Moorpark-area residents will see their water bills go up by 15 percent next month.

The Ventura County Board of Supervisors on Tuesday unanimously approved a 15 percent increase in water rates for basic, or Tier I, use by residential and industrial customers, and a 22.7 percent increase for agricultural customers in Ventura County Waterworks District No. 1.

The district includes Moorpark and areas north and west of the city limits.

The increase will be reflected in February water bills.

The average monthly water bill in Moorpark is now $32, and residents will have to pay about $4.25 more on average.

Water rates were increased in Moorpark by 9.5 percent for residents and 14.1 percent for agricultural customers in February 2008.

Reddy Pakala, director of the county Water and Sanitation Department, said a rate increase must again be passed on to water users in District 1 because its supplier, the Calleguas Municipal Water District, increased water rates by 17 percent at the beginning of the year. The Calleguas increase, in turn, reflects a rate hike by its supplier, the Metropolitan Water District.

The increase also factors in water system improvement costs by Calleguas, and Southern California Edison electricity costs, which will be increase by 15.7 percent in 2009, officials said.

Metropolitan Water District officials have said rate increases are inevitable because of the need to secure new sources of water at greater cost. A federal court has curtailed water deliveries from Northern California because of environmental factors in the Sacramento-San Joaquin Delta. A record dry spring last year that dramatically curtailed snow runoff from the Sierra Nevada and drought conditions in the Colorado River basin also were factors.

Pakala said other water districts in Ventura County are looking at similar increases this year.

County Supervisor Peter Foy, who represents the Moorpark area, reluctantly voted in favor of the increase, saying more reductions could probably be made to water district and supplier staffing or infrastructure.

Pakala said District 1 is already doing its best to reduce costs, and that the Metropolitan Water District might increase its rates again by 21 percent next year to fix some of its infrastructure.

Pakala said that without the rate increase, District 1 would face a deficit. “We won’t be able to pay our bills. Water will be shut off,” Pakala said.