Gov. Jerry Brown’s plan for a massive, $24 billion water project rests on the innocuously named Bay Delta Conservation Plan, which weighs in at a door-stopping 30,000 pages and took seven years to complete.

An early version of the draft environmental impact report, released recently, killed another 20,000 pages worth of trees.

In the interests of time, here’s a synopsis of the heated discussion over the plan:

Northern California has the water. Central Valley farmers and Southern California cities and developers want the water.

Supporters of the plan to build hulking twin tunnels to carry fresh water from the Sacramento River under the Delta 35 miles to Tracy for transport south argue vehemently that the politics of geography have nothing to do with it.

“The current water supply is vulnerable and the costs of its failure would be enormous,” John Laird, the state’s secretary of natural resources, said this week. “As public officials, we are duty bound to address these threats.”

Brown’s people say independent studies show the water project will bring the state at least $5 billion in benefits over the 50-year life of the project. The price tag — $24.7 billion and rising — would provide California with a more secure water supply, improved water quality and new and needed environmental protections for the Delta, they argue.

“It’s about the science, not the politics,” is the rallying cry.

As a rule of thumb, when someone starts saying a government project “is not about the politics,” it’s about the politics. And anyone who thinks the Delta tunnel plan isn’t political must have dozed through his California history class in high school.

A quick example: On Thursday, five members of Congress held a Sacramento news conference to slam Brown’s water plan.

Not one of them represented a district south of Stockton.

It was 32 years ago that Jerry Brown, the state’s once and future governor, signed a bill authorizing a Peripheral Canal to take water from the Sacramento River, carry it around the edge of the Delta, then ship it south.

Northern California residents, outraged that Southern California was “stealing our water,” collected enough signatures to put a referendum on the Peripheral Canal on the June 8, 1982, ballot.

Long-standing regional rivalries combined with memories of TV shots of Southern Californians filling swimming pools and hosing off their sidewalks during the state’s 1976-77 drought to turn the election into a rout. Brown’s water plan was rejected, 63 percent to 37 percent.

But it’s the voting map prepared by the Secretary of State’s office that shows just how dramatically the fight over the Peripheral Canal and Delta water split California on north and south lines.

The numbers are mind-boggling. In all but one county north of Stanislaus, at least 90 percent of the voters opposed the canal (Shasta County was “only” 89.5 percent opposed.)

More than 97 percent of Marin County residents voted against the canal, along with 95 percent of the voters in San Francisco and Alameda counties. No place above Kern County supported the Peripheral Canal, but every county south of Kern, except for coastal Santa Barbara County, backed Brown’s plan. The “yes” vote was 61 percent in Los Angeles County and 73 percent in San Diego.

Those are secession numbers. Experts have called it the most geographically lopsided state election not just in California, but likely in the entire country.

But even with all that geographic anger in 1982, a majority of voters surveyed by veteran California pollster Merv Field said it was the plan’s high cost that was their main reason for rejecting the plan.

Supporters of the new water plan can argue that California’s north-south rivalry has eased in the past 30 years. But the anti-tax, anti-spending feeling has only gotten stronger, especially in the wake of the state’s recent hard times.

While there’s no referendum looming on the horizon over Brown’s new and improved water plan, the financial key to the project is an $11.1 billion bond now set for the November 2014 ballot.

With the bond measure for the water project dubbed “The Safe, Clean, Reliable Drinking Water Supply Act of 2014,” it’s clear the governor already is looking at the politics of California’s latest battle over water.

John Wildermuth is a longtime writer on California politics.