Editorial:

How proud is San Francisco of its water?

You can buy it in a bottle as if it were Perrier, that's how proud.

"Hetch Hetchy," reads the bottle's label. "Contains mountain water from a municipal source high within the Sierra Nevada."

What's missing is the fine print about how the "municipal source" is a once-magnificent valley in Yosemite National Park. That valley now lies submerged under 300 feet of water, water that supplies San Francisco and much of the Bay Area.

Over the years, San Francisco and environs have acquired a taste for the naturally filtered water that flows over granite into a reservoir in the park. That addiction explains why the Bay Area will instinctively resist an emerging effort to restore Hetch Hetchy, a valley inundated for San Francisco's water supply in 1923 and a source for the cherished bottled water today.

There is one difference between the water you can buy in a half-liter bottle for $1.25 and the water that flows from taps in San Francisco. Because of state regulations, Hetch Hetchy water is filtered before being bottled. Hetch Hetchy water that comes out of faucets in San Francisco is not.

Every other major urban water department in California has to filter its river water supply. For San Francisco and three surrounding counties that depend on the Hetch Hetchy reservoir, there is no such requirement. Yosemite does the filtering. As the snow melts in the high country and tumbles down Yosemite's granite falls, the granite naturally filters away most impurities.

The label on the bottled water features the feathery Tueeulala and thundering Wapama waterfalls of Hetch Hetchy, but it cannot reveal the lost national treasure that is the Hetch Hetchy Valley.

The valley is Yosemite Valley's smaller twin, the object of a crusade by naturalist John Muir nearly a century ago. Muir failed when Congress gave San Francisco the go-ahead to build a dam in Hetch Hetchy. Now the valley is the least visited feature in the park.

San Francisco's occupation of the national park is attracting a fresh look, and deservedly so. The Bush administration for one, has questioned why the city should continue occupying such a treasure for the paltry fee of $82.19 a day. A University of California, Davis, computer analysis shows that the Hetch Hetchy dam is expendable. Three other dams on the same Tuolumne River seem capable of capturing the necessary water for all who depend on the river. And on the political front, Environmental Defense is mobilizing a campaign to restore Hetch Hetchy, a crusade unmatched since Muir's time.

The challenge is technical, to be sure. Draining Hetch Hetchy would require capturing the same quantity of river water downstream and outside the park. And the water would need filtering.

But the challenge doesn't end there.

Former San Francisco Mayor Willie Brown came up with the idea of bottling Hetch Hetchy back in 1998 because, in his words, "the quality of the water is superior to anything else we produce in the city." Hetch Hetchy, he said in the San Francisco Chronicle, "will be a brand name, with national appeal."

Anyone considering a restoration of Hetch Hetchy should not underestimate the political realities of the San Francisco palate or of San Francisco's pride.

But, in all due respect to Brown, who remains one of the state's sharpest political minds, the national appeal of Hetch Hetchy goes beyond what's found in a plastic bottle. If given the choice, wouldn't the nation prefer the chance to visit the Hetch Hetchy Valley? The national park's Yosemite Valley is crowded and growing more so. Wouldn't it be remarkable to have a second valley, Hetch Hetchy restored?

Would San Francisco be willing to swallow the change?