- Scientists find reed-covered mounds hiding fresh groundwater.
- Electromagnetic surveys reveal a vast underground plumbing system.
- Research explores whether groundwater could reduce dust pollution.
Friday, September 5, 2025 — As the Great Salt Lake continues to shrink, scientists are uncovering unexpected features
emerging on the exposed playa.
A playa is the flat, often cracked surface left behind when a lake dries up. At the Great Salt Lake, the playa is the exposed lakebed that appears as water levels drop, creating dusty, salt-encrusted ground that can be carried by the wind.
Reed-covered mounds have appeared along the southeast shore, puzzling researchers for years. University of Utah geologists now believe these circular islands form at spots where fresh groundwater is pushed upward under pressure, creating hidden oases in the drying lakebed.
Professor Bill Johnson of the Department of Geology and Geophysics described the phenomenon during a visit to a mound known as Round Spot 9. He explained that water may spend long periods underground before surfacing in the lake, though the exact pathways remain unclear. Using piezometers to measure underground pressures, Johnson and graduate student Ebenezer Adomako-Mensah are tracking how water moves beneath the playa.
Mapping Beneath the Surface.
In February 2025, Johnson partnered with Expert Geophysics, a Canadian company, to conduct airborne electromagnetic surveys over Farmington Bay. A helicopter equipped with specialized instruments collected data that will help create a three-dimensional image of the subsurface. Researchers hope the results will reveal the boundaries between fresh and saline water and pinpoint locations where groundwater springs emerge.
The work comes at a critical time. As lake levels remain low, exposed sediments contribute to windblown dust that can harm nearby communities. Earlier studies by atmospheric scientists showed that when submerged, lakebed crusts can reform and reduce dust emissions. Johnson’s research will investigate whether groundwater flows can help restore these fragile surfaces.
A Complex Water Budget.
Groundwater has long been considered a minor part of the Great Salt Lake’s water supply. Estimates once placed it at just 3 percent of the total budget. However, recent studies suggest it may account for as much as 12 percent. Johnson’s team has already located freshwater beneath areas once believed to contain only saline water.
Preliminary data show freshwater deposits at various depths, in some cases up to 30 feet below the surface. These findings suggest the presence of a deep reservoir, potentially extending thousands of feet underground. Still, researchers caution against viewing this as a new water supply to exploit. Johnson emphasized that the system is fragile and must be understood before any practical uses are considered.
Collaboration and Next Steps.
The project involves several senior University of Utah geologists. Kip Solomon’s lab is analyzing isotopes to determine the age and origin of the groundwater, while Mike Thorne is constructing resistivity profiles to refine subsurface mapping. Michael Zhdanov and Michael Jorgensen are processing the airborne survey data to build detailed models.
Together, the team seeks to uncover how much groundwater exists, where it originates, and whether it plays a larger role in the lake’s hydrology than previously recognized. The research has received preliminary funding from the Utah Department of Natural Resources.
For Johnson, the work is personal. Years ago, while crossing the North Arm of the lake, he noticed water and gas bubbling from a circular patch twice the size of his airboat. He has pursued the mystery ever since. With new tools and growing urgency around the lake’s decline, he and his colleagues are closer than ever to understanding what lies beneath the Great Salt Lake.
Citation:
University of Utah. “Scientists stunned as strange islands and hidden springs appear in the Great Salt Lake.” ScienceDaily. August 31, 2025. www.sciencedaily.com/releases/2025/08/250831010526.htm.
Image is AI-generated.
