Permanent water wisdom

California did it. This month, the Legislature passed a package of bills that includes a statewide urban water conservation goal of 20% by 2020. We have confronted the kind of conservation that will be needed to secure the water supply of Los Angeles, and the state, in the face of population growth and climate change.

Or have we?

Population: A Nov. 22 Op-Ed article on water conservation stated that the population in Southern California is expected to grow as much as 43% by 2020. The correct figure, as forecast in 1998 by the California Department of Housing and Community Development, is 13.8%, and for statewide growth, 48.3%. —

It all depends on where you put the goal posts.

If the goal is 20% conservation from the date of the legislation -- Nov. 10 -- then that would indeed be meaningful. The mandate would capture and build on the rising momentum across Southern California to finally use water as if we lived in a dry place, and to finally prepare for life in what forecasters say will inevitably be a drier one.

Only a cynic would scoff at the steady savings recorded this summer and autumn by cities across the Southland, which responded to drought conditions with emergency cutbacks. Beverly Hills is down 13% compared with the same period last year. Huntington Beach achieved a 10% savings, and in markedly progressive Long Beach, consumption has been more than 17% below the historic average. In the foothills, Glendale achieved a little more than 18% savings this summer, and in the baking-hot Inland Empire, savings ranged from 5% to 15% over the same period. Even at the edge of the Mojave Desert, where conservation is orders of magnitude more difficult, Lancaster exceeded a 10% goal.

All that said, the most impressive achievements might just belong to the city of Los Angeles, which, after dragging its feet in 2007 with only a voluntary call to save, demanded mandatory cutbacks, the most draconian in the form of two-day-a-week lawn watering rules starting June 1. Now, the Department of Water and Power is justifiably proud to announce that from the start of mandatory conservation through Oct. 31, single-family residential water use dropped 23.2%; governmental use, 28.8%; commercial use, 15.2%; and consumption by apartment dwellers, 11.7%.

To put the numbers in a more understandable form, since June 1, DWP customers alone saved 17.6 billion gallons, or enough water to supply 100,000 homes or 400,000 people for a year. All that water saved -- even while, as we all know, scofflaws and cheats were so common, and so flagrant, that they included the mayor.

Regionwide, the effect is tangible. Heal the Bay reports a notably better-than-average year for beach water quality, which is traditionally infused every summer by 100 million gallons a day of sprinkler runoff.

Every city canvassed for this article was within its water allotment from the Metropolitan Water District of Southern California, despite mandatory cuts caused by pumping reductions in the Sacramento-San Joaquin River Delta. That achievement translates not only as savings for cities but also as freshwater stored in reservoirs for later use, instead of running down gutters in the form of sprinkler overflow.

Yet there is a fearful aspect to this triumph. Does the new state water law compel these same cities to save another 20% by 2020, on top of their already impressive achievements?

As it turns out, not necessarily. Wade into the fine print of the freshly signed act and you’ll discover that cities have the choice of selecting baseline years against which to measure their 20% conservation, anywhere from 2004 to the end of this year. This means, most likely, all we’ll have to legally do by 2020 is what we did this summer, but differently. This time the savings won’t be elective. Rather, the water companies will force us to essentially plumb the savings into the system.

The reason boils down to the difference between drought-austerity measures and conservation. Most of the savings we achieved this year are the result of temporary restrictions. Implicit in the rules since June 1 is the idea that the drought will end and we can go back to our old watering habits.

As one commentator pointed out, it’s one thing to call citizenry to action to endure a year or two of brown lawns and randomly flushed toilets. It’s quite another to see water-greedy lawns permanently removed and sprinklers and toilets replaced with low-flow models so water authorities can confidently bank on long-term savings.

But do we really need to backslide? Or more to the point, should we really want to?

Peter Gleick, president of the Pacific Institute and the state’s leading commentator on water issues, sympathizes with the cities worried about making their short-term economies permanent. “It’s not unreasonable to ask cities that have done very little to do more,” he said, “and it’s not unreasonable to say that cities that have done a lot shouldn’t be held to the same standard as cities that have done nothing. I also think it’s completely reasonable to ask any of us for a 20% reduction from where we are.”

Ultimately, the latter will be imperative. Federal climate change projections estimate that even in a best-case scenario, the American Southwest, including Southern California, will lose 20% of its precipitation by the end of the century. Meanwhile, the population across the Southland is expected to grow by as much as 43% by 2020.

So as our cities parse the details of the 20% urban conservation mandate and set baseline dates for compliance with the new targets, they ought to start where we left off this summer and aim higher. The scofflaws have to be corralled; the rest of us have to save steadily and learn to save even more. But if Southern California proved anything this summer, it’s that its urbanites -- even the mayor -- are ready and able to do the right thing.

Emily Green writes the Dry Garden column for The Times. She is completing a book on water in the Great Basin Desert. Her website is