Splitting California into three new states would scramble nearly every segment of government that touches residents' lives, from taxes to Medi-Cal to driver's licenses.

New agencies would have to be created to operate prisons, highways and universities. CalPERS, CalSTRS, Cal Fire and the California Highway Patrol, to name a few, would have to be reconfigured and replaced.

But of all the gargantuan tasks facing Californians should they choose to divide themselves by three — a proposal that has qualified for the November ballot — none is arguably more daunting than carving up the state's water supply.

California has spent more than a century crafting one of the world's most elaborate — and interdependent — networks for storing, allocating and delivering its water. Billions of dollars have been poured into reservoirs, pumping stations and aqueducts, mostly to move water from the rainy north to the arid and densely populated south.

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The entire apparatus is governed by two state agencies, one federal agency, hundreds of local districts and a convoluted pecking order of water rights, contracts and court rulings.

Separating this intricate and almost hopelessly tangled web into three workable parts? Go ahead and try.

"In a word, it would be a nightmare from a water standpoint," said Sacramento water lawyer Kevin O'Brien. "You have got multiple questions about how the different water-related assets would be divided. That would include water rights, reservoirs, conveyance facilities like the California Aqueduct. ... How exactly you would carve those assets up would be extremely complicated."

The plan to split up California is the brainchild of venture capitalist Tim Draper, who argues that the state is so large that it has become ungovernable. If the plan is approved by voters and Congress gives its OK — hardly a sure thing — California would be replaced by Northern California, which would include Sacramento and the Bay Area; Southern California, covering much of the San Joaquin Valley along with San Diego and Orange counties; and the state known simply as California, a slimmed-down coastal area stretching from Monterey to Los Angeles.

The implications for water supply are staggering. For instance: Could the new state of Northern California, blessed with ample water and the mechanism for delivering it as far away as San Diego, decide to shut off the spigot?

Probably not, legal experts say, but no one really knows for sure. It's no secret that many Northern Californians resent the fact that much of the region's water winds up irrigating the south part of the state and would love to withhold or curtail deliveries.

"People in Northern California have always been very protective of water and water rights and always will be," said David Guy of the Northern California Water Association, an alliance of mostly agricultural water agencies in the Sacramento Valley. "We don't know what that means if you start splitting the state."

At the very least, the idea of a standoff with Northern California is unnerving for people like Jeff Kightlinger, general manager of the Metropolitan Water District of Southern California. Metropolitan's 19 million customers get a quarter of their water from Northern California through a decades-old contract with the State Water Project.

"I would think you would have to somehow respect the pre-existing rights and contracts," said Kightlinger, whose own agency would be split in two by the Draper initiative.

If the new Northern California tried playing hardball, "we would sue them," Kightlinger said.

Right now, every drop of water in California is property of the state; it doesn't belong to one region or another. If the state gets dissolved into three parts, the question of ownership obviously becomes complicated. But water-law experts agree with Kightlinger: It's doubtful Northern California could simply hoard its supply and refuse to do business with the other two states.

Even so, the prospect of chaos looms.

"Every time you turn around, there's a new question that faces you, and none of them have ever been addressed before," said Barton Thompson, a water law expert at Stanford University.

Draper says his "Cal 3" plan would remedy much of what ails the current state, including its almost chronic water shortages. But so far he hasn't offered many details about how California's water woes would be alleviated.

"Cal 3 would allow for innovative solutions to California's current water crisis that empowers each region to cooperate more effectively than the current state system," his initiative's website says. Calls to Draper's public relations team went unanswered.

Of course, states can and do cooperate with one another, even on water issues. California shares the Colorado River with six other states. But the arrangement, originally brokered in 1922 by then-U.S. Commerce Secretary and future President Herbert Hoover, is more of an uneasy truce than an olive-branched armistice, and the states periodically have engaged in major legal and political tussles over the river.

Two major systems move much of California's water from north to south: the federal government's Central Valley Project and California's own State Water Project. They work in concert with one another, especially in the Sacramento-San Joaquin Delta, the hub of the two systems. How they would be affected by Draper's plan is unclear. But they have so many moving parts that dividing up the state seems like a huge complicating factor.

Look at the State Water Project. Built in the 1960s by Gov. Pat Brown, the project takes water largely stored in Lake Oroville in Butte County and runs it down the Sacramento River to the Delta. From there it's pumped via the 444-mile California Aqueduct to parts of the Bay Area, a few coastal regions like San Luis Obispo County, the southern San Joaquin Valley and the vast urban stretches of Southern California.

It's complicated enough as it is. Now the water would have to wend its way from the new Northern California, home to Oroville and the Delta pumps, to the mostly inland state called Southern California and the coastal entity known as California.

"It's fraught with politics. Just imagine Southern California and Northern California, two new states, trying to figure out how much each would get," said Thompson, the Stanford law professor. "There's no easy way of doing it."