azcentral.com
Warming winters, earlier springs shrink vital snowpacks
Don Thompson
Associated Press
May. 6, 2004 02:15 PM
ECHO SUMMIT, Calif. - 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, the Rockies and the 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 percent of the West's water flow. But the icy trickle is becoming a roar earlier, as spring has creeped into what used to be winter over the last century.
Spring temperatures in the Sierra have increased 2 degrees to 3 degrees since 1950, bringing peak snowmelt two to three weeks earlier and prompting trees and flowers to 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 percent over the last four decades.
The trend is consistent with global warming, scientists say, though they're less sure of the consequences. The Pacific Northwest could become wetter or drier as weather patterns shift; Northern California could develop the desert Santa Ana winds that fed Southern California's record wildfires last fall - or not.
The uncertainly 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.
The Northwest, for instance, has had four alternating warm-and-dry and cool-and-wet phases since the mid-1920s. Measurements 50 years ago were during a cold-wet period, so a decline in the snowpack is to be expected, critics say. Researchers respond that they've accounted for the patterns.
"Lots of things can happen, and right now it's way beyond what the computer modelers can even pretend to understand," said Myron Ebell, director of global warming policy at the Competitive Enterprise Institute.
Global or not, if the warming trend across the West 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 some ski resorts as well alpine meadows that will see encroachment from plants and trees that today grow only at lower elevations.
A pair of 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 came 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. Four decades ago, the family's cabin near Yosemite was snowed in each winter; now the snow comes and goes.
The Pacific Northwest National Laboratory this spring predicted snowpack reductions of up to 70 percent in the Sierra Nevada and Cascade mountains of California, Oregon and Washington. The 400-mile-long Sierra range supplies water to two-thirds of California's population and to much of northern Nevada, irrigates 3 million acres of California farmland, and provides about a quarter of California's power through hydroelectricity.
"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 percent declines, in some places 100 percent declines," said Philip Mote, a University of Washington climate researcher who has studied snowpack records dating to the 1940s.
Climate changes are muted farther inland, where average temperatures are generally colder. But as much as a 30 percent 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.
Skiing could disappear in the Rockies by 2070 if trends continue and if the computer models are accurate, with resorts below 5,000 feet out of business much sooner.
Soot is darkening 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 in December. The process accelerates each spring, as soot accumulates on the surface of melting snow, making the remaining snow even 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," said Mote. "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 percent 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 the Colorado River could see runoff drop 14 percent to 18 percent, 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.
Forests would dry out more quickly, with more potential for wildfires during a longer fire season.
More spring flooding and longer summer droughts means pressure for more 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 because of 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.
Earlier melting means more hydropower in cooler months, when it's needed in the Pacific Northwest - but less to be shipped to California and the Southwest during the hot summer.
Agriculture could be hard-hit as increasingly scarce water is funneled to urban areas, as already is happening in Southern California. Fights over endangered species could escalate, with tens of thousands of salmon already piling up dead when there's not enough water.
Even if there is enough water, it could be too warm to support their spawning.
KJC |
