Great Salt Lake is rapidly shrinking, and experts say that they finally know why

In 2022, the Great Salt Lake – celebrated as the largest saltwater lake in the Western Hemisphere – dropped to unprecedented low levels. 

This alarming decline has triggered widespread concerns in Utah regarding the lake’s economic value, ecological significance, and potential threats to public health.

Guiding decisions about Great Salt Lake

A new study from Portland State University (PSU) represents the first peer-reviewed effort to quantitatively assess the contributing factors behind Great Salt Lake’s record-low water volume. 

According to the researchers, this detailed analysis is critical for predicting and guiding future decisions about lake management.

“The lake has a lot of social and economic relevance for the region and Utah,” said Siiri Bigalke, the lead author of the study and a PhD candidate in PSU’s Earth, Environment and Society program. 

Bigalke’s research builds upon earlier work conducted during her master’s studies at Utah State University.

Far-reaching importance of Great Salt Lake

Bigalke highlighted the multifaceted significance of the Great Salt Lake. “It provides over $1.9 billion in annual economic revenue, serves as a vital feeding ground for millions of migratory birds and enhances snowfall over the Wasatch Mountain Range.” 

The Wasatch Range hosts 11 ski resorts, and the Winter Olympics will return to Salt Lake City in 2034. The lake influences weather patterns that sustain this recreation and tourism. A compromised lake could have extensive repercussions.

Yearly changes in lake volume

Bigalke collaborated with co-authors Paul Loikith, an associate professor of geography and director of PSU’s Climate Science Lab, and Nick Siler, an associate professor in Oregon State University’s College of Earth, Ocean, and Atmospheric Sciences.

The team developed a model to track the lake’s annual water volume fluctuations. This model incorporated water inputs – primarily from streamflow and precipitation – as well as water loss from evaporation.

“We developed a model that created alternate scenarios where only one of the input or output variables changed as observed in order to isolate the relative contributions of streamflow, precipitation and evaporation to the record low volume in 2022,” Bigalke explained.

Causes of the lake’s decline

The commonly cited cause of the lake’s decline is reduced streamflows in its three major tributaries, driven by a combination of drought, water diversions, and climate change. 

While the PSU study confirmed that shrinking streamflows accounted for about two-thirds of the total water volume drop, it also identified another critical factor: increased evaporation resulting from rising temperatures.

Warmer conditions intensify the rate at which water evaporates off the lake’s surface. This effect, already significant, is likely to worsen over time if temperatures continue to climb.

“As the climate is warming, evaporation off the lake increases, so the contribution from warming to the evaporation is significant,” Loikith said. 

“Without the warming trend, 2022 wouldn’t have been a record low. Even though streamflow is dominant, the increase in evaporation was necessary to reach the record low.”

Short-term rebound vs. long-term pressures

Although boosting streamflows through measures like water conservation could temporarily help the lake recover some of its lost volume, the longer-term picture is more troubling. 

The escalating heat linked to climate change is expected to further intensify evaporation, potentially outpacing any near-term improvements.

Health risks of a shrinking lake

Beyond economic and ecological losses, a shrinking Great Salt Lake also poses serious health concerns for the roughly 1.2 million residents in the Salt Lake City metro region. 

As more lakebed is exposed, dust events could become more frequent, degrading air quality and carrying toxic particles.

“As the lake shrinks, it’s exposing this dry lakebed that could possibly increase dust events into the metropolitan area, affecting the air quality for nearby residents,” Bigalke noted.

Future directions and key questions

The study authors call for further research to determine precisely how much each factor – rising evaporation, shifting precipitation, and human-driven water diversions – impacts the flow of water into the lake.

This knowledge is pivotal for crafting policies that effectively address the lake’s ongoing decline.

The PSU-led team believes that understanding these variables can help officials plan for a range of scenarios. This is especially crucial in regions susceptible to drought and extreme weather events, where the lake’s status could shift rapidly.

Managing a critical resource

The Great Salt Lake’s record low in 2022 stands as a stark reminder of how climate change and resource management decisions intersect. 

Policymakers, conservationists, and local stakeholders must collaborate to safeguard the lake for future generations, balancing economic demands with ecological sustainability.

Ultimately, the lake’s future hinges on measures that address water scarcity, curtail water diversions, and mitigate the effects of global warming. The research highlights the urgency of these efforts and the consequences if they are delayed.

The study is published in the journal Geophysical Research Letters.

Image Credit: NASA Earth Observatory 

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