Airborne Electromagnetic Survey Reveals a Freshwater Reservoir Up to Four Kilometers Deep Beneath the Great Salt Lake
University of Utah geophysicists have discovered a vast freshwater system saturating sediments beneath the shrinking Great Salt Lake, potentially spanning its entire 1,500-square-mile footprint.
Overview
A team of University of Utah geophysicists has discovered an extensive freshwater reservoir hidden beneath the Great Salt Lake, one of the most saline bodies of water in the Western Hemisphere. Using airborne electromagnetic surveys flown by helicopter over Farmington Bay, the researchers found that freshwater saturates the sediments beneath the lake’s hypersaline surface to depths of three to four kilometers, far exceeding expectations and raising the possibility that the reservoir could extend beneath the lake’s entire 1,500-square-mile footprint, according to Phys.org.
The study, published in Scientific Reports on March 20, 2026, arrives as the Great Salt Lake continues to shrink under pressure from decades of water diversion and persistent drought, exposing roughly 800 square miles of lakebed that generates hazardous dust affecting surrounding communities.
What We Know
The discovery began with an unexplained observation: reed-choked mounds, each 50 to 100 meters in diameter and up to 15 feet tall, appeared on the exposed playa of Farmington Bay in recent years. The mounds indicated pressurized freshwater welling up from below, prompting the University of Utah team to investigate the subsurface, as reported by Phys.org.
Led by Michael Zhdanov, a Distinguished Professor of Geology and Geophysics and director of the Consortium for Electromagnetic Modeling and Inversion (CEMI), the team flew 154 miles of survey lines across 10 east-west transects spanning Farmington Bay and northern Antelope Island in February 2025. The airborne electromagnetic (AEM) equipment detects differences in electrical conductivity between saltwater and freshwater-saturated rock, allowing researchers to build three-dimensional subsurface images, according to Phys.org.
The survey revealed that bedrock beneath the bay sits at less than 200 meters under the playa before dropping abruptly to three to four kilometers, creating a vast basin of sediment saturated with freshwater. “We were able to answer how deep is this potential reservoir, and what is its spatial extent,” Zhdanov told Phys.org.
Hydrologist Bill Johnson, a co-author and professor of geology and geophysics at the University of Utah, noted that the freshwater extends much farther toward the lake’s interior than scientists typically expect for a terminal lake. “The freshwater underneath it extends so far in towards the interior of the lake and possibly under the entire lake,” Johnson said, according to Gizmodo.
The Great Salt Lake’s surface water can reach salinities up to eight times that of the ocean, making the presence of a deep freshwater system beneath it a striking geological contrast, as reported by Gizmodo.
What We Don’t Know
The February 2025 survey covered only Farmington Bay, a southeastern section of the lake. The full extent and volume of the freshwater reservoir remain undetermined. The research team plans to survey the entire 1,500-square-mile lake footprint to produce a comprehensive volume assessment, according to Gizmodo.
It is not yet clear whether the freshwater is practically accessible for extraction, how quickly it recharges, or what its precise relationship is to the regional aquifer system. The study also does not address whether drawing from the reservoir could have unintended consequences for the lake’s already fragile hydrology.
Why It Matters
The discovery has immediate practical implications. The Great Salt Lake has been rapidly shrinking for decades, exposing hundreds of square miles of lakebed. The resulting dust contains toxic metals and poses a public health risk to millions of Utah residents, according to ScienceDaily. If the freshwater beneath the lake can be accessed, it could potentially be used to dampen hazardous dust hotspots on the exposed playa.
Beyond Utah, the airborne electromagnetic methodology demonstrated in the study could be applied to other shrinking saline lakes around the world, offering a new tool for subsurface water resource assessment in arid regions, as noted by Phys.org.