Reposted from College of Science.
Sometimes geologic inquiry presents itself so forcefully and on its own timetable that researchers have little choice but to “go with the flow,” as it were. That has been the case of late in the American Southwest as megadrought conditions have plunged the nation’s largest reservoirs to new lows and terrain, underwater for decades, is quickly being daylighted.

Brenda Bowen examines sediments exposed by dropping Lake Powell water levels. Credit: Elliott Ross. Banner photo: San Juan arm of Lake Powell.
University of Utah geologists Cari Johnson and Brenda Bowen are part of a collaborative effort to understand the transformation of the river corridors entering southern Utah’s Lake Powell, impounded behind a massive dam on the Colorado River.
Deep time, modern moment
Johnson studies sedimentary layers millions to billions of years old, reconstructing ancient landscapes by deciphering clues left in rock formations. But now she finds herself in a “time machine”—the Colorado River, its tributaries and their surrounding landscapes – where she can observe sedimentation processes in near real-time.
“The Glen Canyon Dam, completed in 1966, created a closed lake basin that’s essentially a living laboratory,” Johnson explains. “We have an incredibly detailed instrumented record of lake-level history, river discharge and sediment load. These records establish the known boundary conditions that acted to form the textures, and features we see in decades-old reservoir sediment along the Colorado and San Juan river corridors.”
It’s like a long-term, region-scale experiment that began with the construction of the 710-foot-high dam and is now available for us to study due to falling reservoir levels. Bowen complements Johnson’s approach by focusing on how landscapes change in response to human infrastructure.
“We’re not just collecting data,” Bowen emphasizes. “We’re contributing to an interdisciplinary community trying to understand active landscape changes and potentially inform management decisions.”

Geology graduate student Sam Bagge on a research expedition in Cataract Canyon. Credit: Meg Flynn.
Cataract Canyon’s returning rapids
Central to their work is the Returning Rapids Project which brings together researchers, government agencies, nonprofit organizations, scientists and tribal representatives. This initiative, established and operated as a nonprofit by Moab-based river runners, has facilitated access to remote and challenging terrains, enabling vital interdisciplinary research in Cataract Canyon, a famed stretch of the Colorado River that was until recent years submerged under the still waters of Lake Powell.
“Returning Rapids doesn’t just give us physical access,” Johnson notes. “They bring together fish biologists, riparian ecologists, geologists, policymakers, land management agencies, and others to create a comprehensive understanding of the landscape.”
Johnson and Bowen’s research, conducted with Returning Rapids help, has yielded fascinating discoveries, such as “sediment volcanoes”—small mud formations that emerge as reservoir levels drop, releasing methane and other gasses from decomposed organic material. These ephemeral geological features not only provide insights into sediment dynamics but also highlight the complex interactions between geological processes, organic matter and carbon release.

Geology professor Cari Johnson and undergraduate Mary Roalstad taking turbidity measurements on Lake Powell’s San Juan arm using a Secchi disk. Credit: Liz Mahon.
Even more compelling is the rapid recovery of previously submerged ecosystems.
“We see native species returning surprisingly quickly,” Bowen explains. “It challenges our assumptions about landscape resilience.”
Lake Powell’s sediment challenge
The researchers are keenly aware of the broader implications of their work. With an estimated 8% of Lake Powell already filled with sediment, Lake Powell’s utility for water storage is finite. Current projections suggest the sedimentation would render the reservoir useless in 70 to 250 years, a nanosecond in geologic time.
“Our primary message is simple,” Johnson states. “Sediment is an integral part of water systems. You can’t separate water management from sediment dynamics.”

Exposed sediments in Cataract Canyon.
The research extends beyond local concerns. Bowen points out the global significance of their work: “Worldwide, reservoirs are disrupting sedimentary processes. We’re both trapping sediment and increasing sedimentation rates through land development. This is a quintessential Anthropocene challenge.”
Looking forward, the researchers envision new ways to collect data, such as a community science project where pilots, tourists and local flyers contribute aerial photographs, providing additional perspectives on the changing landscape.
“We’re witnessing amazing landscape changes over short time scales,” Bowen reflects. “Our role is to document, understand and help inform future management. It is both daunting and exciting to be collecting sedimentologic data with direct implications for important and pressing water management decisions.”
In the dynamic terrain of the American Southwest, these geologists are not just observing change—they’re helping humanity understand its own impact on the natural world. And sedimentation is telling that story.