Wednesday, January 14, 2009

Weather News

Balmy weather could drop Lake Shasta to near-record low

The McCloud River makes its way into Lake Shasta near Gilman Road. If the dry weather persists through the spring, officials say the lake could match or pass its record low in the fall. Dry winter weather is not what those who manage Lake Shasta want to see.

Last year, the lake dipped to a 16-year low. This year, the reservoir could come close to its record low if sunshine keeps trumping rainfall in what typically is the north state's storm season.

"We are just really, really waiting on rain," said Sherri Harral, spokeswoman for the Bureau of Reclamation's Northern California Area Office. So far it just hasn't happened.

Shasta Dam averages 11.3 inches of rain in January, she said. Halfway through this January, only a quarter of an inch has fallen. And forecasters don't predict a weather reversal in the next week and a half.

"We don't see anything out there right now," said George Cline, a forecaster for the National Weather Service's Sacramento office. He said the recent springlike weather is a contrast from the north state's usually rainy winter. "This is the most productive period, normally," Cline said. Rainfall is particularly important for Lake Shasta.

Although snowy Mt. Shasta is nearby, Harral said snowmelt plays a small part in filling the lake. She said the lake is 90 percent filled by rainfall. On Tuesday, Lake Shasta was at 150 feet below its high waterline, said Larry Ball, the bureau's operations chief at Keswick Dam, which regulates releases from Shasta Dam.

If the dry weather trend continues throughout the spring, he said, the lake could be down to 230 feet by the end of October — nearly matching 1977's record low of 230.32 feet. Such a drop could all but stop the bureau's power production at Shasta Dam, Ball said.

If the water drops to 240 feet below the crest, he said, there is not enough to turn the turbines at the base of the dam. Already the current low conditions have slashed power produced by the turbines nearly in half, he said.

At full production, they can produce 725 megawatts of electricity, or enough to power about 725,000 homes, Ball said. Currently — at 150 feet below the crest — they're producing 450 megawatts, or enough to power 450,000 homes.

Last fall, Lake Shasta reached 157 feet below the high watermark, then started to rise after an influx of rainstorms. It had been rising since, but the dry weather has changed that, Harral said. "We are letting out what is coming in," she said.

While a typical year sees 62 inches of rainfall at the dam, she said this could be the third dry year in a row. There were 47 inches of rain last year and 37 in 2007. To fill the lake, Harral said it'd take an exceptionally wet year with 70 to 80 inches of rain.

Although that might seem impossible now, she said February and March have had more than 30 inches of rain in the past, but those totals came during much wetter patterns. "We've had a miracle February and March before," Ball said. "But a full month of January without much rain is not a good omen."