Editors note: We received two interesting commentaries on our Hetch Hetchy cover story ("Damn the Dam," 8/10/2011). They appear below, offering very different perspectives on the issue.

OPINION Thank you for writing about our campaign to restore Yosemite's Hetch Hetchy Valley and return it to the American public. We do not, however, propose "to remove SF's main water and power source." Most of San Francisco's water comes from the Tuolumne River and will continue to do so; SF will simply store it elsewhere. As for power, removal of the O'Shaughnessy Dam will not reduce the power delivered to the city, but will mean less power sold to agribusiness in the Central Valley.

You erred in your conclusion about the impact of the restoration on the city's Community Choice Aggregation (CCA) program; large hydropower is not considered "renewable" by state standards, so Hetch Hetchy power cannot be included in CCA's stated goal of 51% renewable energy by 2017.

And please don't buy in to the notion that America can no longer afford big ideas. The restoration of Hetch Hetchy Valley will be the most significant environmental restoration project in human history. It will strengthen not only the fragile Yosemite ecosystem but also the field of restoration science. It will inspire restoration efforts worldwide.

Mike Marshall is the executive director of Restore Hetch Hetchy

Rebecca Bowe's recent article regarding efforts by the Restore Hetch Hetchy organization to tear down Hetch Hetchy Reservoir provides a fairly balanced telling of the two sides of the story. However, some key facts were omitted.

First, the case for tearing down Hetch Hetchy is largely based upon a paper written by a masters student at UC Davis in 2003 (see "Re-assembling Hetch Hetchy: Water Supply Implications of Removing O'Shaughnessy Dam", by Sarah E. Null, December 2003). In her paper, Null bases the feasibility of tearing down Hetch Hetchy on the availability of replacement storage in New Don Pedro Reservoir, which is owned and operated by the Modesto and Turlock Irrigation Districts. Null's premise is that if San Francisco were to lose Hetch Hetchy it could use storage space in the New Don Pedro reservoir.

This is not possible, as San Francisco has no ownership interest in NDP. Rather, it has the right to pre-deposit water it owes to the districts due to the districts' senior water rights. Then when the city needs water, it withholds the water upstream at Hetch Hetchy and the districts debit the city's account in NDP.

The districts have made it clear they do not intend to let the city take over part of their reservoir.

A second key fact is that if the city does not use Hetch Hetchy — and since it can't use NDP — its water rights will be of little use. While state water rights laws are complex and esoteric, seniority is the general rule. The city's water rights are junior to those of the districts. If San Francisco can't exercise its water rights through the Hetch Hetchy system, it would have to take its water from the Delta. The result would be a substantial loss of water and water quality to San Francisco.

As to the loss of hydropower, the article correctly records the permanent loss of 400 megawatts of clean hydropower. The result would be a major new customer for Pacific Gas and Electric Company.

Tom Berliner is a former deputy city attorney who helped negotiate the city's water and power contracts with the Turlock and Modesto Irrigation Districts.