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Season of the Switch

The good news: After five years of historic drought, California is awash in water again. The bad news: Schizophrenic weather is going to be our new normal.


Water flows down the Oroville Dam’s damaged main spillway at 55,000 cubic feet per second.

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Before-and-after satellite photos of three major California reservoirs display the (mostly) welcome effects of this winter’s historic precipitation.

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Editor’s Note: This is one of many stories about our relationship with the natural world, which San Francisco is publishing over the next month as part of the May 2017 Great Outdoors Issue. To read stories as they become available online, click here.

In a 1988
piece in Discover magazine, Peter Gleick, a scientist at the Pacific Institute, a think tank focused on global water issues, made a bold prediction about California’s weather in the age of global warming. “California will get the worst of all possible worlds—more flooding in the winter, less available water in the summer,” Gleick said. “This will reverberate throughout the state.”

At the time, Gleick’s view was uncommon. Thirty years later, his forecast has been vindicated. California has just been whipsawed by the weather gods. From 2011 through late 2016, the Golden State experienced the hottest, driest weather in more than a century of record keeping. Parched Central Valley farms and communities pumped so much water out of the ground that wells dried up and the earth subsided. There was an unprecedented die-off of 102 million coniferous trees. The state suffered billions of dollars’ worth of agricultural losses. Severe water-rationing measures were imposed. And experts warned that such water shortages would become chronic: Drought was the new normal.

Then, starting in mid-September last year, the storms came. And came. And came some more. As of February 28, California had received 190 percent of its average annual precipitation, making this the ninth-wettest winter since record keeping began in 1895. As of the same date, San Francisco had received 25.75 inches of rain since October 1—146 percent of the average. The statewide snowpack was at 185 percent of the average; Squaw Valley announced it would be open for skiing on the July 4 holiday for just the fourth time in its 68-year history. Of the 12 key reservoirs listed by the California Department of Water Resources, 10 were above average capacity, and Hetch Hetchy, which provides San Francisco’s water supply, was 90 percent full, even before the spring snowmelt.

All this water was fabulous news—until it wasn’t. So much rain fell that reservoirs and dams couldn’t hold it. The spillways of the vast Oroville Dam were badly damaged, forcing the evacuation of more than 180,000 people living downstream. More than 100,000 people in Southern California lost power during one of the February storms. Big Sur was cut off from the world when a bridge washed out. A San Jose neighborhood was flooded when a creek overflowed its banks. In all, infrastructure repairs due to storm damage in California could cost more than $1 billion. 

To the casual observer, the abrupt change from no water at all to way too much water was baffling. One moment California was cracked-lipped Clint Eastwood, marched through the burning desert by Eli Wallach in a sadistic remake of The Good, the Bad and the Ugly; the next, the state was sodden Russell Crowe in Noah. It was meteorological schizophrenia.

But for those who have been paying even minimal attention and believe in scientific evidence and logical causation—a group that unfortunately does not include the president of the United States or the head of the Environmental Protection Agency—California’s extreme weather oscillation comes as no surprise. Gleick’s 30-year-in-advance Cassandra act is the most dramatic example, but climate scientists have known this was coming for years. Noah Diffenbaugh, a professor at the School of Earth, Energy & Environmental Sciences at Stanford University, says, “A new normal is emerging in which we have greater frequency of hot, dry periods punctuated by extreme wet conditions.”

That apparently paradoxical outcome is the result of two different sets of atmospheric conditions, both related to global warming. The reason global warming leads to warm, dry weather is obvious; the reason it leads to wet weather, less so. California gets most of its precipitation from “atmospheric rivers,” wonderfully named plumes of moisture that travel from the subtropics. “When we don’t get these atmospheric rivers, we get low-precipitation years, and when we get extra, we get wet years,” Diffenbaugh says. “And what we’ve seen this year has been a rapid succession of atmospheric river events.”

Despite great scientific advances in the field, meteorologists still cannot make accurate long-range weather predictions. That’s why no one predicted this winter’s Great Deluge. But the big picture is becoming increasingly well understood. Because global warming increases the amount of water vapor in the atmosphere, Diffenbaugh says, it increases the likelihood that atmospheric rivers will be wetter and turn into rain, not snow, when they make landfall. He says there is also some evidence, though not yet conclusive, that global warming will increase the frequency of atmospheric rivers. So as we continue to heat the planet, California can look forward to being inundated by warmer and wetter storms, as well as the possibility of more of them.

But if we’re likely to get more rain in the future, why do experts also keep saying that we have to worry about chronic drought? Laura Feinstein, a senior research associate at the Pacific Institute, explains, “It’s a question of ‘How do you define drought?’ We live on the surface of the earth, so we tend to be sensitive to how much water there is at the surface, but there is a groundwater drought going on.” For decades before the drought, we drew more water out of the ground, especially in the Central Valley, than we replaced—and in the past five years, farmers in that region have pumped so much groundwater that levels have dropped precipitously. “Even though we’re getting so much rain this season, our groundwater is not even close to recovering from these past five years of overdrafting,” Feinstein says. “The water comes up in the wet years, but never as much as it went down in the preceding years. The overall march is downwards.” Feinstein points out that as of February 7, there were 1,185 verified active well outages in California—meaning that thousands of people, mostly in Tulare County, south of Fresno, are getting nothing when they open their taps and have to drink shipped-in water. 

The other reason for concern, Feinstein says, is our threatened snowpack. California’s water system requires both rain and snow in order to function properly: We get 30 percent of our water from snowpack. But despite this winter’s near-record dumping in the High Sierra, the snow part of the equation is inexorably shrinking, both because warmer storms drop more rain and less snow and because warmer temperatures cause the snowpack to melt sooner. “Snowmelt is what carries us through our long, hot, dry summers,” Feinstein says. “When the snow melts faster, we’re going to have a hard time making it through our dry periods.” She notes that the state actually had an average winter snowpack in 2015–16, but that by late spring it was far below average. That pattern is expected to continue.

To stretch our water supply, Feinstein says, we need to both replenish our groundwater and reduce demand. Creating new floodplains in the Central Valley and capturing urban water runoff by creating permeable strips next to roads would add to the supply. A Pacific Institute study found that capturing water runoff in the Bay and L.A. areas alone could increase California’s water supply by as much as 630,000 acre-feet each year, enough to meet Los Angeles’s annual needs. Increasing our groundwater storage would be six times cheaper than building new reservoirs and would also bank a lot more water: The capacity of California’s 515 groundwater basins, estimated to be as high as 1.3 billion acre-feet, dwarfs the 50-million-acre-feet capacity of our reservoirs. On the demand side, installing low-flow toilets and using gray water would have a significant impact.

But knowing that we should recharge our groundwater banks and actually doing it are two different things. California’s reservoir-centric system is set up to work with a colder climate than the one that now exists. We have an inadequate delivery system to take water from across California and deliver it to underground aquifers, and we don’t currently have adequate laws controlling who pumps groundwater. (Governor Jerry Brown has signed a three-bill package, the Sustainable Groundwater Management Act, that when implemented will address both of these concerns.) California is awash in water right now. But it needs to move quickly to bank its most precious resource in the safest place there is: the ground. If it doesn’t, the benefits of wet winters like this year’s will be rapidly sucked dry. 

Originally published in the May issue of San Francisco

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