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You hear this every time there’s a drought or deluge in California: “Why haven’t they built more dams?” Truth is, they’ve built a bunch. And they’re about done with it. Tally them up. There are more than 1,400 dams in the state. At least 1,000 are major and 55 can hold 100,000 acre-feet or more of water. One acre-foot is enough to supply two average households for a year. There are 36 reservoirs that can contain at least 200,000 acre-feet. Eleven can hold 1 million or more.

Bill Croyle stood in front of an aerial photo of Lake Oroville and swept his hand across the top of the emergency spillway that was helping drain water out of the brimming reservoir. “Solid rock. All this is rock,” Croyle, acting director of the Department of Water Resources, said with an air of confidence at the Feb. 11 briefing. The flows over the concrete lip of the unpaved spillway were tiny compared with what it was designed to handle. Oroville’s first-ever emergency spill was going smoothly.

How did a giant, gaping hole tear through the massive Oroville Dam’s main concrete spillway last week, setting in motion the chain of events that could have led to one of America’s deadliest dam failures? Dam experts around the country are focusing on a leading suspect: Tiny bubbles.The prospect is simple, yet terrifying and has been the culprit in a number of near disasters at dams across the globe since engineers discovered it about 50 years ago.

A powerful atmospheric river storm is bringing rain Friday to much of California, resulting in a flood watch for three counties down south and strong winds to the Bay Area. In Southern California, a flash flood watch will be in effect from 7 a.m. Friday through Saturday morning for Santa Barbara, Ventura and Los Angeles counties, according to the National Weather Service. The weather service has issued a high wind warning for parts of the Bay Area and Central Coast, including the Monterey Bay area.