Bringing silver home: Cloud seeding
November 19, 2010
The removal of snow fences from the Independence crest reminded me of snowmaking in the 1960s, and the ways humans tamper with nature; some are useful, others absurd. I remember my geomorphology professor, on a field trip to a beach, showing how the Army Corps of Engineers had built artificial jetties to reduce sand migration. Many popular beaches were rapidly losing sand. Unfortunately, the jetties accelerated the migration of sand, rather than trapping it. Making sand go where you want is a complex problem, as is getting snow to fall where and when you want it.
One evening in the mid-1960s, a gentleman knocked on my uncle’s door. He was Frank Bosco, a college acquaintance of my uncle’s, who graduated from the Colorado School of Mines in the 1930s. Bosco was selling commercial cloud seeding to the Aspen Ski Company and community. There was no snowmaking at that time. Delayed opening dates for ski season and poor November skiing conditions plagued Colorado resorts. Cloud seeding seemed to offer a simple and relatively inexpensive solution.
Cloud seeding had reached a level of viability by the 1960s. A 1959-1960 study by Colorado State University, in conjunction with the Bureau of Reclamation (known in our family as the “bureau of wreck the nation” because it diverted Aspen’s water to the Eastern Slope), established baseline data that suggested the practice had merit. In the study, generators expelled silver iodide, which is known to act as a nucleus for water droplets. The generators were placed where upslope winds would propel the nuclei into passing clouds. They were placed above Ruedi Reservoir and on Aspen Mountain. Airplane cloud seeding also figured in the experiment.
An increase in snowfall of about 12 percent was noted when the winds that spread the nuclei were right and an appropriate temperature prevailed. But that was an uncommon confluence of conditions.
Commercial cloud-seeding took hold to respond to the needs of farmers in the arid West and ski resort owners who dreamed of deeper powder. The Denver Water Board, Colorado River Basin Association and the Bureau of Reclamation all invested in cloud-seeding. Whether it was cloud-seeding or the construction of miles of snow fences building up cornices to delay spring runoff, every gallon of extra water was worth the effort. Even the U.S. military experimented with cloud seeding in Vietnam to make the Ho Chi Minh Trail too muddy for travel.
My memory of the first commercial attempt to increase Aspen’s snow depth is of Gunnison recording extra snowfall, suggesting that cloud-seeding was working, but just not on Aspen Mountain. Over the years, techniques have improved and cloud-seeding continues to increase precipitation in the Western states.
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Bosco’s visit had a bit of irony to it. I remember watching my uncle during their conversation. At the time, increasing commercial use of silver, especially for photographic film, was causing a commensurate price increase. A leaseholder of Aspen’s Midnight Mine was tunneling below the Little Annie Basin in search of extensions of old veins. My uncle was giddy with the prospect of renewing silver mining in Aspen.
It seemed odd to listen to someone talk about injecting silver into Colorado’s clouds. I thought that Aspen’s miners were rolling over with laughter in their graves. They had labored to extract silver from the mountains, and now someone would spray it into the air, only to have it fall back to where it started.