With little discussion, and unanimous approval, city council members in Sonoma started a process to significantly raise water rates in the city. 

The action Wednesday sets in motion ten years of annual rate increases, totaling a cumulative 53.4 percent.

The average monthly bill would rise for just shy of $43 a month to more than $104. Teresa Jurotich, a consultant from the firm Raftelis, which performed a study and devised the rate plan, said without the increases, the city's water fund would dry up.

"The rates need to keep pace with the cost for the city to operate its water system and provide the level of service that your customers have come to expect," Jurotich said.

According to the study, buying water on behalf of customers accounts for just over a third of the agency's budget. The rest is taken up by major construction projects termed capital spending, salaries, other expenses and debt service.

Increases would be phased in, with five annual 5 percent jumps, followed by five annual 4 percent increases.

If approved, the rate plan would increase monthly service charges, variable charges, and zone charges, along with potential surcharges that could be added during a serious drought.

While the proposed rate increases are steep and make comparable bills higher than ones in Petaluma and Cotati, rates would remain lower than those charged by the Valley of the Moon Water District and Marin Water.

The council's vote enables the city to mail notifications to customers, as required by state law. Officials plan to finalize and adopt the new rates following a public hearing scheduled for October.