Science. Storm drenches California, but it's only a drop in state's drought.

Science.

Storm drenches California, but it’s only a drop in state’s drought.

By Brittny Mejia, Matt Stevens and Joe Mozingo, Los Angeles Times.

LOS ANGELES — The first major Pacific storm of the season drenched much of California on Tuesday, slaking a parched and dusty region, but still leaving the state deep in a historic drought.

The stream of subtropical moisture dropped more than an inch of rain over much of Los Angeles County by evening, with higher numbers in the local mountains. In foothills and canyons where fires recently burned desiccated brush, residents scrambled to set up barricades to divert debris flows and prepared to evacuate.

In Camarillo, gushing mud and water prompted a mandatory evacuation of 75 homes where a slide had buried a residence on Halloween. In Glendora and Azusa, homeowners and fire crews worked feverishly to buttress sandbags with plywood and concrete blocks. Rock slides hit the road in Malibu Canyon, and in Silverado Canyon residents moved horses and other large livestock to lower, flatter terrain.

The rain was expected to taper off during the night, with another band of moisture arriving in the morning.

But fears of nature’s destructive power were tempered by optimism.

The storm and deluge that hit Northern California last weekend gave state water officials the first glimmer of hope in more than a year; on Monday they increased 2015 water allocations in response to improving precipitation forecasts.

Lake Oroville — the keystone reservoir of the California State Water Project, which delivers water from Northern California south — took in 5 billion gallons over the last 10 days, officials said. Still, that is less than 1 percent of its capacity.

State water experts said it would take 150 percent of the average rainfall for California to recover from the current drought. That would mean a total 75 inches of rain from Oct. 1, 2014, through Sept. 30, 2015, recorded at eight stations in the northern Sierra.

“Even if you had a tremendous downpour this weekend, who knows what’s going to happen in the next two months,” said Doug Carlson, spokesman for the California Department of Water Resources. “We certainly hope that the rainfall we have now pushes us toward normal — but we’re still below normal ... We’re just trying to get to average.”