West’s Snowpack Shrinks
Frank Gehrke skied out on an unseasonably warm March day to take the final Sierra Nevada snowpack measurements of the season near this mountain pass south of Lake Tahoe -- only to be stopped short by a muddy meadow where usually there would be deep snow.
Something is happening to the snowpack, according to measurements Gehrke has collected for 20 winters as chief of California’s water survey program.
Near-record snows are melting under record-setting early temperatures this year, a harbinger of the Sierra Nevada spring -- and of a trend that is bringing vast changes across the West.
The snow that piles up in the Sierra, Rockies and Cascades forms an immense frozen reservoir that drives western power turbines, waters crops and cattle, and flows hundreds of miles to thirsty lawns and throats in desert cities like Las Vegas, Phoenix and Albuquerque.
Snowmelt provides roughly 70% of the West’s water flow. But the icy trickle is becoming a roar earlier as spring creeps into what used to be winter.
Spring temperatures in the Sierra have increased 2 to 3 degrees since 1950, bringing peak snowmelt two to three weeks earlier. Trees and flowers bud one to three weeks sooner.
Western rivers are seeing their peak runoff five to 10 days sooner than 50 years ago. Glaciers are melting from Alaska through the Cascades and east into Montana. And in the Pacific Northwest, snowpack has dropped by as much as 60% over the last four decades.
The trend is consistent with global warming, scientists say, although they’re less sure of the consequences. The Pacific Northwest could become wetter or drier as weather patterns shift; Northern California could develop the Santa Ana winds that fed Southern California’s record wildfires last fall -- or not.
The uncertainty illustrates that scientists still have too little information to conclude that the trend is more than a regional cycle, said Bonner Cohen, a senior fellow at the National Center for Public Policy Research.
“Lots of things can happen, and right now it’s way beyond what the computer modelers can even pretend to understand,” said Myron Ebell, global warming policy director at the Competitive Enterprise Institute.
Global or not, if the warming trend continues as projected, scientists say it means a smaller snowpack no matter if precipitation increases or diminishes.
More moisture will fall as rain instead of snow, endangering ski resorts as well as alpine meadows that will see encroachment from plants and trees that today grow only at lower elevations.
Two studies last year showed the range of many species has moved north at nearly 4 miles per decade over the last century, while spring activities like egg-laying, flower blooming and ending hibernation have come three to five days earlier each decade.
“The elevation of the snowpack keeps creeping up. That affects us quite a bit,” said Scott Armstrong, whose family has operated All-Outdoors Whitewater Rafting for nearly 40 years.
The Pacific Northwest National Laboratory this spring predicted snowpack reductions of up to 70% in the Sierra and Cascade mountains of California, Oregon and Washington. The 400-mile-long Sierra range supplies water to two-thirds of California’s population and much of northern Nevada, irrigates 3 million acres of California farmland, and provides about one-fourth of California’s power.
“There are a lot of places in the Cascades and the Northern Sierra where the average winter temperature is above freezing. It’s those places that have seen 50% to 80% declines, in some places 100% declines,” said Philip Mote, a University of Washington climate researcher.
Climate changes are muted farther inland, where average temperatures are generally colder. But as much as a 30% reduction is predicted for the Rocky Mountains of Colorado and New Mexico over the next 50 years, with snow melting about a month earlier than it does now.
Soot darkens snow and ice, deadening their ability to reflect sunlight, contributing to a near-universal melting and causing as much as a quarter of global warming, the National Aeronautic and Space Administration reported. The process accelerates each spring as soot accumulates on the surface, making the remaining snow darker and speeding the melting cycle.
The economic and social impacts flow downstream along with the earlier snowmelt.
“That’s where the river really meets the road,” Mote said. “Then you’re talking [about] affecting a lot of people’s lives, a lot of people’s livelihoods.”
The changes mean less water flowing down western rivers in the dry summers when it is needed most. The Columbia and Sacramento rivers could be hardest hit because of warmer temperatures there. Runoff into the Sacramento River has dropped 11% over the last century even as needs have grown exponentially in the nation’s most populous state.
A University of Washington study this spring predicted that the Colorado River could see runoff drop 14% to 18%, sparking more water warfare between Southern California and upstream states. But the Colorado’s Rocky Mountain headwaters are colder and the basin has more existing storage capacity to mute the effects.
More spring flooding and longer summer droughts mean pressure for reservoirs to capture more water when it’s available. Dams and reservoirs “are not politically correct to talk about right now both because of cost and ... environmental impact. But there may be a cost to not building reservoirs as well,” said David Kranz of the California Farm Bureau Federation.
Environmentalists say water conservation is the answer, with desalinization and water transfers between regions.
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