FutureStructure

Water Release from California's Folsom Lake Prompts Experts to Seek Guideline Revisions

Although the state is in the midst of a historic five-year drought, water is being released from Folsom Lake based on its operations manual from 1956.

by Ryan Sabalow, Phillip Reese and Dale Kasler, The Sacramento Bee / February 16, 2016
California's Folsom Lake in February 2016, sitting 60 percent full. Flickr?Cheryl Beadle

(TNS) -- Northern California’s El Niño winter has been on pause lately, with barely a drop of rain for two weeks. Yet federal dam operators recently increased the flows out of Folsom Lake by thousands of acre-feet a day as a precaution against flooding. They did so even as the reservoir sat 40 percent empty.

The dam operators weren’t acting on their own initiative. They were adhering to a 60-year-old manual, drawn up by the U.S. Army Corps of Engineers, that requires them to release water when Folsom Lake rises to a specified height. The requirement holds even if no major storms are forecast, and the state is trying to conserve water during the fifth year of an epic drought.

Similar operating manuals, all created by the Army Corps, govern flood-control releases at 33 dams in California. The vast majority haven’t been updated since at least the 1980s; Folsom’s manual dates to the year the reservoir opened, in 1956.

Now, a small but growing chorus of Sacramento-area water managers and hydrology experts says it’s time to revise the guidelines to permit more flexibility on water storage, particularly given a warming climate expected to bring more frequent and longer dry spells.

“There’s this … simple solution that really simply boils down to updating your manuals,” said Ann Willis, a researcher at the UC Davis Center for Watershed Sciences. She said Californians should “look at that and say, ‘Are you kidding me? Fifty years we’ve been dealing with this, and a solution is to update a manual and you haven’t done it?’ That’s really frustrating.”

The ramped-up releases didn’t occur in a vacuum; they followed a remarkable surge in which the lake’s water level tripled in less than two months. Officials with the Army Corps said flood safety remains a paramount concern, particularly with hundreds of thousands of Californians living on flood plains below dams.

“Our first responsibility is to ensure public safety by reducing risk to downstream communities and the people that live and work there,” Christy Jones, chief of water management in the corps’ Sacramento district, said in an emailed statement.

“We are always mindful that we operate these projects as part of a larger system. At Folsom, for instance, we have to take into account what’s happening in the reservoirs upstream as well as any conditions downstream that may impact our ability to safely route water through the river.”

The ramped-up releases, which began Feb. 5, spilled enough water to supply the Sacramento region for weeks. Water managers, under orders from the state to meet stiff conservation targets, say it’s difficult to get people to take shorter showers and rip out their lawns when extra water is flowing out of Folsom even amid prolonged forecasts of sunny skies.

“If we can’t trust people to make forecast-based decisions, then you need new staff,” said Shauna Lorance, general manager of the San Juan Water District, which relies on Folsom Lake to supply its 160,000 retail and wholesale customers.

At the nearby Fair Oaks Water District, the heavy releases from Folsom sparked similar frustration.

“Customers see water being dumped down the river,” said General Manager Tom Gray. “If we’re in the dire straits of a drought, shouldn’t you be looking at actual (weather) projections? Shouldn’t you maybe not use the regular playbook?”

Local water officials don’t take issue with flood control in concept. The last major Northern California flood, in January 1997, killed eight people and caused $1.8 billion in damage. And even ringed with levees, Sacramento remains among the nation’s most flood-vulnerable regions.

But the federal government, they say, has been slow to adapt to improved data, science and engineering, particularly when it comes to weather forecasting. The oldest of the Army Corps flood-control diagrams were created when weather forecasting had a shorter range and was far less reliable than it is today. Some are so old, they’re drawn by hand.

Willis said the guidelines amount to a straitjacket that assume reservoirs need to be kept comparatively empty in winter to make way for heavy snowmelt in the spring – a philosophy that gradually is being rendered obsolete by climate change.

“When the spring season comes along,” the UC Davis scientist said, “there’s no snowmelt to capture.”

Responsibility for Folsom Lake operations is shared by the Army Corps and its sister agency, the U.S. Bureau of Reclamation. Water is released year round, in varying amounts, to meet downstream water quality standards and other needs.

The reservoir’s operating manual, which the Army Corps released to The Sacramento Bee, includes a key chart consisting of a series of lines penned on graph paper and dated “24 May 1956.” During the winter, the lines plunge downward sharply to indicate how much unfilled “safe space” must be preserved in the reservoir to prevent flooding. Between mid-November and early February, the guidelines say the lake should hold no more than 577,000 acre-feet of water, the point where Folsom is about 60 percent full.

On Feb. 5, with the lake topping 577,000 acre-feet, releases jumped from around 500 cubic feet per second to 3,000, according to state data, sending thousands of acre-feet downstream.

Even with the additional increases, the lake has risen about 25,000 acre-feet above the Army Corps’ flood-control threshold. The threshold itself is a moving target and will gradually rise through the rest of winter and into spring, enabling more water to be stored, as the rainy season winds down.

The Folsom manual indicates the guidelines are based on the limitations of the dam, the size of the drainage area above and below it, and precipitation patterns from the 1930s, ’40s and ’50s.

Jones, the Army Corps flood manager in Sacramento, said changing the guidelines would require complex and costly engineering and environmental studies. Each time a dam’s flood-control manual is updated, the reviews “can easily cost several million dollars per project,” she said.

Corps officials said they do incorporate weather forecasting models in flood-control management at Lake Oroville, a giant reservoir in the northern Sacramento Valley. Jones said they are discussing the possibility at Folsom, as well.

The discussion is taking place in tandem with construction of a $900 million auxiliary spillway. The new gates, to be completed next year, 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.

Changes to Folsom’s operating manual could lead to significant water savings. Under current guidelines, federal officials aim to keep Folsom at or below 575,000 acre-feet, or 60 percent of capacity at this time of year. As an example, allowing the lake to hit 65 percent of capacity before making flood-control releases would permit an extra 50,000 acre-feet to remain in storage.

That 50,000 acre-feet would be equivalent to all water used in 2015 by the roughly 220,000 retail customers in Roseville, Folsom and the San Juan Water District, the three agencies most reliant on Folsom Lake for drinking water.

This month’s ramped-up releases weren’t the first time that extra water poured out of Folsom during the current drought to guard against a flood that never came.

During the week of Christmas 2012, Folsom Lake had more water than what was called for in flood-control plans – but was nowhere near capacity. The Bureau of Reclamation opened up the gates on orders from the Army Corps and let water flow out at 9,100 cubic feet per second on average, according to records kept by the California Department of Water Resources.

That was more than three times the average December flow out of the lake, and the highest sustained flow recorded between 2012 and 2015. The result was tens of billions of gallons of water poured into the American River.

During that week and the following, it rained 2.4 inches in Sacramento; hardly a deluge. The rest of the winter was abnormally dry, and it didn’t rain again until the following October. By Christmas 2013, one year after the water dump, the lake was nearing record lows, causing area suburbs to fret about their water supply and placing strains on fish populations downstream.

Some environmentalists take issue with the notion that water flowing out of Folsom Lake is a wasted opportunity. Jon Rosenfield, a biologist at the Bay Institute in San Francisco, said every drop that flows into the river helps with fish populations and the water quality in the fragile Sacramento-San Joaquin Delta.

“This whole ‘wasted to the sea’ argument,” Rosenfield said, “is propaganda.”

Joe Countryman, a former Army Corps engineer, was in charge of the Sacramento-area dams, including Folsom, until he retired in 1988. He now sits on the Central Valley Flood Protection Board. He said not every dam the Corps manages lends itself to a rewritten manual that would incorporate short-term weather forecasts. For instance, dams on the San Joaquin River system, he said, have too narrow a channel below the spillway for water to be quickly released to accommodate a major storm.

But, he said, Folsom would be an ideal candidate. The reason? The river channel below the dam is wide enough to accommodate sudden gushes of flood-control releases when storms are spotted developing over the Pacific Ocean.

“We have the great advantage here where we can see out in the Pacific and we can tell when a large storm is coming in,” Countryman said. “It’s not a secret. It can’t sneak up on us.”

But change comes slowly at the Corps. Jay Lund, director of the Center for Watershed Sciences at UC Davis, said there is strong institutional reluctance to a sweeping reworking of the agency’s dam guidelines.

“Nationally, the Army Corps of Engineers takes a look at this and says, ‘Wait a minute, if we open this little can of worms in California, there’s another 600 reservoirs across the country, each of which have their stakeholder groups who are just itching to fight to see if they can ... get something else out of the system,’” Lund said.

“Bureaucracies are risk-averse anyway, so this puts them all in a bad situation. We should be making these changes, but there are real human reasons why there’s reticence to do it.”

©2016 The Sacramento Bee (Sacramento, Calif.) Distributed by Tribune Content Agency, LLC.