The appearance of unusual ‘islands’ covered in reeds on the Great Salt Lake’s drying playa has been linked to a hidden network of underground freshwater. Extensive surveys conducted by scientists, including Bill Johnson from The University of Utah, reveal that this underground system is supplying fresh water to mounds that support thriving plant life. This discovery could significantly enhance understanding of the lake’s complex ecosystem, offering insights into its preservation.
The Great Salt Lake is a vital ecological resource in the United States. Scientists have been monitoring its declining water levels since the 1980s, with 2022 marking a record low. As the water diminishes, the lake’s salinity increases, disrupting the delicate balance necessary for sustaining life. The consequences extend beyond ecological concerns; as the lake dries, sediment from the lakebed becomes airborne, impacting nearby communities.
Determining the sources of water feeding the Great Salt Lake is crucial. While most water originates from rainfall and surface runoff, the role of groundwater remains uncertain. To investigate further, Johnson and his team have employed various methods, including nested piezometers and salinity profiles. In February 2025, they intensified their research by partnering with Expert Geophysics to conduct aerial electromagnetic surveys over Farmington Bay. These surveys analyze magnetic fields to create a 3D reconstruction of subsurface features.
The data indicates that the freshwater reservoir may extend down more than 3,000 meters (10,000 feet) below the surface. Initial measurements suggest that the water is freshest at the center of the mounds, becoming saltier as it moves outward. Johnson cautions against hyping this discovery as a water resource, emphasizing its fragility and the need for careful management.
“The last thing we wanted to do is for this to be characterized as a water resource we should be tapping,” Johnson stated. “It’s much more fragile than that, and we need to understand it better.” He believes this reservoir could play a role in mitigating dust generation from the exposed playa, an issue that affects local air quality.
The findings were presented at the Goldschmidt conference in July 2025, showcasing the potential of this underground freshwater system. Understanding its dynamics is essential for the future of the Great Salt Lake and the surrounding communities. As researchers continue their efforts, the implications of this discovery may offer a path toward better management of one of America’s most critical ecosystems.
