Please pardon the technical term, but I can't think of a better word to describe California's historically derived water rights system than cattywampus.
Our water rights system leads to challenging situations in many areas throughout the state. The Tuolumne River, where San Francisco derives 85% of its water, is a case in point. The statutes are clear that San Francisco's water rights are "junior" to those of the Turlock and Modesto Irrigation Districts.
What does "junior" mean in a year like 2014 - one of the driest on record? The Tuolumne's natural flow for the year was 600,540 acre-feet - about 1/3 of the river's average annual volume. Under California statute, the Turlock and Modesto Irrigation Districts accumulated 576,893 acre-feet, or 96%, while San Francisco was left with only 23,647 acre-feet, or only 4%!
Two clarifications: First, these annual river flows are measured by "water year" -- from October 1 through September 30 -- the customary practice. Second, the Turlock and Modesto Irrigation Districts bear responsibility for releasing water to the lower river - 120,286 acre-feet in 2014.
So it might be more correct to say that in 2014, the natural flow of the Tuolumne River was allocated 76% to the Turlock and Modesto Irrigation Districts, 4% to San Francisco, and 20% to the lower river.
In years like 2014, San Francisco relies on withdrawals from storage to meet demand. Due to their junior rights and the historical tendency of drought years to come in bunches, San Francisco has invested heavily in surface storage. The city stores water in nine different reservoirs in the Bay Area and Tuolumne River watershed. The total storage capacity is about 1,533,000 acre-feet - more than five times San Francisco's average annual demand. See Figure 2.
Hetch Hetchy Reservoir holds 360,000 acre-feet, or a bit less than 25% of San Francisco's total storage capacity. To accommodate restoration of Hetch Hetchy Valley, San Francisco will have to replace this storage with storage at other sites, below or above ground, and/or additional supplies.
Restore Hetch Hetchy has done extensive research to show how replacement of this portion of San Francisco's storage/supply can be accomplished and additional research is underway at this time. Other California water agencies have done much more to restore fishery populations on our rivers and waterfowl population in our wetlands. San Francisco can contribute to restoration as well.
Last night I was explaining the water rights situation on the Tuolumne River to my oldest child. He asked why somebody does not simply run a state initiative to modernize our water rights system. I told him there would be strong arguments for making changes, as well as strong arguments to work within the current system. I also told him that a statewide initiative would be revolutionary and, even if successful could only begin the process of making meaningful change.
So we won't try to change our cattywampus water rights system at present. We will stick to the relatively simple task of restoring Hetch Hetchy Valley and returning it to Yosemite National Park and all people.
P.S. Tickets are now available for our star-studded annual dinner on April 25 in Berkeley