Scientists Discover Fresh Water Beneath Great Salt Lake’s Drying Bed

Great Salt Lake’s Shrinking Surface Reveals Hidden Fresh Water

Since 1989, Utah’s Great Salt Lake has lost approximately 70% of its surface area, drastically reducing its ecosystem services and exposing vast stretches of drying lake bed (playa). These exposed areas release toxic dust into the air while also providing scientists with unprecedented opportunities to survey what lies beneath the lake’s floor.

A study published in Geosciences has uncovered fresh water and salt water layers just meters below the surface, offering critical clues for conserving the lake—a vital resource for both ecology and the regional economy.

Electrical Resistivity Tomography Reveals Subsurface Water

In 2023, researchers led by Michael Thorne, a geophysicist at the University of Utah in Salt Lake City, employed electrical resistivity tomography (ERT) to detect fresh or salty water at multiple locations near the southern and eastern edges of the Great Salt Lake. Thorne, a coauthor of the study, noted that the lake’s desiccation allowed access to areas that were previously underwater, making measurements impossible.

The team, including lead author Mason Jacketta, conducted extensive fieldwork by placing electrodes into the ground a few meters apart, creating lines that stretched hundreds of meters. By measuring electrical resistance between electrode pairs, they distinguished between salty and fresh water. Salty water, rich in conductive ions, exhibits lower resistance than fresh water. Combined with data on subsurface rock and sediment, as well as nearby well measurements, the ERT data enabled the researchers to map how electrical resistance varied with depth and identify the type of water seeping through underground pores.

The team published their findings on the southern part of the lake in Geosciences. More detailed results about the eastern shore will appear in an upcoming publication.

Fresh Water Found in Unexpected Locations

Elliot Jagniecki, a geologist at the Utah Geological Survey (not involved in the study), emphasized the significance of the findings:

"What this is really showing is that [fresh water is] prevalent all over the place."

The team discovered fresh water near the surface at numerous sites. In some areas, fresh water was found in close proximity to patches of salty groundwater. For example, at one southeastern site, a shallow layer of brine sat atop fresh water just 5 meters below. At the northernmost study site, fresh water was detected around 2 meters deep, while on the southern shore, it was found as shallow as 2.8 meters in some locations.

Mysterious Formations Linked to Subsurface Water

The study also shed light on unusual geological features around the Great Salt Lake, including salt mounds and islands. These formations may be connected to the distribution of fresh and salty water beneath the surface.