Water wisdom for California

Southern California’s water needs are met primarily by snow falling and water flowing from distant mountains. From the rugged eastern side of the Sierra comes the Owens River, which the city of Los Angeles tapped not just once — with William Mulholland’s century-old aqueduct — but repeatedly with extending and parallel arteries. From the gentler western slope come the tributaries that feed the San Joaquin and Sacramento rivers, which historically flowed through a marshy delta to the San Pablo Bay into the Pacific; and the complex of dams, canals and pumps that now sends much of that water to East Bay cities, Silicon Valley, Central Valley farms and farther south over the Tehachapis. From the Rockies comes the Colorado River, which Western cities and farms drain so that barely a trickle now reaches the Gulf of California.

And there is a fourth source, long underused but growing in importance: the local supply. It is a combination of groundwater, captured storm runoff, reclaimed and purified sewage water and desalinated seawater. And it includes an entire virtual river in water-wise practices, from low-flow toilets to drip irrigation and inventions as yet unimagined. Southern Californians will have to continue developing that source as they mitigate damage to the Owens Valley and the delta with more restricted — but, with some luck, more predictable — flows of mountain water.

The final draft chapters of the Bay Delta Conservation Plan, released last week by a broad array of water agencies, environmental groups and state and federal offices, set forth one route toward making the supply from the western Sierra more predictable in the face of potential drought, sea-level rise and levee-damaging earthquakes, as well as existing mandates to protect and partially restore the fragile delta ecosystem. There are few surprises. The “preferred alternative” is still to build twin tunnels that would divert water to aqueducts from farther up the Sacramento River, keeping endangered fish out of pumps as they direct water to the state’s south-flowing aqueducts.

Water contractors, farmers, residential customers, environmentalists and courts all want a better measure of certainty about their supplies, the fish, the costs and the consequences. But the only certainty is that without action, everyone will continue to lose. The plan is an attempt to balance uncertainties.

The formal public comment phase for the conservation plan won’t begin for several months, but the dialogue is well underway and is already shaded with arguments based more on emotion — on regional rivalry, on ancient resentments, on identity and culture — than on the realities of the state’s threatened environment and economy, and on Californians’ interdependence.

Those emotional arguments must be borne with patience and understanding, and corrected, when possible, with facts. All Californians must hear and consider alternatives, and must weigh potential costs — for example, $5 to $7 a month more on local water bills — against the enormous costs of failing to act.