With rocks, tiny dams on a roll
Confronting the impacts of climate change, volunteers in western Colorado have turned back to the Stone Age, constructing hundreds of “one-rock dams” across semi-arid landscapes in an effort to slow accelerated erosion and prevent the formation of gullies.
This buttressing, led by state and federal biologists, is designed to de-rut rain runoff and retain soil, reflecting rising concern about land degradation. Devotees of one-rock dams aim to spread this practice around the West and arid regions worldwide.
Crews of volunteers hoist, haul and position the rocks to create structures that include multiple rocks, but are only one rock high — work that can be finger-crushingly brutal but addictive.
“The minute you’re involved, you’re invested,” said Sue Navy, 70, of Crested Butte, who has built dozens of these dams each summer for seven years. “It has a feeling of potentially healing something that has gone awry.”
The dam builders are responding to impacts of a climate shift in western Colorado toward hotter temperatures, periodic droughts and less snow, punctuated by
hard rain, which is creating conditions where runoff depletes soil and groundwater eventually drains away.
“We’re trying to build resiliency back into wet meadow habitats, so they can hold water longer, act more as sponges and hopefully be more resistant to climate change — to a warmer and drier climate,” U.S. Forest Service biologist Matt Vasquez said last week after a weekend of work along a creek west of Monarch Pass. “Human nature may be more reactive rather than proactive. It would have been great if folks decades ago had the foresight to understand and care about the consequences of their actions. But it is never too late to act.
“We know these changes are happening,” he added. “We’ve seen the data that demonstrates temperatures are increasing. We’ve seen the changes in precipitation, more rain instead of snow. And we see extreme weather more frequently. There are things we can do.”
“We have erosion everywhere”
One-rock dams emerged 25 years ago in dry parts of New Mexico, Arizona and Mexico, where restoration ecology guru Bill Zeedyk, a retired federal forester, revived techniques derived in part from ancient Zuni natives. Global warming, as it intensifies, has spurred interest.
Zeedyk has guided work in Colorado that began after a drought in 2012, leading to the construction of more than 1,500 tiny dams, project summaries show. Most were built on highly erosive sagebrush steppe in the Gunnison River Basin. Volunteers also have installed dams east of Telluride in the San Miguel River Basin, near Grand Junction and northwest of Fort Collins.
Colorado Parks and Wildlife officials have embraced the practice, motivated to preserve wildlife habitat and save species facing extinction, such as the Gunnison sage grouse. Nonprofit organizations including the Nature Conservancy provided support.
Conservationists inspired by Zeedyk, whose methods are laid out in a 2018 federal Natural Resources Conservation Service technical report, have installed tiny dam structures in Spain, South Africa, China and other regions where rising temperatures and changing precipitation accelerate erosion. Zeedyk estimated there may be more than 100,000 one-rock dams worldwide.
“We have erosion everywhere. This is a way to save water on the landscape to support the variety of vegetation and animals that depend on it, as well as people,” Zeedyk, 84, said from his home in New Mexico. “Gullies have to be actively confronted. Otherwise, they just get constantly deeper, more extensive, in a network that drains the landscape. And we lose much of the most productive land.
“We are in for gullies becoming more extensive. We are in for draining subsurface water off the landscape faster. We are in for changes in vegetation and species composition. … There are a lot of prices to be paid if we allow gully erosion to become more severe and more extensive. No matter where you are, the landscapes become more impoverished where we get gullies and eroding soil.”
At project sites, organizers amass heaps of rocks, up to 1 foot in diameter each, sometimes using heavy machinery. They identify sites were water flows have cut channels, typically in areas where roads, cattle grazing trails, wagon-wheel ruts from a century ago and other disturbances triggered changes that now are exacerbated. And they prep groups of volunteer workers, which have ranged from high school sports teams to land restoration clubs from around the state.
Then the volunteers, wearing leather gloves and boots, start lifting. The rocks can weigh up to 100 pounds each. Teams typically install a few dozen dams over several days.
While one-rock dam structures vary — participants refer to “Zuni bowls,” “run-downs,” “rock mulch,” “lay-backs” — they’re only one rock high, and no more than one-third the height of a channel or rut. The dams consist of 10 to 100 rocks fit together to form the structure.
“Incrementally, these add up to slowing down water, stopping the erosion, healing these meadows,” Vasquez said. “It really does make a difference.”
“We have helped this landscape be resilient”
Across a mesa above Ohio Creek north of Gunnison, ranchers and federal land managers have welcomed the erosion control work over seven years — most recently at the start of this month. Poorly placed roads and trails had set off erosion that worsened to the point where, around 2011, spring runoff surges were carving out gullies, ravaging riparian habitat, and threatening cottonwood trees and the grasses in meadows leased for grazing cattle.
Mini-dams now have stabilized the mesa, said conservation biologist Tom Grant, wet meadow project coordinator for the Upper Gunnison River Water Conservation District, checking out one former gully recently. Soil had filled in behind dams. Trickling water now spread, more the way water flows in sheets as snow melts than during rain on rutted terrain. Native riparian plants had sunk roots, attracting bugs.
“When you do have a drought, this landscape is going to have some vegetation on it. We have helped this landscape be resilient,” Grant said. “The goal is to scale this up … do it in a lot of different places.”
Proponents say the aim isn’t altering nature, as large-scale dam developers have done to enable settlement of the West with huge environmental disruptions that in many cases proved ruinous. After all, erosion is a natural process in watersheds, relocating soil.
But a preponderance of scientists have established that global warming, largely caused by human use of fossil fuels, is accelerating those processes, throwing already arid Western landscapes out of balance. Proponents of one-rock dams contend their level of manipulation to try to restore balance is appropriate.
“It is a humble, bottom-up approach, rather than command control. And the impact is dispersed — a lot of people working over wide areas,” Grant said. “That’s what is going to make this successful.”
Monitoring in western Colorado between 2013 after intense drought and 2018 documented an average 62% increase in wetland plant cover on treated terrain, Forest Service officials said.
Climate warming is affecting water flows across Colorado, state and federal agencies have found. In the past, precipitation in the form of snow favored a slow release of water over months. Higher temperatures have shifted precipitation toward rain, often falling in surges that cut into soil and wash it away from unstable slopes, favoring erosion. This prevents new vegetation.
And land managers worry about barren slopes and invasive weeds replacing native plants. Riparian corridors and wet meadows widely have been degraded, resulting in deepening gullies and lower groundwater levels. Droughts such as those in 2002 and 2012 worsened these problems.
“You’ve got proof that this works”
Now as temperatures rise, droughts and intense runoff that speed erosion are expected to become more frequent. Plants and animals are suffering. The numbers of endangered Gunnison sage grouse this year decreased to fewer than 3,000, according to the latest state surveys. Loss of habitat because of climate change looms as a driving factor.
State wildlife biologists have supported one-rock dams on grouse habitat because increased riparian vegetation draws insects that grouse eat to survive.
“What I really enjoy is when you find grouse fecal pellets on a rock structure you built. You’ve got proof that this works,” said CPW biologist Nate Seward, who has helped lead one-rock dam installations.
Under the Endangered Species Act, Colorado is obligated to prevent extinction of this species.
“And with some of these climate projections, we would see a greater decline in sage grouse numbers throughout their range,” Seward said. “We could see an expedited decline and potential extinction without continued habitat enhancement work.”
Degraded landscapes around Gunnison also pose threats to ranchers, who already face pressure from developers who envision housing and facilities for tourism as higher-value uses of land. Ranchers have welcomed the dams because, ultimately, stable meadows mean more vegetation for cattle to eat.
“This is fixing something”
The key to the effort has been people power. And organizers say climate change concerns are creating growing numbers of volunteers willing to camp out for multiday erosion-control projects.
“A lot of the motivation I’m seeing in the younger participants is climate change,” said electrical engineer Deidre Witherell, 58, who began hoisting rocks last year and worked again this month at the site west of Monarch Pass.
“Even though it may be a small impact, if you get enough people together the impact may be big,” Witherell said. “This is fixing something. We as humans have disturbed the environment. The effects of climate change in the West include drought. This can help manage the impacts of drought.”
This week, climate action “strikes” across the country will include western Colorado marches through Crested Butte and Gunnison. Scores of residents have been busy making signs.
But beyond the protest, said Navy, who chairs the board for the local conservation group High Country Conservation Advocates, residents seek opportunities to directly deal with climate impacts that may affect their lives.
“Sure, everything would have been better done a while ago. But right now, the fact that we’re doing this now, is really important. It makes a difference you can see in only a year or two,” she said.
“Obviously, with climate change, no matter what we do we’re not going to fix it in a short time. But these dams get quick results. And it almost feels as if you are putting a mosaic together. It is rock. Some of us don’t intend to quit. It feels good. You’re actually accomplishing something. People really need that feeling of accomplishment.”