A new study conducted by researchers at Oregon State University and other regional institutions found that snowpack is in decline in 90 percent of monitoring sites in the western United States. Making matters worse, one third of those sites were found to have suffered “significant' declines.
The full results of the study were published in the nature publication known as NPJ Climate and Atmospheric Science.
According to researchers, the average snowpack in western states has declined by 15 to 30 percent since 1915. The cumulative quantity of water lost from those peaks is roughly equivalent to Lake Mead, near Las Vegas. Those losses contribute to water shortages for municipal, industrial and agricultural use, in addition to fresh supply for fish and other wildlife.
“It is a bigger decline than we had expected. In many lower-elevation sites, what used to fall as snow is now rain. Upper elevations have not been affected nearly as much, but most states don’t have that much area at 7,000-plus feet,” said Philip Mote, director of the Oregon Climate Change Research Institute at Oregon State and lead author on the study, in a university press release. “The solution isn’t in infrastructure. New reservoirs could not be built fast enough to offset the loss of snow storage — and we don’t have a lot of capacity left for that kind of storage. It comes down to managing what we have in the best possible ways.”
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Researchers have blamed the dwindling snowpack on warming temperatures as opposed to a lack of precipitation. It was noted that the early onset of spring-like conditions means that more snowpack is melting away quickly instead of being stored until summer and fall drought months, when snow melt is essential to maintaining instream flows and temperatures.
The study looked at data from 1,766 sites in the western United States. Most of those locations were within lands operated by the U.S. Department of Agriculture’s Natural Resources Conservation Service and the California Department of Water Resources. Researchers focused on measurements taken on April 1, which has historically been the high point of snowpack accumulations, although measurements also were observed on Jan. 1, Feb. 1, March 1 and May 1.
“We found declining trends in all months, states and climates,” Mote said in the release, “but the impacts are the largest in the spring, in Pacific states, and in locations with mild winter climates.”
Researchers explained that coastal states of Washington, Oregon and California receive more precipitation than other western states because of the proximity of the Pacific Ocean. However, because the Cascade Mountains are not as steep as the Rocky Mountains farther inland, they are more susceptible to temperature fluctuation.
“When you raise the snow zone level 300 feet, it covers a much broader swath than it would in the inland states,” Mote explained.
The study also found that:
▪ California had the highest number of positive snowpack trends since 1955, but lingering drought during the past decade erased most of those gains and snowpack declines still dominated.
▪ Most of the other western states had only one or two sites that reported increases in snowpack.
▪ Regions with the most significant decrease in snowpack were eastern Oregon and northern Nevada, though snowpack decreases in excess of 70 percent also occurred in California, Montana, Washington, Idaho and Arizona.
“The amount of water in the snowpack of the western United States is roughly equivalent to all of the stored water in the largest reservoirs of those states,” Mote said in the release. “We’ve pretty much spent a century building up those water supplies at the same time the natural supply of snowpack is dwindling.
“On smaller reservoirs, the water supply can be replenished after one bad year. But a reservoir like Lake Mead takes four years of normal flows to fill; it still hasn’t recovered from the drought of the early 2000s.”
According to Mote, snowpack levels in most of the western U.S. this winter have been recorded at far below their average. Those conditions have been blamed on a cyclical La Nina event and the continued trend of warming temperatures.
The snow study was funded by the National Oceanic and Atmospheric Administration’s Regional Integrated Sciences and Assessment (RISA) program, and the U.S. Environmental Protection Agency’s Office of Atmospheric Programs.