Drought-ravaged Folsom Lake rises 28.5 feet in just one month

A view of Folsom Lake reservoir on Dec. 31, 2015. California's ninth-largest reservoir reached its lowest levels in early December 2015. Later that month, it finally started to slowly fill back up and reached 25 percent capacity. less A view of Folsom Lake reservoir on Dec. 31, 2015. California's ninth-largest reservoir reached its lowest levels in early December 2015. Later that month, it finally started to slowly fill back up and reached ... more Photo: Greg Tuppan Photo: Greg Tuppan Image 1 of / 34 Caption Close Drought-ravaged Folsom Lake rises 28.5 feet in just one month 1 / 34 Back to Gallery

Water-starved Folsom Lake is beginning to slowly fill up and recover from its lowest water levels ever.

The state's ninth-largest reservoir, the main water source for the sprawling Sacramento suburbs, shrank to a mere 135,561 acre feet on Dec. 4, 2015. The previous lowest level at Folsom was 140,600 acre feet, recorded during the 1976–77 drought. An acre foot is enough water to flood an acre of land under a foot of water, and roughly the amount required by a family of four over a year.

With the recent rains, Folsom's water level has risen 28.5 feet and the reservoir is now holding 246,497 acre feet of water.

"The lake continues to slowly rise," Karl Swanberg, a forecaster with the National Weather Service in Sacramento, said in an interview. "While this current storm isn't dropping a lot of rain on Folsom, we're getting runoff from the Sierra from past storms and some snow melt."

The Central Sierra snow pack is at 107 percent of average and the American River, which feeds into Folsom, travels through these mountains.

That said, Swanberg adds the lake is still only at 25 percent capacity. "It's kind of a good news, bad news situation," he said. "The lake has risen 28.5 feet in the past month. However it's still at 51 percent of average for this time of year."

Over the summer, photographs showing large swaths of exposed lakebed with parched, cracked earth circulated online, becoming a symbol of the California drought. Images taken late last month, before our wet start to 2016, show a slightly more promising outlook for the lake (see before and after photos above).

Folsom fell to historic lows this year mainly due to the California drought and record-low rainfall over the past four years. But also the state relied more heavily on the reservoir and released additional water, Jay Lund, a University of California at Davis professor in civil and environmental engineering, said, "to help make up for reductions in releases of warm water from Shasta needed to keep winter run salmon safe on the upper Sacramento River."

Californians hope El Niño storms will fill up Folsom and other reservoirs throughout the state, but Swanberg said the future is unknown. Forecasters are already warning that a dryer La Niña pattern may follow on the heels of a wet winter and spring.

"We can be hopeful in the future," he said. "We have rain in the forecast. Each weather system will add water into the reservoir. But it's way earlier in the year. We really don't know how much more rain will fall."