SAN DIEGO - A California judge on Thursday tentatively invalidated a landmark pact to curtail the state's overuse of water and allow other Western states to claim their fair share.
The 2003 agreement ended of years of bickering over how to divide the Colorado River between California and six western states: Arizona, Colorado, Nevada, New Mexico, Utah and Wyoming.
More than 30 million acre-feet of water - enough to cover the state of Pennsylvania a foot deep - would move from farms to cities in Southern California over the 75-year life of the deal.
Superior Court Judge Roland Candee ruled in Sacramento that the state improperly agreed to pick up much of the cost of saving the shrinking Salton Sea in the southeastern California desert. Restoring the state's largest lake was a crucial piece of the agreement.
The state put no limit on costs, "even if they ultimately amounted to millions or billions of dollars," violating a constitutional limit on assuming debts, Candee wrote.
"The Court has no ability to sanction a way to contract around the Constitution," he wrote.
The judge will hear arguments next Thursday to decide whether to make the ruling final.
Cities like San Diego and Los Angeles were taking billions of extra gallons of Colorado River water over the years, angering other Western states. The pact outlined a plan for California to wean itself.
Much of the water affected by the deal goes to San Diego. It calls for Imperial Valley, California's biggest user of Colorado River water, to sell as much as 90 billion gallons each year to San Diego - roughly a third of the city's future water needs.
Kevin Kelley, spokesman for the Imperial Irrigation District, said the ruling "might have the makings of a perfect storm" if it is upheld.
The San Diego County Water Authority board will consider its next steps at a board meeting next week, said Dennis Cushman, assistant general manager.
"The water is flowing and will continue to flow indefinitely until the legal issues are sorted out," he said. "There's no panic button to press right now."
Imperial asked the judge to bless the agreement, a tactic to blunt legal challenges from landowners and other opponents.
Critics challenged the state's commitment to pay for restoring the Salton Sea, which is fed by Colorado River irrigation channels. Four Southern California water agencies had agreed to cap their costs at $133 million. The state would pick up the rest.
One estimate in court documents pegged the total cost at $193 million, which would leave the state on the hook for $60 million.
Malissa McKeith, an attorney representing Imperial Valley landowners, called the ruling a "fatal blow" to the deal.
A spokesman for California Attorney General Jerry Brown, Evan Westrup, did not immediately respond to a request for comment Thursday night.