So they proposed a workaround: The U.S. agencies would provide financing to improve the water-supply system in the Mexicali Valley, primarily by making canals there more watertight. The water saved through those improvements would – while technically part of Mexico's 1.5 million acre-feet cut of the river – count as the U.S. contribution to the Delta.
But that proposal, in turn, proved tough for Mexico to swallow. "Mexico saw that the U.S. was putting up cash, and called it 'paper water,' " says de la Parra. "The negotiators for Mexico knew that it wasn't going to be easy to sell it within the country. Cash wasn't enough."
The ultimate breakthrough hinged on a commitment by U.S. agencies to help Mexico stretch its water supplies farther than ever. The two countries agreed on a $1.7 billion laundry list of possible future water-supply projects, including desalination plants in Mexico. More importantly, at least in the short term, U.S. water agencies pledged to make $21 million in water-efficiency investments in the Mexicali Valley.
In exchange, they'll receive more than 175,000 acre-feet of water over the next five years – roughly a third of which will be earmarked as the U.S.'s portion of the pulse flow. After that, Mexico will receive all the water freed by the U.S.-financed improvements to its irrigation system.
"We get the front part of that (water-efficiency) yield," says the Central Arizona Project's Chuck Cullom, "and then for the next 30 or 40 years, the continued savings goes to Mexico."
Finally, on Nov. 20, 2012, after several months of intense, face-to-face final discussions, the negotiators met at the Hotel del Coronado in San Diego and signed Minute 319.
The meetings had blurred traditional lines in water politics, giving conservation organizations unprecedented access to decision-making about the river's future. And, as Pitt points out, international negotiations proved to be a realm in which many conventional environmentalist tactics – such as using lawsuits to force change – simply don't work.
"Those tools aren't there, because you can't apply them across the border into another country," she says. "Everything has to be through consensus; there's no rolling anybody."
The agreement also gives conservation organizations much of the responsibility for turning their vision of a restored Delta into reality, and for contributing the 52,696 acre-foot yearly base flow. "This agreement obligates the NGO community to put up one-third of the water – as much water as the U.S. or Mexico is putting up," says de la Parra. To raise the roughly $10 million necessary to buy that water and carry out additional restoration and monitoring, the Sonoran Institute, Pronatura and the Environmental Defense Fund have partnered with The Nature Conservancy, National Fish and Wildlife Foundation and the Redford Center.
The agreement also – in roundabout fashion – addresses many of the issues central to the endangered-species legal battles at the turn of the millennium. The water-efficiency investments that the Big Three have pledged to make in Mexico will free up additional water for their own use. But they will also help improve water supply, and habitat, for species that are endangered in the U.S. – and help keep the Big Three off the hook for liability under the Endangered Species Act.
"Restoring the Delta is important for the U.S., too," says Zamora. "When you think about the amount of money that the U.S. is investing in (recovery) programs for some of these species, a little bit of investment in Mexico makes a lot of sense."
Although Minute 319 will be relatively short-lived, it was fashioned as a launch pad for a longer-term successor agreement, and the Delta's champions hope they can show enough success over the coming several years to win a bigger commitment to restoring the Delta. Still, the Big Three have been careful to not commit to too much.
"It's still very touchy," says Silva. "The concern by the U.S. states was to not make a long-term commitment. Minute 319 is very carefully written."
Roberto Salmón is the head of the Mexican branch of the International Boundary and Water Commission, under whose auspices the negotiations were officially carried out. Salmón's office, in Ciudad Juárez, is just a quarter-mile south of the arsenal of steel fence, surveillance towers and Border Patrol vehicles that the U.S. has deployed along the border it shares with Mexico.
That fearsome bulwark stands in contrast to the increasing openness between both countries' Colorado River water bosses. "The Delta is part of the (Colorado River) system. And it doesn't matter whether it's in Mexico, or in China, or wherever – if it's part of the system, we all have to take care of it," says Salmón. "It was important for everyone to realize that we share a common resource – that the world doesn't end at the borderline."
This is the moment of greatest promise for the Delta since the rise of the big dams, over 75 years ago. The river's water bosses have morphed their positions tremendously since the beginning of the 21st century. Ironically, this would probably never have happened but for the drought.
"It made them loosen their grip on the strict law-of-the-river interpretations that they held for so long," says Gillon. "They get a lot more flexible when there's a drought."
In August, the U.S. government announced that—under the terms of an agreement between the seven U.S. states—it will reduce water deliveries to Lake Mead, the main source of water for Las Vegas, Phoenix and Tucson, and a significant source for Los Angeles and San Diego, by about 9 percent next year. That will accelerate the drop in Mead's water level toward 1,075 feet above sea level, the trigger for an official shortage declaration by the U.S. secretary of the Interior. There is a fifty-fifty chance of a shortage in 2016, and the odds will only get worse in the years that follow.
"Everyone knew this day was going to come," says Pitt. "But nobody really expected conditions to go south so quickly."
If a shortage is declared before the end of Minute 319 in 2017, it's extremely unlikely that a pulse flow could be released for the Delta. And so, Zamora and Hinojosa's teams are scrambling to prepare for a pulse flow this coming April.
They are racing to map the Delta with laser altimetry, to better understand how the released water might behave. Zamora is deploying even more heavy equipment to clear tamarisk from the floodplain and open pathways for the water to flow into the river's old meanders. Under Minute 319, an additional 2,300 acres will be restored throughout the Delta. This year, Zamora and his compatriots boosted the 800 acres of forest they've already restored with another 30,000 cottonwood and willow trees, which will provide a source of seeds for the pulse flow.
On a 114-degree day this summer, Zamora walked with a local project manager named Guadalupe Fonseca at a demonstration site some 50 miles downstream from where the river crosses into Mexico. They were in the process of repurposing some of the local irrigation district's canals as water-delivery points for the Delta. A few days earlier, a backhoe had scratched out a new ditch – just part of the bigger infrastructure they're laying in preparation for next year's flood.
They needed to test the ditch, so Fonseca removed an improvised dirt check dam with a quick twist of a shovel. A thin sheet of water slowly sizzled forward, finding its way along the contours of the channel like flame, pushing ahead a scummy froth as it sought the river from which it had been turned. Several hours later, Zamora peered over the edge of a berm and watched the water cascade into a pool that was slowly rising in the thick bosque of an old meander.
"This hasn't been easy. But if it works," he said, "it's going to go into the history books."
Matt Jenkins has covered Western water politics since 2001, Year Two of the Colorado River drought. He writes from Ciudad Juárez, Chihuahua, Mexico.
This story was made possible with support from the Kenney Brothers Foundation.