Del Puerto Canyon, just outside of Patterson, CA, has long been identified as a significant ecological, geological, and cultural site in the Diablo Range, part of California’s coast ranges. The canyon and Del Puerto Creek, which runs through it, provide important ecological, recreational, cultural, and educational services, including critical habitat for a host of local species.
The canyon also happens to be the site where dinosaur fossils were first identified in California. It is popular among day hikers and educational groups, and the city of Patterson once outlined plans for a local park in the canyon.
In spite of all this, the Del Puerto Water District proposes to construct a new dam at the narrow outlet (the “puerto,” “door” in Spanish) of Del Puerto Creek into the San Joaquin Valley. The proposed reservoir would inundate 800 acres of undeveloped and picturesque California grassland and oak woodland. It would have the capacity to store roughly 82,000 acre-feet of water at a cost that’s risen from $500 million to $1.18 billion and counting.
In most years, the existing nearby San Luis Reservoir (possessing 2-million acre-feet of storage space) already provides ample south-of Delta off-stream storage for the federal Central Valley Project and the State Water Project, the state’s two largest water systems. Moreover, in 2024 the U.S. Bureau of Reclamation announced a consensus agreement to expand this reservoir by 130,000 acre-feet.
Critics have also highlighted the dam’s vulnerability to known and potential Coast Range seismic risks, heightening local concerns over the safety of the dam.
Local opposition to the project is steadily growing. Save Del Puerto Canyon is a local grassroots organization based in Patterson that has been advocating on behalf of the local community and the canyon. Membership has grown to more than 2,000 members. Save Mt. Diablo has also taken an interest in problems with the project. Friends of the River has been active in opposing the project from the beginning and stands with these groups to protect Del Puerto Creek from this unnecessary project.