SAN DIEGO -- In a court battle with hundreds of millions of dollars at stake, the San Diego County Water Authority won a round Tuesday versus its archenemy: the Metropolitan Water District of Southern California.

A judge in San Francisco tentatively ruled that Metropolitan violated the California Constitution in setting the rates it charged for transporting water from the Colorado River to San Diego County through its aqueduct and other water transportation facilities.

The lawsuit will now proceed to a second phase and, most likely, an appeal from the losing side.

"This is a great day, not only for San Diego, but for the more than 18 million people who pay MWD's water rates and charges," said Thomas Wornham, chairman of the San Diego County Water Authority.

But Jeffrey Kightlinger, general manager of MWD, warned that the ruling "is one step in a very long process."

The lawsuit, heard in San Francisco County Superior Court by Judge Curtis E.A. Karnow, had all the technical complexities and deep-set passions that mark water disputes in California.

The San Diego County Water Authority has long been at odds with MWD, finding itself the regional agency's largest and yet most unhappy customer. Much of the unhappiness begins with discontent over being forced to join MWD more than six decades ago.

In a 66-page tentative decision, Karnow found that MWD had violated Proposition 26, approved by voters in 2010. The proposition requires public agencies to prove that they are not charging more than the actual cost of services.

San Diego has accused MWD of retaliating for the San Diego County Water Authority's deal to buy water from the Imperial Valley and reduce its purchases from MWD.

By increasing the costs of delivering the Imperial Valley water, MWD was making San Diego's deal look less economically attractive, officials say.

"Clearly what Metropolitan was trying to do was keep the golden goose [San Diego] in the henhouse, to keep us captive," said Dennis Cushman, assistant general manager of the San Diego County Water Authority, which serves 24 local agencies.

The second phrase of the litigation will include the issue of how much of a rebate San Diego County should receive, and what the delivery cost for additional deliveries of the Imperial Valley water should be.

San Diego officials estimated that the stakes exceed $2 billion over the 45-year deal with the Imperial Irrigation District.

Some $135 million has already been set aside, representing the amount of the alleged overcharges from 2011 to 2014, according to court documents.

Kightlinger said his agency is confident it will prevail, noting that in a previous lawsuit, San Diego County won at a lower court but was reversed on appeal.

"We look forward to the coming steps in the judicial process," Kightlinger said.

 

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tony.perry@latimes.com