Bringing the River Back to the Sea | The story of the Colorado River pulse flow
Environmental Defense Fund logo

It's been half a century since the Colorado River flowed regularly to the sea.

On March 23, 2014, the gates at Morelos Dam on the U.S.-Mexico border were opened to release a temporary "pulse flow" of water into the dry delta in hopes of restoring some of the natural bounty the river once provided. Nearly eight weeks later, in the final days of the pulse flow, the river reached the sea in a brief reunion that was more than a decade overdue.

Equivalent to approximately one percent of annual Colorado River flows, the pulse flow was a modest amount of water delivered to bring many environmental benefits to the delta region. Plants, animals and communities have benefitted from the flows, which shocked the system back to life.

The atmosphere during the pulse flow was one of jubilee. Birds could be heard trilling in the trees, while children were found splashing about. But the journey to restore the delta has been long and laborious, at times even somber. Before we take steps forward to bring more restoration to the Colorado River Delta, let's first take a look at what got us to this point.

Bringing the River 
Back to the Sea

At the dawn of the 20th Century, the vast domain of the Colorado River lay almost entirely untouched. Within two decades, everything changed. 


Western water law at that time was based on the simple rule that whoever used water first had the right to that water. This led to a free-for-all among the seven basin states –Colorado, Utah, New Mexico, Wyoming, Nevada, California and Arizona – which spent much of the decade leading up to 1922, when the Colorado River Compact was signed, squabbling over their share of the river. 


By the time the U.S. and Mexico signed the 1944 treaty governing shared waters, the basin states were well versed in fighting over water. The treaty allocated some 10 percent of the Colorado’s water to Mexico, and increased the certainty regarding future water uses in Mexico for those looking to develop additional Colorado River resources in the U.S. Some scholars believe that Mexico secured the right to Colorado River water only because the U.S. wanted to improve relations with Mexico to ensure access to Mexico’s petroleum reserves.

Conservation leaders organize several meetings with U.S. and Mexican water managers at the border [above], where major progress is made. Eventually, the two countries announce official, bilateral discussions about a "holistic" approach to binational management of Colorado River water.

U.S. and Mexico International Boundary and Water Commissioners Carlos Marin and Arturo Herrera die in a tragic plane crash.

An April 2010 earthquake damages water infrastructure in Mexico [below].

U.S. and Mexico International Boundary and Water Commissioners Edward Drusina and Roberto Salmon [below] sign Minutes 316, 317 and 318, which together improve shared management of the river and set the stage for Minute 319. 

Conservation groups help federal officials from the U.S. and Mexico broker a deal to sign Minute 319.

The agreement – an amendment to a 1944 treaty – allows the two nations to share Colorado River surplus water in times of plenty and reductions in times of drought, rules that heretofore did not exist. It also includes commitments to deliver environmental flows to the Colorado River Delta.

On March 23, 2014, the U.S. and Mexico follow through with their 2012 commitment, opening the gates at Morelos Dam [above] to begin releasing the pulse flow into the delta.

On May 15, 2014, the pulse flow reaches the sea – the first time that water from the Colorado River flows into the Sea of Cortez since the '90s.

Allocating surplus water for the Colorado River Delta is considered "beyond purpose and need."

The first binational, federally organized delta summit is convened in Mexicali on September 11, 2001. The day's terrorist attacks disrupted the meeting, suspending any progress on solutions for the delta.

United Nations Security Council votes to support the invasion of Iraq. Mexico abstains from the vote.

On March 31, 2003, the Defenders of Wildlife v. Norton decision asserts the U.S. does not have discretion to deliver additional water for delta restoration under the Endangered Species Act. 

Cooperation between the U.S. and Mexico hits a new low when, during the worst eight-year period of drought in over a century, the U.S. issues domestic rules for water shortages that make specific assumptions about how Mexico will share the pain, without having secured an agreement with Mexico.   

Just Add Water and Life Begins
10 Years to Produce a Minute

In the following decades, a whole slew of statutes was passed that together comprised the foundation of the Law of the River. These guiding principles paved the way for the damming and diverting of the Colorado River to meet human needs and enabled ever-increasing growth of the American West. But there were consequences for the environment: over the course of several decades, river flows diminished. Eventually, between 1960 and 1980, as Lake Powell began to fill behind Glen Canyon Dam, the Colorado River stopped flowing regularly to the sea. 


In the popular imagination, the Colorado River was broken, and its delta was dead. But as it happens, the delta wasn’t dead at all. In the 1980s, several years' worth of huge mountain snowpack in the Rockies resulted in tremendous spring floods that inundated the delta. Moreover, small unintentional flows – the result of less than perfectly efficient dam operations – were released inadvertently nearly every year. In the delta, where there is plenty of rich soil and hot desert sun, these flows brought about a revival. More high quality native habitat flourished in the river’s last 100 miles in Mexico than could be found on the entire reach between Lake Mead and the U.S.-Mexico border. 


This revival was first documented by Dr. Ed Glenn, a professor of Environmental Science at the University of Arizona, who had spent his career looking at ways to grow food with salty water in drought-stricken regions of Africa. Dr. Glenn began studying the Colorado River Delta, and hypothesized that a modestly-sized “pulse flow” every few years, in addition to small base flows delivered on a regular basis, could keep the delta’s habitats healthy. Environmental Defense Fund and our conservation partners took notice of Dr. Glenn’s work and began advocating to protect flows for the delta.


One of the first attempts to engage federal river managers took place in the late 1990s when the Department of Interior began working with the seven Colorado River Basin states to develop rules for “surplus” water allocations, which until that time were made on an annual basis at the secretary’s discretion. 


This got people thinking, If surplus water can be released for the benefit of water users in the U.S., why can't we allocate surplus water for the delta?


Taking this idea to federal leaders, conservation organizations asked then Secretary of the Interior Bruce Babbitt if rules could be made to allocate surplus water for the protection of habitat and restoration of the Colorado River Delta. Unfortunately, the secretary saw this as "beyond purpose and need" of the rulemaking. However, eager to be seen as a problem-solver and a friend of the Colorado River, Babbitt asked Deputy Secretary David Hayes to convene a meeting for Colorado River stakeholders to come up with some form of a solution for the delta. 


That's when then International Boundary and Water Commission (IBWC) Foreign Secretary for the United States Bob Ybarra suggested a "minute." Minutes are binational agreements issued by the IBWC providing additional interpretation of the 1944 U.S.-Mexico treaty.


Minute 306 was birthed in the 11th hour of the Clinton administration and signed on December 12, 2000. It established a conceptual framework in which the United States and Mexico would cooperate in studying and making future recommendations concerning the Colorado River Delta.


As a first step, U.S. and Mexico officials worked with Colorado River stakeholders, including lower basin states, water contractors and conservation groups, to organize the first binational delta summit, which included speakers with legal, engineering and ecological expertise. Nearly 200 people from each country traveled to Mexicali to attend the summit on September 11, 2001. 


While the summit did convene, the September 11th terrorist attacks disrupted the meeting, suspending any substantial progress before it could even be made. 


The relationship between the U.S. and Mexico became more fraught in the following months and years, as Mexico chose not to vote in support of America's position on the invasion of Iraq in the United Nations Security Council. Tensions thrashed through border relations, with the U.S. showing more of an interest in building walls rather than breaking down barriers.


In 2003, there was yet another blow to efforts to protect the Colorado River Delta when a significant legal case – Defenders of Wildlife v. Norton – was decided. Defenders of Wildlife argued that, under the Endangered Species Act (ESA), the Bureau of Reclamation should consult with the U.S. Fish and Wildlife Service about management of its deliveries of Colorado River water so as to not harm endangered species habitat, including that of the southwestern willow flycatcher and other species that thrived in the delta.


The case did not succeed. The court noted that ESA law only bears on activities for which the U.S. has discretion. And since the U.S. and Mexico signed a 1944 treaty guaranteeing 1.5 million acre-feet of water per year from the Colorado, the court decided that the U.S. did not have discretion to deliver any additional water for restoration purposes. 


In the meantime, drought conditions had gripped the Colorado River Basin. By 2005, Colorado River water stored in the basin’s vast reservoirs had declined by more than 50 percent, and flows to the Colorado River Delta had ceased almost entirely, as all Colorado River water was either delivered to water users or captured in reservoirs. There was nothing “extra” for the delta anymore, and the habitat revived in the 1980s started to disappear. The U.S. federal government started working with the seven U.S. Colorado River Basin states to formalize rules for shortages in the event that the basin’s water supply diminished even further. 


The final shortage rule was issued in 2007.  While the rulemaking was generally heralded as a success, and the conservation community lauded water managers for finally addressing the hard work of allocating shortages among U.S. water users, the rulemaking also did additional damage to U.S.-Mexico relations on the Colorado River. In the process of analyzing how river operations would change with the new shortage rule, the U.S. federal government assumed Mexico would also take shortages. Mexico took note of the study and complained, not only about the shortage assumption, but also about the fact that there had been no bilateral discussions of when and how Mexico would be subject to shortage.


Cooperation between the two countries hit a new low.


In the context of high tensions and bitter affections, the conservation community forged ahead with the understanding that, without a legal mandate, and with no end to drought in sight, the only way to help the Colorado River Delta was through binational cooperation. Conservationists convinced U.S. representatives from the lower basin states to begin a conversation with Mexican Colorado River water managers regarding opportunities to improve management of their shared resource. Clearly, others agreed it was time to turn the corner in the relationship, and by the end of 2007, the two countries announced official, bilateral discussions about  a "holistic" approach to binational management of Colorado River water. 


In a devastating turn of events, the U.S. and Mexico International Boundary and Water Commissioners – U.S. Commissioner Carlos Marin and Mexican Commissioner Arturo Herrera – died in a tragic plane crash near the Rio Grande, due to adverse weather and flying conditions. The accident was a great misfortune, and two leaders who had dedicated their careers to improving relations between the United States and Mexico were lost. The crash also took the lives of Jake Brisbin Jr., a prominent West Texan and executive director of the Rio Grande Council of Governments, and Matt Juneau, a pilot and co-founder of Volare Air Charter. But even in the darkest of hours, all hope was not lost.


By 2010 – more than a decade after delta discussions had been initiated – conservation groups made remarkable headway in U.S.-Mexico hydraulic relations. Discussions that had been ongoing for years finally yielded a series of binational agreements. Minutes 316, 317 and 318 were signed by representatives from both countries, with commitments to protect the water supply for Colorado River Delta wetlands, grant Mexico temporary storage rights in Lake Mead after an April 2010 earthquake damaged great portions of the Mexicali Valley water infrastructure, and formalize a framework for the Colorado River negotiations that would eventually yield the most significant U.S.-Mexico agreement on the Colorado River since the 1944 treaty.   


The persistence of the U.S. and Mexican negotiators working on the Colorado River was impressive. The barriers were significant, including substantive differences in law, language, culture, economic structure and geography. But the specter of climate change and future extended droughts meant the stakes were high, and the negotiators overcame these obstacles to reach a comprehensive five-year agreement in November 2012 with the signing of Minute 319. The policy was finally in place to allow delivery of water to the delta. Specifically, the agreement allowed a temporary "pulse flow" of water –approximately one percent of annual Colorado River flows – to flow into the delta for restoration purposes. 


But there’s even more to Minute 319 than delta restoration. The broad agreement also included benefits for water users in both countries and in all sectors, with interim approaches for the U.S. and Mexico to resolve shared Colorado River issues including: sharing Colorado River surplus in times of plenty, sharing reductions in times of drought, providing operational flexibility for Mexico to store water in U.S. reservoirs, maintaining salinity standards, and encouraging water conservation and binational water development projects – rules that heretofore did not exist.


Today, Minute 319 stands as one of the most significant international and environmental water policies of this era.

In addition to designating water for the pulse flow, the U.S. and Mexico have collaborated to establish a program to monitor the impacts of the limited-duration flows to tell us what happened: Where did the water go? How much groundwater recharge took place? Did the flow change the river channel itself? How many new trees were generated and where? What was the wildlife response? Only time will tell what happens, and we need to make sure that all of these answers are available.


The science team monitoring the pulse flow will have some of the answers; the rest will come from the people – from those who remember the Colorado River as it once was, flowing naturally to the Sea of Cortez, to those who are seeing the Colorado River for the first time. These firsthand accounts are essential parts of the delta story.


“We are witnessing what appears to be a paradigm shift in the way we manage water. Historically in the West, everyone has approached water with an 'us against them' mentality. Now we’re talking about how we can share water, conserve water and invest in new water projects and the health of the river itself. It’s truly refreshing.”

- Jennifer Pitt, director of the Colorado River Project at Environmental Defense Fund 
A boy in San Luis Rio Colorado –  a town named after the Colorado River –  sees water in the delta channel for the very first time. 
 Justice for the Delta

The Cucapá tribe – Cucapá meaning "river people" – lives on the banks of the Hardy River, a tributary of the Colorado River in Mexico. 

The elder Cucapá Colin Soto wrote, “El pueblo Cucapá es el rio. Toda nuestra vida esta basado en el rio.” The Cucapá people are the river. Our whole life is based on the river.  

With fishing as a primary source of food and income, the Cucapá know more than anyone the value of a healthy river. Their livelihood literally depends on it, and they have suffered greatly in recent decades, as fishing opportunities have become sparse and tribe members have had to travel farther to find fish.

Doña Inocencia Gonzalez Sainz, an older woman who has excelled in her craft work and in preserving and teaching the language and culture of the Cucapá to new generations, recalls the greatness that once was the Colorado River.

"We went fishing on pangas, when the river was carrying a lot of water – very strong running river water. Sometimes we camped beside the river when there was good fishing. We spent several days there and we brought back a lot of fish to El Mayor," recalls Inocencia, who now spends her days tending the Community Museum in the indigenous town of El Mayor, where she also creates and sells her crafts.

Inocencia remembers the last time she went fishing. It was in the late '80s. After that came a long dry period in the lower basin.

Inocencia says that it's very good to see water running in the Colorado River Delta again, because without water, the Cucapá are destined to become extinct.

Alfonso Rubio Russel is a farmer in the Mexicali Valley and chairman of Irrigation Module 2, which serves several farms along the river channel producing wheat, cotton and vegetables. He also worries what the future will bring, understanding that there is increasing demand for water.

"We would like to see the Colorado River as it was before, understanding that there are population pressures and cities require more and more water," said Alfonso. "It is because water is increasingly sought after that we must take care of the river."

Even now that the two countries are working together to bring water back to the delta, Alfonso remains doubtful that the pulse flow will bring any long-term benefits.


In San Luis Rio Colorado – a town named after the Colorado River – children and families have been found swimming where, only a few weeks before, there was nothing but dry, cracked land.

That's all that many children have known here, since water has not flowed regularly to the delta region in Mexico for many years. While local conservation organizations and newspapers did as much as they could to announce the arrival of the pulse flow, it still came as a surprise to many people. And a pleasant one at that.

During the pulse flow, celebrations took place almost daily beneath the bridge in San Luis Rio Colorado, where food trucks served lunch, bands played upbeat music and families picnicked along the riverbank. For most people, the sight of water in the river was a reason to rejoice. And a sign of good things to come.

With great hope and anticipation, delta communities look to the future. Aside from a few, there is optimism that U.S. and Mexico negotiators will continue to make the health of the Colorado River a priority, and that, one day soon, there will be justice for the delta.

For two months, the Colorado River flowed in its delta – a region that has been deprived of regular river flows for half a century – thanks to the "pulse flow."

The pulse flow started on March 23, 2014, and lasted nearly eight weeks, ending in May 2014. It was designed to mimic – albeit at a small scale – the spring floods that historically inundated the delta and were crucial to the community of plants and animals that thrived there. The small size of the flow – less than one percent of the river’s annual yield – was nonetheless significant because so little water has reached the Colorado’s delta in recent years.

While the pulse flow made its way downstream, scientists eagerly followed the progress, wondering how far it would go as water seeped into the sand, recharging the depleted aquifer that straddles the border. As the release ended, experts from both countries began studying its effects. Will water be left standing or will it be absorbed into the soil? We will have to wait and see.

The scientists monitoring the pulse flow will continue to collect valuable data that will be made available to U.S. and Mexico negotiators as they think through next steps.

In the meantime, nature has already started to respond.

willows – the native trees critical to high quality river habitat. A portion of the seeds that land on newly wetted soils will germinate; some already have, sinking their new roots down in search of water. This is how the riverside forests rejuvenate and stay healthy.

The birds have also responded. Hawks, egrets and ospreys have been spotted flying above the pulse flow’s path. People who have walked along the channel or paddled down the river have heard riots of birdcalls. Ornithologists confirmed that it does seem like the birds have been vocalizing more than usual, indicating their excitement.

Other animals have taken an interest in the pulse flow, too. Beavers have been found approaching the river channel, as have goats from nearby farms.

One local farmer who lives along one of the driest and sandiest stretches of the river channel said that he routinely herds his goats through this area, and he was very surprised to see water flowing there again. He said he hasn't seen water there in decades, but he is very happy.

"It’s great for the plants and animals," he said. "And my goats are especially happy."

Even happier is the conservation community that first put the pulse flow in motion more than 10 years ago. They stand by, watching and celebrating each development as the delta shows more signs of life.

"Notwithstanding the fact that I started talking about the pulse flow 15 years ago, spoken and written about it countless times, I was nonetheless astounded,

overwhelmed and speechless when I saw the water appear in the river," said Jennifer Pitt. "It's almost like we conjured a river back into being."

In addition to the eight-week pulse flow, some 52,696 acre-feet of “base flow” will also be delivered over the next four years to support key restoration sites in the river’s riparian corridor, thanks to commitments under Minute 319.

A non-profit coalition including Environmental Defense Fund, National Fish and Wildlife Foundation, The Nature Conservancy, Pronatura Noroeste, Redford Center and Sonoran Institute launched the “Raise the River” campaign to raise funds for long-term habitat restoration projects as well as the Colorado River Delta Water Trust, which acquires base flows through the purchase and lease of water rights from willing sellers throughout the Mexicali Valley.

“The base flows acquired by the trust will help to nourish and maintain any new growth that appears this spring as a result of the pulse flow and other on-the-ground restoration investments,” said David Yardas, director of the National Fish and Wildlife Foundation’s Southwest and Interior Water Programs. “The delta ecosystem’s response should demonstrate the incredible value of these companion restoration strategies, and the importance of bringing water back to the delta over the long term.”

"All the rivers flow into the sea, Yet the sea is not full. 
To the place where the rivers flow, There they flow again."

On May 15, 2014, celebrations reached a new high as aerial photographs confirmed the reunion of the river and sea.

"The pulse flow meeting the sea marks completion of a journey that the Colorado River has not made in a long time, and I take it as a sign of hope not only for our efforts to restore the Colorado River Delta, but also rivers and watersheds everywhere in the world where climate change promises an uncertain future," said Jennifer Pitt.

As the pulse flow comes to an end, we mustn’t forget what it took to bring the river back to the sea. If we are going to make any effort to restore the delta in the long term, we need an ambitious plan to reform water management along the entire length of the Colorado River. Only then, if increased water conservation leads to increased water supply reliability throughout the basin, can political decision-makers in the U.S. and Mexico make commitments to deliver water to the delta.

EDF and our partners are trying to do exactly this. Bringing together groups that have not always cooperated with each other, we want to reduce pressure on the river and restore healthy flows throughout the basin by:

Ensuring that agriculture remains vital in this region, while creating incentives for ranchers and farmers to modernize irrigation infrastructure that increases their productivity and allows them on a voluntary basis to share the saved water with other users.

Creating incentives that promote conservation and efficiency in cities. 

Supporting the adoption of flexible management agreements that prevent one class of water users or one particular area from having to shoulder the full burden of shortages. Innovative agreements that compensate willing sellers can help prevent the most devastating impacts of extended drought.

With a more holistic approach to river management, and additional negotiations on the part of U.S. and Mexican federal and water agencies, there is hope for water users and ecosystems throughout the basin, but especially in the delta.

Like the Mexican farmer and irrigator Alfonso Rubio Russel said, "Hay que estar en armonía con la naturaleza." We must be in harmony with nature.


"It was almost like a seven-handed poker game, and the pot sitting in the middle of the table was the water of the Colorado River. Sitting at the end of the table was an eighth player, Mexico, eager to join the game."

-  Colorado River Water Users Association website
Produced by Chandler Clay 
with support from Jennifer Pitt, Julie Benson, Jeremy Proville, 
César Angulo, Gabriela de la Vega, Levi Chronister and Brandi Jones
- Ecclesiastes 1:7
Lake Powell and Glen Canyon Dam
The Hardy River [above] – a tributary of the Colorado – is home to the Cucapá Tribe.

Doña Inocencia Gonzalez Sainz [below] shows her identification card. The occupation reads "Pescador," fisherman.  

Mexicali Valley irrigation chairmen Alfonso Rubio Russel [top] and José Fidencio Arroyo González [bottom].
[Clockwise from top left] A recently planted cottonwood seedling; a dredged ditch to carry pulse flow water to the restoration site; a barn owl resting in the shade of a salt cedar (an invasive tree); rows of planted tree seedlings that will eventually grow into a riparian forest.
Jennifer Pitt, U.S. co-chair of the environmental work group that helped negotiate Minute 319, touches the leading edge of the pulse flow. 
Take a tour of the pulse flow through the delta region in Mexico, beginning with the release of water at Morelos Dam and ending in the Gulf of California, where the river reached the sea.

"The pulse flow is a good idea, but it will hardly restore a river that has spent years suffering from a lack of water."

In the short term, Alfonso has had to deal with questions from farmers who are concerned about what river restoration means for their water deliveries. He has tried to assure them that the pulse flow will not affect the amount of water their farms receive, but there are still lingering suspicions. 

José Fidencio Arroyo González is chairman of Irrigation Module 22, not far from Alfonso's module. He is in a similar position to Alfonso, having to educate and assure farmers who are concerned about where the water for restoration is coming from, and who believe that the first priority should be to irrigate plots to produce food, not to waste water for ecological uses.

But José is more excited about the pulse flow and other restoration projects. He believes that the pulse flow is good for local farmers, since it reduces the temperature along the river and recharges the aquifers that are used by the agricultural sector.

The newly recharged aquifers are also nourishing large tree planting projects along the river. Just south of the two irrigation modules is one such project – Laguna Grande.

Cottonwood and willow trees are being planted along the river channel at the Laguna Grande restoration site – designed to restore the previously lost riparian corridor along the Colorado River Delta. Several bird species, including many endangered species, are expected to return to this place. Some already have. 

The Laguna Grande restoration site is also being prepared as a recreational destination for locals to come bird-watch, swim and picnic. Workers said that they have already started leading bird-watching tours and have seen local community members coming here to enjoy the natural environment. 

For the dozens of restoration workers employed by Pronatura Noroeste, Sonoran Institute and other local conservation organizations, the Colorado River is more than a river. It's their livelihood and their passion.   

Salvador Chávez Alacaráz is a restoration coordinator for Prontara Noroeste who has been working on delta restoration projects for more than six years. He says he can't imagine what he would be doing otherwise. Salvador describes his job as high in quality with good pay, relatively flexible hours and less physical labor than a lot of other jobs.

For Salvador and his colleagues, the pulse flow also brings a great sense of fulfillment.

"The pulse flow is very exciting for us, as we have been waiting for it for more than a year," said HéctorPatiño Garduño, a restoration technician for Pronatura Noroeste. "We are hopeful that there will be positive impacts for the flora and fauna here, but also for the local communities."

Scientists are monitoring the results for the flora and fauna, but Héctor's hopes for the local communities have already transpired.

“We have worked hand-in-hand with our partners over the years to achieve the best results possible for the delta. We are working together to monitor the pulse flow to determine its impacts on the delta and to inform future efforts to stimulate river health.” 
- Francisco Zamora Arroyo, director of the Colorado River Delta Legacy Program at Sonoran Institute
All along the river channel through the delta, there is ample evidence that the banks are wet. This is the perfect condition to start seedlings, as scientists have suggested that habitat creation is promoted when flows rise out of the river banks and inundate the soils, particularly in locations where year-round groundwater is available to sustain any new seedlings.

The timing of this was intentional, with the pulse flow occurring at the same time that seeds were dropping from cottonwoods and 

The front page of a Mexican newspaper reads Water Flows for the River!
The leading edge of the pulse flow blankets a dry, sandy stretch of river channel.

Representatives from conservation organizations stand alongside policymakers from U.S. and Mexico federal agencies at the pulse flow event on March 27, 2014.

On May 15, 2014, the Colorado River reunited with the sea. Photos by  Francisco Zamora, with aerial support provided by LightHawk.

“Rivers affect the health of our seas, wildlife, communities and economies. Restoring freshwater habitats is no longer optional; it’s imperative.” 
- Osvel Hinojosa Huerta, director of the Water and Wetlands Program at Pronatura Noroeste