SAN FRANCISCO — California, just finished with its second consecutive year of drought, might well be facing a third. If so, state authorities may be forced to impose water rationing on farmers, homes and businesses.
With the rainy season well under way, early partial measurements indicate that the amount of water stored in the Sierra snowpack, the state’s natural reservoir, is higher than the amount at this time last year but well below average, said the state’s meteorologist, Elissa Lynn.
The deficit can be made up if January, February and March are full of big Pacific storms. But this week, the National Oceanic and Atmospheric Administration announced that the weather phenomenon known as La Niña, which is characterized by cooler waters in the western Pacific Ocean and drier conditions, had returned for the second consecutive year.
“The worry is that La Niña does again what it did last year,” Ms. Lynn said Wednesday, noting that the rainy season, which often lasts through April, ended in February last year. “When we missed March and April, we lost 20 percent of the normal precipitation.”
In 2008, runoff from the Sierras was 57 percent of normal flows; in 2007, it was 53 percent of normal.
There was little or no rain early last month, but several storms swept through the state in the 10 days before Christmas, bringing a pillow of fresh powder to the Sierra ski resorts.
Last June, Gov. Arnold Schwarzenegger declared the first statewide drought since 1991. Building projects were curtailed as a result.
The demand for water is perpetually high in this fast-growing state, which is expected to add half a million people annually for the next decade. Its $30-billion-a-year agricultural industry produces more than half of the nation’s fruits, vegetables and nuts.
Among those clamoring for supplies of fresh water are wildlife biologists. Endangered species like the delta smelt have been disappearing from rivers whose flows are well below average. A year ago, a federal judge ordered water authorities to curtail the use of large pumps in the Sacramento-San Joaquin River Delta water system to help preserve the smelt.
A separate worry for commercial fishermen is the coming salmon season. Last year, a collapse in the population of returning fall Chinook salmon in the Sacramento River led to the closing of the salmon season off the coast of California and much of Oregon.
Since this year’s returning salmon were spawned three years ago, there is little direct connection between the low numbers of 2008 and the prospects for 2009. But, said Sheila Green, an environmental scientist with the state’s Department of Water Resources, though the 2009 adults are the offspring of a robust population of 2006 fish, the water flows that took these young salmon out to sea in 2007 were low.
Ms. Green said the complex interplay of factors affecting salmon’s survival — freshwater conditions, predators, ocean currents and the levels of food rising from the ocean’s bottom — made it impossible to predict how strong the 2009 salmon runs would be, particularly the fall Chinook run, which is the most important.
Among the other indicators of the state’s increasingly parched condition are water levels in reservoirs. Ms. Lynn said that water levels in the two federal reservoirs, Shasta and Folsom, were lower than they were during one of the state’s worst dry spells, in 1976-77, but that the levels in state reservoirs were a little higher than they were then.
