At the confluence of White Canyon and the Colorado River, bubbling gas billows from a cone made of mud.
This "mud volcano" was discovered by staff from the Glen Canyon Institute and the Returning Rapids Project, where Davide Ippolito is a boat operator, according to the Institute's 2022 fall journal. The Returning Rapids River Project is run under the Glen Canyon Institute by a “group of river loving folks based in Moab” who document the Colorado River, according to its website.
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"A giant cone of sediment that looked like a pimple, bubbling water up from below," staff wrote. "None of us had ever seen anything like it. The brown, glistening mountain bubbled and burped. Mike DeHoff (the project's principal investigator) wondered if it was methane. "Could we light it on fire? Would it explode? We lowered David to the rim of the cone with a lighter in hand. He flicked the lighter as the volcano gurgled a release, and a small fireball erupted. Cheers of excitement would have been heard for miles."
The Colorado River and its tributaries are sediment-rich, depositing large amounts of mud, dirt and other debris in Lake Powell. This has resulted in a loss of storage capacity in the reservoir, among other issues. And it's not just sediment buildup that's a concern — mud volcanoes can form as water levels fluctuate.
"There's just whole fields of them, just emitting greenhouse gases," Ippolito told St. George News while walking through Lake Powell's muddy canyons.
This geological phenomenon is an outward manifestation of a process underway underneath lakes and reservoirs in Southern Utah and across the world. And it could have broader implications for the planet's climate.
Dr. John Harrison spoke at a webinar hosted by Columbia Riverkeeper, explaining how this happens. Harrison is the Edward R. Meyer Distinguished Professor at Washington State University at Vancouver's School of Environment.
In most free-flowing river systems, oxygen-rich water and organic matter flow to the sea, where they are exposed to salty ocean water, oxygen and sulfate, transforming methane into CO2, Harrison said.
"Still a greenhouse gas, but a less potent greenhouse gas than methane," he said, adding that while methane doesn't last long in the atmosphere; when it's present, it is approximately 80 times more effective at holding heat.
In a dammed system, water is held back, creating "stagnant and slow-moving conditions," in which oxygen and sulfate-starved carbon are emitted from the reservoir as methane, Harrison said.
"Much less of that organic carbon is ultimately transformed into CO2 and lost to the atmosphere or dissolved in water," he said.
Anaerobic bacteria degrade organic materials fed into Lake Powell by the sediment-rich Colorado River. During this process, called methanogenesis, the bacteria produce methane that becomes trapped under sediment due to the pressure from the water above it, said Dr. Ed Simpson, a physical sciences professor at Kutztown University in Pennsylvania. Simpson has also studied mud volcanoes at Lake Powell.
However, when that pressure is reduced, such as when water levels recede in the reservoir, the gas is allowed to expand, Simpson told St. George News. This can cause cracks in the mud, which create additional breaks and eventually a network of fractures, allowing the gas to move toward the surface, as methane is lighter than water.
"When it comes to the surface, it's going to bring water up with it," he said. "It's going to bring a variety of things up with it. And it's also going to bring some of that mud up. So it'll come up, and it'll start boiling onto the surface, and as it boils, it's going to bring the mud up … and the mud volcano will start to actually, physically build."
Mud volcanoes are similar to regular volcanic vents that erupt in circular conduits, and as mud is shed outward from the vent, a water-gas chamber is formed, Simpson said.
"When the water level dropped, that was like releasing a coke bottle. Then, that methane could start coming out," he said, adding that the chamber will typically collapse at the end of the cycle, which can cause crater 10 to 15 meters across.
Over time, if water levels remain lower, the number of volcanoes will likely reduce, but when water levels rise again, it could trap more methane. Later, if the water recedes, the cycle could start again.
Greenhouse gases are emitted in various other ways, including degassing as water flows through pump houses and turbines, according to the U.S. Office of Energy Efficiency and Renewable Energy.
While all inland waterbodies can produce greenhouse gases, Simpson said there have been fewer mud volcanoes observed in lake settings, primarily because lake water levels don't typically fluctuate as much or as quickly as they do at Lake Powell.
Gas bubbles up from waterlogged sediment in Lake Powell, Utah, March 25, 2024. Photo by Alysha Lundgren, St. George News
"They take water out, they store it up, they move it out," he said. "So it's kind of a speeded-up laboratory for other lake systems."
Still, reservoirs, on average, are six times more effective than lakes at storing carbon in temperate climates, burying more than they emit, according to the Office of Energy Efficiency and Renewable Energy.
"However, conditions that promote carbon burial are similar to those that produce methane emissions," the agency states. "This balance between carbon storage and emissions is greatly influenced by several factors, including water temperature, sedimentation rate, organic matter inputs, and the shape, size, and depth of a reservoir.
"Nevertheless, only the fraction of methane generated by carbon decomposing in a reservoir represents an actual increase in net (greenhouse gas) emissions relative to potential carbon emissions that would have occurred without the reservoir."
U.S. Bureau of Reclamation officials told St. George News via email that "it is generally agreed that newer reservoirs tend to emit more greenhouse gas emissions than mature reservoirs."
The bureau said reservoirs stewarded by the agency trend older and are located in more arid climates, meaning there is less biomass to decompose under the water and sediment.
For this reason, the bureau said reservoirs like Lake Powell "are expected to contribute limited greenhouse gas emissions."
"The amount of biomass inundated by a reservoir is generally recognized as a proxy for the overall reservoir greenhouse gas emission potential," officials state. "The creation of Lake Powell inundated low amounts of biomass compared to reservoirs in areas that are more heavily vegetated."
A mud volcano bubbles in White Canyon, Utah, date not specified. Photo courtesy of the Glen Canyon Institute
Harrison said that CO2 emissions from reservoirs appear to have peaked in the mid-1980s, but "it's only part of the story."
"Reservoirs emit a lot of carbon dioxide early after being flooded, but then, as organic matter that's been flooded decomposed, the CO2, the carbon dioxide emissions decrease," he said. "But as reservoirs age, methane emissions continue to take place. So, as reservoirs globally are aging a greater fraction of the total greenhouse gas that's emitted from reservoirs is occurring as methane – this super potent greenhouse gas."
Standford University geophysics student Margariete Malenda, Simpson and others traveled to Lake Powell to study how mud volcanoes are formed and the composition of gases they release. They published a study in 2020. Malenda told St. George News that most similar studies have been conducted in peat bogs and other swampy areas, so it was a novelty for the team to study mud volcanoes in Lake Powell's desert environment.
In this file photo, a delta forms where the Escalante river “dies” at Lake Powell, Utah, March 26, 2024. Photo by Alysha Lundgren, St. George News
The amount of greenhouse gases produced by reservoirs is estimated to be much lower than that emitted by fossil fuels industries, which account for approximately 74% of human-caused emissions in the U.S., according to the U.S. Energy Information Administration.
Still, Malenda said more rigorous studies are likely needed to see the whole picture.
"I'm not sure if we have a good sense of how much CO2 is being released, how much methane is being released," she said, adding that it can be difficult to factor in any lake-based sources of CO2 or methane into climate change models and predictions without additional data.
"Lake Powell is kind of a weird example of having these gasses emitted," she added. "It's very unique. It's not what you generally might think of, like a peat bog, right? And so, we don't know how many these weird – other weird systems are out there."
Additionally, Malenda said the public should consider the issue through a wider lens, as there could be "crazy unknown outcomes that we can't even account for."
"And maybe have them think twice about, you know, something that, on the surface, seems really amazing, like a reservoir, and also think of all the other ways it has impacts and maybe think of solutions to mitigate those impacts."
What about local reservoirs?
Many of Washington County's reservoirs are built off-stream, so water and sediment don't flow directly into them. So there isn't an issue with sediment in most reservoirs in the short term, said Zach Renstrom, general manager for the Washington County Water Conservancy District.
"The one exception to that is Gunlock," he added. "And so Gunlock is built on the Santa Clara River, and so with that one, we do have a sediment problem. And we just have to simply dredge that every, like 10 to 15 years to just stay in front of it. … If we didn't do that, then the reservoir would lose a significant portion of its capacity, and then, it would be a problem."
Because the county removes excess sediment and organic materials, Renstrom said the right conditions don't exist at Gunlock to produce methane.
However, Renstrom said dredging likely wouldn't work to mitigate methane emissions from Lake Powell, as it is too expansive at approximately 186 miles long at full pool.
Still, Renstrom said a balance needs to be struck with reservoirs.
"People want flushable toilets," he said. "People want showers, and there is a huge aspect to not having those. I mean, there's a public safety issue, there's a public health issue there to making sure that we have all these wonderful technologies and clean, safe drinking water. And we wouldn't be able to do that without reservoirs.
"But on the flip side, we have to think about where we're building reservoirs. And when we do build the reservoir, are we using the best science? Are we thinking about it? And so, I think there is a balance there that, as a society, we just have to work on and always think about."
