Proponents say cloud seeding is the cheapest way to bring more rainfall to the Southwest, but admit it’s not the perfect solution to the region’s water problems. .

Research takes place at critical times. According to Nature Climate Change, the massive drought that has hit Arizona since 2000 is the driest in more than 1,200 years and is expected to continue for the foreseeable future. Moreover, as of November 16, Lake Mead was only 150 feet above the “dead zone.” This is the level at which there is not enough water in the reservoir to generate electricity at the Hoover Dam.

The ProPublica study also highlights that Arizona’s climate is warming rapidly and water supplies are dwindling. This could make Arizona unsustainable in the future.

Cloud seeding technology has been around for 70 years and allows clouds to get more rain and snow than any other method. It consists of many technologies, but the ice field technology that SRP is researching sends silver iodide into the cloud and freezes the supercooled liquid floating in the cloud.

Colorado has been trying to change its weather since the 1950s.

“Silver iodide is what we burn in our[ice nucleus]generators, and it evaporates and floats in the clouds,” said Andrew Rickert, Colorado’s weather modification program manager. . “Its molecules are pretty much the same as water molecules. It just helps supercooled liquid water bind to something.”

He states that the water in these clouds is below freezing, but too small to form ice crystals and too light to fall to the ground. It provides a platform for collecting and forming ice crystals in liquids.

“Ice is difficult to form, but once it does, it grows faster than water at the same humidity,” said Frank McDonagh, associate research scientist in atmospheric sciences at the Desert Research Institute in Nevada. I’m here. “It’s a tough one. When the ice forms, it’s like ‘sweet.’ I’m in a drippy spot right now, so I’m in the perfect place to grow.”

When these ice crystals get big enough, they fall off as snow or rain.

Role of the White Mountain Apache Tribe

SRP partnered with the tribe to conduct initial surveys in the mountains of eastern Arizona, where the utility’s watershed is located. The $140,000 study, which is nearing completion, is primarily focused on computer models and weather patterns. This study was funded by SRP, the Arizona Department of Water Resources, and the cities of Phoenix and Tempe.

James Walter, SRP’s head of water quality measurement, said Arizona has a history of research into cloud seeding, but it has never been done in the White Mountains.

“It’s kind of a hole, a gap,” he said. “But geographically speaking, it seems like the most promising area for cloud seeding.”

According to Walter, the study shows that the White Mountains can be seeded using ground-based ice nucleators, unlike other areas of the Mogollon Rim. This means it is much more cost effective than seeding from the air, which requires an aircraft with specialized flares.

Air and ground cloud seeding

There are two types of generators: manual generators and remote generators.

He said the remote generator is “a state-of-the-art generator that can be fully controlled by a (computer) tablet.” They also put out more silver iodide solution and don’t have to be where someone can reach them.

“It can be placed high on ridgelines that would otherwise be impossible to reach without a snowmobile in the winter,” Rickert says. “These higher areas are more conducive to cloud seeding.”

Pilot Gary Walker, who founded a Texas cloud seeding company called SOAR, said an airborne-based method that Arizona might later consider would use planes equipped with injectable in situ-burning flares. I was.

Fireable flares are dropped from the cloud base and used when the cloud ceiling drops below safe flight levels.

“You dive into the top of the clouds – and I’m generally talking about 18,000 to 20,000 feet – and then break through the clouds and launch flares from the bottom of the plane,” Walker said. “It’s a lot like a shotgun shell. The casing itself stays in the plane and only the self-burning flare comes out from underneath.”

The flare “will roll in that cloud,” he said. There is generally enough updraft for the flare to just sit there, roll, flare up, and distribute the silver iodide grains. ”

In situ combustion flares are used when pilots can fly through clouds and disperse silver iodide directly into supercooled liquids.

Cloud seeding program cost

A study conducted by the State of Wyoming found that ground seeding methods using remote generators cost between $35 and $107 per acre-foot of water produced (1 acre-foot is about 326,000 gallons).

The cost was even lower in Texas. Texas generated 956,657 acre-feet of additional rainwater at $11 per acre-feet through seven cloud seeding projects.

For now, Arizona is only considering ground generators for winter seeding in the White Mountains.

An airborne cloud seeding program for one aircraft in Texas and New Mexico costs about $50,000, Walker said. Most of these costs will depend on the fuel cost of the plane, the cost of living while you’re there to plant, and the number of flares you use (10-12 on average).

“Even if you pay $50,000 a month, the water we make from cloud seeding is very cheap,” says Walker.

He lives in the rolling plains of north Texas and has seen the effects of drought, which is why he supports cloud seeding.

“I left the Navy and actually went to the Panhandle and was a cowboy for about 20 years,” Walker said. “Besides my family, the first love I had in my life was farming.”

In the 1980s, when drought plagued the New Mexico Panhandle and water levels in the Ogallala Aquifer were dropping, he took a job with a water conservation company.

“God gives us groundwater and rainwater, and that’s all God gives us in that part of Texas,” Walker said. “There is no surface water at all.”

From his experience at a conservation company, he says, “we know we can’t make more groundwater, but we can make a little more rainwater,” so cloud seeding is a viable option for more water. say that you have learned After serving as a Texas legislator in the 90s, he started his SOAR.

The history of cloud seeding

Cloud seeding was invented in 1946 by American chemist and meteorologist Vincent Schaefer after dropping 6 pounds of dry ice into a cloud to make it snow. Since then, Cloud his seeding has been used for a variety of purposes, from commercial use in ski resorts to military use.

In the Vietnam War, the Department of Defense launched Operation Popeye, using a silver-iodine-based cloud-seeding method to extend Vietnam’s monsoon season. Extra mud from the rain made it difficult for the Viet Cong and North Vietnamese to use the roads to transport military equipment.

An operation with the tagline “Make mud, not war” led to the United Nations Environmental Alteration Convention, an international treaty banning weather modification for hostile use, ratified in 1976.

Since then, countries around the world have seeded clouds to increase rainfall or control hail.

Colorado Cloud Seeding Program and Restrictions

Arizona is already investing in cloud seeding. The Central Arizona Water Conservation District has committed up to $470,000 annually to programs in Colorado. The snow made there melts and flows into the Colorado River, where it is used in Arizona and her six other states.

Rickert does primarily ground-based glacial cloud seeding with the Colorado weather modification program, which may provide insights for researchers in Arizona.

“All the different characteristics of a storm have to be there for us to be able to plant,” he said. , you can’t sow if the temperature isn’t right.”

For his program to be successful, Rickert said the storm would need to stay below a certain wind speed while remaining between 5 degrees Fahrenheit and 23 degrees Fahrenheit. This means that his program can be unpredictable.

“A successful seeding program depends a lot on the winter variety,” said Likert. He detailed how his program beat records last December, but January and he said February were “basically like nothing.”

DRI research scientist McDonough also says cloud seeding has limited drought control benefits.

“Cloud seeding is not a surefire solution to drought,” McDonough said. “Most of the research we’ve done over the years has shown that a properly executed cloud seeding program can add perhaps 10% more total precipitation over the winter.

Despite these limitations, he said cloud seeding is a worthwhile endeavor.

“It’s the only tool that can theoretically increase precipitation,” McDonough said. “‘Oh! We’re going to put a pipe in the Mississippi River and put these desalination plants on the shore.’ It’s been done over and over. ”

Environmental impact of cloud seeding

Opponents of cloud seeding argue that silver iodide is dangerous because it is considered toxic to aquatic life.Critics say the compound accumulates in the environment over time However, many studies reviewed here have found that cloud seeding has a negligible environmental impact.

“All silver iodide in the environment has been studied for 50 years without any noticeable effects,” says McDonough. “It just leaves inert dust particles on the ground.”

Silver iodide that occurs naturally in the Earth’s crust is “a million times more” than the amount released during cloud seeding, he said, adding that silver iodide does not interact with the environment.

“Normally, plants and roots use electrical charges to bring nutrients into plants,” McDonough said. “And because silver iodide is not electrically charged, it doesn’t become part of the plant biome, so it doesn’t become part of the ecosystem.”

He also said that clouding the seeds doesn’t change weather patterns or take water away from other places.

“Most of the moisture associated with storms doesn’t even turn into clouds, it just stays as vapor,” he said. “You are not stealing the rainfall. You are not extorting the payment from Peter to Paul.”

He added that researchers will study where runoff from cloud seeding occurs to stop flash floods.

“It’s safe,” said McDonough. “I think it’s a good tool. I think you should use it. The impact is minimal and it seems to work pretty well.”