more expected.
The new results indicate that freshwater may be moving into the subsurface toward the lake's interior rather than staying near the edges, which is what scientists typically expect. Hydrologist Bill Johnson, a co-author on the groundwater studies, highlighted how unusual this pattern is.
"The unexpected part of this wasn't the salt lens that we see near the surface across the playa. It's that the freshwater underneath it extends so far in towards the interior of the lake and possibly under the entire lake. We don't know," Johnson said on a recent appearance on KPCW's Cool Science Radio show. "What we would normally expect as hydrologists is that that brine would occupy the entire volume underneath that lake. It's denser than the freshwater. You'd expect the freshwater from the mountains to come in somewhere at the periphery. But we find it's coming in towards the interior. And there's what appears to be deep volume of this freshwater coming in underneath that saline lens."
Freshwater Could Help Reduce Toxic Dust
The research was prompted by the appearance of circular mounds on the dried lakebed in Farmington Bay over recent years. These features measure 50 to 100 meters across and are covered in tall reeds reaching about 15 feet. As water levels in the lake have dropped, around 800 square miles of exposed lakebed have become a growing source of dust pollution affecting nearby communities.
Johnson and his colleagues are investigating whether the artesian groundwater could be used safely to reduce dust, which contains harmful metals.
"There are beneficial effects of this groundwater that we need to understand before we go extracting more of it. A first-order objective is to understand whether we could use this freshwater to wet dust hotspots and douse them in a meaningful way without perturbing the freshw