‘Rivers of chocolate milk’: BYU research finds a troubling trend of sediment pollution into Utah Lake

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Courtesy of Brigham Young University

PROVO (ABC4) – It sounds like something out of a Willy Wonka-ish fantasy, but for researchers at Brigham Young University, the description of water samples taken after a massive wildfire and heavy rainstorm in 2018 were anything but sweet.

“The combination of extreme wildfire and torrential rain caused landslides and flooding that turned the rivers into chocolate milk,” BYU plant and wildlife science professor Ben Abbott recalls of the aftermath of the Pole Creek “megafire” in the fall of 2018. “I mean, it was really amazing to see the amount of sediment that was transported.”

Without having to taste the muddy brown water to see if it was chocolate-flavored (it wasn’t), Abbott and his students realized that the area had suffered massive amounts of erosion due to the severity and size of the megafire that had scorched nearly 100,000 acres around Spanish Fork and Diamond Fork Canyons.

The wildfires were the result of one of the driest summers on record, and the storm was the remnants of Hurricane Rosa, the Category 4 hurricane that made landfall in Baja California. The intense system dropped 3-months’ worth of rain in just a few hours, turning the badly burned area of ash into a bowl of brownie mix ready to flow into a ‘chocolate’ river of sediment.

The research team estimated that this one event caused as much sediment movement into Utah Lake as would normally take 100 to 200 years to occur naturally.

“The reason why that’s of concern is it’ll clog all of the canals and pipelines and catchment dams that we depend on for water supply and flood control. Also, that sediment carries with it ash and organic matter that can degrade water quality. There were fish kills in many of the rivers and when it hit the lake, you could see the ash plume from space,” Abbott explains.

Removing all the extra sediment can be a very expensive process for the water treatment facilities. In addition, the excess of nutrients like nitrogen and phosphorus, which can be helpful in the proper amounts, can result in algal blooms that harm the ecosystem and create toxins unsuitable for drinking water.
While the findings in the wake of a giant fire and a ton of rain were startling, an additional discovery was even more unsettling; the tributaries that run through human-affected areas were even higher in the nutrients that cause algal blooms.

“If you compare the urban and agricultural areas to the burned natural areas, we’re talking about 5 to 100 times more nutrients in those human affected areas,” Abbott illustrates. “We’ve got to remember that the wildfire and flood only lasted a few weeks, but our human footprint is there all the time. That means it has a much larger effect over the course of a year. But day in day out, you have people in the landscape, flushing our toilets, fertilizing our lawns, and having agricultural runoff.”

Looking ahead, if changes aren’t made in human behavior and the treatment of the affected water, the damages could be catastrophic for Utah Lake. With Utah Valley’s population expected to double in the next couple of decades, increased human activity could severely lower the lake’s water levels. Farther north, the Great Salt Lake is reeling from rapidly lowering water levels, Utah Lake could soon follow, creating a bevy of issues for a bustling area.

There’s still time to turn things around, but it’s going to take a combined effort to restore water flow to the lake while also reducing nutrient sources and greenhouse gases. Because wildfire extent has doubled since the 1980s, the only long-term solution is to get serious about climate change, Abbott states.

“In the past, we’ve thought about humans as separate from the environment, but as the population grows, and as the environment is changed more and more, it is crystal clear that human wellbeing depends on how well we’re taking care of the environment around us,” he explains. “It literally is our home, so we need to be thinking ahead so we can reduce our nutrients and conserve water.”

After all, the basic law of ecology is that “everything is connected,” Abbott shares.

While it may sound fun to imagine a river of chocolate, the reality is such a thing should be saved for the magic of the books and movies inspired by Roald Dahl’s works.

Besides, things didn’t bode well for Augustus Gloop, who was way too excited about the river of chocolate, anyway.

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