Colorado snowpack at record levels

What a difference a year makes -- at least, in mountain snowpack throughout the West.

Last year, snowpack levels were below normal in every Colorado drainage basin and in every Western state. Warm winter days played havoc with the ski industry and scanty snowfall seemed to presage an era of reduced water availability throughout the West.

Today, the snowpack is at record levels.

In Gunnison, for example, they're not worrying about drought, but about spring flooding. A series of powerful storms has dumped so much snow in the upper reaches of the Gunnison drainage that flooding is inevitable. According to the Upper Gunnison Water Conservancy District, the snowpack, at 153 percent of normal, exceeds 1984 levels. That's significant because 1984 saw the biggest floods since 1918.

At Lake Tahoe, snowpack is more than 100 percent of average, compared with 31 percent last year. And in Arizona, the Feb. 1 snowpack measured 138 percent of the 30-year average, compared with 71 percent a year ago.

In Colorado, the snowpack is at 134 percent of average. That's the highest level since 1997, when the statewide figure was 161 percent.

No La Nina effect

Meteorologists who had predicted a dry winter last October because of La Nina were surprised by this year's massive snowfalls. La Nina years, characterized by cooler than normal sea-surface temperatures in the central and eastern tropical Pacific Ocean, often feature drier than normal conditions in the Southwest during late summer through winter.

But thanks to the southward movement of the jet stream, storms that usually pummel the Pacific Northwest migrated south and west to Colorado.

An analysis of snowpack data for the last 40 years seems to indicate that this year might be an anomaly, rather than the beginning of a long-term trend.

During the 10 years between 1997 and 2007, the February statewide snowpack averaged 84 percent, rising above 100 percent only during 2005.

Despite this season's record snowfall, the National Atmospheric and Oceanographic Administration still says that March, April and May will bring above average heat and below average moisture to Colorado.

But Kevin Lusk, who monitors snowpack data for Colorado Springs Utilities, isn't so sure that the experts are right.

"Weather is what you get -- and climate is what you expect," he said. "They're experts, and I'm not, but they've been wrong so far this year."

Lusk said that this year's weather isn't necessarily anomalous and Colorado Springs will benefit.

"It fits into a trend of greater variability that we're seeing because of climate change," he said. "We'll capture and hold as much of the runoff as possible, and store it for drier years -- that's how we got through 2002. Also, the Colorado River basin will benefit and some of that water will get to Lake Powell and Lake Mead."

That scenario, Lusk agreed, would take some of the pressure off those reservoirs and lessen the likelihood of severe drought in the lower basin states.

Colorado State University climatologist Nolan Doesken said that predictions, however soundly based, can often be confounded by events.

"It's really a picture of optimism, considering that the forecast called for a greater likelihood for warmer and drier than average conditions resulting from La Nina conditions in the tropical Pacific," he said. "So far, where it was predicted to be driest is where some of the wettest weather has occurred."

Drier in the long run

NOAA's pessimism, at least for the long run, is echoed by a study in the Journal Science. Using data collected during the last half- century, scientists confirmed that more precipitation is falling as rain rather than snow, that the snowpack is melting faster during the spring and that more watercourses are running low or dry during the summer, even when adjusting for the effects of urban and agricultural withdrawals.

That's important to the West, and particularly to Colorado Springs, because the winter mountain snowpack is the source of almost all drinking water. The snowpack functions as a vast reservoir, storing moisture and releasing it during the spring to flow into reservoirs.

Warm temperatures and late-season rain accelerate winter melt and evaporation, reducing yield.

"We've known for decades that the hydrology of the West is changing, but for much of that time people said it was because of Mother Nature and that she would return to the old patterns in the future," said lead author Tim Barnett of the Scripps Institution of Oceanography at the University of California at San Diego. "But we have found very clearly that things will be getting worse."

"Our results are not good news for those living in the western United States," the researchers wrote, adding that the changes may make "modifications to the water infrastructure of the western U.S. a virtual necessity."

The data collected showed that since 1950, the water content of the snowpack on April 1 of each year has decreased in eight of the nine mountain regions studied by amounts ranging from 10 percent in the Colorado Rockies to 40 percent in the Cascades.