The great drawdown of Castaic Lake began this week. Officials are slowly lowering the surface level of the popular lake 45 miles northwest of Los Angeles to allow for a once-a-decade series of repairs.

The lake should reach its lowest point — 60 feet below normal summertime levels — about Dec. 22, said Lori Mathis, a spokeswoman for the state Department of Water Resources.

But boaters can rest assured.

The drawdown is expected to have little effect on boating and fishing, said Lori Bennett, regional superintendent for the Los Angeles County Parks and Recreation Department, which oversees recreational activities at the lake.

"Boaters will have to be cautious about submerged objects, but there will still be plenty of water in the lake," Bennett said Monday.

The 2,235-acre lake is open every day except Christmas from sunrise to sunset for boating, fishing, camping, hiking, picnicking and seasonal swimming.

Bennett said visitors may call the department's information line at (661) 257-4050 to check conditions. Refilling is scheduled to start Jan. 1 and will take about four months to reach normal levels, Mathis said.

The lake can hold up to 320,000 acre-feet of water, and usually contains about 315,000 acre-feet in the summer. The lake will be reduced by 50,000 acre-feet in the drawdown. An acre-foot is 325,821 gallons, roughly enough water to supply two families for a year.

Several projects will be completed during the drawdown:

•  Repair of erosion damage to Elderberry Dam;

•  Repair and refurbishment of parts of the Castaic power plant that are usually submerged;

•  Completion of silt removal from cooling water systems at the power plant;

•  Dredging of Elderberry forebay;

•  10-year inspection of pipelines.

The Department of Water Resources operates and maintains the State Water Project, which includes Castaic Lake.

The water released from the lake will go to the Metropolitan Water District and Castaic Lake Water Agency and will be distributed to their customers.

amanda.covarrubias@latimes.com