The Oroville Dam in Northern California may seem far removed from San Diego. But there are millions of reasons, most in gallon form, for locals to be keeping an eye on the ongoing battle to keep its emergency spillway from collapsing.

The dam, as the L.A. Times puts it, is the “linchpin” of the statewide water system that brings water from the Sierra Nevada mountains to Southern California. Its fate affects our water supply.

And that’s not all. As California’s little-known second-deadliest disaster and our own grim local history reveals, the reliability of dams is crucial to our own personal safety.

Here are questions and answers about the Oroville Dam crisis.

What’s going on up there?

The Oroville Dam, the tallest dam in the nation, keeps water in the Lake Oroville, the largest reservoir in the so-called State Water Project, “the system of reservoirs and canals that supplies nearly a third of Southern California’s drinking water,” KPCC reports.

As the Sacramento Bee explains, “the engineering crisis facing Oroville Dam — and repeated swings in strategy — started last week, when Department of Water Resources engineers discovered a cavernous hole in the lower section of the dam’s main spillway following a series of strong storms.”

The spillway is essentially an escape valve to allow water to leave the reservoir created by the dam. Water started topping an emergency spillway, and erosion threatened to cause it to collapse. This created a conundrum: Where should officials send the excess water, down the unstable main spillway, which could collapse, or the unstable backup spillway (ditto)?

There’s a bigger question now: What will the storms coming later this week do to the supply of water to the dam and the risk of partial collapse? The hope is that officials will safely release enough water now to allow the dam to handle runoff from the storm.

Is the whole dam going to fail?

Officials say that won’t happen, but a barely controlled rush of water would still create a tremendous amount of havoc downstream. That’s why almost 200,000 people were told to evacuate. This afternoon, the mandatory evacuation order was lifted.

Who’s to blame?

The McClatchy News Service says the threat at the dam has hardly been a secret, but “California water districts that helped pay for Oroville resisted calls to armor the backup spillway, which would have required construction outlays in the tens of millions of dollars. Environmentalists, meanwhile, opposed an earlier proposal to install gates atop the structure to raise the dam’s elevation and prevent water from topping it during a flood.”

How can I keep track of the crisis?

The L.A. Times has a live blog here, along with photos and a graphic explaining what’s going on. The Sacramento Bee has its latest coverage here. Local TV station KRCR has been live-streaming its coverage, and station KCRA, with a live-stream here, has gotten praise.

How does the dam affect how we get water?

The Oroville Dam is part of the State Water Project, which since 1960 “has helped to protect Northern California cities, towns and farms from floodwaters while providing usable water to Central Valley farms and Southern California homes,” according to the L.A. Times. “A catastrophe at Oroville Dam — for example, spillway-loosened detritus blocking flow to the delta — could cause a water-supply emergency here, despite all the rain.”

As for the reservoir behind the dam, KPCC says we don’t get much water from Lake Oroville right now in the winter. But it becomes crucial for Southern California in the summer, and an engineering professor tells USA Today that repairs are likely to last past the summer this year, potentially forcing officials to limit water in the reservoir.

The gist of all this: We could lose a significant chunk of our water supply, perhaps even 20-25 percent. But there are many unknowns, such as the potential for the return of drought restrictions.

How are our dams doing?

South Bay’s Sweetwater Dam, which has overflowed in the past, has gotten the most attention lately in terms of potential risks to the public.

The board that oversees the dam had declined to pay for repairs to its spillway, prompting the director of the state Division of Safety of Dams last September to warn its members last fall that they made the wrong choice. “I’m concerned about the people that live downstream from this dam. That’s my job,” he said, according to 10News. “The consequence of a failure is extreme.”

The water board changed its mind, and the dam is now scheduled to get upgraded by 2018. For more, check this state report.

What about other local dams?

There’s good news, sort of. As The Atlantic notes, “California is by some standards among the best states for dam safety in the country. While it has an enormous number of high-hazard dams — a classification meaning that lives are at risk if they fail — they are also inspected far more regularly than in some other states.”

According to inewsource, 20 dams in the county were considered high-hazard in 2002; new information isn’t available due to concerns that terrorists will use it. But, as it reported last year, the state considers all the county’s 54 dams to be safe. (Click here to see an inewsource map of where the dams are; the county has a map too.)

As of 2016, “among 41 publicly owned dams, 34 had emergency action plans and seven did not,” including two that had been thought to be especially dangerous if they were to fail, inewsource reports.

Still, there’s a lot of talk of new dam inspections. The city of San Diego tells City News Service that it’s been inspecting the nine dams it owns over the past year — but a report isn’t expected for four years. The dams are inspected weekly for problems like erosion and leaks, while cracks are measured each month.

How much danger could a failed dam pose?

In California’s history, there’s been no greater disaster outside of the 1906 San Francisco earthquake than the 1928 failure of the St. Francis Dam in the Los Angeles area. As many as 600 people lost their lives in what Smithsonian Magazine calls “the worst civil engineering failure of the 20th century.”

“It demolished 1,200 houses, washed out 10 bridges and knocked out power lines,” the L.A. Times reports. “Bodies would wash ashore as far south as San Diego.”

Water engineer and urban visionary William Mulholland would be blamed for the disaster, and — in a rare moment of a public person accepting blame — he said: “If you’re looking for human error, fasten it on me. I built it, I designed it, I failed. I’m responsible.”

However, “to this day, no one believes that Mulholland was personally responsible,” historian Les Standiford told me two years ago. He’s the author of “Water to the Angels: William Mulholland, His Monumental Aqueduct, and the Rise of Los Angeles.”

Here in San Diego County, the Sweetwater Dam failed during the epic rains of 1916, reportedly killing eight people. You can see a remarkable photo of the dam damage here; look for the photographer at the upper left. Here’s another amazing photo.

But that wasn’t the worst of it. The dam at Lower Otay Lake in the South Bay also gave way, flooding a Japanese settlement and reportedly killing 11 people, although some reports put the number at much higher. “Of the Japanese killed in the flood, eleven are memorialized on a fine granite shaft dedicated by the local Japanese American community at San Diego’s Mount Hope Cemetery,” says the text accompanying a 2016 exhibit on the 1916 flood at the Chula Vista Civic Library.

The deadly 1916 dam failures in the South Bay prompted state legislation that gave the state engineer authority over many dams in California.