Bill Johnson, an assistant professor in the Department of Geology & Geophysics, was after the world’s most elusive mystery. Most recently, he has been researching the circular mounds cloaked with invasive phragmites along the southeast shore of Great Salt Lake. These mounds, big enough to be titled mystery islands, are what first piqued Johnson’s interest. He thinks they might be tied to a subsurface plumbing system that feeds new groundwater into the lake and adjacent wetlands.
In recent years, scientists have discovered at least 18 of these man-made mounds still lining the shoreline. Johnson’s archaeological work focuses on one specific mound, called Round Spot 9. His team has strategically installed three sets of four piezometers at varying distances from the edge of this 250-foot-diameter island. These piezometers are able to monitor subsurface water pressures and gradients under the mound at various depths and locations around the mound.
In the past, direct groundwater discharge was estimated to only add 3% of water into the lake’s total water budget. However, emerging data from Johnson’s team indicate that this figure may be significantly higher, with estimates suggesting that groundwater discharge could account for as much as 12% of the lake’s water budget. The team has found the freshwater in large quantities so far, finding it every time they look in dense sediments 30 feet below the surface.
To better understand the makeup of this groundwater, Johnson’s team is using isotope analysis. This technique will help determine the age of the groundwater and the elevation at which it was recharged, providing insight into its origins and movement beneath the lake.
Then, in February 2025, Johnson made a radical move to increase his research influence. He called in the expertise of Expert Geophysics to conduct airborne electromagnetic surveys over Farmington Bay. Surveys are being conducted with a large, circular device flown from a helicopter. Their overarching aim is to obtain critical baseline data on the geological characteristics and makeup beneath the lake. Early results indicate that sediment in this region could exceed 10,000 feet deep.
Photo via Utah State University Johnson proposes that hundreds of groundwater-fed oases exist under Great Salt Lake’s revealed playa. These oases are vital to supporting the region’s rare and beautiful ecosystem. Their importance to wildlife and vegetation cannot be understated.