It was like lovely manna from the sky, the snow blanketing the mountains as I drove home from Lake Tahoe, flakes turning to heavy showers as we headed down the pass towards Davis.

It may not be the best conditions for driving, but the storms pounding the Bay Area and covering the Sierra Nevada with the white stuff have come just in time to rescue the state from what promised to be the worst drought in its history. In fact, new surveys taken (above) show the Sierra Nevada snowpack is at 80 percent normal for the season so far.

But how much is enough ? State officials tell the San Francisco Chronicle that while the February and early March storms are improving our circumstances, it has all come too late to assure adequate water supplies this summer.

Essentially, sunny California would need its water content in the snow to be between 120 to 130 percent of normal by April to fill the state’s reservoirs, the largest of which is only half full. It could take a miracle. Rains are still persisting on this fine March morning, so never say never.

Still, two years of drought have taken a huge toll, threatening central California growers as well as consumers.

In February, the water content measured just 61 percent of normal after the eighth-driest January on record – so dry Gov. Arnold Schwarzenegger declared a statewide drought emergency and has called for cities to cut water use by 20 percent. He learned that snowmelt runoff in the spring will be just 57 percent of normal.

Heeding the call, at least 25 water agencies have imposed mandatory water restrictions while 66 others (including San Francisco) have voluntary restrictions in place.

Frank Gehrke, chief of snow surveys for the California Department of Water Resources, has been out with reporters on snowshoes, measuring the snow depth and water content at Phillips Station, a state measuring site near the Sierra-at-Tahoe resort.

“Reservoir storage is still way below average, and the likelihood of large-enough storms to have significant recovery drops way off as we move into March,” Gehrke told the Chronicle.

Meteorologists figure the drenching would need to be relentless to raise the level of the water content in the snow enough to replenish the state’s reservoirs.

Apparently, it’s the amount of rainfall in the mountains that makes the difference in the water supply. That’s because 60 percent of California’s water is contained in the snow-covered mountains during the rain season. When it melts, farmers rely on the runoff to irrigate 775,000 acres of growing fields.

Thousands of those farmers are now being warned that their permission to pump water from rivers and creeks could be cut back if the drought worsens, according to a new report in the Sacramento Bee.

This kind of warning hasn’t been issued since 1988 and includes every city and farm with state water rights in the watersheds of Sacramento, San Joaquin and Russian rivers, as well as the central coast and areas encompassing the city of Sacramento.

It’s all a big wake up call for consumers who take water – our most precious natural resource – for granted.

“We are giving you fair warning that even if you start the season with water, by the end of the season you may not have water,” Bill Rukeyser, spokesman for the water board, was quoted as saying in the Bee. “People would be able to continue to boil their spaghetti, brush their teeth, take showers, drink water. They would not be able to water their lawns.”

Lawns are the least of it when it comes to severe droughts brought on by climate change.

There are even public health concerns, according to the Centers for Disease Control and Prevention, which has been addressing how we can be better prepared to cope with injuries and illnesses from severe weather: flood, heat exposure, allergies, respiratory problems, illnesses carried by insects in water and threats to the safety and availability of our food and water supplies.

The CDC says less direct effects can include worry, depression, and the negative impacts of mass migration and regional conflicts.

Images: San Francisco Chronicle, Great Valley Center