Under the Great Salt Lake playa lies a potentially vast reservoir of pressurized freshwater that has accumulated over thousands of years from mountain-derived snowmelt, according to new research from University of Utah geoscientists. This groundwater occupies the pore space in sediments that fill the basin west of the Wasatch Mountains and below a 30-foot-thick salty layer. Windows through this salt lens exist in the form of odd circular reed-choked mounds or islands that have formed where the freshwater pipes through to the lakebed of Farmington Bay, which is otherwise left dry by receding water levels thanks to drought and diversions.
Funded by the Utah Department of Natural Resources and the Great Salt Lake Commissioner’s Office, a team led by U hydrologists Bill Johnson and Kip Solomon working with the U.S. Geological Survey Water Science Center and the Utah Geological Survey is conducting a multi-prong investigation of this invisible body of water, using an array of instruments and methods to determine its depth and breadth, chemical properties, age, source and other characteristics.
“Fresh water exists under the periphery of the lake and maybe even under the lake itself. And we need to better characterize it to understand how we can use it as a resource,” said Johnson, a professor of geology and geophysics. While he does not view the aquifer as a potential water source for replenishing the depleted lake, Johnson believes it could provide water for restoring lakebed crusts that naturally prevent exposed sediments from contributing to dust storms blowing into Wasatch Front cities.
“We proposed that for higher elevation dust spots, you drop a well and flood the area and douse the dust spot. What we’re trying to check out is whether we can use a modest amount of that water without weakening the nice upward pressure,” Johnson said. “That needs to be checked out and we proposed to do some of that work.”
Artesian water under the lakes appears to be ancient
The Great Salt Lake started taking its present shape about 8,000 years ago as a remnant of the vast freshwater Lake Bonneville that once covered most of northwestern Utah. Johnson suspects some of the water contained in the aquifer dates back to the Bonneville era.
“The age of the water at depth is thousands of years old. It may be left over from the Ice Age,” he said. “That tells us that playa groundwater is not getting to the lake anytime soon. We know from complementary to-be-published studies that there is a big groundwater flux coming off the mountain front, but it seems to get to the lake via seepage to incoming rivers rather than via direct groundwater inflow in the playa.”
The first of several anticipated papers associated with the project was posted last month, reporting the results of piezometer data collected at mounds forming in Farmington Bay, sandwiched between the Great Salt Lake’s southeast shore and Antelope Island. These findings are upending scientists’ understanding of how spring runoff reaches the terminal lake.
About 9 meters below the playa, there is a freshwater-saltwater interface that was previously unknown and researchers now call the “saltwater lens,” according to lead author Ebenezer Adomako-Mensah, a graduate student in Johnson’s lab.
Read the full story by Brian Maffly in @ The U.