Gin Flat is a small meadow surrounded by pine and cedar trees that sits in the thin air at seventy-two hundred feet above sea level in Yosemite National Park, in California’s Sierra Nevada. In winter it is covered with layer upon layer of deep snowpack, the snow that accumulates at high altitude in regions that are cold for most of the year. Snowpack “stores” water like a giant reservoir, which it then slowly releases during the spring and summer snowmelt. Snowmelt from the Sierra flows into streams and rivers that empty into the Sacramento and San Joaquin Rivers, which flow through the Sacramento–San Joaquin Delta, a vast estuary near the state capital. The Delta supplies freshwater to millions of Californians and thousands of acres of farmland around San Francisco, Los Angeles, and as far south as San Diego. The Sierra snowpack is California’s most important source of freshwater.
Gin Flat has been called the Rosetta Stone of the California water supply because it has just the right conditions—a balance of snow, sun, and air temperature—to help scientists predict snowmelt, water flows, and potential floods and droughts in coming seasons. Because it is just above the altitude where snow turns to rain, Gin Flat is an ideal spot to test the theory that global warming will lead to more rain and less snow at higher elevations. Such a shift, climatologists hypothesize, will result in major hydrological changes: less water stored as snowpack, and more runoff, flooding, and evaporation, which could in turn lead to less freshwater flowing to arid Southern California in the spring and early summer, when it is needed most.
Every winter Frank Gehrke clips into his cross-country skis, harnesses himself to a sled loaded with equipment, and slips and slides his way up a three-mile-long trail to Gin Flat. Gehrke is chief of California’s Department of Water Resources’ (DWR) Cooperative Snow Surveys Program. He is considered the dean of the state’s snow studies experts, and thus an expert on the future of California’s water supply. Gin Flat (named after a former speakeasy) is a “snow course” that has been providing DWR with valuable snowpack data since 1930. California has two hundred and eighty similar sites, eighteen of them in Yosemite. Because of its location and long data record, Gin Flat is always the first and most important site for testing.
Having skied out of the close-wooded trail and onto the white expanse of Gin Flat, Gehrke took a moment to catch his breath. Then he and a colleague began to check scientific instruments that had been placed around the meadow to monitor conditions year-round. The devices, which automatically transmit data to laboratories in Sacramento and Virginia every three hours, measure the depth, temperature, and weight of the snow, the moisture of the soil under the snow, the humidity and wind speed, and the intensity of the sun’s rays. Gehrke used a long aluminum tube to measure the water content of the thick drifts of powder and to check the snow-pack’s depth.
As California struggled in 2008 with the effects of a second year of drought, Gehrke’s readings from Gin Flat and other sites helped to determine California’s water rates, how much water farmers and industry could use, and whether homeowners’ car washing and garden watering would be restricted.
Though he is a careful scientist, reluctant to make bold statements or far-reaching predictions, Gehrke noted that in twenty-seven years of taking measurements he’d noticed snowpack levels becoming “erratic”—meaning that California winters had become “either really dry or really wet.” Sierra-wide, snowpack was only 40 percent of average in 2007, but in 2008 it would rise to 118 percent.
Gehrke measures snow water equivalent (SWE), which is the amount of water in snowpack: the depth of water that would result if you melted the entire snowpack. The average SWE at Gin Flat is thirty-two inches a year. In 1988, during the previous drought (1987 to 1992), Gin Flat’s SWE dropped severely, to only 5.1 inches. Since then it had risen. In 2007, Gin Flat’s SWE was 11.4 inches; in 2008 it was 33.8 inches; and in 2009 it was 30 inches. In 2010, heavy rains seemed to ease the latest drought, and Gin Flat’s average SWE was 43 inches. But Gehrke cautioned that La Niña conditions (low ocean surface-water temperatures) were expected, and that 2011 would be dry again.
When climatologists talk about a hotter climate, they often depict a world of too much water, an era in which the coasts of today are submerged by rising oceans. But in recent years they have begun to focus on a different aspect of climate change, and to imagine a world in which the snowpack of the Sierra, the Rockies, the Himalayas, and other important mountain ranges liquefies earlier in the year, faster than ever.
In 2006, Steven Chu—the Nobel-winning physicist whom President Obama named secretary of energy in 2009—said that decreasing supplies of freshwater from snowmelt might prove a far more significant problem than slowly rising oceans. “There’s a two-thirds chance there will be a disaster,” Chu told the New York Times Magazine. “And that’s in the best scenario.” By disaster he meant the possibility of a modern Dust Bowl in the Southwest, which would cause grave ecological harm and cause millions of people to evacuate desert cities.
Even the most optimistic climate models for the second half of the twenty-first century indicate an alarming 30 to 70 percent chance that snowpack could disappear, Chu added.
Other experts are just as concerned about the Sierra’s 497 glaciers. While snowpack is made up of seasonal layers of snow, glaciers are relatively permanent features of the landscape. They flow, extend, and retreat according to changes in climate, which makes them important indicators of long-term trends.
Among those studying glaciers in Yosemite are Hassan Basagic and Andrew Fountain, climatologists from Portland State University, in Oregon, who studied ten glaciers in the park, comparing their size in 2007 to that of a century earlier. They hiked up to the ice fields to measure, then compared modern photographs to those from 1883, 1944, and 2004. They found that all ten glaciers were in retreat. To take just one example, the west lobe of Lyell Glacier had been reduced by 30 percent since 1883, and the smaller east lobe had been reduced by 70 percent. The Basagic and Fountain report points to an unavoidable conclusion: the climate is warming and the ice is melting.
The US Forest Service has characterized the Sierra Nevada as a “canary in the coal mine,” an early-warning system for the effects of a hotter, drier future.
The four-hundred-mile-long range in Northern California has many different ecosystems: as altitude changes, so does the climate, soil, and plant life (it is believed the Sierra houses some ten thousand to fifteen thousand different species); each of these zones wraps around the peaks like a belt. As the climate warms, the bands are forced upward; eventually, some of the bands will run out of room and disappear. There is already evidence of this. By 2008, ponderosa pine trees were growing five hundred meters upslope from the top of their traditional elevation. Sugar pine was also advancing upslope, as the lower elevations became too warm for comfort. Wildlife species that depend on the trees followed. This uphill march will change the ecosystem: with sustained aridification, vulnerable species could become extinct, invasive species could move in, and the risk of fire could spread—thanks to more dry underbrush, dead trees, and an increase in lightning strikes.
When he checked on the Phillips snow course in March 2008, Frank Gehrke was surprised to find a pencil he’d dropped on a previous trip. It was lying in the dirt, in an area that would usually be covered by snow at that time of year. After checking his instruments, Gehrke found that the snowpack was only 67 percent of normal, significantly lower than it had been only a few months earlier. Over the summer, the drought deepened. Governor Arnold Schwarzenegger asked people to cut back on water use by 20 percent. “It’s pretty grim,” observed the usually laconic Gehrke.
On June 4, 2008, two months after Gehrke’s trip to Phillips, and a year after Peter Gleick and Lester Snow jousted over dams at the ACWA conference, Governor Arnold Schwarzenegger leaned into a bristle of microphones in front of the statehouse in Sacramento and said, “This March, April, and May have been the driest ever in our recorded history. Some local governments are rationing water. Developments can’t proceed. Agricultural fields are sitting idle. We must recognize the severity of the crisis.”
After the driest spring in eighty-eight years, California’s rivers and reservoirs had dropped to 41 percent of their average depth. Governor Schwarzenegger issued the state’s first drought proclamation in sixteen years and declared a state of emergency in nine of the state’s fifty-eight counties. Schwarzenegger also directed Lester Snow and the state Department of Water Resources to improve efficiency and coordination among local water districts, facilitate water transfers, and expedite grant programs. The governor said these measures would aid water conservation and struggling farmers. But if people didn’t voluntarily cut back on water use, he warned, every California resident would face mandatory water rationing.
Then, with great urgency, he proposed an $11 billion bond to underwrite the construction of new dams at Temperance Flat, at Sites and Los Vaqueros Reservoirs, and a Peripheral Canal around the ailing Sacramento–San Joaquin Delta, just a few miles from where he stood. “Water is like our gold,” Schwarzenegger said. “We have to treat it like that. There is no more time to waste.”
When I asked Peter Gleick about this, he responded tartly, “No new dams are needed! Efficient toilets would save California more than 130 billion gallons of water every year—more than the annual yield of the Hetch Hetchy Reservoir.”
The battle occasionally grew personal, as when Michael Wade, executive director of the California Farm Water Coalition, wrote to the San Francisco Chronicle, “Peter Gleick demonstrates his disdain for California farmers by claiming the taking away of water … and adding a few more low-flow toilets … is the solution to our state’s water woes…. He thinks cotton doesn’t contribute enough to California’s economy because other crops have the ability to generate more income. What’s next on the chopping block, cheaper varieties of lettuce? … Does his thinking include jobs?”
As Gleick saw it, Governor Schwarzenegger, Lester Snow, the ACWA men, the agricultural lobby, and their mostly rural sympathizers remain fixated on the idea that dams have to be part of the solution to California’s water problems simply because that has always been the answer in the past. “It’s a mind-set, an inability to believe that serious water problems can’t be solved by more storage,” Gleick said. “I get frustrated by this formulation. After so many years, it’s still a fight about dams versus no dams. But if that was really the solution, then why haven’t our problems gone away before?”
Even if Schwarzenegger succeeded in funding the Sites and Temperance Flat Reservoirs, Gleick predicted, California’s water problems would remain. “Our water problems will be exactly the same tomorrow, only we’ll be billions of dollars poorer,” he said, eyes blazing. “My question is, why hold up other solutions just because you want to make dams part of the package?”
As he zips from water conferences in California to Senate hearings in Washington, DC, and global forums in Sweden, China, and Dubai, Gleick’s mantra is always the same: “Almost everything we do on earth, we could do with less water.”
Humans cannot prosper without a clean, reliable supply of H2O. But is there enough freshwater to sustain the world’s growing population?
In a 2006 report, the UN declared, “There is enough water for everyone” but added a caveat: “Water insufficiency is often due to mismanagement, corruption, lack of appropriate institutions, bureaucratic inertia, and a shortage of investment in both human capacity and physical infrastructure.” These human failings are not likely to disappear, and as water stress grows, they will have exponentially greater impacts than ever before.
Water is unevenly distributed and strategically important, and it confers great temptations of power: it will almost certainly be at the center of rising political, economic, and environmental tensions this century. The imbalance between water supply and demand has already led to societal unrest around the world, and experts fear that as the effects of population growth intersect with those of global warming, tensions will ratchet up further and could become violent.