SAN FRANCISCO -- What will it be: Righting an environmental wrong done 99 years ago or preserving a water source that supplies more than 2.6 million people? Should the 117-billion-gallon Hetch Hetchy reservoir in Yosemite National Park be drained?

For the first time, those questions will be before San Francisco voters next month.

The controversy goes back to the San Francisco earthquake of 1906, when a lack of water allowed fires to burn unchecked. The next year a long-simmering idea to dam the Tuolumne River and flood a valley high in the Sierra Nevada mountains was pushed by San Francisco and nearby towns. It was opposed by environmentalist John Muir and the Sierra Club he founded.

After years of debate, President Woodrow Wilson signed the Raker Act of 1913, allowing the dam to be built. It was completed in 1923, but ever since, some environmentalists have dreamed of restoring the Hetch Hetchy valley - named for the Miwok Indian word for a grain that grew there - to its natural state.

On Nov. 6, that dream will be put to voters as Proposition F.

San Francisco Mayor Ed Lee has publicly called the plan "insane." It is opposed by the entire San Francisco city council, both of the state's Democratic U.S. senators, mayors of several cities that also get Hetch Hetchy water, and a long list of local and state public officials and organizations.

About 16,000 voters signed petitions to put the issue on the ballot. The measure would create a five-person panel and allocates $8 million to write a plan on how the city could conserve water and drain Hetch Hetchy "so the environmental damage done to Yosemite" since 1913 could be undone, says Mike Marshall, campaign director of the Yosemite Restoration Campaign.

It also requires the city council to vote on whether to place an amendment to implement the plan on the 2016 ballot.

The Hetch Hetchy reservoir holds 117 billion gallons of water. Currently one-third goes to San Francisco and two-thirds to the 30 cities in three counties that make up the Bay Area Water Supply and Conservation Agency. A generator fed by the water produces 726 million kilowatt hours of electricity annually.

Eight studies have been done in the past 30 years looking at the feasibility of taking down the O'Shaughnessy Dam that created the 8-mile Hetch Hetchy lake, restoring the valley and making up the water and electricity shortfall. The cost has been estimated at $3 billion to $10 billion, says Tyrone Jue of the San Francisco Public Utilities Commission. The water districts that share the reservoir are in the final stages of a $4.6 billion seismic upgrade and water conservation project for the entire Hetch Hetchy water system, he notes.

The feasibility study "is such a colossal waste of money," says P.J. Johnston, spokesman for Save Hetch Hetchy, which opposes the initiative. Given that water is a scarce resource and a major source of conflict in California, "The idea that we could voluntarily eliminate the single largest water resource in the state and spend $10 billion to do it is just irrational."

The people behind Restore Hetch Hetchy have their hearts in the right place but need to face reality, he says. "Most of us would not choose to build the reservoir where it is now if we were faced with that question in 2013," says Johnston. "But the decision was made in 1913."

Marshall says water lost from destroying the reservoir could be made up if San Francisco only "imports a little less" water from the Tuolumne River and builds up its local water supply. The electricity lost could be made up "if we just put solar panels along the right-of-way from Yosemite to San Francisco," he says.

Another sticking point is who makes the decision. San Francisco owns the dam and the water rights, but the land belongs to the National Park Service. The vote is only in San Francisco, leaving out the 1.9 million people who live in Silicon Valley communities that get the majority of the reservoir's water under a sharing agreement that dates back to 1913, Jue says.

Twice as many people outside San Francisco get water from Hetch Hetchy than in the city, says Art Jensen, general manager of the Bay Area Water Supply and Conservation Agency in San Mateo,which represents those communities. "We would like to establish a mechanism for the people outside of San Francisco or their representatives to get to vote on any plan that's put forward."

Marshall counters that one of the five members of the panel that would write the plan to drain Hetch Hetchy would be a representative of the Bay Area agency.

The usual onslaught of fliers and mailers that heralds election season in San Francisco has not yet begun and the proposition has a fairly low profile so far. However, the San Francisco Bay Guardian, a left-liberal weekly that's influential among voters, has suggested a no vote. The proposition is "being pushed by a combination of wishful (although largely well-meaning) sentimentalists and disingenuous conservatives," the newspaper says.

USA Today