SAN DIEGO (AP) — A California judge gave San Diego a big victory Wednesday in its quest for water independence, ruling that the region’s water agency is owed $188 million it overpaid for having Colorado River water brought to the coast.

San Francisco Superior Court Judge Curtis Karnow ruled last year that Metropolitan Water District of Southern California’s rates for carrying water on its 242-mile aqueduct were invalid but held off on awarding damages. Wednesday’s tentative decision gives the San Diego County Water Authority the full amount it requested for charges from 2011 to 2014.

San Diego began buying Colorado River water from California’s Imperial Valley in 2003 in an effort to diversify supplies, but it needs Metropolitan’s aqueduct to bring that water to the coast.

Metropolitan, a giant Los Angeles-based wholesaler that serves an area covering 19 million people, said it planned to appeal. It said it disagreed with the ruling but wasn’t surprised.

If the ruling survives appeal, the San Diego County Water Authority said it will distribute the money to the city of San Diego and its 23 other member cities and agencies, which will decide how to spend it. It anticipates the appeal could take about two years and may go to the state Supreme Court.

“This is a total, complete, unadulterated victory,” said Dennis Cushman, the San Diego agency’s assistant general manager.

The ruling addresses only the last four years, leaving open the possibility of additional litigation. San Diego claims that it would be overcharged up to $2.1 billion over 45 years if Metropolitan’s rate structure isn’t changed.

San Diego sued Metropolitan over its rates in 2015 and 2016, but that complaint, also before Karnow, has been on hold pending Wednesday’s ruling. San Diego says it is being overcharged $55 million this year.

San Diego ended its near-complete dependence on Metropolitan after an earlier drought tightened the spigot in the early 1990s. It began a costly effort to diversify supplies that includes construction of the Western Hemisphere’s largest desalination plant in Carlsbad and, most significant, a 2003 agreement with California’s Imperial Irrigation District for the nation’s largest farm-to-city water transfer.

San Diego purchased 95 percent of its water from Metropolitan in 1991. That figure dropped to 49 percent last year and will fall to 30 percent in 2020.