The San Diego County Water Authority has adopted an 11.3 percent increase in rates.
The increase will apply to what its 24 member retail agencies pay next year for treated water.
How much of the increase trickles down to residents will depend on things like how much water each local district buys.
The water authority said the pricing decision was driven by higher costs from the Metropolitan Water District, the main wholesaler for Southern California as well as increasing expenses for operating, maintaining and financing the region's water system.
The hike starts January 1.