Restoring the Colorado River Delta

How building binational support brought water, trees, funding, and birds back to the Colorado River Delta.

By Jennifer Pitt, Colorado River Program Director, Audubon
Verdin. Photo: Lisa Langell/Audubon Photography Awards

Today, the United States and Mexico, through the International Boundary and Water Commission (IBWC), released an implementation report documenting the first environmental progress under Minute 323, a binational Colorado River agreement adopted in late 2017. The report documents more than $3 million spent and nearly 7,000 acre-feet water delivered for habitat restoration during the first year of the agreement. The story behind these numbers is remarkable.

First, there’s the fact that restoration is taking place at all. Not long ago, the United States and Mexico were locked in a bitter battle over Colorado River management, disputing lining of a canal that saved water for the United States and depleted water availability in Mexico. Today the two countries are collaborating to put habitat back in the Colorado River Delta—an extraordinary success of diplomacy that stands out at a time when U.S.-Mexico relations are otherwise fraught.

Throughout the 20th century, both countries developed water for farms and cities that desiccated the Colorado River Delta throughout its 250,000 square mile watershed. A vast expanse of wetlands and riparian forests disappeared as the river ceased to flow through its final hundred miles towards the sea.

Now, more than 1100 acres thrive with native trees and wetlands vegetation. In 2018 alone, restoration crews cultivated more than 50,000 native plants in on-site nurseries before planting them—significantly hard labor in the desert sun.

It takes extraordinary effort to make this landscape bloom again. Hard-working non-governmental organizations (NGO) restoration crews spend countless days in the hot sun preparing lands and planting trees. An NGO environmental water trust cooperates with the vast Mexicali Irrigation District to ensure those trees are watered. A binational team of scientists travels the area repeatedly to collect data on the ecological and social impacts so that the effort might improve in the future. An impressive, binational collection of organizations, including federal and state agencies, NGOs, and universities work together to coordinate the work and ensure dollars and water are available to support it.

We know from past monitoring reports that birds are returning—species diversity is 27 percent greater and populations are a stunning 80 percent greater in restored sites along the Colorado River in the delta when compared to lands not yet restored. Birds recently spotted include: Albert’s Towhee, Ash-throated Flycatcher, Blue Grosbeak, Black Phoebe, Black-tailed Gnatcatcher, Cactus Wren, Crissal Thrasher, Gila Woodpecker, Hooded Oriole, Ladder-backed Woodpecker, Song Sparrow, Vermillion Flycatcher, Verdin, Western Kingbird, and Yellow-breasted Chat. We expect more good news when the IBWC publishes the next monitoring report later this year.

Originally appeared on, May 7, 2020

Water to Flow in Colorado River Delta Again

Canal maintenance a reminder of the 2014 pulse flow

By Jennifer Pitt, Colorado River Program Directo. Reprinted with permission from The Audubon Society

Tomorrow, water will flow again in the Colorado River along the US-Mexico border. The long-dried out channel—the final 100 miles of the Colorado River before it ends at the Gulf of California—has not seen this much water since the 2014 “pulse flow.”

However, this is brackish water. For a few months, we will see it in the Colorado River below Morelos Dam, reminding us of the river that once flowed there. It is agricultural drainage that comes from farms in southwestern Arizona that use the Colorado River to irrigate in the desert. Because these farms sit above salty groundwater, their drainwater is too saline for return to the Colorado River. The drainwater is usually sent down a concrete-lined canal that takes it on a path parallel to the Colorado River, across the border into Sonora, Mexico. There it empties into the Ciénega de Santa Clara, the last great wetland of the Colorado River Delta.

But the nearly 50-year-old canal is badly in need of repair. So the U.S. Bureau of Reclamation (Reclamation) will close it temporarily, and with nowhere else to put the brackish water (which cannot be used for farming, or even for swimming), they will divert it back into the Colorado River, below Mexico’s diversion at Morelos Dam, where it does not mix with Mexico’s water supply.

Repairs to the canal will extend its life, which is a good thing, because the Ciénega and the birds that call it home rely on this water. When first built, the canal’s terminus was dry mudflats, land that was once the eastern extent of the lush Colorado River Delta ecosystem of nearly two million acres. When the Colorado River Delta went dry, that entire ecosystem shriveled. The canal was not designed to resurrect delta wetlands, but inadvertently it did.

Today the Ciénega de Santa Clara is a watery and green expanse, standing in extraordinary contrast to the Sonoran Desert that surrounds it. It harbors hundreds of thousands of birds, including the world’s largest remaining population of Yuma Ridgway’s Rail, an endangered species. On a visit you can see long lines of White-faced Ibis in flight, squadrons of pelicans, ducks and cormorants by the hundreds. It is a spectacular oasis, 40,000 acres protected in Mexico as a Biosphere Reserve.

Scheduled repairs mean the canal must sit dry for 3-4 months. In the short term, the Ciénega de Santa Clara is deprived of that water supply. Migrating waterfowl are not present in the fall, although resident and partially-resident species like the Yuma Ridgway’s Rail will be impacted. Fortunately, the disruption to flows will be relatively short-lived, and the United States has funded a binational team that includes Audubon scientists to document the impacts and the recovery. The monitoring effort has been coordinated with the International Boundary and Water Commission, and includes scientists from both the United States and Mexico.

However, a more serious threat to the Ciénega de Santa Clara looms. If operated, the dormant Yuma Desalting Plant could divert the canal’s flow on a more permanent basis. Reclamation might do that to increase water reserves in Colorado River reservoirs. In the wake of the 2019 Lower Colorado River Drought Contingency Plan, that is a real possibility as it commits Reclamation to work on approaches to find 100,000 acre-feet of water (about 100,000 football fields in water one-foot deep) annually. Finding “new” water is a tall order for an agency that does not have a Colorado River allocation. The desalting plant would deplete the water in the canal, replacing it with super-salty brine waste. That would be a double-hit to the Ciénega de Santa Clara, severely reducing both quantity and quality of the water that sustains it. The wetlands and the birds that call it home would be devastated. Because the United States and Mexico do not yet have a treaty agreement to protect the Ciénega de Santa Clara’s water supply, the threat is real.

Fortunately, Reclamation has alternatives. The agency is already implementing infrastructure improvements and other programs that can help, and there is more that can be done. Rehabilitation of faltering pumps, improved operations of existing infrastructure, and paying water users to conserve could create just as much “new” water—and for far less cost.

In the meantime, water will flow in the Colorado River Delta. Though the drainwater is not safe for human contact (both the United States and Mexico have posted warnings), and is too salty to help the few native trees that grow riverside, it is an important reminder that this river needs water.

Back in 2014, the United States and Mexico, in accordance with a binational agreement (Minute 319), created a “pulse flow” in the Colorado River Delta to simulate, at a small scale, the spring flood that once took place every year. The pulse flow was celebrated near and far as an unprecedented nod from the governments, that nature and local communities were worthy beneficiaries of a flowing river. It was an infusion of life-giving water that – at least temporarily – created habitat for hundreds of species of birds, and the return of the river to the sea.

In a successor agreement signed in 2017 (Minute 323), the United States and Mexico committed again to send a modest—but ecologically significant—volume of Colorado River water for the environment into the Delta. While cooperative planning is underway, their water has not yet been delivered, and it must soon.

The canal repair reminds us of what is at stake, including a Delta ecosystem that still needs water, communities that mourn the loss of the river in their midst, and a large wetlands oasis sustained by an uncertain water supply. Can the United States and Mexico commit to provide water to these last remnants of nature in the Colorado River Delta?

Bird Abundance Increases in Colorado River Delta after 2014 Pulse Flow, New Report Says

U.S.-Mexico Colorado River collaboration leads to 20% increase in bird abundance.

Collaboration between the U.S. and Mexico—supported by a coalition of nonprofits including Audubon—which resulted in a pulse flow through the Colorado River Delta, lead to a 20% increase in bird abundance and a 42% increase in bird diversity. A new study from the International Boundary and Water Commission (IBWC), which also showed an increase in greenness along the river corridor, demonstrates the importance of binational cooperation between the two countries for environmental causes. In 2012, the United States and Mexico adopted Minute 319, an innovative agreement to change how Colorado River water is managed at the border.

“The findings of the study prove that this binational cooperation was good for birds and the health of the Delta. Water temporarily reached all the way to the sea and along the way, it made the formerly dry river corridor into viable habitat,” said Jennifer Pitt, Audubon’s Colorado River Program Director. “The restoration work of our partners in Mexico resulted in nearly 300,000 newly planted native trees—creating a haven for birds and possibly future recreation sites for local communities. We’re thankful to the IBWC and the Raise the River coalition for this remarkable success.”

Raise the River is a unique partnership of six U.S. and Mexican NGOs committed to restoring the Colorado River Delta. In addition to Audubon, members include: The Nature ConservancyPronatura Noroeste, the Redford Center, Restauremos El Colorado, and the Sonoran Institute. The coalition has worked with policymakers, water agencies and governmental representatives from the U.S. and Mexico since 2012 to cooperatively create historic change for the Colorado River Delta.

Through the 5-year term of Minute 319, more than 150,000 acre-feet of water was sent into the Delta. Some of that water went directly to restoration sites to ensure the staying power of newly planted native trees. Most of the water was delivered as a “pulse flow,” engineered to mimic the natural cycle of spring snowmelt that created vast riparian forests and wetlands in the pre-development Delta ecosystem.

Now, one year after the end of Minute 319 (and the extension of its measures under a new agreement known as Minute 323), the U.S. and Mexican sections of the International Boundary and Water Commission published conclusions of a binational science team that monitored impacts, comprised of federal, university, and NGO researchers. Audubon helped lead these efforts with binational conservation partners. The science gives us lessons learned that can be applied as water is delivered and new habitat is created under Minute 323.

Included in Minute 323 were provisions to share Colorado River water surpluses and shortages, and to incentivize water conservation (especially keeping more water in Lake Mead). These measures look more important than ever as we approach the first-ever declared shortages on the Lower Colorado.

About Audubon:

The National Audubon Society protects birds and the places they need, today and tomorrow. Audubon works throughout the Americas using, science, advocacy, education and on-the-ground conservation. State programs, nature centers, chapters, and partners give Audubon an unparalleled wingspan that reaches millions of people each year to inform, inspire, and unite diverse communities in conservation action. A nonprofit conservation organization since 1905, Audubon believes in a world in which people and wildlife thrive. Learn more and how to help at and follow us on Twitter and Instagram at @audubonsociety.

The Western Water Initiative is Audubon’s multi-state effort to protect the Colorado River and the West’s network of Saline Lakes. Some 65,000 members strong and growing, the network advocates for science-based, non-partisan water policies and management that benefit rivers and lakes for the birds, wildlife, habitats, cities, and economies they support. To learn more, visit:


Originally published in the National Audubon Society Western Water News:

Collaboration Drives Results

A first-hand account of what it has been like being a member of the Science Team measuring the results of the 2014 Pulse Flow and subsequent water deliveries into the Colorado River Delta by Karen Schlatter.

“As a result, going forward under a new 9-year binational agreement that was signed in September 2017, water flows will be used to ensure that the people of the river have recreational and cultural benefits, in additional to the benefits to critters and plants.”

Go to Sonoran Institute Blog to read the complete story by Karen Schlatter, Associate Director, Water and Ecosystem Restoration

Collaboration for the Colorado River Delta

Final report on historic environmental flows results in hopeful roadmap for Colorado River Delta restoration

Cooperation between the U.S. and Mexico governments, supported by a coalition of non-profit organizations, has demonstrated the power of community to achieve environmental benefits as recently released scientific findings in the Colorado River Delta have documented.

On November 28, 2018, the International Boundary Water Commission (IBWC) published the “Minute 319 Colorado River Limitrophe and Delta Environmental Flows Monitoring Final Report“, the final report on the environmental impact of planned water deliveries to the riparian corridor of the Colorado River along the U.S.-Mexico border and Delta from 2013 through 2017. An interim report on the environmental impact of this 2014 pulse flow was published on October 21, 2016.

The background

As one of the world’s most endangered rivers, the Colorado River is depleted by upstream dams and water diversions for farms and cities in both countries before it meets its natural end in the Gulf of California. Its delta, once a vast region of vibrant habitat for wildlife and migrating birds, is now dry, as the river stops 70 miles short of the sea. A unique and landmark bi-national collaborative effort to revive the dry delta landscape on behalf of the environment came to fruition in 2012 with the passing of a binational agreement between the U.S. and Mexico to restore habitat and dedicate water to the Delta. The agreement called for an engineered release of water into the region in 2014 – known as a ‘pulse flow’ – which flooded the dry Colorado riverbed in the Delta and reconnected habitats, wildlife, and local communities with the river for the first time in decades.

The U.S. and Mexico sections of the International Boundary and Water Commission (IBWC and CILA, respectively) are federal agencies that negotiate and implement binational water treaties and water allocations. In 2012, the IBWC and CILA successfully negotiated Minute 319, an agreement that helps the two countries better implement the 1944 U.S.-Mexico Water Treaty under current basin conditions (these types of supplementary treaty agreements are referred to as ‘Minutes’). Minute 319 has provided multiple benefits for water users on both sides of the border and is a result of the extraordinary binational collaboration among government agencies, conservation organizations, water users, and other Delta stakeholders.

In addition to the water flows for the environment, it more broadly has provided for the U.S. and Mexico to share surpluses in times of plenty and reductions in times of drought, offered incentives for leaving water in storage, and conserved water through joint investments in projects from water users in both countries. The agreement also served to recognize the Colorado River Delta as a place of ecological significance for both countries.

Following the signing of Minute 319, Colorado River stakeholders and a multinational, multidisciplinary, multi-organizational science team worked for over a year to prepare for implementation of the Minute, including designing the pulse flow and establishing the monitoring program to assess its hydrologic and ecological responses. Then, from March 23 to May 18, 2014, 105,392 acre-feet (130 million cubic meters [mcm]) of water was released from Morelos Dam into the dry Delta, flooding more than 4,000 acres of riverbed landscape, and once again – briefly – the river met the sea for the first time since 2001.

Following the pulse flow, small amounts of water known as base flows were periodically released into the Delta to maintain and augment the pulse flow’s effects and maintain existing and restored habitat. A total of 57,621 acre-feet (71 mcm) of base flow deliveries were made during the five-year term of the Minute, ending December 31, 2017.

An important inclusion of the Minute was the requirement for ongoing scientific monitoring of results to help inform more effective applications of environmental water in the future. This work was conducted by a binational team of scientists led jointly by the University of Arizona, Sonoran Institute, The Nature Conservancy, and El Colegio de la Frontera Norte (COLEF). Included among the researchers were environmental experts from The Nature Conservancy, Pronatura Noroeste, and the Sonoran Institute. These three organizations are all members of Raise the River, a coalition of conservation organizations working to protect and restore the Colorado River Delta. Other members of Raise the River include the National Audubon Society, The Redford Center, and Restauremos El Colorado.

“Like the pulse flow itself, this report was a binational collaboration. Scientists from government agencies, academia, and conservation organizations on both sides of the border contributed to the monitoring efforts,” said Eloise Kendy, a senior freshwater scientist with The Nature Conservancy.

The team and the study

More than sixty scientists from universities, government agencies, and nongovernmental organizations from both Mexico and the U.S. were involved in either conducting the research or preparing the report, including El Colegio de la Frontera Norte, Pronatura Noroeste, The Nature Conservancy, Sonoran Institute, the Universidad Autónoma de Baja California, the University of Arizona, the U.S. Geological Survey, and the U.S. Bureau of Reclamation.

The study results published on November 28, 2018, detailed the changes in birds, plants, and groundwater in the delta since the pulse flow, which signifies that these ongoing water flows in the Colorado River Basin are helping to restore the native environment and bring back native flora and fauna to the arid Colorado River delta.

“The findings confirm that what the United States and Mexico are doing for the Delta is working”, said Jennifer Pitt, Director of the National Audubon Society’s Colorado River Project, who has been among the leaders of the delta restoration effort for many years. “It’s proof positive that adding a little water back into that ecosystem, coupled with active management of restoration sites, can work for people and birds.”

Not only was this the first‐ever scheduled delivery of water by the United States or Mexico into the Colorado River delta dedicated to improving the environment, but it was also the first time to have a formal monitoring program in place to measure the ecosystem response. The research effort was coordinated by a binational Environmental Work Group, established to oversee the monitoring process under Minute 319.

Notable findings

Included among the findings of the study are the following four notable achievements that resulted from this historic cooperative effort:

  1. Plants: Plants thrived in the river floodplain following the pulse flow in 2014, with a 17% increase in vegetation greenness, a measure of plant health. Greenness declined in subsequent years.
    1. Three managed habitat restoration sites were established or expanded, totaling 915 acres (371 hectares); in addition, 145 acres (59 hectares) were passively restored.
    2. More than 275,000 trees were planted, and year-to-year survival rates ranged from 75% to 95%.
    3. Native plants – including cottonwood, mesquite, and willow trees grew much better in restoration areas where non-native vegetation was removed before the pulse flow, as well as in actively managed areas.
  2. Birds: The abundance and diversity of birds in the riparian corridor increased in 2014 after the pulse flow but declined thereafter.
    1. The abundance and diversity of birds continues to be greater in restoration sites than in non-restored areas of the riparian corridor and remains higher than it was before the pulse flow.
    2. In 2017, bird diversity was 27% higher and the abundance of the 15 indicator species was 80% higher in the restoration areas than in the rest of the floodplain.
  3. Groundwater: Results indicated that the pulse flow also recharged groundwater in the Delta, an important resource for riparian tree and shrub species – as well as for local farmers who irrigate with pumped groundwater.
  4. Precedent-setting: The study results will be used to inform future bi-national cooperation efforts on behalf of the river. The science team learned a great deal about how to restore native habitat to the delta ecosystem and is, for the first time, equipped with data-driven recommendations for future restoration activities. Notably, the Minutes are setting a precedent for water-sharing agreements globally, as well as inspiring water rights advocates far beyond the region. Raise the River coalition members say that groups involved in water management and river restoration from as close to home as the Rio Grande to as far as Central and Eastern Asia have reached out to express interest in the water sharing concept

The Social Impact

While social science was not a part of the study, the impact upon the neighboring communities was significant. Beyond wildlife, when the pulse flow occurred, it brought together local residents, including older generations who remembered the river, and younger generations who had never before seen it flow. In the subsequent years, Raise the River organizations have employed local community members for on-the-ground restoration work, conducted environmental education programs for area students of all ages, and have offered recreational and tree-planting days in the restoration sites. All of these activities have served to integrate the ongoing active restoration work into the fabric of the community.

“The social response has been truly remarkable,” says Gaby Caloca, Coordinator, Water and Wetlands Program, Pronatura Noroeste. She has observed the impact these activities have had in the region. “Experiencing these newly green areas and seeing water in places which previously had been dry and barren has had the added benefit of rejuvenating the spirit of the local community.”

Small amount, large impact

Less than 1 percent of the Colorado’s historic flow to the delta was returned by the flows sanctioned under Minute 319, yet the strategic timing and placement of the water supported the thesis that a small amount of water is sufficient to restore crucial habitat for the birds and wildlife that have historically lived in the delta. It also provided lessons learned to be applied to future water deliveries.

“The most important lesson we learned is that a relatively small amount of water can go a long way toward restoring the Delta,” states Karen Schlatter, Associate Director of Water and Ecosystem Restoration, Sonoran Institute. “Efficient water application to managed restoration sites has established new native trees that are already 30 feet tall.”

The work continues

Minute 319 concluded in December 2017, and in September 2017 government officials, researchers, and coalition members of Raise the River successfully negotiated a successor agreement, Minute 323, to support continued cooperative work between Mexico and the U.S., covering a nine-year period through 2026. Minute 323 commits the United States and Mexico to work together to address potential Colorado River water shortages and to meet new water conservation and storage objectives. It represents the joint efforts of local, state, and the federal governments of both countries to set a course for a more secure water future for the more than 36 million people who rely on the Colorado River in the United States and Mexico.

When diverse stakeholders collaborate on Colorado River water management, governments, communities, and the environment have much to gain,” adds Schlatter. “This project demonstrates that active restoration and targeted environmental water releases can provide significant benefits to managed rivers with little or no natural flows.”


The binational collaboration significantly advanced knowledge about how to restore native habitat in this region and how water supports the ecosystem. The results of this binational investigation provided a foundation of data and analysis which will inform future cooperative actions.

The report results confirm that the environmental flows created new habitat, and increased bird diversity. The broader results of this work also included a meaningful reconnection of local communities to the environment, as well as garnering broad community and philanthropic funder support. Just as the report showed that active restoration sites achieved the highest success rate, is also underscores the fact that the restoration of the delta is a long-term process.

Working together, greater good can result, as the recent final monitoring report on the environmental water deliveries into the Colorado River Delta has validated.


Official Report from the IBWC – Minute 319 Colorado River Limitrophe and Delta Environmental Flows Monitoring Final Report; November 28, 2018: