Massive Freshwater Reservoir Discovered Deep Beneath Great Salt Lake

Hidden Underground Ocean Could Combat Toxic Dust

Scientists have uncovered a stunning secret beneath Utah's shrinking Great Salt Lake: a massive freshwater reservoir extending up to 13,000 feet deep into the earth . University of Utah geophysicists used electromagnetic data from airborne surveys to locate the deep freshwater reservoir under Farmington Bay , marking the first time that airborne electromagnetic methods have successfully detected freshwater underneath the thin layer of conductive salt water at the surface of the Great Salt Lake .

The discovery emerged from an unlikely clue. Strange circular phragmites mounds appeared on the dried-out bed of Farmington Bay, each 50 to 100 meters in diameter and covered with 15-foot-tall thickets of reeds . These mysterious formations puzzled researchers until they realized the plants use large amounts of fresh water, leading them to question where this water comes from and discover it originates from underground .

Scientists hired a Canadian geophysical team to fly instruments suspended beneath a helicopter in February 2025, completing 10 east-west survey lines across Farmington Bay and the northern part of Antelope Island, covering a total of 154 miles . The electromagnetic surveys revealed something extraordinary: a sudden and substantial drop in the depth of underlying bedrock below the Great Salt Lake, leaving a massive space for sand and silt to fill—sediment that appears to be saturated with freshwater .

Fighting Utah's Growing Dust Crisis

The declining water levels of the Great Salt Lake have exposed 800 square miles of lake playa, becoming a major source of dust pollution blowing into Utah's population centers . This isn't ordinary dust— it contains toxic metals that regularly blow into urban areas of Utah . The newly discovered freshwater could provide a practical solution to this escalating environmental crisis.

Researchers want to explore whether the artesian groundwater could be safely tapped to wet dust hotspots and douse them in a meaningful way without perturbing the freshwater system too much . Lead researcher Bill Johnson explained that this approach is very practical because it's unlikely they'll be able to fill Farmington Bay and other parts of the playa enough to avoid dust spots appearing at higher elevations, making this a great way to address the problem .

The scale of the potential solution matches the magnitude of the problem. Researchers can now calculate the potential freshwater volume because they know how deep the reservoir extends, its width, and the porous space available , giving them crucial data for developing targeted dust mitigation strategies.

Unexpected Underground Geography

Perhaps most surprising to hydrologists was where they found the freshwater. Scientists would normally expect brine to occupy the entire volume underneath the lake since it's denser than freshwater, with freshwater from the mountains coming in at the periphery, but instead they found freshwater coming toward the interior with what appears to be a deep volume underneath the saline lens .

Some of the water contained in the aquifer may date back thousands of years to the Ice Age, when the area was covered by the vast freshwater Lake Bonneville . This ancient water tells researchers that playa groundwater is not getting to the lake anytime soon, and that groundwater from the mountain front reaches the lake via seepage to incoming rivers rather than direct groundwater inflow in the playa .

Expanding the Search

Researchers believe they can fly airborne electromagnetic survey lines across the lake's entire 1,500-square-mile footprint, which could help guide regional water-resource planning and inform similar searches for freshwater beneath terminal lakes worldwide . Preliminary discussions about further studies are already underway with the Utah Legislature and the Utah Department of Natural Resources .

The implications extend far beyond Utah's borders. As one researcher noted, this desert could hide fresh water, similar to discoveries in the Sahara and Africa, but scientists don't know very well the subsurface groundwater distributions in Utah . This groundbreaking technique could revolutionize how scientists search for hidden freshwater resources in arid regions worldwide, potentially offering solutions for water-stressed communities facing similar environmental challenges.