10/03/2012 07:37 pm ET Updated Dec 03, 2012

It's the Tuolumne, Stupid.

Over the course of this wild and woolly campaign to bring the Hetch Hetchy Valley back to life, I have been asked many questions and have, on occasion, been hissed at. But there is one question asked by friend and foe alike that strikes at the root of the issue: where will our water come from?

And the answer is simple: the exact same place.

But the explanation of that fact is not so simple. The Hetch Hetchy Valley is not the primary source of San Francisco's water supply. It is the wild and scenic Tuolumne River that provides San Francisco and its customers with 85 percent of their water. This water is stored in nine different reservoirs, one of which is called Hetch Hetchy. The Hetch Hetchy reservoir accounts for only 22 percent of San Francisco's stored water supply. The Tuolumne River originates at the base of Lyell Glacier in Yosemite National Park and is nurtured and fed by torrents of melting snow every spring. Nine miles of the river was lost when the Hetch Hetchy Valley was dammed.

Today, the entire system is called -- and aggressively branded as -- the "Hetch Hetchy Water & Power System," leading many of us in the Bay Area to falsely believe we drink "Hetch Hetchy water." Truth be told, we drink Tuolumne River water. Consolidating San Francisco's nine reservoirs into eight will not change that fact -- San Francisco will continue to draw most of its water from this sparkling national asset.

What would be nice is if we could stop using so much of it. Currently, San Francisco uses Tuolumne River water to irrigate our golf courses, hose down our streets and wash our Muni buses. The San Francisco Business Times recently characterized San Francisco's use of the Tuolumne River as "a disgraceful and even disgusting waste of one of California's most precious resources."

We've been awarded this distinction because we do not recycle one drop of water; we treat most of the 20 inches of rainfall we receive each year as sewage, instead of recharging our aquifer and have mostly abandoned use of our local groundwater supplies. What's worse, if you read the San Francisco Urban Water Management Plan , you'll find that San Francisco policy makers are planning on mostly maintaining the status quo well into the distant future.

San Francisco can and should plan to do better. This November, San Francisco voters will have the opportunity to vote on the Water Conservation & Yosemite Restoration Initiative, known locally as Prop F. Should Prop F pass, the city of San Francisco will have to develop a plan to increase its local water supply by 2025, improve flows on the wild and scenic Tuolumne River and return the iconic Hetch Hetchy Valley to the National Park Service so it can be restored beginning in 2035. It's just a plan. Voters would have to approve its implementation at a subsequent election, ideally in 2016.

The planning guidelines are clearly laid out in Prop F ( The Tuolumne River will continue to be the primary source of San Francisco's water supply, but the planning process should identify ways to use less Tuolumne River water and store the water we do use in a less environmentally damaging manner.
Restoring Hetch Hetchy will require San Francisco to think differently about how it uses and reuses Tuolumne River water. But none of this fits easily into an elevator pitch. So, when asked again "where will our water come from," I'll steal a page from the successful Clinton playbook and simply answer: "It's the Tuolumne, stupid."