Why ‘Cloud Seeding’ is Increasingly Attractive to the Thirsty West

Machines that prod clouds to make snow may sound like something out of an old science fiction movie. But worsening water scarcity, combined with new proof that “cloud seeding” actually works, is spurring more states, counties, water districts and power companies across the thirsty West to use the strategy.

Last month, a study funded by the National Science Foundation proved for the first time that the technology works in nature. That study, combined with other recent research, has helped make cloud seeding an attractive option for officials and companies desperate to increase the amount of water in rivers and reservoirs.

Scientists discovered in the 1940s that certain molecules make a good foundation for snow. In one famous experiment, a chemist made it snow by dumping six pounds of dry ice out of an airplane over western Massachusetts.

It didn’t take long for states, localities and ski resorts to start experimenting. Colorado’s Vail ski area began cloud seeding in the 1970s, for instance. Today California, Idaho, Nevada, Utah and Wyoming have winter cloud seeding programs, and Texas and North Dakota have summer programs, which aim to increase rain and decrease hail. 

Cloud seeding machines are nothing like the “snow guns” used to blast water over ski slopes. Instead, when they’re turned on they generate smoke that floats into the air like incense. Some state programs rely on ground-based machines. Others use airplanes to drop flares that generate silver iodide smoke into clouds, or to fly into a storm with flares strapped to their wings.

The January National Science Foundation-funded study, which was conducted in Idaho, was the first to show real-world observations of silver iodide forming ice crystals inside clouds and falling out as precipitation.

Such research has increased interest in cloud seeding, particularly among private companies and utilities, said Neil Brackin, president of Weather Modification Inc., a North Dakota company that does cloud seeding. “We’re able to now really demonstrate the technology, and they can see it’s not something conceptual that works in a lab — it’s measurable.”

Other recent studies have used computer modeling to estimate the increase in snowfall from cloud seeding. A 2014 study across two Wyoming mountain ranges found that cloud seeding could increase snowfall by 5 to 15 percent — but only when the right conditions for seeding were met, or during 30 percent of snow events.

Although it’s hard for scientists to gauge the effectiveness of cloud seeding, many water districts are willing to take a chance on the technology because cloud seeding is relatively cheap. 

Read the full article at The PEW Charitable Trusts

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