Shooting dust into clouds to make them produce more rain or snow … does it sound like something from a science fiction movie?
According to meteorologist Frank McDonough, the technology for the process known as cloud seeding first arrived nearly a century ago, during the 1930s. Scientists were studying the way clouds could act as an aviation hazard, when pilots would fly through them and their aircrafts became weighed down by ice.
“When the airplane crashes into a cloud with water drops that are below freezing … [it] can actually accrete enough ice where it can no longer fly,” McDonough says. “[Scientists] accidentally realized that if we can artificially introduce ice into a water cloud, we can make it snow or rain.”
As program manager of Desert Research Institute’s cloud seeding projects for the past eight years, McDonough has overseen several efforts that have increased area precipitation by about 10%, according to DRI data.
The nonprofit Save Red Rock is fundraising a cloud seeding project in response to prolonged drought in the beloved, well-worn national recreation area west of Las Vegas. According to data from the National Oceanic and Atmospheric Administration, average annual precipitation levels have fallen from a mean of 11.3 inches (1981-2010) to 6.9 inches (2011-2017).
Climate change and years of less-than-average rainfall have taken a toll on plant and wildlife, says Pauline van Betten, land and water specialist for Save Red Rock. During a webinar about cloud seeding, the organization’s leaders discussed why the intervention is needed. “We all love Red Rock Canyon … [and] it’s not doing so well,” van Betten said. “The Joshua trees are really dying, and it’s really in dire condition.
“Fifteen years ago, the lower Cottonwood Springs was a 15-foot deep swimming hole. The upper Cottonwood Springs was full of reeds and frogs and birds and all kinds of water plants. And … they’ve been bone dry for years,” she said, adding that her group sees evidence of wildlife seeking water and food sources in the city.
But while cloud seeding can give the canyon a needed boost, McDonough says it’s “not a drought buster. … It’s not going to fill Lake Mead.” But it will have a measurable impact and yield valuable information for further research about water and groundwater systems in Red Rock Canyon, he says.
According to results from 2021 cloud seeding in the Spring Mountains, the project added nearly 3,360 acre feet to winter precipitation in the Lee Canyon area—“enough water to supply all the water needs for a year for about 6,700 households,” McDonough says.
How it works
So, back to shooting dust into clouds. How exactly do the scientists make it rain?
“At its simplest, cloud seeding is a method to enhance a cloud’s ability to produce precipitation … to produce snowflakes, in general,” McDonough explains.
Save Red Rock and DRI are aiming for a project start date of November 15—timed for the months when Red Rock Canyon receives the majority of its precipitation. About 70% of groundwater recharge in the Spring Mountain range, which includes Red Rock, comes from winter storms, McDonough says.
To enhance a cloud’s ability to make snowflakes, “ice-forming dust”—a type of aerosol—is introduced into “liquid water cloud layers,” which leads to the creation of ice crystals and, ultimately, snowfall. Silver iodide, a naturally occurring inorganic molecule, is a choice aerosol, since it has a molecular structure similar to ice water.
Although it sounds rather unnatural, the use of silver iodide has little to no negative environmental impact, McDonough says.
“Since the 1980s, more than 100 Sierra Nevada rivers and lakes have been studied to address potential issues regarding cloud seeding. And no detectable silver above the natural background has ever been found in the seeded target area water bodies, precipitation or lake sediment samples,” he says. “Nor is there any evidence of silver accumulating, even after 50 years of continuous seeding.”
McDonough and his team, which includes another meteorologist and two technicians, install the aerosol generators and monitor weather conditions—looking for cloud patterns and temperature ranges at which the aerosol can accumulate ice crystals within clouds. Once the storm moves through the project area, they can turn the generators off.
DRI scientists also collect data on precipitation to better understand water systems including groundwater recharge, which is particularly important in Red Rock Canyon, a lower-elevation area of the Spring Mountains.
“When you get snow, it melts and usually heads down toward the creeks,” McDonough says. “In the Spring Mountains, there are a lot of places where the water disappears into cracks and then pops back up in a spring somewhere else,” he explains, adding that hydrologists are studying the water systems in the area to understand best strategies for intervention.
Other states have turned to large-scale cloud seeding projects to stave off some of the effects of climate change. Amid record low levels on the Colorado River and its reservoirs, Utah, Colorado and Wyoming have state-funded cloud seeding programs that “try to produce additional runoff coming down the Colorado River, serving the lower Basin,” McDonough says.
He estimates cloud seeding projects cost $8 to $10 per acre foot of project area.
Save Red Rock has raised more than one-fifth of its $150,000 goal to fund cloud seeding projects this winter through May 2023. Those interested in donating can visit saveredrock.com/make-it-rain.
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