Vast Freshwater System Discovered Beneath Great Salt Lake

A new study led by researchers from the University of Utah has identified an extensive underground freshwater system beneath the Great Salt Lake, particularly beneath Farmington Bay and Antelope Island along the lake's southeastern edge. This research revealed freshwater occupying sediments at depths of 3 to 4 kilometers (approximately 10,000 to 13,000 feet) beneath the lake's surface, utilizing airborne electromagnetic (AEM) surveys. The findings, published in Scientific Reports, significantly contribute to understanding the region's hydrological framework and hold important implications for water management strategies.

Discovery and Extent

Researchers from the University of Utah meticulously mapped this extensive freshwater system using airborne electromagnetic (AEM) surveys to analyze geological formations. Lead author Michael Zhdanov highlighted the groundbreaking nature of this work, stating that this research marks the first successful application of AEM technology to detect freshwater beneath the Great Salt Lake's highly conductive saltwater layer.

The team successfully mapped the freshwater's extent beneath Farmington Bay and estimated the depth of water-saturated sediments by identifying the underlying basement structure. This crucial investigation forms part of a broader initiative funded by the Utah Department of Natural Resources, aimed at understanding groundwater beneath the Great Salt Lake.

How the Discovery Was Made

The study was initially prompted by fascinating observations: freshwater was seen emerging under pressure in parts of the exposed lakebed in Farmington Bay, creating circular mounds, 50 to 100 meters across, covered in phragmites reeds.

To investigate further, airborne electromagnetic surveys were conducted by helicopter. These surveys measured electrical resistivity to depths of approximately 100 meters, a technique vital for differentiating between resistive freshwater and conductive saltwater.

In February 2025, a geophysical team completed 10 east-west survey lines, spanning 154 miles across Farmington Bay and northern Antelope Island. The Consortium for Electromagnetic Modeling and Inversion (CEMI) research group developed an innovative method, combining AEM data with magnetic measurements to generate detailed 3D images of the subsurface.

This advanced tomographic model revealed a relatively shallow basement (less than 200 meters) beneath the playa, which then sharply drops to depths of 3 to 4 kilometers directly under some phragmites mounds. This sharp drop indicates a major structural boundary.

Crucially, one reed-covered mound was found to be situated directly above a point where freshwater was actively rising through a break in the impermeable layer beneath the lake.

Key Findings

The research conclusively identified a deep volume of freshwater entering beneath the lake's saline lens. Hydrologist Bill Johnson, a co-author of the study, noted a particularly surprising pattern:

"Freshwater moving towards the lake's interior rather than just its edges—was unexpected, as denser brine would typically be anticipated to occupy the entire volume under the lake, with freshwater confined to the periphery."

Zhdanov emphasized that by understanding the depth, width, and porous space of this newly discovered system, researchers can now calculate its potential freshwater volume.

Implications and Next Steps

The declining water levels of the Great Salt Lake have exposed approximately 800 square miles of lakebed, which has become a significant source of dust pollution containing harmful metals. A critical implication of this discovery is whether this artesian groundwater could be safely utilized to reduce dust in critical areas without excessively perturbing the overall freshwater system.

Johnson and his colleagues are actively seeking additional funding to expand the research and cover a larger portion of the lake. Zhdanov underscored the necessity of surveying the entire 1,500-square-mile Great Salt Lake to fully comprehend the system's true scale and dynamics. Such a comprehensive survey could significantly inform regional water management decisions and provide a valuable model for similar efforts globally to locate vital freshwater resources beneath other terminal lakes.