Posted on November 6, 2024
LAKE POWELL — In 1963, the Glen Canyon Dam was built. It created Lake Powell Reservoir, which straddles Utah and Arizona, to ensure a water supply for the lower Colorado River basin states and Mexico. Over the past six decades, it has also become a recreation destination for millions.
The dam has experienced its fair share of unexpected trauma, threatening river flow levels, depleting water storage and exposing sediment.
Sediment is the walled molded mud that contains the Colorado River. It’s always been there, but historic droughts like those in 2002 and 2020 have caused the lifeline of the West to drop to alarming levels, exposing the mud.
Before the water is potable, it’s brown and murky.
“The Colorado got its name from the color. Colorado means colored red in Spanish. That red color comes from suspended sediment floating down,” according to Davide Ippolito, Returning Rapids researcher and the OARS river guide on our trip.
“I spend a lot of my days here just convincing people that this river isn’t just water. A lot of material is being transported. So when you have a lake at the bottom of that, the water stops moving, and that material, that sediment, just sinks to the bottom. And now we’re seeing, with the drought, all this exposed sediment that’s sunk to the bottom.”
Why should we care? Because the mud is being trapped above the dam, depriving the river below, and suffocating it above.
Shrinking storage and rising sediment levels
The silt buildup has decreased Lake Powell’s storage capacity by almost 7% since it was first created. “On average, the equivalent of 30,000 dump truck loads of sediment are deposited into Lake Powell daily. This is approximately 100 million tons annually,” per the Glen Canyon Institute, with most of the load coming from the Colorado and San Juan rivers.
While some sediment is natural and even beneficial for habitats and forming riverbeds and beaches, an excessive amount can lead to myriad environmental issues that harm the river’s health.
Mike DeHoff, Returning Rapids principal investigator, Susannah Erwin, National Park Service Water Resources Division river program lead, and Paul Grams, USGS Southwest Biological Science Center research hydrologist, talk about changes along the Colorado River by Gypsum Canyon rapid in Cataract Canyon on Sept. 21.
Mike DeHoff, principal investigator for the nonprofit Returning Rapids Project and lifetime river guide on the Colorado, recalled his experience boating down the river during the drought in 2002 and 2003.
“In Cataract Canyon, there are places where it felt like you were boating in this giant mud canal of ooze going down to the lower part of Cataract,” he said. “There are places where you couldn’t get out of your boat. It wasn’t safe,” emphasizing that he pulled people out of the mud that went in chest deep.
“That’s when many of us were like, what’s happening here? … That’s when we started to see remobilization of all the stuff that was starting to be exposed.”
Eric Balken, Glen Canyon Institute executive director, gives a talk in Clearwater Canyon during a Returning Rapids trip through Cataract Canyon on the Colorado River on Saturday, Sept. 21. Where the group is standing would have been under 20-30 feet of water when Lake Powell was at its highest, estimates Mike DeHoff, Returning Rapids principal investigator.
In the original Colorado River Compact of 1922, the seven basin states agreed to “remove causes of present and future controversies.” Sediment is not mentioned once in the compact.
More than 100 years later, and after the construction of multiple dams, it seems the issues caused by sediment were not anticipated by the original signers. Yet, on a six-day river rafting trip down the Colorado River, I witnessed firsthand masses of sediment falling from the banks into the river on multiple occasions.
On Friday, the National Parks Service published a press release reporting that “300-350 meters of shoreline slid from the river-left bank into the river channel,” creating a small rapid in the river’s main channel.
Mud deposits, referred to as mudbergs by Returning Rapids researchers, are pictured in the Colorado River and lining the river banks by Mille Crag Bend, between Cataract Canyon Glen Canyon Dam, on Sept. 22. The sediment filled in when this area was submerged under Lake Powell. After the lake receded, mud remains.
At what point does Lake Powell become a mud reservoir?
All dams have a lifespan, which is ended by structural aging, sediment build-up or other natural causes. The longer the issue goes unmanaged, the more expensive it is to fix. Without a sediment management plan, Lake Powell will cease to exist.
If nothing is done regarding the sediment flowing into Lake Powell, it will take approximately 750 years to be considered a mud lake. Though that might not sound imminent, it would likely lose its value as a reservoir much sooner than that.
Scientists, lawyers, river guides, even librarians and welders have devoted their careers to managing this issue, each with different insights into the best solution.
Dam reconstruction
Newer dam systems, like the Three Gorges Dam in China, are built with sluice gates that release sediment from the dam’s base. However, the only way for the system to operate is to drain the reservoir to get the momentum to carry the sediment out of the reservoir, Paul Grams, a research hydrologist at the USGS’ Grand Canyon Monitoring and Research Center, explained.
“Rivers carry sediment. Lakes collect sediment,” Grams said. “So the only way to carry sediment through is to turn it into a river. And you could do that artificially with a pump and a pipe, or you can do it by redesigning the dam to do it that way.”
While adding sluice gates to the Glen Canyon dam could theoretically move some sediment downstream, most experts agree that the costs, potential environmental impacts and the engineering nightmare alone make it too complex of a solution that wouldn’t lead to a long-term fix.
Jack Schmidt, USU’s Janet Quinney Lawson Colorado River Studies chair and Center for Colorado River Studies director, and Meg Flynn, Returning Rapids researcher, climb partially up a 40- to 60-foot high wall of sediment buildup called the Dominy Formation during a Returning Rapids trip in Cataract Canyon on the Colorado River on Sept. 20.
Targeted dredging
“In the early 1900s, the river went in all different directions because of all of the sediment that was pouring into it, and the channel was jumping and going from place to place,” Jack Schmidt, program director for the Center for Colorado River Studies at Utah State University, told me. Now, “it’s jammed into a tiny place.”
Lake Powell is not regularly dredged like a harbor or smaller reservoir would be, but dredging occurs occasionally and is typically done to clear channels or maintain access for boat ramps and marinas, especially when water levels drop due to drought or lower inflows.
