Dispatch from Mexico: a historic pulse of water to restore the delta
Just south of the Mexican border town of Los Algodones, last Thursday dawned with a whipping breeze. Maintenance workers hustled to sweep, shovel dust and repaint the yellow speed bumps in the road alongside Mexico’s main Colorado River dam, named for the patriot José María Morelos, who was executed by Spain in 1815 for his role in the Mexican War of Independence.
The workers were preparing the facility for a wave of Mexican and U.S. dignitaries, who soon arrived to commemorate a landmark international water deal. Since the early 1960s, water has — thanks to an aggressive program of dam building upstream — only occasionally reached the delta at the mouth of the Colorado River. But Minute 319 — an amendment to a U.S.-Mexico water treaty — calls for, among other things, the release of a “pulse flow,” a substantial shot of water to boost the delta’s suffering riparian ecosystem.
After a long round of speechifying, the U.S. officials would be chauffeured through the Colorado River Delta in what locals referred to, with considerable amusement, as “el convoy” — an armada of five-ton, bulletproof Suburbans seconded from the Tijuana consulate. Yet in spite of all the bureaucratic pomp, the event felt like a week-long beach party.
That party had actually started four days earlier, when the dam keeper — shadowed by a very small dog — made his morning rounds to check that the dam’s equipment was functioning. As the sun lit a statue of José María Morelos, on the north side of the dam, a gaggle of onlookers gathered at the toe of a levee downstream. On the U.S. side of the river, a couple of Border Patrol agents stopped to keep watch.
Just after 8 a.m., with little fanfare, one of the gates on the dam opened. At first, the change was almost imperceptible. Then someone piped up, “There it goes! Right in the middle”: water boiling out from the dam. “Wow,” murmured someone else. A pair of drones, piloted by videographers, buzzed over the crowd. Several of the advisers and environmental professionals who have worked tenaciously to get water back to the Delta — among others, Osvel Hinojosa, Francisco Zamora, Yamilett Carrillo, Jennifer Pitt, Peter Culp and Carlos de la Parra — broke out bottles of champagne for a spontaneous toast. Then they did it again for the cameras.
As more and more water rushed from the dam, the onlookers tightened into a denser and denser group to avoid the rising river. Finally, a local policeman reefed on his whistle and summoned everyone to higher ground.
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South of the border, the Colorado — even if dry — becomes a bewildering tangle of channels that ultimately dissolves into the Gulf of California. In A River No More, Philip Fradkin wrote: “To follow the river from Morelos Dam to the gulf is a tricky business.”
It helps to have an airplane. The day after the release began, I met Pitt and Culp at Mexicali’s spare, dune-hugged airport, and we crammed ourselves into a Cessna flown by Bob Allen, a volunteer pilot for the nonprofit group LightHawk, a kind of environmentally-oriented barnstorming service.
Soon, we were spinning tight orbits over Morelos Dam, and began following the water downriver. Several miles downstream, we spotted the front of the pulse flow, slowly finding its way, in long, probing fingers, through the sandy riverbed. The leading edge shimmered in the sun: water on the move. Allen cranked the Cessna Cardinal into a tight turn overhead. “Oh – I can see the water running,” he said. “Look at that. That is so cool.”
We winged our way some 90 miles downstream, along dry channels to the mouth of the river. The desolate salt flats at the foot of the Sierra San Pedro Mártir glimmered in the distance, and the Delta took on a kind of otherworldly splendor.
“Welcome to Mars,” Allen quipped over the intercom.
We flew on in silence. The world below felt like a place beyond human reach. Except, of course, that it has been dramatically reshaped by human design. Yet with the pulse flow, that world is being shaped again: perhaps not to what it once was, but into something other than what it has become.
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Back upstream, the party continued over the next several days. The populace of the town of San Luis Río Colorado turned out at the river en masse. What had served as an improvised dune-buggy area in the long-dry riverbed became a veritable waterpark of people splashing in the newly returned river. Much of the real action, though, is happening deep in the Delta, far from where it is so easy to see.
Hydrologists and environmentalists anxiously watched a particularly dry stretch of the river dubbed “the black hole,” where some people worried that large amounts of the pulse flow might simply disappear into the sand. To stack the deck in their favor, the pulse flow’s designers used local irrigation ditches to surgically boost inflows of water at strategic points along the river channel. But scientists have also been heartened to see that the release of water was perfectly timed to catch and carry the spring “seed rain” from cottonwood and other trees along the river: Seeds were being washed from near Morelos Dam deep into the Delta, where they will germinate when the flood recedes, send their roots chasing groundwater, and help re-establish native forests. For good measure, the Mexican environmental group Pronatura and the U.S. Sonoran Institute are growing more than 100,000 trees in nurseries this year, which they will plant in the Delta, as well.
Over the past two decades, the Delta’s advocates have argued their case with perseverance, and a lot of good numbers. By monitoring the effect of the pulse flow, they’re hoping to make the case for a followup agreement — a Minute 320 — to kick off a long-term program of regular floods that mimic the natural dynamics of the river.

It has taken a lot of hard work to get to this point, and everyone recognizes that much hard work lies ahead. But one of the biggest victories has already been won, not so much in the Delta itself, but in the realm of the Colorado River’s broader politics. Some of the best minds on the river were behind this deal — some publicly, others much less so. The Delta’s champions have earned respect, and are now real participants in the river's broader politics. And they will be a fundamental part of the constant negotiation that will keep the river going into the future.
These are difficult times on the river, to be sure. Because of the 14-year drought and the sharp competition for water, this is an era of real anxiety about whether a comprehensive, long-term restoration program is politically feasible. Yet this much is assured: It will be impossible to ever again talk about the Colorado River without talking about the Delta, too.
Matt Jenkins is a contributor to High Country News.