This article from California Magazine points the way.
On February 12, 2017, nearly 200,000 Californians got the order to flee for their lives.
Record winter rains had filled Lake Oroville, the vast reservoir that anchors the California State Water Project, to the brim. To avoid overtopping, project managers had released massive quantities of water down Oroville Dam’s main spillway, but fissures in the concrete slabs that lined it were blown open by the torrents. The spillway was briefly closed to assess the newly formed crater, but repairs were impossible under the parlous conditions. The reservoir continued to rise, and water flowed over the wingwall atop the dam’s emergency spillway for the first time in the structure’s almost 50-year history. The slope below this auxiliary spillway was not lined with concrete and the hillside began eroding back toward the reservoir with alarming rapidity, threatening to undermine the wingwall.
The dam itself—at 770 feet high, the tallest in the country—was not at immediate risk. Collapse of the wingwall would be disaster enough, unleashing a 30-foot-high wall of water down the Feather and Sacramento Rivers, ultimately flooding large swaths of the city of Sacramento, blowing out levees in the Sacramento–San Joaquin Delta, and knocking out the gigantic pumps that send water to tens of millions of Southern Californians. Hundreds, maybe thousands of lives could be lost; the economic damage would spiral into the tens of billions of dollars or higher. The state’s electric grid could be impaired for months, and its water delivery infrastructure for years.
The evacuation of so many people downstream of the dam made national news, but few seemed to realize that the state was on the brink of a disaster that would have dwarfed the tragedy of Hurricane Katrina. As it happened, a break in the weather and ceaseless work by state Department of Water Resources (DWR) staffers prevented a catastrophe, but the incident revealed essential flaws in California’s water infrastructure.
Just as the five-year drought had made it clear that California’s reservoirs were unable to store sufficient water to see the state through extended dry spells, so did last winter’s record-setting precipitation highlight the obverse: Our dams and bypasses may not be adequate to prevent calamity during anomalously wet winters. That’s especially sobering because most computer models indicate that extreme weather—droughts and floods—will be part of California’s future as the climate changes. And a water storage and delivery system that more or less met needs from the 1950s to the 1960s, when the big dams and aqueducts were built, now seems lamentably inadequate in addressing the realities of the emergent geologic epoch: the Anthropocene.
Anthropocene is the voguish and not yet officially adopted term to describe the first geologic epoch in Earth’s history to be characterized primarily by the impacts of human activity, global warming foremost among them. To date, the societal response to climate change has mostly centered on efforts to reduce greenhouse gas emissions. But scientists concede that, even if we are fabulously successful at reducing emissions—and so far, CO2 levels continue to climb—concentrations of greenhouse gases in the atmosphere will increase for centuries to come. So, even as we struggle to wean ourselves off fossil fuel dependence, we will also have to adapt to its consequences.
Along with extreme weather events and climate swings, those consequences include rising sea levels, more and fiercer wildfires, and the rapid spread of vector-borne diseases. This winter’s crisis at Oroville was a disaster narrowly averted, but it should also be seen as a wake-up call of things to come.