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By Tom Howarth
Science Reporter (Nature)
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Lake Powell, an iconic centerpiece of the Colorado River Basin and the second-largest reservoir in the United States, is facing an escalating crisis as decades of sediment buildup threaten its future.
Created in 1963 by constructing the Glen Canyon Dam, Lake Powell was intended to be a critical water storage reservoir for the arid western United States. Sixty-one years later, sedimentation has reduced the lake's storage capacity by nearly 7 percent, with an estimated "30,000 dump truck loads of sediment" settling daily, according to the Glen Canyon Institute (GCI).
"In the long term, sedimentation is a very serious problem at Lake Powell," Eric Balken, executive director of the GCI, told Newsweek. "When Glen Canyon Dam was built, the Bureau of Reclamation told the public it wouldn't silt in for 700-1,000 years. Now we know that's not true."
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According to Balken, the dam, which traps sediment, stopping it from flowing downstream, could need to be dredged or reengineered within the next 40–50 years.
"In the near term, with low reservoir levels, we could see major sediment problems in the next decade," Balken said.
This sediment buildup has triggered a cascade of impacts throughout the Colorado River ecosystem. Toxic heavy metals like arsenic and lead are trapped within these sediments rather than flowing out to sea.
As water levels drop as a result of prolonged drought, concentrations of these harmful materials increase, posing greater risks to fish, wildlife and people.
Downstream, beaches at the river's mouth are eroding, as sand, meant to replenish coastal areas, remains trapped in Lake Powell and Lake Mead, another struggling reservoir further along the river.
Within the river channels, a process known as "aggradation"—the accumulation of sediment where the river slows—has caused sediment to build up upstream, reaching heights hundreds of feet above the current reservoir level and burying large stretches of the Colorado River and its tributaries.
With no immediate solution, sediment continues to pour into the lake.
On Friday, the National Park Service reported a landslide of about 300 to 350 meters of shoreline from the river's left bank into the channel. The slide created new rapids at the entry point, with sediment and mud continuing to shift, altering river conditions along a three-mile stretch upstream.
Lake Powell's immense size means sedimentation does not immediately threaten the Glen Canyon Dam itself. However, experts are pressing for proactive measures.
The GCI, advocating for restoring Glen Canyon and allowing a free-flowing Colorado River, warns on its website that "the longer we wait to address the temporary nature and ultimate risks of Glen Canyon Dam, the more costly it will become. The true and staggering costs of sedimentation will ultimately be borne by the next generation unless practical solutions are developed now."
"What can be done? Eventually, Glen Canyon Dam will have to be reengineered in one form or another," Balken said.
"What would make the most sense in our opinion would be to completely bypass Glen Canyon Dam by opening up the old diversion tunnels and building new ones.
"If nothing is done, the dam will silt in, and water delivery to the 25 million people downstream will be compromised. It's just a matter of time."
Do you have a tip on a science story that Newsweek should be covering? Do you have a question about Lake Powell? Let us know via science@newsweek.com.
Update 11/5/24, 5:26 a.m. ET: The article was updated with comments from Eric Balken.
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