Folsom Lake, shown in June 2015, will soon be sending more water into the American River than it has at any point since 2012. The federal officials who manage Folsom Dam say they must reduce the lake’s storage to save room for coming snowmelt. Autumn Payne Sacramento Bee file
Folsom Lake, shown in June 2015, will soon be sending more water into the American River than it has at any point since 2012. The federal officials who manage Folsom Dam say they must reduce the lake’s storage to save room for coming snowmelt. Autumn Payne Sacramento Bee file

Water & Drought

Under sunny skies, Folsom Dam operators to double releases

By Ryan Sabalow and Phillip Reese

rsabalow@sacbee.com

February 22, 2016 11:41 AM

Even with unseasonably warm temperatures and little to no rain in the forecast for at least the next seven days, the operators of Folsom Dam are going to more than double the flows in the lower American River to protect against flooding.

“We are required to maintain safe space in the reservoir,” said Louis Moore, a spokesman for the Bureau of Reclamation. “That’s what we’re doing.”

Moore said the releases are mandated in Folsom’s nearly 30-year-old manual drawn up by the Army Corps of Engineers. Similar flood-control releases from Folsom this year have drawn criticism from local water agency officials and some hydrology experts.

They say there’s a lack of flexibility in a system that requires dam operators to release water when Folsom Lake rises to a specified height, even if no storms are forecast and the state is trying to maintain stored water supplies in Year Five of a historic drought.

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The new releases were particularly irksome for some local water district officials, who learned Monday that regionwide conservation numbers for January – a mere 11 percent – were by far the lowest since the state mandated cuts last summer.

Tom Gray, general manager at the Fair Oaks Water District, said it’s hard to tell customers to keep conserving in a drought when federal dam operators are letting billions of gallons wash out from the very reservoir that supplies much of the region’s water supply.

“I think some of our customers are going to believe we are crying wolf,” Gray said.

Reclamation officials said Monday they’re preparing to increase releases below Nimbus Dam into the lower American River from 3,000 cubic feet per second to around 7,200 cubic feet per second to create space for runoff from Sierra snow. A storm last week – the only significant precipitation in February – dropped more than a foot of snow across much of the Sierra.

Officials say the releases are necessary because the reservoir’s storage is at 131 percent of the 15-year average for late February, and the snowpack in the central Sierra is more than four times greater than at this time last year.

“Should inflows into the reservoir continue at current levels or increase, additional releases may be required,” Reclamation officials said in a statement.

Officials warned that starting at 5 p.m. Monday, they’ll start incrementally increasing flows by 500 cubic feet per second and continue until flows on the lower American River reach 7,200 cfs by 1 a.m. Tuesday.

After two days at this rate, flows will be gradually ramped down, officials say.

The last time Folsom Lake operators released water at a sustained level of 7,000 cfs or more was in late 2012, during the beginning of the drought, state data show. Those releases also were dictated by the flood-control manual, which was last updated in 1987.

Similar operating manuals, all created by the Corps, govern flood-control releases at 54 dams in California. The majority haven’t been updated since at least the 1980s.

Federal officials say the manuals ensure there is ample space in Folsom and other reservoirs to ward against unforeseen floods to protect communities below the dams.

Folsom’s flood-control manual will get its first update in 30 years next year as part of the construction of a $900 million auxiliary spillway. The new gates will be 50 feet lower than the main gates. That would allow for earlier and safer water releases from Folsom Lake during periods of high water, federal officials say.

Officials are discussing the possibility of revising the manual to allow for more forecast-based decisions at Folsom.

But nothing has been decided.

Meanwhile, most of the region’s water districts are under state orders to cut water use by at least 28 percent from June 2015 through February 2016 or face penalties.

They have largely succeeded. From June through December, the city of Sacramento achieved 31 percent savings; the Sacramento County Water Agency cut use by 37 percent and the city of Roseville reduced use by 36 percent, state figures show.

The 11 percent figure for January released by the Sacramento Regional Water Authority on Monday suggests the effort may be slipping. Previously, the lowest conservation savings were in December, when the region cut its use by 26 percent.

Water officials say it’s harder to conserve water in the winter than in the summer because there’s less need to water lawns, so residents can’t just shut off their sprinklers to save a large amount of water. Instead, they must try to achieve savings through smaller, indoor efforts such as taking shorter showers or reducing toilet flushes.

The weather also likely contributed to the low savings. It rained more than five inches in Sacramento during January, convincing some residents that the urgent need to conserve water was fading. Gray, general manager at the Fair Oaks Water District, said three factors contributed to the lower savings in January: the challenges of conserving water in the winter; the reports of heavy January snow in the Sierra and news that water operators at Folsom Dam had started making large water releases from a rising Folsom Lake.

“You put those three together, it’s a new hardship on the districts,” he said.

Amy Talbot, water efficiency program manager at Regional Water Authority, said lower water-use reductions weren’t surprising given the season.

“With limited opportunities to further reduce water use outdoors, people have to squeeze their savings from indoor conservation, which is a much more difficult task,” she said. “In spite of that challenge, residents continued to conserve.”

While January was a gusher of rain and snow, February has so far been a disappointment, particularly after the hyped announcements that one of strongest El Niño weather patterns in recent history should be dumping precipitation around this time.

Usually one of the wettest months of the year, February has been characterized by warm days in the 70s and blue skies. The average rainfall in February is 3.82 inches in the Sacramento area. But as of Monday – with just a week left in the month – only 0.85 inches had fallen.

Gray, the Fair Oaks water manager, said federal dam operators ought to have the flexibility to change their playbook during such unseasonable conditions.

“I would think the operators – if they would just look at the forecast,” he said, “they perhaps would move away from normal operations.”

The Bee’s Bill Lindelof contributed to this story.

Ryan Sabalow: 916-321-1264, @ryansabalow