Water Released at 2 Dams to Forestall Flooding Later : Reservoirs: Flow over the spillways at Oroville and Shasta Lake is first since 1986, confirming drought’s end.

For the first time since heavy winter storms in 1986, water has begun flowing over spillways at the state’s two most important dams, providing dramatic confirmation that California’s six-year drought has ended.

State officials began releasing water Tuesday into the Feather River from Oroville Dam, the nation’s highest, in anticipation of another storm in Northern California and the continued melting of the Sierra Nevada snowpack.

About 40,000 acre-feet of water was expected to rush through the spillway gates Tuesday and early today, the equivalent of a two-week supply for the city of Los Angeles. A similar amount is flowing into the river through the dam’s power plants, which have been cranked up to full capacity to take advantage of the excess water.

“It is fairly spectacular when it gets going good,” said Alan Jones, a spokesman for the state Department of Water Resources. The releases will continue indefinitely, he said.

Federal officials, who operate the dam at Shasta Lake farther to the north, began discharging water into the Sacramento River on Friday and expect to continue at least through the weekend. Shasta is the state’s largest reservoir and the releases are projected to double those from Oroville, according to John Burke, a hydrologic engineer for the U.S. Bureau of Reclamation.

In both instances, the water is being dumped now to avert flooding later. The reservoirs were built to store water for drinking and farming, but they are also intended to control flooding in the Sacramento Valley.

Neither of the reservoirs is filled, but the likelihood of them reaching capacity this year is great enough to warrant opening the spillway gates, officials said. The projection is based on the depth of the Sierra snowpack, weather forecasts and historic runoff patterns.

Although discharging the water now runs the risk of flooding some low-lying farmland along the Sacramento River, officials said the danger of uncontrolled flows later in the year would be far more serious.

“It is a good sign that they are making these releases,” said Huxley Madeheim, who oversees reservoir control operations for the Corps of Engineers. “I don’t think anybody would have dreamed it was possible at the start of this year.”