The Colorado River Delta Is Proof of Nature’s Resiliency

After decades-long decline, a dying wetland gets a second chance, with the help of cross-border collaboration between the United States and Mexico.

An aerial view of a river winding through a mountainous landscape

A pulse flow moving across the Colorado River Delta


Peter McBride/National Geographic Creative/Alamy

The Morelos Dam groaned open at the Arizona−Mexico border on March 23, 2014, unleashing a surge or “pulse flow” of water into one very thirsty stretch of the Colorado River. As the gray-green torrent roared south, residents of the Mexican town of San Luis Rio Colorado joyfully waded into spontaneous pools and instant lagoons.

People stand and wade in shallow waters in a riverbed

Following the pulse flow, children who had only known a dry riverbed play as they watch the Colorado River come back to life.


Pete McBride

A woman stands with her arms in the air in a narrow dug trench

Jennifer Pitt, former director of the Environmental Defense Fund’s Colorado River Project, celebrating the pulse flow.


Chandler Clay

From an overhead bridge, Jennifer Pitt watched the ebullient celebration. As the director of the Environmental Defense Fund’s Colorado River Project at the time, she’d been a key player in launching this release of 106,000 acre-feet of water (enough to fill some 52,000 Olympic-size swimming pools), aimed at jump-starting restoration of the Colorado River Delta. Formed where the river meets the Gulf of California, the delta was once a vast, wildlife-rich wetland. But dams on the Colorado had diverted most of its water to thirsty cities and farms north of the border, leaving much of the delta to slowly dry up. Now there was a chance to reverse that decades-long decline.

“A cheer went up when the water began to pour down, first in a trickle, and then a steady gushing flow,” she wrote. She also mused on how long it might take the river to move downstream.

Her wait was brief. Some eight weeks later, a small, white Cessna circled high above quilted sand flats to the south, where a delicate tendril of water was slowly weaving toward the Gulf of California. In the plane’s passenger seat, a scientist named Francisco Zamora snapped away on his camera. It was the first time the river—which starts its journey 1,450 miles away, in the Colorado Rockies—had reached the sea in nearly 20 years. And for almost that long, Zamora had worked toward this reunion. As director of the Colorado River Delta Program for the Tucson-based Sonoran Institute, he’d teamed up with Pitt (and more than 50 other scientists and water managers) back in 2002. Together they began plotting their vision for the rebirth of what was once North America’s largest wetland, a 3,300-square-mile oasis populated by vast migratory flocks, prowling jaguars, and rustic fishing villages. That trickle of water, more than a decade in the making, buoyed their hope.

An aerial view of a river flowing through a dry landscape and meeting a larger body of water in the distance

Colorado River briefly reunited with the Sea of Cortez in its delta


Sonoran Institute Mexico

Plight of the Delta

A black-and-white image of a person standing in a canoe in a narrow river

Aldo Leopold, Colorado River delta, Baja California, Mexico


Courtesy Aldo Leopold Foundation and the University of Wisconsin-Madison Archives

Paddling the delta in 1922, naturalist Aldo Leopold was entranced by the flourishing world beyond the tip of his canoe. “Verdant walls of mesquite and willow . . . a hundred green lagoons,” he wrote. “The river was everywhere and nowhere.”

That vision was not to last. In short, the saga of the Colorado River Delta has for decades been tied up in the struggle between two countries thirsting for the arid West’s precious, over-allocated water. Halfway through the 20th century, the delta began to dwindle as the Colorado was increasingly diverted to farms and cities. By the late 1970s, the huge wetland had deteriorated into a scattering of disconnected habitats. The delta’s fortunes did temporarily improve in the '80s and '90s, when heavy Rockies snowpack runoff forced the dams to release water at unusually high rates, reviving parts of the delta ecosystem.

Today, on the U.S. side of the border, the river not only provides water to nearly 40 million people, but also irrigates roughly six million acres of land and generates more than 4,200 megawatts of hydropower at its dams. But south of the border, it’s hardly an industrial powerhouse. By the time the Colorado reaches Mexico, nearly 90 percent of its water has been siphoned off. There, for the most part, the delta has been reduced to a desiccated wasteland, dominated by invasive tamarisk trees and discarded trash. It remains a far cry from the wilderness that once dazzled Leopold. Nevertheless, its supporters haven’t lost hope that they can someday see it as he once did.

A map shows the route of the Colorado River starting in Colorado and ending in Baja California

Boots on the Ground

This past April, four years after that pulse flow was first set free, I headed down to the delta to witness the aftermath of the momentous surge. It’s since been followed by less dramatic but more sustaining “base flows,” made possible in part by groundbreaking agreements between the United States and Mexico. These smaller releases of water are engineered to deliver nourishing flows over longer periods to specific restoration sites, and they’re partly due to the direct purchase of water rights from local farmers here by a coalition of six U.S. and Mexican environmental groups called Raise the River.

  • A wide, shallow trench dug into a flat, dry landscape, with a construction truck in the background

    Channel in Laguna Grande Restoration Area, shortly before and during the pulse flow


    Courtesy Dale Turner/The Nature Conservancy

  • Water fills a small trench dug into a flat, dry landscape, with small trees and brush growing nearby

    Colorado River Delta, Mexico


    Courtesy Dale Turner/The Nature Conservancy

The results of this collaboration are already visible on the narrow lane we’re traveling, a once-barren road now flanked by dense stands of native cottonwood and willow and punctuated by flitting birds. Our van is filled with Sonoran Institute scientists en route to a 1,400-acre restoration site called Laguna Grande. The group is heading to a weekend event showcasing the restoration’s progress and the institute’s impressive binational outreach. Forty staffers live in the nearby city of Mexicali, capital of the Mexican state of Baja California.

A man and woman stand in front of a narrow section of river with trees in the background

Karen Schlatter, associate director of Water and Ecosystem Restoration, with Francisco Zamora, director of Water and Ecosystem Restoration at Sonoran Institute


© Bill Hatcher/Sonoran Institute, 2018

Karen Schlatter is our driver. As associate director of the institute’s Colorado River Delta Program, she has overseen every square inch of this recovery—and spared no detail. Here’s a thumbnail: The pulse flow was designed to coincide with the peak season for native cottonwood seed release. In the months following that flow, cottonwood and willow seedlings sprang up all along the delta. According to remote sensing, the pulse flow fueled a 16 percent increase in vegetation. With it came a notable uptick in migratory and nesting waterbirds and nesting riparian birds.

The institute has also helped to construct a wetland next to Mexicali’s wastewater treatment plant and to transform the city’s trash-filled drainages into green corridors. Those projects have boosted local goodwill toward delta environmental work, which involves partners ranging from the Nature Conservancy and the National Audubon Society to the Mexican nonprofit Pronatura Noroeste. Much of the labor that’s gone into the delta’s transformation—from clearing the ubiquitous, invasive tamarisk to installing irrigation and planting trees—has been carried out by area residents. “We currently have about 22 local village members on our restoration team, and they are from the communities along the river,” Schlatter says. “We teach them the restoration techniques; we teach them ecological monitoring methods that are often pretty technical and complex. So people are learning skills and developing leadership.”

A woman kneels down in the dirt while a man digs with a shovel and another woman holds a tree sapling

Community members participating in the 2018 annual tree-planting event at the Laguna Grande Restoration Area, Colorado River Delta, Mexico


© Bill Hatcher/Sonoran Institute, 2018

A woman examines a tree sapling in an indoor greenhouse

Yuliana Dimas, from Mexican conservation group Pronatura, at the organization’s native tree nursery near San Luis Rio Colorado


Jill Replogle/KPBS

That local engagement has been key to building support for the restoration among residents of Mexicali and the surrounding area notes Yuliana Dimas, a project coordinator with Pronatura. “If you don't work with the community, they won’t adopt the river as their own,” she says. But it took some time to cultivate that connection. Prior to the 2014 release, many people had forgotten that there was a river in their midst—a dormant force in the thriving city of Mexicali, with its fertile farm fields, noisy thoroughfares, and activity from numerous maquiladoras, manufacturing plants that assemble goods for export. The pulse flow wound up being key to getting residents back in touch with the river. “Now they see all of the trees growing and habitat coming back more and more,” says Dimas.

Meanwhile, says Schlatter, local government leaders saw how much joy the river brought to their communities, and that helped to move the binational agreement along. “It made them realize that having a river and these green spaces for recreation is an important thing for their constituents,” she says. Eventually, the plan is to turn more control of the restoration sites over to local folks, but that transition isn’t imminent—the coalition first has to meet its 20-year goal to build the capacity and sustainable funding mechanisms needed for local governments and organizations to maintain and manage these sites.

A man stands holding four caught fish while people look on smiling

Locals celebrate the pulse flow moving its way across the dry Colorado River Delta.


Peter McBride/National Geographic Creative/Alamy

Our van crunches into a gravel lot near the river. There, on the banks of the Colorado, the institute will be unveiling its new education center, where visitors can peruse displays about water, the delta ecosystem, and the wildlife that once again calls it home. A crowd is already gathered as I traipse over to this mini-museum, where rows of chairs are arranged beneath broad awnings. Beyond us stretches the river itself, languid and lush, looking as if time had never taken a toll. A pair of orange kayaks are pulled up on the damp bank.

Zamora stands near the shoreline, almost protectively, as he addresses the crowd. “This has been a dream for us, to bring the river back,” he says, his voice staccato in the thin breeze. “This area, Laguna Grande, we began seven years ago with a few acres. And now we have over 800 acres of new habitat. Here at Laguna Grande, we have the largest cottonwood and willow forest along the Colorado River in Mexico . . .”

The crowd applauds, the trees rustle, and the river shimmers in the morning sun. At that moment, the scene seems almost magical. But of course, magic has nothing to do with the return of the delta. Its revival is the result of meticulous planning, painstaking negotiation, and a level of international cooperation that seems endangered itself in these tense times.

A crowd of people stand and talk outside under the shade of large trees

Visitors from the community take part in a Family Saturdays event at the Colorado River delta’s Laguna Grande Restoration Area, which are held several times each year.


Francisco Zamora/Sonoran Institute

A Fragile Partnership

Few have questioned the delta’s ecological importance, but for many years the question of who bore responsibility for its preservation cast its future in doubt. The United States had long held the position that, since the delta was mostly in Mexico, it was mostly Mexico’s responsibility. Mexico pointed out that the United States controlled the Colorado River—allocating only 1.5 million acre-feet to Mexico annually (about 9 percent of the river’s yearly flow, enough to supply about three million homes)—and that depletion of the river largely occurred north of the border. Meanwhile, all the surplus water that had flowed from the Rockies during the period of heavy snowmelt in the 1980s and ’90s evaporated in recent years as drought seized the West, and storage reservoirs such as Lake Mead—the country’s largest reservoir, which bridges Arizona and Nevada—were depleted by more than half. In the late 1990s, the U.S Department of the Interior, on behalf of the thirsty Colorado Basin states, did work to engineer pulse flows on a semiannual basis, supplemented by smaller, routine base flows. But the drought put an end to any serious revitalization efforts.

A clear, straight watermark is visible on the rocky surfaces facing a body of water, with several feet of bright clean rock below darkened black rock above the waterline

Lake Mead’s watermark shows how depleted the reservoir became during the drought, 2013


Julie Jacobson/AP

As the delta languished, environmental groups who sought to bring about an understanding between the American and Mexican governments began rethinking their strategy. “My colleagues and I decided that the only way we were going to move the conversation forward was not to start with Mexico City and Washington, D.C., but rather with water managers who were closer to the resource,” says Pitt, who is now the Colorado River Project director for the National Audubon Society. So in 2007 the groups convened a series of workshops that brought together state-level water managers from both countries to talk about the delta and the progress they hoped to make.

What emerged from those meetings was a series of minutes—or addenda—to the original 1944 treaty defining Colorado River water rights between the United States and Mexico. In 2010, tragedy intervened in the negotiations when a 7.2 magnitude earthquake ripped through the Mexicali Valley, ravaging canals that delivered water to its croplands. But the disaster had a silver lining.

“There was, in the wake of that earthquake, a quick negotiation on how to come up with what was called Minute 318,” says Pitt. Because the damaged canals weren’t able to deliver Colorado River water to farmers and other Mexicali Valley users, Mexico would, for the first time, be temporarily allowed to store some of that water in U.S. reservoirs (diverted from the channel by various dams, including the famous Hoover Dam, which supplies Lake Mead). This new arrangement ultimately benefited both countries. Mexico could store water it wasn’t able to use because of its damaged canals. And Mexico’s extra share helped keep Lake Mead’s water levels higher, avoiding water-shortage emergencies that are triggered when Lake Mead sinks too low.

It was also the perfect opening for delta proponents, says Stephen Mumme, an expert on border-region water issues at Colorado State University. “They could see that we were going to have a big discussion about water in the Colorado River, so they very smartly inserted themselves into that conversation.” From that starting point, Mumme says, environmentalists began persuading stakeholders to think about the ecological needs of the delta “and to find additional water for restoration.”

Forging a Future Together

Minute 323, signed in September 2017, allocated 210,000 acre-feet of water for delta restoration over the next nine years. Since that’s just a fraction of what’s needed (representing about 2 percent of the pre-dam annual flow through the Colorado), Raise the River also established a Mexican trust to purchase water rights in the Mexicali Valley. The coalition has since raised more than $10 million toward that end, with donations from foundations, philanthropists, government agencies, and corporations on both sides of the border.

Two men sit at a table on a dais with a row of people standing behind them

Officials with the International Boundary and Water Commission, United States and Mexico, signing Colorado River agreement Minute 323


Bureau of Reclamation

Still, negotiations involving American access to Mexican water can be a bit touchy. Alfonso Cortez teaches water resources management at El Colegio de la Frontera Norte in Mexicali. He calls the purchases of water rights a “sensitive issue” among some in the Mexicali Valley irrigation district. While many irrigators “are happy to receive some money from the United States in order to save and then transfer some volumes of water for delta restoration,” he says, others believe transferring water rights to American NGOs compromises a priceless Mexican resource. “They argue that the money for water conservation programs in Mexicali must necessarily come from the Mexican government.” As a result, it becomes “an issue of lost sovereignty,” he says.

Nonetheless, many believe this groundbreaking accord has global implications. “I think it’s a model that we can carry around the world,” says Albert Flores, an environmental specialist based in El Paso, Texas, with the International Boundary and Water Commission, a binational government agency that helped broker the deal. “Everybody was brought to the table. Some people lost a little bit, but I think everybody gained something. Nobody walked away feeling like a loser.”

Even amid President Trump’s anti-Mexico rhetoric, senior Interior Department officials were onboard with the agreement, according to Thomas Buschatzke, director of the Arizona Department of Water Resources. On February 22, 2017, Buschatzke traveled to Washington, D.C., to meet with Alan Mikkelsen, deputy commissioner for the Bureau of Reclamation, the largest wholesale water supplier and second-largest producer of hydroelectric power in the United States. “He wanted to make sure the states wanted this,” Buschatzke says. “When I told him that they did, he was very supportive.”

A Glimpse Through Leopold’s Eyes

Three men stand near shallow water with tall grasses and trees behind them

Jaime Roberts exploring the Colorado River delta, April 2014


Pronatura Noroeste Archive

Back at Laguna Grande, the orange kayaks are carrying visitors through placid water, weaving among reeds and small eddies. Watching from a few feet away is Jaime Roberts, a Mexicali businessman whose family develops industrial parks. He also serves on the Pronatura Noroeste board of directors. “The last generation has disconnected from the river,” Roberts tells me. “My grandfather lived along the river, hunting and fishing. But the last generation, we weren’t able to do that. When the water was cut off, we lost a lot of the fishing. There were a lot of different impacts on the environment. This is an effort to bring nature back to its place.”

He pauses, motioning toward the shoreline and abundant trees. “I wanted to get involved because I was born here,” he says. “I wanted to give the river back to the community, so that we could come here and enjoy part of the river, hopefully all the way to the Gulf of California.”

As we look out at the water, a heron slowly lifts into the breeze and gently follows that river toward the sea.

Birds fly over shallow waters and patches of land with tall grasses

Birds in the Cienega de Santa Clara, Colorado River Delta, Mexico


Edith Santiago/Sonoran Institute, 2011

This article was originally published on onEarth, which is no longer in publication. onEarth was founded in 1979 as the Amicus Journal, an independent magazine of thought and opinion on the environment. All opinions expressed are those of the authors and do not necessarily reflect the policies or positions of NRDC. This article is available for online republication by news media outlets or nonprofits under these conditions: The writer(s) must be credited with a byline; you must note prominently that the article was originally published by and link to the original; the article cannot be edited (beyond simple things such grammar); you can’t resell the article in any form or grant republishing rights to other outlets; you can’t republish our material wholesale or automatically—you need to select articles individually; you can’t republish the photos or graphics on our site without specific permission; you should drop us a note to let us know when you’ve used one of our articles.

Related Issues
Fresh Water

Related Stories