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Magazine Articles

The River's Return

June/July 2015

Photographs by Nick Hall

In 2014, water flowed into the final miles of the Colorado River’s dry channel for the first time in more than a decade. Six months later, signs of new life were showing.

"When the sun peeped over the Sierra Madre, it slanted across a hundred miles of lovely desolation, a vast flat bowl of wilderness rimmed by jagged peaks,” wrote environmentalist Aldo Leopold, after canoeing the Colorado River delta in 1922. “On the map the Delta was bisected by the river, but in fact the river was nowhere and everywhere, for he could not decide which of a hundred green lagoons offered the most pleasant and least speedy path to the Gulf.”

The delta signals the terminus of the 1,450-mile Colorado River, whose broad basin encompasses seven U.S. states and two states in Mexico. Dur-ing Leopold’s time, the river’s last 87 miles splayed across more than 3,000 square miles of flat land, fanning out into a great tangle of river channels, wetlands and pools before reaching the sea in Mexico. Historically, the river pushed miles out into the Gulf of California every spring at a rate of 1.8 million gallons per second, leaving layers of sedi-ment 3 miles thick in places. Waves would mount high enough to upend a small boat when the ocean tides clashed with the river. The sodden land burst with cottonwoods, willows and mesquite. The river and wetlands teemed with fish. It was home and a respite for millions of birds a year, as well as jaguars, bobcats, coyotes, foxes, deer and raccoons, to name just a few species.

Today, the picture is different. So much of the Colorado’s water is now siphoned off for agriculture, industry, cities and other uses—providing water to an eighth of all Americans—that it no longer reaches the sea. From a bird’s-eye view looking south, the river dwindles to a tattered green thread flanked by miles of checkerboard farmland, then dissolves into a seemingly endless expanse of salt-encrusted, sterile gray mudflats.

The delta appears lifeless, the victim of what’s been called a death by a thousand cuts. Last year I traveled to Mexico to witness its quiet resurrection.


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The Colorado River’s dry southern reaches got a long-awaited drink in March 2014 as part of an innovative water management agreement between the United States and Mexico. A nourishing “pulse flow” of water released from the Morelos Dam coursed down the dry riverbed in the weeks that followed, eventually making it as far as the ocean. © Nick Hall

The Colorado River traces the California-Arizona border in its final stateside stretch, losing strength in a series of dams and diversions before meeting the Mexican border near Yuma, Arizona. Here, the river effectively ends at the Morelos Dam, built by Mexico in 1950 to capture its share of the Colorado’s flow and divert it for irrigation and municipal needs.

On March 23, 2014, all but one of the dam’s 20 gates lifted, releasing a pulse of water into the river’s historical channel in Baja California, Mexico’s northwestern state, for the first time in more than a decade, thanks to an unprecedented international agreement.

The river’s return was a spectacle to behold. With dignitaries, scientists and citizens watching under a blazing desert sun, the unleashed river drenched the dry bed. The leading edge advanced in a bubbling froth as water poured into the parched ground, creating a kind of underground waterfall and forcing pockets of air to pop to the surface.

A few days later, the water reached the wide, sandy channel abutting the Mexican city of San Luis Rio Colorado, named for the once-mighty river. Citi-zens there had spent weekends picking up trash from the derelict riverbed in anticipation of the river’s arrival, says Nancy Saldaña Navarro, a native of San Luis and an environmental and business leader: “It was like preparing your house for a guest when you’ve been waiting many decades for him to return.”

Now, people turned out by the thousands to rejoice, splash and swim in the cool water.

Over the next eight weeks, this “pulse flow”—roughly 0.7 percent of the Colorado River’s current average annual flow—made its way down toward the sea, as natural surges once did in the spring flood season. Scientists watched closely all along the way because this pulse of water was at the heart of an ambitious experiment, one that tests a hope-ful hypothesis: It’s not too late for the Colorado River delta. Even a relatively small amount of water could go a long way toward reviving the once-grand habitat along the riverbanks.

Weeks later, a trickle met the ocean tides, and by late May the channel was dry again. The delta had gulped down its long-deferred drink. Scientists waited in suspense, hoping the soaking would cause seedlings to sprout in this parched landscape, restoring a dwindling refuge for migra-tory birds and animals.


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A release of water from the Morelos Dam temporarily revived the Colorado River in northern Mexico in spring 2014, encouraging the regrowth of native trees. The Nature Conservancy scientist Eloise Kendy finds cottonwood seeds. © Nick Hall

Six months after the river’s historic return, I join Nature Conservancy scientists Eloise Kendy and Dale Turner as they travel the length of the Colorado River in Mexico’s state of Sonora. Kendy is a veteran hydrologist who helped coordinate the hydrologic design of the pulse flow and its monitoring program. Turner is a conservation planner for the Conservancy in Arizona with a background in wildlife biology.

They last saw the river full and inching toward the sea, right after the pulse flow. Now, in late September, they are investigating the effects of all that water by looking for changes in the vegetation—the growth of cottonwood and willow saplings and plant life in general. Turner took photos before and during the pulse flow at various sites along the river; now we are returning to snap “after” photos.

It’s a warm, cloudless morning, and as we bump along dusty roads en route to our first photo site, Kendy and Turner fill me in on the ecology behind the pulse flow. They start by explaining that rather mysterious term: The pulse flow was a carefully controlled release of water designed to mimic the annual spring floods that once scoured the river channels of accumulated salts and debris, leaving the banks clear and damp for native cottonwood and willow seeds to germinate. Those native species are essential to the region’s wildlife, particularly birds.

Of the 380 bird species that live in the delta year-round or migrate through it, more than 20 depend on cotton-woods or willows for nesting sites, including the endangered southwestern willow flycatcher and the threatened western yellow-billed cuckoo. Many of the bird species that travel the Pacific Flyway—migrating as far south as Costa Rica and as far north as the arctic reaches of Canada’s boreal forests—funnel through the delta and depend heavily on this region as a rest stop.

Since the early 2000s—the last time any water entered the river in Mexico—the overall “greenness,” or presence of any vegetation, in the region has declined by 35 percent. Aggressive and invasive saltcedar trees now dominate the riverbanks and remaining delta. Researchers have found that as the delta’s habitat has declined, so have the bird populations that rely on it. Even if birds manage to make the long journey, their ability to reproduce is diminished. But conservationists estimate that the region can still sup-port birds and other wildlife if it includes 10 to 15 percent cottonwoods and willows.

As Turner pulls the truck to a stop in San Luis, I’m startled to realize we’ve arrived at the first photo site. A dry, shallow trough some 300 feet wide, crisscrossed with tire tracks, is all that remains of the reborn river where people had splashed so joyfully in March 2014. An elderly man appears to be collecting discarded bottles from the middle of the riverbed, while a young woman strides with purpose across it and up the bank past us toward town. Other than a low bridge spanning the empty dip in the land, there is little sign that a river once flowed here.

“I stood here with kids and a full river,” says Kendy. “Everyone was full of joy and happiness. It’s sad to see it like this now.”

Kendy and other scientists have been collecting extensive data about the pulse flow’s effect, monitoring wells and conducting vegetation surveys. But all that information will take time to process. Meanwhile, Turner’s photos offer a cursory and immediate glimpse of the results. We scruti-nize the “before” photos as he readies the camera.

“At the end of the summer, I would expect to see less vegetation,” Turner says.

Compared with the spring photos, we certainly see more now. The shrubs and saltcedar bushes along the banks are fuller and taller, as if they’ve had a long, healthy drink.

Our impressions from the ground are later confirmed by satellite images of the region. University of Arizona pro-fessor Edward Glenn, a member of the pulse flow scientific team and an expert on the delta, says there has been an impressive 43 percent increase in the inundated area’s overall greenness since the pulse flow. “We’re really happy to see that,” Glenn says.



As we continue our journey, we reach a special area called Laguna Grande. Here, the Colorado River once collected in lagoons and split into channels that meandered back and forth across the main stem. If there’s any place in the delta where willows and cottonwoods can naturally reseed and survive, it’s likely to be a place like this, where groundwater is high enough to pool above the surface.

Towering stalks of arrowweed have shot up since the pulse flow, forcing us to bushwhack toward the main channel. The vegetation is so dense that Turner can’t even take a good “after” photo—a wall of green blocks the way.

Despite the region’s meager 2 inches of average annual rainfall, scientists anticipated that saplings’ roots would have a chance to reach the water table and sustain themselves here after the pulse flow. But when we reach the riverbank, we see little sign of saplings. Instead, the muddy slopes are choked with cattails and grasses.

Everyone is quiet on the walk back to the truck.

Fortunately, there is much more to see. Laguna Grande is also the site of an ambitious habitat-restoration project led by the Sonoran Institute, an environmental group integral to the pulse flow and a close Conser-vancy partner. Next, we visit an area the Sonoran Institute had cleared entirely of vegetation before the pulse flow in an effort to make space for tree seeds to germinate.

Here, we find clusters of small, waist-high willow and cottonwood saplings lining the banks of the river, their leaves shimmering in the breeze. A handful of chirping birds fly by. “My faith is restored,” says Kendy.


Later, we find ourselves trudging through a half-mile of shin-deep mud and water at the delta’s southern end, following Francisco Zamora Arroyo, director of the Sonoran Institute’s Colorado River Delta program. Zamora and some of his staff are collecting data on the water quality here and want to show us the site of a proposed project.

About 15 miles north of the ocean, we reach roughly the spot where the ocean tides met the water from the pulse flow. The slick gray mudflats are featureless, other than a frostlike layer of encrusted white salt that has built up for lack of a river to flush it out to sea.

Sloshing through the thick muck, Kendy, Turner and Zamora deliberate about what we’ve seen on our previous stops. Why haven’t more seedlings sprouted? Had the pulse of water moved too slowly, risen too high on the banks, soaked too quickly into the dry soil? Was the groundwater high enough, the banks clear enough? Had enough of the airborne seeds landed in the right place at the right time?

These questions are difficult, if not impossible, to answer from the banks of the Colorado, but they will be addressed in the coming months and years as more data come in, says Kendy. And she, for one, is not discouraged. “The Nature Conservancy is committed to science, and we’ve just helped run an unprecedented experiment.”

It’s an opportunity to learn not only about the response of vegetation and wildlife to an influx of water, but perhaps most critically about the movement of the water itself, says Kendy. She explains that the science team has already determined that weeds and other vegetation in the river channel slowed the water down—allowing it to soak into the ground or pool on the surface to evaporate or be used by plants—so much that less than 10 percent of the pulse was still flowing 40 miles downriver from the Morelos Dam. These insights will be used to inform and improve any future pulse flows.

“This is really a unique, new thing, to be able to understand the infiltration of a river into a dry river channel,” says Kendy as we finally reach solid ground. We’re not on terra firma for long. Soon we climb out of the vehicles and begin another long, muddy slog. Now we’re going to a place where the ocean tide reaches far inland—almost 20 miles north of the open sea—through countless twisting channels. Zamora and other conservationists call this the “upper estuary” or “new estuary.”

It is here that it really hits me: Though the pulse flow has come and gone, the delta’s resurrection story is still very much unfolding. The water’s release was the most visible part of a much larger, long-term effort involving an impressive coalition of Mexican and U.S. groups whose members ultimately have an even more ambitious goal in mind. They want to bring back the delta—or at least a smaller but functional version of the wetlands, green pools and great estuary that Leopold explored more than nine decades ago.

The vision is to revitalize and maintain a mosaic of delta habitats, says Osvel Hinojosa Huerta, an ornithologist and director of the water and wetlands program for Pronatura Noroeste, a Mexican environmental organization. “We [know we can’t] restore it to what it was 100 years ago … but we know that there are a lot of opportunities.”

The Conservancy, Pronatura, Environmental Defense Fund and the Sonoran Institute—among others on both sides of the border—are pursuing their vision at an impressive clip. This includes creating a necklace of riparian restoration sites along the river, protecting wetlands and purchasing enough freshwater rights to reestablish a piece of the once-massive estuary.

At sites such as Laguna Grande, the Sonoran Institute is leading an effort to plant cottonwood-willow forests throughout the delta, initially irrigating the saplings with water purchased from local farmers. Its staff of 20 has so far hand-raised 96 acres of cottonwoods and willows, and plans to establish another 650 acres by 2017. Though they had hoped the pulse flow would do more of the work for them—by inundating the riverbanks enough to germinate seeds “passively”—they’re moving ahead undaunted toward a goal of creating a 50- to 100-acre restoration site every 10 miles along the river, giving birds and wildlife a string of steppingstones from the sea to the U.S. border.
“It hasn’t been easy,” says Zamora, “but we have been very persistent.

Despite the challenges and setbacks, we have always been there trying to look at the positive side of things, and demonstrate little by little that the habitat could be enhanced.”

As we watch several Sonoran Institute staffers collect data from a water monitor hung on a pole in the middle of a flowing channel, Zamora describes his vision for reestablishing a piece of the once-great estuary, an ecological zone in which freshwater mingles with the sea to provide a brackish nursery for juvenile fish and crustaceans.

A trickle of freshwater from the Hardy River, a tributary of the Colorado, feeds a 1,000-acre pilot project nearby, but Zamora wants to increase that project to about 30,000 acres. That, he says, will require procuring enough water rights from local farmers to increase the Hardy’s flow to the area and dredging some old channels to reconnect the area to the sea.


La Ciénega de Santa Clara is roughly 15 miles northeast of where the Colorado once met the ocean. This 14,000-acre wetland is a breathtaking example of what a little water in the desert can do. It’s existence is a sort of happy accident, the result of a drawn-out international squabble that began in the 1960s over highly saline water that an Arizona water district had been discharging into the Colorado River. After Mexico complained that the water was killing crops, U.S. officials built a canal and disposed of the questionable water in Sonora’s tidal mudflats. By the 1990s an extensive verdant marsh had sprung up.

Today, Santa Clara is the best place to get a glimpse of what the delta used to be. And it is magical.

At dusk, Hinojosa from Pronatura takes me on a boat ride into the heart of La Ciénega. The shallow, open marsh is ringed by thick stands of cattails, host to a circus of raucous birdlife. In the shallows, striking black-and-white avocets cluster together while flocks of greater yellowlegs stab at the water. There are coots and cormorants, egrets and ibis. A raft of cinnamon teal ducks slides past us. We catch sight of an endangered and elusive Yuma clapper rail darting from the reeds. Fish break the glassy water’s surface, and a testy great blue heron takes flight, scolding everyone, its call echoing across the open water. As the bright half-moon climbs the lavender sky, hundreds of swallows surround us, diving and darting in a chaotic dance. They are mesmerizing. And then, like a mirage in the desert, they are suddenly gone.

If a small amount of water can raise a teeming marsh from gray mudflats in 40 years, imagine what a river could do.

Later, I ask Taylor Hawes, director of the Conservancy’s Colorado River program, if she thinks the Colorado can ever be brought back permanently to Mexico. “There is still
a lot of work to do, but we know that a little bit of water goes a long way,” she says. “Last spring’s pulse flow proves that it is possible to include nature’s needs when managing our water supplies—even in the desert.” •