The Bonneville Salt Flats have shrunk by 75% in the last 100 years, and they could vanish entirely by the end of the century, new research has found.
The flats — beloved by land speed racers, endurance runners, hobbyist rocket launchers and Instagram photographers — are losing about 1 square kilometer, or around 250 acres, per year, according to a study published this month in the journal Geomorphology. At that rate, the flats could completely disappear sometime between 2072 and 2126.
“The rate of decline definitely surprised me,” said Mark Radwin, lead author of the research who completed a Ph.D. in geology at the University of Utah this summer. “That’s potentially within my own lifetime.”
Once thought to be a remnant of the ancient Lake Bonneville, the salty expanse east of Wendover actually formed millennia after the Ice Age lake dried up. Lake Bonneville evaporated about 13,000 years ago. The salt flats, meanwhile, are only about 5,000 years old, created by dense, briny groundwater accumulating near the surface. They currently cover 35 square miles. But a drying West and human disruption have caused the salt crust’s size and volume to rapidly decline.
Radwin analyzed hundreds of satellite images of the Bonneville Basin to better understand the evolution of the region’s salt crusts. Satellites collect the unique light wavelengths emitted by halites, or salts.
“Every material has its own color fingerprint,” Radwin said. “We can get at that color fingerprint and use that to map out specific material types.”
He also reviewed photographs dating back to the 1940s, and a map created by the U.S. Geological Survey of the Bonneville Salt Flats in 1925.
“There’s some uncertainty in how well they could have done just mapping on foot in 1920s,” Radwin said, “but it does give us a nice reference. ... And their map shows that the salt [crust] was much, much larger than it is today.”
The Bonneville Salt Flats aren’t the only salt formation in Utah’s west desert that Radwin found is shrinking.
The Newfoundland Basin crust, which is much bigger and thinner than the Bonneville Salt Flats, is losing an average of 1.5 square miles each year.
That salt pan formed in the late 1980s, after Utah’s leadership pumped water from the Great Salt Lake into the west desert to control catastrophic flooding.
(Christopher Cherrington | The Salt Lake Tribune)
“They actually pumped out about 10% of the salt that was in the Great Salt Lake,” Radwin said. “Now there’s a massive human-made salt crust out in the Newfoundland Basin.”
That saline crust currently covers around 310 square miles, but will likely disappear between the years 2154 and 2353 if its shrinking pace continues.
And after adjusting for the considerable size difference between the two crusts, Radwin found the rates of decline are similar — which means the Bonneville Salt Flats must also be losing a lot of salt volume per year, since they are considerably thicker.
After decades of reports noting the Bonneville Salt Flats’ decline, the Bureau of Land Management and the neighboring Intrepid Potash mine began pumping nearby groundwater, mixing it with leftover mining salts and flooding the flats in attempt to regrow the crust. The process, called “salt laydown,” started in 1997, and has continued nearly every winter since.
(Francisco Kjolseth | The Salt Lake Tribune) The Bonneville Salt Flats were temporarily flooded each winter for decades through a process called "salt laydown" as seen Friday, Jan. 27, 2023. The Bureau of Land Management has paused the flooding after recent studies showed it was likely further contributing to the salt crust's decline.
Radwin’s research showed the flats briefly reversed their decline between 2000 and 2009, soon after laydown began. But the shrinking started again after that period, even as the salt flat flooding continued.
Other recent studies led by the U. found the laydown process probably backfired. Combined with groundwater pumping for the potash mine, it likely drained the aquifers surrounding the salt flats, causing groundwater that created the formation to flow away.
“They’ve been drawing so much water that they’ve significantly altered the local hydrology in that region,” Radwin said.
A spokesperson for the BLM confirmed the agency paused laydown in 2024 and 2025.
“We remain committed,” the spokesperson wrote in an email, “to identifying new and more effective strategies to preserve this unique landscape.”
Loss of the salt crusts also raises questions about where all the salt is going. While Radwin’s study did not address that point, he has his suspicions.
In the Newfoundland Basin, it’s mostly a natural process. Snowmelt likely runs down the Newfoundland Mountains and flows over the crust, moving the material to its original source.
“It’s very possible, and suggested by satellite imagery,” Radwin said, “that a portion of the salt is being transported via surface water [and] flowing back into the Great Salt Lake.”
The Bonneville Salt Flats’ decline, meanwhile, is likely due to human activity.
(Francisco Kjolseth | The Salt Lake Tribune) (Francisco Kjolseth | The Salt Lake Tribune) Intrepid Potash's brine canals near the Bonneville Salt Flats.
“We know there’s a really massive mining operation” next door, Radwin said. “The mine has been cooperative with restoration efforts, but the scale of their operations has a significant impact.”
Radwin’s study also looked at the Pilot Valley crust, a natural salt pan that seasonally comes and goes depending on the water cycle. While variable year to year, its crust typically covers around 10 square miles when present. Located in a remote section of the Bonneville Basin with little human interference, the crust has seen no long-term trends of decline. During dry periods, its salt sinks into the subsurface, then the crust reforms again in wet periods.
“That system seems to be healthy,” Radwin said.
Pilot Valley also shows salt laydown could still theoretically work to build up the Bonneville Salt Flats again, Radwin found, as long as the water comes from somewhere other than aquifers immediately around them.
“We have learned more about salt dynamics, what controls salt growth events and what controls salt dissolution events,” Radwin said. “It really is water availability. Wet years are good for salt.”
But, as with discussions about saving the nearby Great Salt Lake, finding an extra source of water in the desiccated Great Basin is an increasingly difficult task.
“There’s no real good answer,” Radwin said.
He starts a new job at the Utah Geological Survey this week to help the state search for solutions.