A recent study suggests the presence of a significant freshwater reservoir beneath the Great Salt Lake, despite its name deriving from its saline waters.
Researchers at the University of Utah have employed a helicopter to conduct an airborne electromagnetic (AEM) survey over parts of the lake, particularly in the Farmington Bay region on its southeastern edge.
The AEM survey serves a dual purpose: it measures electrical conductivity to distinguish saltwater from freshwater and examines rock compositions. This data can reveal the location and depth of any freshwater bodies.
The survey revealed a sudden and significant reduction in the depth of the bedrock beneath the Great Salt Lake. This creates a large cavity filled with sand and silt, which appears to be saturated with freshwater.
“We were able to answer the question of how deep this potential reservoir is, and what its spatial extent is beneath the eastern lake margin,” says geophysicist Michael Zhdanov.
“If you know how deep, you know how wide, you know the porous space, you can calculate the potential freshwater volume.”
The research team estimates that the freshwater reservoir might extend between 3 and 4 kilometers (nearly 2.5 miles) deep. However, a comprehensive survey of the entire Great Salt Lake is necessary to confirm this, as only a small portion was examined.
Previously, it was suspected that freshwater could lie beneath the Great Salt Lake, partly due to the emergence of reed-covered islands in the basin. This study marks the first serious effort to determine the size of this freshwater reserve.
Although the existence of freshwater was anticipated, its extensive coverage came as a surprise. The AEM survey showed the sediment-holding bedrock ‘bowl’ extending deeper into the Farmington Bay playa than initially thought.
Freshwater presence near the lake’s edges is expected, as it flows down from surrounding mountains. However, the data indicates significantly more freshwater is spread across the lake’s approximately 2,500 square kilometers (950 square miles).
“The unexpected part of this wasn’t the salt lens that we see near the surface across the playa,” Johnson explained on Utah radio station KPCW’s Cool Science Radio show recently.
“It’s that the freshwater underneath it extends so far in towards the interior of the lake and possibly under the entire lake. We don’t know.”
The researchers believe this water could be beneficial: as the Great Salt Lake continues to evaporate, pollution from the dust becomes a growing health issue for nearby communities.
This dust frequently blows into Utah’s urban areas, carrying toxic metals. Applying freshwater might help reduce this issue.
“There are beneficial effects of this groundwater that we need to understand before we go extracting more of it,” says hydrologist Bill Johnson.
“A first-order objective is to understand whether we could use this freshwater to wet dust hotspots and douse them in a meaningful way without perturbing the freshwater system too much.”
The researchers are actively seeking funding to expand the AEM survey and further explore the lake. They aim to map the boundaries of the sudden bedrock drop.
Understanding the extent of freshwater storage could aid water resource planning and provide insights into similar lakes globally that may also contain hidden reservoirs.
Related: Strange Living Islands Have Appeared on The Great Salt Lake, And Now We Know Why
The same techniques could be applied to other sites and the remainder of the Great Salt Lake, using magnetic readings to estimate rock depths and electrical conductivity readings to identify freshwater areas.
“This is why we need to survey the entire Great Salt Lake,” says Zhdanov. “Then we’ll know the top and the bottom.”
“We use different techniques to study the vertical extent of these freshwater-saturated sediments, to find the depth to the basement.”
The research has been published in Scientific Reports.
