Thomas Donlan of Barron’s explains how California’s recurring water problems relate to the state government’s ill-considered policies.

As happened in New Orleans in the aftermath of Hurricane Katrina, and as so often seems to happen when people try to control nature, public works turned into a public-relations disaster. There came a sudden realization that people faced an old, well-understood problem, magnified by neglect. The Oroville Dam spillway problem surfaced in 2005, when the Federal Energy Regulatory Commission was considering relicensing the dam’s hydroelectric power station. Three environmental groups urged the commission to require a concrete structure for the earthen auxiliary spillway.

“You don’t have unarmored spillways unless you are really sure you aren’t going to use them,” said a policy advocate with Friends of the River in 2005. The dam had never needed support from the auxiliary spillway, not even in the worst rainfalls that had occurred since it was completed in 1968.

But the Oroville Dam had been designed with an incorrect assumption—that a second dam, upstream in Marysville, would collect water on a tributary of the Feather River. That would have reduced the amount that the Oroville Dam would have to hold in major floods. That dam was never built, but the assumption was never changed.

Nature and neglect leave California with a seemingly permanent water crisis: There’s always too much or too little, and never enough money to get ready for the future.

The Sierra Club opposes new water-storage projects and blames climate change for everything. “The days of predictable weather patterns are gone,” the organization declared recently, which is what the group also had said at the height of the drought.

Scientists were making the ridiculous assumption that there ever had been predictable weather patterns in most of California. It’s a certainty that there will be droughts, which will end with floods. But when? The pattern has always been wildly variable.

Even if climate change makes the weather worse, both in the direction of floods and the direction of droughts, California has been resisting all of the obvious solutions.

It could build more dams and reservoirs for flood control and water supplies. It could reinforce the need for conservation with permanently higher prices for the water they do have. Or, as Gov. Jerry Brown has suggested, the state could capture billions in new revenue by seceding from the U.S. For every dollar that Californians send to the feds in taxes, 79 cents is spent in the state.