By Shannon Marvel
Modifying storm clouds to increase rain totals and suppress hail is a practice seldom, if ever, used in South Dakota.
But that’s not the case for the state’s neighbor to the north. Seven western North Dakota counties are part of a weather modification program.
Cloud seeding is the process of using airplanes that “seed” storm clouds by releasing silver iodide into them during cloud formation, said James Telken, a meteorologist with the National Weather Service in Aberdeen. He spent time working with North Dakota’s weather modification program last summer.
Cloud seeding can bring out the rain in arid regions, which is crucial for agriculture. Proponents might say the process gives more bang for the buck than the average storm cloud.
Silver iodide is a chemical that speeds up the formation of precipitation, causing rain to fall from the cloud more quickly, Telken said.
“You get a 5 to 10 percent increase in rainfall,” he said.
Telken said cloud seeding also helps reduce hail by up to 40 percent. Seeding causes hail to gain weight and fall before getting larger in higher altitudes.
“We try to get to thunderstorms before they form, which is hard to do,” Telken said. “Once you see cumulus clouds start to tower, which is an indication a storm is about to form, what we do is launch airplanes up there and they fly to that location and they’ll fly next to it, but they’ll fly in the inflow area. Then they start releasing the chemical into it. Then it would take the chemical into the cloud as it’s forming. We try to make the hail fall before it gets too big.”
Telken said the silver iodide speeds the precipitation process.
The last time the South Dakota Department of Environment and Natural Resources received a permit application for cloud seeding was in 1989 for an area near the Pactola reservoir in the Black Hills, according to Water Rights Permit Administrator Ron Duvall.
Duvall said a state law requiring a permit to cloud seed in the state was repealed in 2012.
“The statutes concerning that had been repealed in large part because they were so rarely used,” Duvall said. “In order to do cloud seeding in South Dakota, you needed a permit for the area you wanted to do it in, you needed to be licensed as an applicator, and now, both of those requirements are gone. There’s nothing I know of in statute that would prevent you from doing it, but you don’t need to come to the state to do it.”
Neil Bracken, the president of North Dakota-based Weather Modification Inc., said cloud seeding in South Dakota is approved and can be done.
“It would make a lot of sense for the folks of South Dakota to develop and review a well-developed cloud-seeding program,” Bracken said.
“I can’t put my finger on why specifically it hasn’t been developed or pursued at a real serious level. There’s excuses or reasons not to do things and it’s easier to not do things. You could say it’s difficult to implement. There’s more benefits for modern cloud seeding. The way it’s been designed, it’s really validated the technology of these days,” he said.
In South Dakota, the popularity of cloud seeding might be hindered because of the cost, said Laura Edwards, state climatologist for South Dakota State University Extension.
“I think that the issue is that it’s pretty expensive, so for farmers it’s probably cost prohibitive,” she said.
Edwards said cloud-seeding aircraft tend to fly higher than crop-spraying planes and there’s more flight time needed to seed the clouds. That adds to the cost.
“It’s kind of mixed benefit, too. It does produce results sometimes, but not 100 percent of the time,” she said.
Telken said silver iodide provides a crystalline structure on which droplets can freeze. Dry ice is used because it is so cold that it helps create additional droplets from water vapor and freezes those droplets instantaneously, he explained.
Super freezing the droplets causes them to drop faster. The silver iodide allows the droplets to freeze faster at a lower altitude, Telken said.
“As far as the actual science of it, it’s fine. I think it’s the cost of doing it,” Edwards said.
Silver iodide is relatively harmless, Edwards added.
Rapid City flood
The practice is somewhat controversial in South Dakota, Telken said, as some people believe cloud seeding is what caused the Rapid City flood of 1972, during which more than 14 inches of rain fell in one night.
At that time, the South Dakota School of Mines and Technology was involved in a cloud-seeding research program, though there has been no evidence to show that the program caused the flooding, said Darin Langerud, director of the North Dakota Atmospheric Resource Board.
“There were some people that wanted to blame cloud seeding on that event,” Langerud said.
“There was a study that was done at the governor’s request after that event to look into all the details, and the conclusion was that the seeding was not the cause of the flood that occurred in Rapid City in 1972, but it did have some negative impact on interest in cloud seeding,” he said. “But that’s 45 years ago now, but a lot of time has passed.
“Here in North Dakota, we’ve been doing cloud seeding operations and research for more than five decades, and the program in North Dakota demonstrates an increase in precipitation by 10 percent and it also reduces crop hail losses by about 45 percent,” Langerud said.
Whether cloud seeding can be used in northeast South Dakota is up to local communities and the state, Langerud said.
“If South Dakota’s rules are similar to North Dakota’s rules, it allows counties to participate in a program to put in funding, then the state cost shares with the county,” he said.
Langerud said efforts to start cloud-seeding programs in North Dakota counties are sometimes grassroots-style efforts.
“So, citizens may bring the issue to county commission for discussion and the commission can enroll the county in a temporary program for four years,” he said.
“They have to have a public hearing and hear from the public on the issue. If they pass that resolution, then they would participate for up to four years. Then after that four-year period, the citizens have to act to make the program permanent or to suspend their activities,” Langerud said.
If the citizens act to make the program permanent, the state and county funding will continue, Langerud said. Two-thirds of the funds are from the counties while the remaining third is covered by the state.
There’s a three-month period that cloud seeding is done through the program, Langerud said. Last year, the total cost of the program was just over $1 million.
The cost of a single cloud-seeding operation varies significantly, Langerud added.
“The cost depends on the type of program that you’re doing and the number of airplanes seeding an area. It’s hard to say because there’s such a wide variety of variables,” he said.
A decision to continue the program establishes a 10-year authority.
Bowman, Slope, Burke, Mountrail, McKenzie, Ward and Williams counties are involved in North Dakota’s weather modification program, Langerud said.
“When you look at the totality of the area, its 11,500 square miles. It’s more arid and it’s a little more prone to hail damage as well,” he said.
Telken said that if there are no storm clouds in the area, cloud seeding is useless.
“If there’s no thunderstorm, we can’t make a thunderstorm,” he said. “We can affect the intensity of the rainfall. Even areas downstream of the storm have had some increased rainfall as well, so we have to watch out for that, too. In Bowman County, some of the workers out there thought we were causing the storms to split and not hit their farm. There’s no way we can do that.”
Follow @smarvel_AAN on Twitter.