FRESNO — The board of the nation's largest irrigation district on Tuesday rejected participation in Gov. Jerry Brown's $16 billion plan to build two giant tunnels to re-engineer California's north-south water delivery system, dealing a major blow to the project.

The board of Westlands Water District, a key player in the project's success or failure, voted 7-1 against the project after more than an hour of tense discussion and comments from farmers, many of whom concluded the tunnels were too expensive.

The district already has invested millions of dollars toward planning but had not committed to shouldering a share of the hefty construction costs.

Westlands general manager Thomas Birmingham said he believes the no vote in Fresno could kill the tunnels project.

"This thing dies, the project will be over," he said.

Westlands is the first water district to vote on the project. Officials in other districts were watching the vote as they prepare to make their decisions on the project that has been on the drawing board for more than a decade.

Thus far, the biggest water project proposed for California in more than a half-century has no firm financial commitments from local water districts. Some fear it would drive up the cost of water delivered to farms and residents.

The vote came a day after The Associated Press reported state plans to put dozens more water agencies and millions of families and farmers on the hook for funding the tunnels.

The approach pivots from long-standing state and federal assurances that only water districts that seek to participate would pay.

The powerful Westlands agency provides irrigation water to 1,000 square miles (2,590 square kilometers) in the San Joaquin Valley, some of the nation's richest farmland.

Brown is pressing to secure the project before he leaves office next year.

It calls for building two 35-mile-long (56-kilometer-long) tunnels east of San Francisco to deliver water from the Sacramento River mostly to farms and cities hundreds of miles away in Central and Southern California.

Backers say the tunnels will stabilize flows, bolster endangered fish and ensure a reliable water supply. Critics say the project will be used to drain Northern California dry and further harm native fish.

Water districts in the Silicon Valley and those in the farm-rich Central Valley and Southern California are due to vote in the coming weeks.