Gov. Jerry Brown's tunnel vision on the Sacramento-San Joaquin River Delta points to a $23 billion disaster. A tipoff: The governor and Legislature refuse to require a cost-benefit analysis of the project, which feeds suspicion that it wouldn't pencil out.

There is no conclusive scientific evidence that the Bay Delta Conservation Plan will improve the health of the Delta, the largest estuary west of the Mississippi. And any plan that further damages the compromised ecosystem will have ramifications far beyond the ability to water Hollywood lawns. That's the main thing this plan will do, just about everyone agrees: make it easier to transport water from Northern California to the thirsty South.

So Los Angeles and Big Ag are cheering. Not us.

The tunnels are an attempt to solve complex problems of water supply and environmental health. But there are simple ways to shore up supply. One is to strengthen the Delta levees that protect farmland and, by the way, Silicon Valley's water supply, which could vanish with the next earthquake or flood. Some work has been done, but at least another $1 billion worth is needed.

Brown presented his plan Wednesday with U.S. Secretary of the Interior Ken Salazar at his side. The state would build two massive, side-by-side 37-mile tunnels under the Delta to transport water from the Sacramento River to the south. This could divert 9,000 cubic feet of water a second -- enough to fill an Olympic-size swimming pool every 10 seconds.

Taxpayers would pay $3 billion to to $4 billion for habitat restoration, and water providers would pay the remaining $19 billion in construction costs and operating expenses.

But don't be misled: That cost will be passed on to consumers (another name for taxpayers). This isn't free. Farmers will pay their fair share, but the vast majority of Silicon Valley residents will see their water bills leap like Old Faithful. And unlike the geyser, rates will stay up there.

The Metropolitan Water District of Southern California promises to pay 25 percent of the cost. But some of Metropolitan's 25 member agencies, including San Diego, have expressed serious reservations about the plan.

Only one thing is sure to improve the health of the Delta: more water, not less, flowing through it. But politics and Southern California's thirst have driven this plan. That's not just our opinion. It's what the prestigious National Academy of Sciences concluded in 2011.

"In my view, politics has been placed before science, and project before policy," Palo Alto Rep. Anna Eshoo told reporters last week. Agreed.

Thirty years ago, then-and-now Gov. Jerry Brown tried to build a peripheral canal around the Delta. In a referendum that killed the plan, more than 90 percent of voters in nearly every Northern California county saw the canal for what it was: a southern water grab.

California shouldn't spend money like water on Delta tunnels without a real cost-benefit analysis and clearer evidence of the effects on the Delta.