Updated Bay Delta Plan and what it means for SF gardens

By Lauren Lewis

In December 2018 the California State Water Resources Control Board voted to update the Bay Delta Plan in an effort to restore habitat for endangered aquatic animals in the delta. The City of San Francisco is now suing the state over the new plan, ostensibly to buy time to work out an alternate plan that is more favorable to water supply in SF but still satisfies the need for more environmental flow. So what exactly is the fight about and what does it mean for water use in San Francisco?

The shortest possible version of the story: San Francisco’s water comes primarily from Hetch Hetchy Reservoir on the Tuolumne River, a tributary of the San Joaquin River, which in turn feeds the San Francisco Bay Delta. So much water gets diverted from the San Joaquin and Sacramento Rivers, for agriculture, cities, etc, that very little is left for “environmental” uses like fish habitat. Scientists argue that 60% of the unimpaired flow (meaning 60% of the water that would flow through the delta if there were no dams and diversions) is needed to support fish populations and their valuable fisheries. The new Plan requires that 40% of the unimpaired flow be restored during Feb-Jun, when it would naturally be flowing, and that will likely mean water restrictions in San Francisco, especially during dry years.

The plan is not yet final due to the lawsuits against it, but however it shakes out there is certain to be a smaller amount of water making its way from Hetch Hetchy to San Francisco. San Francisco is going to have to get more serious about various conservation strategies, like water recycling. If we want to continue being able to grow ornamental plants, there is going to be even more need to take full advantage of the rains when we have them, which means (1) maximizing water infiltration rather than losing water to the drains and (2) planting the right plants in the right places.

For the city, water infiltration efforts means installing permeable paving when possible, and building rain gardens, which you’ll see popping up around the city. For individuals with some outdoor space it means going for soil and plants over hard surfaces whenever possible, and planting the right plants densely. (If pure water conservation was the goal then of course zero plants is better than any plants, but if we’re trying to balance water conservation with our desire to live among plants, then there are ways to do it thoughtfully. Summer-dry adapted plants are key.)

To start taking really good advantage of the rain water we receive, now is the time to be observing in your outdoor space. When it rains hard, watch the way the water moves and collects. You can have a diverse summer-dry garden and still minimize irrigation needs by planting thirstier plants in those places where the rain infiltrates most: the small depressions and low points.


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