SACRAMENTO — Gov. Jerry Brown’s $23 billion proposal to build two massive, 35-mile-long tunnels that would make it easier to move water from Northern California to farms and cities in the south and other parts of the state took a step forward Thursday with the release of the plan’s first details.

But even as the Brown administration rolled out four of 12 chapters of its “draft Bay Delta Conservation Plan” amid fanfare and a Capitol news conference, hanging over the event was the reality that the project faces a series of huge hurdles, any of which could kill it:

“There are so many interests, from anti-tax to anti-development, and they collide again and again. It’s hard to find a center,” said Larry Gerston, a political-science professor at San Jose State University. “These things take decades, if ever. These are difficult times for big projects and for building consensus. The state is so fractured, and so many interests all have levers of power.”

Nevertheless, the Brown administration put the best face on the project Thursday. The hundreds of pages in the documents it released contained historic information about salmon, smelt and other species in the Sacramento-San Joaquin River Delta, an overview of the years-long planning process and 22 conservation measures that planners said the tunnels project could help achieve.

Brown administration officials said the plan would help make water from the Delta more reliable and restore crashing populations of fish, which at times have caused federal officials and judges to curtail Delta pumping.

“We are making real progress,” said Mark Cowin, director of the California Department of Water Resources. “Getting to this point has been a long, complicated journey, but we … are now closer than ever to finally safeguarding a water supply critical to California’s future and restoring vitality and resiliency to the Delta ecosystem.”

Absent from Thursday’s document release, however, were key details of the proposal, including details of where funding will come from, who will pay and engineering specifics. Those details are expected to come out in other news conferences and document releases on March 27 and mid-April.

The twin tunnel plan was first championed seven years ago by Schwarzenegger. Supporters, including large urban water districts and farmers, say it will help the state’s most important water source return to health and reliability after years of collapsing fish populations and court rulings limiting pumping.

But critics said Thursday that the plan is a boondoggle that will hasten the Delta’s demise, while raising water bills for millions of Californians because much of the plan will be paid for through higher water rates. They said the ultimate way to restore the Delta is to pump less water from it and provide new water sources around the state through more underground storage, expanded use of recycled water and better conservation — particularly from agriculture, which uses 80 percent of the water that people consume in California.

“I think that Gov. Brown, between the high-speed rail and this big water project, sees these things as his legacies,” said Zeke Grader, executive director of the Pacific Coast Federation of Fishermen’s Associations in San Francisco. “They are big monuments. If he wants to have a good legacy, he should be less concerned with monuments and more concerned with long-term workable solutions.”

Eight Northern California members of Congress issued a statement Thursday opposing the project.

“Draining more water from the region is not a sustainable policy and will jeopardize local fisheries, endangered species, and the livelihoods of thousands of farmers, fishermen and business owners who all depend on a healthy ecosystem,” said Rep. George Miller, D-Martinez.

Under Brown’s plan, two side-by-side underground tunnels, each 33 feet in diameter, would carry fresh water 35 miles from the state’s largest river, the Sacramento, under the Delta to giant federal and state pumps near Tracy.

There it would flow into canals run by the State Water Project and the Central Valley Project, which deliver Delta water to 25 million Californians, from the Bay Area to San Diego, and to irrigate 3 million acres of farmland.

Construction would start in 2017, and the project would be completed by 2026.

The idea is to allow more flexibility, so fish that are killed in the existing pumps in Tracy would be less affected if the water was pumped out farther north. The documents released Thursday show that the Brown administration is proposing to take roughly the same amount of water from the Delta — about half of its total freshwater every year — as has been taken in recent years.

Assemblyman Jim Frazier, D-Oakley, said that the plan’s first four chapters “is pretty much in parallel with what they’ve been saying” at previous meeting he’s attended on prior drafts. “But they’re still proposing a conveyance of water, and I can’t support that,” he said.

As to the conservation goals laid out in the draft plan, Frazier said there is a bill on the Senate floor by Lois Wolk, D-Davis, that would address the Delta’s health and integrity at a more reasonable cost and would not be subject to the likely legal battle.

During the last 20 years, the state and federal projects have exported an average of 5.3 million acre feet of water a year from the Delta. The modeling for the current project shows a potential average export ranging between 4.8 million to 5.6 million acre feet.

“To pass voters, a bond needs to have Delta and Bay Area support,” Wolk said. “To get that support, it cannot include a project that is this controversial.”

Staff writers Paul Burgarino and Steven Harmon contributed to this report.

Paul Rogers covers resources and environmental issues. Contact him at 408-920-5045. Follow him at Twitter.com/PaulRogersSJMN