June 01, 2017

Great Salt Lake Dust Model: Lake Levels and Air Quality

Great Salt Lake dust model spells trouble for Utah if more water is diverted

LEIA LARSEN, Standard-Examiner Staff

While much of the future fallout from a desiccated Great Salt Lake remains unclear, one study is showing Northern Utahns should expect worsening air quality.

The Great Salt Lake hit the brink of a record low last year due in part to human water consumption on the Wasatch Front. With a major diversion planned for the lake’s main tributary, the Bear River, many environmental advocates worry the state’s poor air quality will reach disastrous levels. 

A model developed by Derek Mallia, a graduate student at the University of Utah’s Land-Atmosphere Interactions Research Group, offers a glimpse of what the future might hold.

“Our model is trying to figure out how much dust is coming from our dust sources, such as the Great Salt Lake, and how much it’s going to be impacting ... air quality,” he said.

RELATED: As Great Salt Lake dries up, Utah air quality concerns blow in

Those air quality impacts include reduced visibility, which is problematic for planes and cars. They also include increased particulate matter blowing along the Wasatch Front, like PM 2.5 and PM 10, which is small enough to enter the lungs and bloodstream. From there, it causes all kinds of problems in the body, from asthma and breathing issues to issues with the immune system.

Drying lakes around the world — from the Aral Sea in Central Asia to Owens Lake in California — cause major respiratory health problems for nearby populations. These lakes have no outlet, like the Great Salt Lake, and were desiccated by human diversions. 

The fine silt and salts deposited by streams over millennia mean the dried lakebed is more prone to create blowing dust than the surrounding land area.

“First off, playa (dried lake bed) is very salty. There’s not a lot of vegetation that can even grow on it,” Mallia said. “The second thing is, it’s very fine. Because it’s very fine, it’s easier for it to be lifted up by wind.”

Mallia’s model simulated conditions seen during a particularly bad dust storm March 30, 2010, that blanketed the Wasatch Front with a thick haze and spiked particulate levels for around eight hours. In Ogden, PM 2.5 levels jumped to 90.8 micrograms per cubic meter. In Salt Lake City, they peaked at 250.2 micrograms.

Air becomes unhealthy after 35 micrograms per cubic meter, according to U.S. Environmental Protection Agency regulations.

Mallia modeled what the same dust storm might have looked like if the lake dropped by 8.5 inches — the level of decline the Utah Division of Water Resources projects once the Bear River is dammed to divert around 250,000 acre-feet of water. Construction of the dam project was recently pushed to 2040. 

RELATED: Secondary water metering could push back Bear River dam project

Results are still preliminary, but the model suggests the March 2010 storm’s bad air would have bumped up PM 2.5 levels in Salt Lake City and the storm would have lasted around twice as long. 

Things get worse farther north.

“Because the lake is most shallow across Bear River Bay, that area saw the most exposure of lake bed when we dropped the water by 8.5 inches. Areas like Brigham City saw a large increase of dust,” Mallia said.

The model suggested an increase in particulate pollution levels by around 275 percent in Brigham City if the Bear River were tapped.

Story continues after the graph.

A model of a dust storm on March 30, 2010, shows the event would have been much more intense along the Wasatch Front if the Bear River were diverted or if the Great Salt Lake dried up completely.

A model of a dust storm on March 30, 2010, shows the event would have been much more intense along the Wasatch Front if the Bear River were diverted or if the Great Salt Lake dried up completely.

While Farmington Bay is also shallow and close to a population center, the model showed lower dust impacts to the area. Mallia speculated it could be due to the interplay of that particular March storm’s weather and the bay’s level of friction, but he also stressed that the model only explored a single dust event. 

“I think if you expose any of those bays, you’re going to see dust,” he said.

He also noted that his model only looks at the intensity of dust storms. Further study is needed to understand whether they’ll increase in frequency with a changing lake and changing climate, Mallia said.

A previous study from Brigham Young University found that in fall 2015, around 40 percent of the particulate pollution blowing from dust storms into Ogden and Logan came from the Great Salt Lake. At the time, around 50 percent of the lakebed was exposed.

While losing 8.5 inches of water elevation might sound small, the Great Salt Lake is long and shallow. In 2016, a white paper on Great Salt Lake diversions co-authored by Utah State University limnologist Wayne Wurtsbaugh found losing 8.5 inches would expose 30 more square miles of lakebed. 

The white paper found that to date, existing diversions on the Bear River and the lake’s other tributary rivers — the Weber and Jordan — have dropped the lake by 11 feet, reducing its volume by 48 percent. 

RELATED: Snowmelt raises Great Salt Lake, but climate, diversions continue to take toll

The Bear River currently provides around 60 percent of the water flowing to the lake. Air quality is one of many reasons why the Utah Rivers Council adamantly opposes further diversions from the river.

“It’s a (another) contaminant to add to Salt Lake Valley airsheds that has major impacts on all people, especially sensitive populations — the young, the old and those with ... pulmonary diseases,” said Zach Frankel, executive director of the Utah Rivers Council.

The Wasatch Front and Cache Valley have issues with elevated particulate pollution in the winter and unhealthy ozone levels in the summer. Most of the region’s major dust storms come in the summer and fall, when southerly winds hit cold fronts to the north. 

Dr. Brian Moench of Utah Physicians for a Healthy Environment also opposes the Bear River development because of its implications for air quality. Elevated particulate levels are known to cause major health issues, but there’s more in Great Salt Lake dust to raise alarm.

“That lake has been on receiving end of decades and decades worth of toxic agricultural chemicals,” he said. “In addition ... there’s an undoubtedly heavy concentration of heavy metals like mercury and radioactive isotopes.”

Those contaminants largely come from the region’s industrial past and nuclear testing in the Great Basin.

The Utah Rivers Council also takes issue with estimates for the Division of Water Resource’s estimated amount of lake decline that will come with the Bear River diversion. Frankel pointed to a 1984 Utah State University study that found diverting 300,000 acre-feet from the lake could drop it by around 2.3 feet, not 8.5 inches. 

“The engineer from Water Resources who claims it’s 8 inches has no data whatsoever supporting that claim,” he said. “It’s marketing hype by an agency that’s been the cheerleader of an unnecessary Bear River development.”

The division engineer who developed the 8.5 inches estimate, Craig Miller, said a better figure will likely come from a comprehensive Integrated Water Resources Management Model for the lake that is still in the works. 

Miller also co-authored the white paper showing the lake’s loss of 11 feet due to current diversions. 

“The 8.5 inches came from a Great Salt Lake model I developed for the express purpose of discovering how much diversions and depletions past, present and future affect the lake,” he wrote in an email.

The Utah Division of Water Resources has claimed harnessing Bear River water is necessary to meet the demands of a growing population in Northern Utah. 

Environmental advocates like the Utah Rivers Council claim those needs can be met through conservation and from water freed up as agricultural land is developed into subdivisions. A 2015 legislative audit of the division found it excluded these sources of water in its projections. 

Mallia also used the model to predict what might happen if the lake dried up completely. 

“Most dust events would get a lot worse. The only places that didn’t were Tooele, because it’s probably too far west and not downwind of the Great Salt Lake, and Provo ... maybe because it’s a tad too far away, but that may not be the case for every dust storm,” he said. “On average, (the dust storm) seemed to be twice as bad to three times as bad.”