S.F. water supply in OK shape, but officials keep on pressure

This image in Yosemite National Park looks across Hetch Hetchy from the trail above the reservoir that stores S.F.’s water supply; it’s more than 90 percent full. This image in Yosemite National Park looks across Hetch Hetchy from the trail above the reservoir that stores S.F.’s water supply; it’s more than 90 percent full. Photo: Tom Stienstra, The Chronicle Photo: Tom Stienstra, The Chronicle Image 1 of / 23 Caption Close S.F. water supply in OK shape, but officials keep on pressure 1 / 23 Back to Gallery

Four years into a drought that has left many cities and farms desperate for water, the vast Sierra-fed water system that serves San Francisco and much of the Bay Area is in relatively good shape — and should get the region through the dry months ahead, officials said Tuesday.

San Francisco’s Hetch Hetchy Reservoir, which captures snowmelt from Yosemite National Park that supplies 2.6 million people, is more than 90 percent full, far better than most of the state’s lower-elevation reservoirs.

But city water officials aren’t taking chances. The San Francisco Public Utilities Commission launched a new conservation push Tuesday to preserve its pristine mountain supply, just as snow vanishes above the lake and runoff begins to dry up with summer.

“Last year, our customers proved they know how to save water,” said Harlan Kelly, general manager of the commission, at a news conference held downtown, about 180 miles west of the Hetch Hetchy Reservoir. “As this historic drought continues, we’re calling on them again to continue this amazing effort.”

The conservation call was paired with the start of a $300,000 sex-themed ad blitz, which piggy-backs on last year’s racy promotions that included slogans like “Make it a quickie,” a reference to showering, and “Get paid for doing it,” meaning replacing an old toilet.

Slogan: ‘Go full frontal’

The latest slogan is “Go full frontal.” The phrase — while revealing that the campaign may have exhausted its best ideas — is a plug for efficient front-loading washing machines.

The continued push for water savings comes as the state’s largest reservoirs are sinking to lower-than-normal levels at a time of year when they should be running high.

“Normally, the reservoirs peak at the beginning of June,” said Mike Anderson, state climatologist with the Department of Water Resources. “This year our peak happened, and it wasn’t even much of a peak. There just wasn’t much snowmelt to fill them.”

Lake Oroville, California’s second biggest reservoir, stands at just 43 percent of capacity at a time when it would normally be more than half full — and with more runoff to come. The bigger Lake Shasta was 52 percent full this week, down from a typical 61 percent for this time of year.

The lackluster supplies and meager snow have water managers across the state cutting back deliveries to farms and households and encouraging conservation, often mandating it by threatening hefty hikes and fines. The goal is to stretch out what limited water is left.

Hetch Hetchy’s relatively rosy level is due in part to slightly wetter weather at the reservoir, officials said Tuesday, as well as strong conservation efforts by Bay Area residents. But it is also a function of how water is managed and measured.

San Francisco officials are holding more water at the reservoir rather than releasing it downstream to other reservoirs and water banks run by the city.

Also, because Hetch Hetchy is smaller than many state and federal basins, it can fill up more than once during wetter years, after releases are made. This year it will hit capacity only once, though, if at all.

System 54% capacity

The entire system’s 1.5 million acre-feet of storage is currently at only 54 percent capacity, officials said.

Still, water managers said the level is plenty to get San Francisco residents and the other 24 cities and water agencies served by the system through the dry summer — as long as customers continue to cut back.

Conservation in the Bay Area has been stronger than in other parts of California. In April, the region used about 20 percent less water than during the same month in 2013, the year state officials are using as a baseline.

“People have recognized that, yes, this is a severe drought,” said Steve Ritchie, an assistant general manager for the city utilities commission.

Kurtis Alexander is a San Francisco Chronicle staff writer. E-mail: kalexander@sfchronicle.com Twitter: @kurtisalexander