Utah's Fabled Great Salt Lake Is Shrinking

By: Mark Mancini  | 
Utah's Great Salt Lake is a remnant of prehistoric freshwater Lake Bonneville, which once covered much of western Utah. It's the largest saltwater lake in the Western Hemisphere, and one of the saltiest bodies of water in the world. MaxPixel (CCO Public Domain)

In the hot summer of 2021, one of America's most spectacular lakes has been in the news and the reason for that is not good.

Salt Lake City, Utah, is just a short road trip away from its natural namesake, a large body of water known as the Great Salt Lake, or the "GSL." Filled with around 4.5 to 4.9 billion tons (4 to 4.4 billion metric tons) of dissolved salt, the lake has certain areas that are roughly 10 times saltier than the ocean.


Utah residents have gotten used to the GSL's inconsistent size.

It's always shallow, that much is a given. Throughout recorded history, no part of the Great Salt Lake has exceeded 44.6 feet (13.6 meters) in depth. Summer heat takes its toll; the water is typically 1 to 2 feet (0.3 to 0.6 meters) higher in May, June and July than it is in the fall and early winter.

Some years are gentler than others. At its maximum recorded size, the Great Salt Lake expanded to cover an area of over 2,300 square miles (5,956 square kilometers), making it bigger than the U.S. state of Delaware.

We are currently witnessing extremes in the opposite direction. Right now, the GSL is shrinking.

Scientists keep tabs on the lake's fluctuating surface elevation. On Tuesday, July 20, 2021, this fell to just 4,191.4 feet (1,277.5 meters) above sea level, tying the lowest GSL surface elevation ever recorded.

And that wasn't the end of it. Over the following weekend, the United States Geological Survey announced that the water level in the southern part of the lake had dropped even lower, a worrying development for conservationists.


Last Stop (For Salt)

"GSL is what's called a terminal lake. It means there's no outlet leading out of Great Salt Lake," explains Jaimi Butler, a field biologist at Westminster College in Salt Lake City.

Fresh water flows into the lake through the Bear, Webber and Jordan rivers, among other routes. However, unlike a body of water such as Lake Superior, for example, the Great Salt Lake isn't connected to any outgoing waterways.


"There are 22,000 miles (35,405 kilometers) of watershed and they're all draining into this basin that is Great Salt Lake," notes Butler. "The only thing that can leave is water through evaporation."

This incoming water naturally carries small amounts of salt and other minerals along for the ride. Yet in a terminal lake such as the GSL, those materials have no place to go. Unlike the water which ferried them over, they can't just evaporate away. So over time, they accumulate — making the lake saltier and saltier.


How the Other Half Lives

"The Great Salt Lake proper is this hypersaline lake that has two pieces; there's a north arm and a south arm," says University of Utah geologist William Johnson.

Separating the two is the Southern Pacific Transportation Co. (SPTC) causeway. Finished in 1959, this railroad cuts right through the Beehive State's signature lake.


Being a solid structure full of rocks, it doesn't allow much water to circulate between the northern and southern ends of the lake.

According to an article Johnson and his colleagues wrote for the book "Encyclopedia of Water: Science, Technology, and Society," over 90 percent of all the freshwater runoff that the Great Salt Lake receives enters the south arm.

With the SPTC causeway now impeding its water flow, the north arm is not only denser, but it also has an incredibly high salinity ("salt content") of 16 to 29 percent. Compared to the south arm — whose salinity can fall into the single digits — this is a pretty intense environment.

The Great Salt Lake captured by the Copernicus Sentinel-2, an Earth observation mission launched in 2015. The distinct color differences are caused by the railroad line, which is visible cutting across the top part of the lake. It acts as a dam, preventing the waters from mixing, causing the north basin to have a much higher salinity than the southern, freshwater side of the lake.
European Space Agency/Flickr (CC BY-SA 2.0)


All About Those Bays

Apart from the north and south arms, the Great Salt Lake includes a handful of bays, like Farmington Bay and Bear River Bay. Most of these are attached to their own wetland systems.

"In some ways, it's really five lakes that are interconnected," Johnson tells us — although he points out that Farmington Bay is "no longer a bay, it's just a stream that's flowing in."


Between the bays, the arms and the incoming water sources, salinity levels vary widely across different parts of the Great Salt Lake. "The GSL is one of the most diverse places on the planet in terms of salt content," Butler says. "It goes everywhere from fresh water to saturated with salt and everything in between."

Which brings us to one of Google's most frequently asked questions about the Great Salt Lake: Are there any fish inside?

"No fish live in the lake," says Michael Vanden Berg of the Utah Geological Survey in an email. "Sometimes, fish will enter the lake via one of three rivers, but will die shortly after. When lake levels are high, fish might be able to survive in places like Farmington Bay (east side of Antelope Island), but can't survive in the lake proper."


Pink Lemonade

None of this is to say that the Great Salt Lake is a desolate, lifeless place. On the contrary: It's a birdwatcher's paradise.

An estimated 17 trillion brine shrimp reside in the GSL, making them an abundant food source for birds. The tiny invertebrates grow up to half an inch, or 1.27 centimeters, long when mature. They periodically lay nutritious eggs called "cysts," which also get eaten. Local brine flies and their larvae make convenient bird snacks as well.


In turn, these little creatures eat algae. By the way, many of the native algae and bacteria species release colorful pigments into the lake.

"Microbes ... can live anywhere and the north arm has so many microbes in it that are colored pink and red and orange that the water looks like pink lemonade," says Butler. South of the SPTC causeway, you'll see green-tinted waters, courtesy of green algae.


Feathered Friends: The Birds of GSL

The Utah state government's official website reports that, annually, "10 million birds from 338 different species come to rest, eat and breed" at the Great Salt Lake. For birds like the eared grebe, it's an essential pit stop on their long migration routes.

Butler tells us that 5 million of these grebes, or "95 percent of the world's population," visit the GSL each year. "There's plenty of brine shrimp and resources for them to eat, even after people harvest [the shrimp] and their eggs for use in aquaculture," she notes.


Then we have the American white pelican, a charismatic bird that treats the GSL's Gunnison Island like a giant nursery. "They nest in the saltiest part of Great Salt Lake on this island," says Butler. Until recently, high water levels kept most predators out. "They trade food for a safe place to raise their young, even if it means traveling 30 to 60 miles [48 to 96 kilometers] to catch fish."

What Comes Next?

Over the past few years, receding shorelines have turned Gunnison Island into a peninsula, where hungry coyotes are now free to wander.

White pelicans have taken notice; in 2019, a preliminary survey found 3,414 pelican nests on Gunnison. That's 66 percent fewer than the 10,000-plus nests documented there in 1992.


What accounts for this downward trend? And why are water levels in the Great Salt Lake hitting record lows this year?

The usual suspects of drought and climate change aren't helping. Another factor — and a major one, at that — is the deliberate removal of fresh water from the GSL's natural sources. "The diversion of water for culinary and other uses is depleting the lake. That's a fact," says Johnson.

"Right now," Butler adds, "the lake is essentially half the size that it would be if we hadn't been diverting water."

"This issue ... affects everybody," she tells us. "I have hope that if we start to take action, good things will follow and there won't be an environmental catastrophe in my backyard."