The blockade is tightening as the water flows. Sonora has been wrenched for three years by conflict over the construction of an aqueduct to supply the capital city, Hermosillo, with water from the Rio Yaqui basin.
Now the water is flowing, and the Yaqui people who live at the end of that exhausted river are maintaining a protest blockade of the main highway that runs north-south from the Arizona border to Sinaloa. From the blockade at Vicam, Sonora, the line of vehicles stretched for miles Wednesday, but on Thursday the authorities shunted traffic onto a four-hour detour.
The scene is not quite apocalyptic, but it makes you wonder what's coming in this region as water becomes more scarce and valuable.
Tucson attorney James Hopkins has been helping residents of the eight Yaqui villages fight the aqueduct. Hopkins, a University of Arizona law professor, has argued in the Mexican court system and the Inter-American Commission on Human Rights that the state of Sonora has violated the Yaquis' rights by taking their water supply. Hermosillo sits in the neighboring Rio Sonora basin.
Hopkins also argues that the aqueduct project violates a treaty with the United States, because some of the Rio Yaqui basin's water comes from extreme Southeastern Arizona. A tiny portion of Arizona surface water supported by much more groundwater feeds the Rio Yaqui, Hopkins said.
This and stronger arguments have not swayed Sonoran Gov. Guillermo Padrés - from Cananea, Sonora, just south of Sierra Vista, by the way - who has pushed the Acueducto Independencia as the signature achievement of his administration.
The situation is comparable to some of the West's big water projects and conflicts, said Nicolás Pineda, a professor of public policy at the Colegio de Sonora in Hermosillo. The project is comparable to the Central Arizona Project in the way it can allow Hermosillo to grow, he said, and the conflict harks all the way back to the seizure by Los Angeles of the Owens River's water, the subject of the movie Chinatown.
However, there is economic justification, Pineda said.
"The productivity of the city of Hermosillo is much greater than that of the Yaqui Valley," he said.
While Hermosillo is home to a huge Ford plant - struggling now to keep up with demand for Fusion vehicles - and a growing aerospace industry, the Rio Yaqui is home largely to growers of wheat, a subsidized crop, he said.
Margaret Wilder, associate professor of geography at the UA, has researched water access in that part of Sonora, and she says there are two conflicts occurring at once. One is an age-old conflict between the Yaqui people and the Mexican government over access to water, land and other resources.
The Yaqui communities of Arizona were largely established by those who left Mexico a century or more ago, fleeing attacks by the Mexican government.
The other conflict, Wilder said, is between the longtime farmers of Ciudad Obregón and the government.
"To me, that's more of what you'd see in Arizona," she said. "These guys have passed their lands on from grandfather to grandson over the generations."
Party politics have also mixed with economic interests and ethnic divisions in the conflict, stoking the protest movement. What's surprised Jeff Banister, a UA researcher and expert in the area, is the reaction of the state government.
"One of the things that's special in the Sonoran case is the boldness with which Gov. Padrés has gone after the water supply, ignoring mass mobilization, ignoring the courts," Banister said.
The water began flowing to Hermosillo in March, and appeals have failed or been ignored. So now the Yaquis have been blockading the roads, off and on, for weeks. Tuesday was the first day they declared a total blockage, prohibiting any traffic from moving, though at times they allow vehicles with children, elderly or sick people to pass.
Following Mexican tradition, the federal and state governments have been reluctant to move in with force, Pineda said.
"There's a lot of fear of creating martyrs or making the conflict bigger," he said.
Hopkins, the UA law professor, sees this conflict as foreshadowing what happens when Hermosillo inevitably saps this supply.
"What's going to happen is something far worse. They're going to drain the Yaqui basin, then they're going to crash it," he said, raising the specter of a million Hermosillo residents running out of water.
Let's hope his apocalyptic vision is exaggerated.
Contact columnist Tim Steller at firstname.lastname@example.org or 807-8427. On Twitter: @senyorreporter