Despite recent rain, drought not over in Sonoma County

A parade of storms have steadily marched through Sonoma County this winter, transforming its brown, drought-parched hills into vales of vibrant green.

But looks can be deceiving. Despite the recent storms, which dropped nearly 4 inches of rain on Santa Rosa last week alone, rainfall totals on the North Coast still trail levels from a year ago.

If it stops raining, Sonoma County and the rest of California could be headed for a fifth year of drought, forecasters warned Monday.

Yes, that’s a worst-case scenario and yes, El Niño is unleashing storms that have begun to replenish reservoirs in Sonoma and Mendocino counties that serve hundreds of thousands of people on the North Coast. But local water experts say current weather conditions must continue through the end of spring to end the drought.

“We’re not going to get out of this drought if it stops raining now,” said Pam Jeane, assistant general manager of the Sonoma County Water Agency, which provides water to about 600,000 customers from Windsor to Marin County.

Only a year ago, she recalled, it rained buckets in December 2014. But the rains soon stopped and the region found itself in its fourth year of drought.

“It rained like crazy in December,” she said. “We did have a decent storm in February but that was the end of it.”

Laura Watt, an associate professor at Sonoma State University and chairwoman of the environmental studies and planning department, says she’s betting on a lot more rain.

“The odds seem pretty strong. All the climate models show this ginormous pile-up of heat in the Pacific, which is what’s driving El Niño conditions,” she said.

So where are we now in terms of rainfall? So far, it hasn’t rained as much as it did last year, according to the National Weather Service. Since Oct. 1, the Charles M. Schulz-Sonoma County Airport has logged 13.37 inches of rain, where “normal” rainfall would be about 16.7 inches.

“Since October, we’re at about 80 percent,” said Roger Gass, a meteorologist with the National Weather Service.

Local reservoirs also are close to normal.

Lake Mendocino is almost at 70 percent of “target capacity,” while Lake Sonoma is at about 77 percent, Jeane said. Target capacity is the amount of water that can be stored in the reservoirs for water supply purposes. During the wet winter season, they are not allowed to hold more water than their target capacities, ensuring they have enough room to protect the region from flooding.

For example, as of Monday morning, the Lake Mendocino reservoir held about 44,000 acre-feet of water. Its target capacity is 68,400 acre-feet during winter, a fraction of its overall capacity of 122,400 acre-feet. An acre-foot is the amount of water it would take to fill an acre one foot deep with water.

Similarly, Lake Sonoma is at 188,000 acre feet, while its target capacity at this time of the year is 245,000 acre-feet. The reservoir has an absolute capacity of 381,000 acre-feet.

Watt said that even though current rainfall levels are lower than last year, the type of rainfall we’ve been getting this winter is more beneficial than the brief deluge of December 2014. That rain resulted in a good deal of runoff, she said, adding that this year rainfall has been steady over a longer period of time.

“Since a lot of portions of the county rely on wells and reservoirs, the ability of water to sink in is really important,” Watt said. “I would guess that even though total rain since October is lower than last year, it’s having a higher impact because it’s coming gradually.”

Statewide, the picture still looks dire, said Doug Carlson, a spokesman for the California Department of Water Resources. For California to get out of the drought, reservoirs would have to reach at least historic averages and the state would have to get 150 percent of rainfall by the end of the year, he said.

“It hasn’t rained as much as it did last year,” Carlson said. “In December of last year, we had some flooding in Northern California ... then it stopped raining.”

“If we don’t get the rainfall and we don’t get the snowfall and it doesn’t stick in the mountains, we’re very likely to be recording a fifth year of drought,” he said.

Even if the situation in Sonoma County is better than in the rest of the state, the drought won’t end until state water officials and Gov. Jerry Brown say it’s over, Jeane said. Statewide drought policies apply to everyone.

For now, the forecast calls for more rain.

Gass, the National Weather Service meteorologist, said heavy rain is expected late Tuesday night and into Wednesday morning. That storm should bring up to an inch of rain in Santa Rosa, with higher elevations in the North Bay getting up to 2 inches.

Gass said that regardless of whether El Niño conditions persist, the rainy season will come to an end in late March or early April.

Watt said that if El Niño conditions endure, “we’re probably going to be locally out of drought conditions by the end of the rainy season.” But she warned there’s no guarantee of that.

“All the indicators are that we’re likely to get higher-than-average rainfall for the rest of the season,” she said. “But the weather is the weather.”

You can reach Staff Writer Martin Espinoza at 521-5213 or martin.espinoza@pressdemocrat.com. On Twitter @renofish.