The good folks at NASA never miss a chance to let us know when vital bodies of water around the world are shriveling up and vanishing. First it was Lake Mead. Then it was the Aral Sea.

Now it’s poor Utah’s turn.

Earlier this week, NASA’s Earth Observatory posted satellite images showing the dramatic decline of Utah’s Great Salt Lake over the past five years. As the two images below from 2011 and 2016 show, water levels at Farmington Bay have plummeted, exposing three-fourths of the lakebed and threatening a key waterfowl habitat:

 (NASA Earth Observatory images by Joshua Stevens, using Landsat data from the U.S. Geological Survey)

Suffice to say, that’s not good. The Great Salt Lake is one of the natural wonders of the West. It’s a terminal bay, which means rivers and streams flow in, but there’s nowhere for water to leave — except through evaporation. As a result, the minerals left behind just keep piling up. Today, the lake’s water is three to five times saltier than the ocean’s, creating a rich ecosystem that sustains brine shrimp, millions of migratory birds, waterfowl hunting, and so on. Mineral industries rely on it. It’s a key part of Utah’s economy, worth some $ 1.2 billion per year.

Why the Great Salt Lake is drying up and shrinking

But the lake is now in trouble. Ever since the first pioneers arrived in 1847, humans have been diverting more and more water from the rivers and streams that would otherwise feed the Great Salt Lake. Today, about 40 percent of that water gets used instead by farms, cities, and industry — causing the lake to recede.

The problem has only been exacerbated of late by brutal droughts (the sort of droughts, note, that are likely to get worse as global warming continues). Water levels in the lake are currently about 11 feet below their historic levels:

 (Wurtsbaugh et al, 2016)

A recent paper, led by Utah State University’s Wayne Wurtsbaugh, warns that if water diversions continue to increase, it’s not impossible to imagine the lake drying up completely. The same thing happened to southern California in the 1920s, when water diversions to Los Angeles desiccated Owens Lake.

When a lake like this goes dry, things can get ugly. The paper notes that Los Angeles has spent at least $ 1.3 billion since 2000 dealing with dust from the exposed Owens Lake lakebed — a major source of harmful particulate pollution that causes asthma and other lung ailments. Utah has already gotten a taste of this future: back in August 2015, a massive (and deadly) dust storm engulfed Salt Lake City.

And that’s just the start. If the lake keeps drying up, the paper notes, the region’s $ 57 million brine shrimp industry will wither. Water fowl will start to disappear, crippling the region’s $ 70 million hunting industry. Industries that harvest brine or minerals from the lake, like Morton Salt, will also suffer.

Can Utah save the Great Salt Lake?

The way to avoid this dire scenario is straightforward: stop diverting so much water from the lake. There’s some reason for optimism here: Wurtsbaugh and his colleagues note that per capita water use in cities dropped 18 percent between 1989 and 2000 (though overall urban water use is up 5 percent, as the population has grown). Conservation is possible; humans are surprisingly good at it when they have to be.

But the real challenge will be convincing farmers, who account for 63 percent of the region’s water use, to join in the conservation efforts. There’s also a debate around nascent plans to develop of Bear River, which is the biggest river feeding the lake. An effort to divert drinking water from that river for fast-growing cities and towns in the Wasatch Front could shrink lake levels an additional 8.5 inches, officials have said.

So it’s your standard tragedy of the commons. Here’s how Wurtsbaugh and his colleagues conclude: “We must be willing to make decisions now that preserve Great Salt Lake’s benefits and mitigate its negative impacts into the coming centuries.”

As water journalist John Fleck told me in this recent interview, states and localities in the American West have actually been surprisingly good at responding to tragedy of the commons-type problems over the past few decades. The Great Salt Lake is going to be an important test case here. Because the last thing anyone should want is to replicate what happened to the Aral Sea.

Further reading

— Seriously, the disappearance of the Aral Sea is an excellent warning for what happens when you let a once-vibrant lake go dry.

— Everyone’s worried the West is running out of water. The reality is more complicated.

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