January through March in the Northern Sierra Nevada is likely to go down as the driest such period since California began surveying its mountain snowpack in the 1920s.

On Thursday, the state Department of Water Resources conducted its final monthly snow survey of the winter, intended to measure snow depth and water content at their winter peak.

This year's peak is rather puny: The survey found the snowpack is just 52 percent of average statewide.

The data also show that the northern Sierra, a region crucial to statewide water supplies, has seen only 5.5 inches of precipitation since Jan. 1. The previous low on record is 1923, which saw 8.4 inches of precipitation in the same three months.

It is a gloomy end to a winter that started out bright. Storms in November and December delivered about 200 percent of average precipitation to the state. Then the tap went dry in January and February, normally the wettest months of the year.

Thanks to November and December, most key storage reservoirs are near average levels. This includes the state's two largest reservoirs: Lake Oroville on the Feather River is at 108 percent of average capacity for the date, while Lake Shasta on the Sacramento River is at 102 percent.

Folsom Reservoir on the American River stood at 95 percent of average capacity on Thursday.

The low snowpack, however, means reservoirs will not remain at these levels through summer.

"It's shaping up to be a much drier year than anticipated, and that means we'll likely have to draw down storage in key reservoirs," said Terry Erlewine, general manager of the State Water Contractors.

The final winter snow survey is crucial to determine how much runoff will be available for water supply through the state's typically dry summers.

Members of Erlewine's agency are public utilities that serve 25 million people and a million acres of farmland from San Jose to San Diego. They buy water from DWR, which diverts Sierra runoff from the Sacramento-San Joaquin Delta.

Early water delivery forecasts are not good.

On March 22, DWR decreased its 40 percent water delivery estimate to 35 percent of requested amounts.

While the state has not formally declared a drought, John Laird, secretary of the California Natural Resources Agency, urged all residents to do their part by conserving water every day.

"Take a shorter shower, be mindful of how long your sprinklers run and fix that leaky faucet," Laird said in a statement.

The U.S. Bureau of Reclamation, which delivers Delta water through a separate canal system, also reduced its delivery forecast on March 22. Farmers in the San Joaquin Valley who buy from Reclamation had their 25 percent allocation cut to 20 percent of contract amounts, while municipal and industrial customers were cut from 75 percent down to 70 percent.

The city of Sacramento is not affected by these water allocations, because it holds its own water rights in the American and Sacramento rivers.

But some suburban water agencies in the region buy water from Reclamation via the Folsom Reservoir, and are predicted to receive 75 percent of average deliveries. This includes areas served by the San Juan Water District, including Folsom, Orangevale, Citrus Heights and Fair Oaks.

Shauna Lorance, the district's general manager, said her board of directors will likely recommend conservation measures later this year - probably voluntary measures because no severe shortages are expected.

"It's the right thing to do," she said.

The poor snowpack means Folsom Reservoir is projected to be drained very low by this fall, she said - which means there will be no water storage cushion going into next winter.

"If we don't get a good snowpack next year, we could have some real concerns," Lorance said.

In the San Joaquin Valley, Westlands Water District estimates its farmers will lose $350 million due to the more severe water shortages there. The irrigation season probably will start early because rainfall has been so sparse, many farmers say.

On her 600-acre citrus farm in Tulare County, Cathie Walker expects to use a lot of well water this summer.

"It's going to be a rough year," she said. "We were born into a farming family. We know this is the way it goes sometimes."

Contact The Bee's Matt Weiser at (916) 321-1264. Follow him on Twitter @matt_weiser. Mark Grossi at the Fresno Bee contributed to this report.

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