Cloud seeding can make it rain in about 20 minutes; drought-stricken areas are investing in the old technology

Cloud seeding has been around in some form since the 1950s, but due to extreme drought across much of the U.S., the technology is experiencing "a renaissance," reports Erice Niiler of The Wall Street Journal. "Across the Western U.S. and Mexico, demand for cloud seeding has skyrocketed as increasing periods of extreme drought and a warming climate make it a cheaper alternative to big-ticket technological solutions such as the desalination of water piped inland from the Pacific Ocean or Gulf of Mexico. Cloud-seeding programs to boost both rain and snowfall are now underway in Texas, Utah, Colorado, Nevada, Idaho, New Mexico and California."

A single-engine aircraft flies over Texas, injecting cloud-seeding particles of
silver iodide. (Photo by Jonathan Jennings and Ilana Panich-Linsman, WSJ)

Cloud seeding can work in the sky or "on the ground, where chimney-like generators send chemicals into air masses as they move up the side of mountains," the Journal reports. "Most cloud-seeding efforts use particles of silver iodide, which have a crystal structure similar to ice. Once the chemicals are injected, the air temperature must reach 20 degrees Fahrenheit—then water vapor begins to freeze around the silver iodide, getting big enough to fall to the ground as either rain or snow," Niiler writes. "In the summer, cloud-seeding firms use the water-attracting properties of salt crystals such as calcium chloride to do the same thing, except in warmer, humid clouds.. . . Cloud-seeding produces rain about 20 minutes after it reaches the cloud."

Not everyone thinks this is an answer to drought. "Some weather experts question its effectiveness and whether it just pulls rainwater from one area to fall in another. They say conservation on the ground is a surer way to preserve scarce water supplies," Niiler reports. "The World Meteorological Organization reviewed cloud-seeding programs across the globe in 2018 and concluded that cloud seeding is a promising technology but that the natural variability in each cloud system makes it difficult to quantify the difference seeding makes."

"Sarah Tessendorf, an author of the study and project scientist at the National Center for Atmospheric Research in Colorado, said the environmental risks of cloud seeding are relatively benign since the amount of silver detected in the snow is below harmful levels," Niiler reports. Tessendorf told him: "The key question we're trying to figure out is under what conditions is cloud seeding most effective." Niiler adds, "In March, the Bureau of Reclamation announced a $2.4 million grant for states in the Upper Colorado River Basin to conduct aerial and ground-based cloud seeding."

"For 73-year-old West Texas farmer Steve Williams, the benefit of occasional extra rainfall is worth the minimal amount he pays in taxes to his local water district that are earmarked for cloud seeding, about $20 a year," Niiler writes. "Williams and his son, Ty Williams, farm 1,774 acres of cotton and wheat in Schleicher County, Texas, one of six counties covered by the aerial seeding flights from the West Texas Weather Modification Association in San Angelo. . . . Williams said he usually only gets one or two cloud-seeded rainfalls directly over his property each planting season. However, the seeding drops rain on farms around him, recharging the underground aquifer that he and his neighbors depend on for irrigation and drinking water." Williams told Niiler: "It is a community effort. Everybody benefits. If you happen to get under one of Jonathan's clouds, you did pretty good."