Hidden Freshwater Reservoir Found Under Great Salt Lake

Beneath one of America's saltiest lakes lies an unexpected treasure: a vast reservoir of ancient freshwater that could help solve a modern environmental challenge.

University of Utah geoscientists discovered a large, pressurized body of freshwater hidden beneath the Great Salt Lake's dried lakebed. The water has accumulated over thousands of years as snowmelt from nearby mountains seeped deep underground, filling tiny spaces within sediments trapped below a 30-foot-thick layer of salt.

The discovery happened almost by accident when researchers noticed strange circular mounds covered with reeds dotting Farmington Bay. These small islands mark spots where pressurized freshwater breaks through the salt barrier and reaches the surface. As drought and water diversions have dried much of the area, these features have become even more visible against the exposed lakebed.

Graduate student Ebenezer Adomako-Mensah and professor Bill Johnson spent two years drilling wells and installing instruments to measure water pressure and flow. Their measurements revealed something unexpected: about 30 feet below the surface, there's a clear boundary where freshwater meets saltwater, forming what scientists now call the "saltwater lens."

Some of this underground water may date back to the Ice Age, possibly left over from Lake Bonneville, the massive freshwater lake that once covered most of northwestern Utah about 8,000 years ago. Chemical analysis and age testing are still underway to confirm the water's origins and characteristics.

While Johnson doesn't see the aquifer as a way to refill the shrinking lake itself, he believes it offers something equally valuable. The water could help restore dried lakebed crusts that naturally prevent exposed sediments from creating dust storms. These dust events have increasingly threatened air quality in nearby Wasatch Front cities as the lake continues to shrink.

The team is now mapping the full extent of the aquifer to understand how deep and widespread it is. They're also studying whether water can be extracted carefully without reducing the natural upward pressure that creates those protective surface crusts.

The Bright Side

This discovery challenges assumptions that have guided water management in the region for decades. Scientists previously believed spring runoff moved directly through the landscape into the lake. Now they know much of it travels underground through complex pathways, sometimes taking thousands of years to complete its journey.

The research, supported by the Utah Department of Natural Resources and the Great Salt Lake Commissioner's Office, represents a collaboration between the University of Utah, the U.S. Geological Survey, and the Utah Geological Survey. Their first paper was published last month, with more findings expected as the team continues to characterize this hidden water system.

Understanding this underground reservoir opens new possibilities for protecting both water resources and air quality in a region facing increasing environmental pressures.