Article by Allen Best
Water – April 2004 – Colorado Central Magazine
LAST OCTOBER a committee from the National Research Council issued a lengthy report that found “no convincing scientific proof of the efficacy of intentional weather modification efforts.” In other words, cloud seeding doesn’t work.
That unyielding conclusion, found in the first sentence of the executive summary, was the nucleus for major stories by the New York Times, National Public Radio, and several other news organizations. Local reporters in Colorado, using the national media as their sources, applied the broad conclusion to cloud-seeding efforts to augment snow pack.
But that simple summary was wrong. In only the second paragraph of conclusions the Research Council qualified the generalization. “There are strong suggestions,” said the committee, “of positive seeding effects in winter orographic glaciogenic systems (i.e. cloud seeding occurring over mountainous terrain).” Nearly 90 pages later, in an appendix, the committee more explicitly explained that the “most compelling evidence in the United States” for successful winter cloud seeding had been experiments near the Climax Mine in the 1960s.
The man behind those experiments was Lew Grant.
Grant gained his interest in clouds as a boy growing up in Henryetta Oklahoma during the drought that beget the Dust Bowl of the 1930s. “In east-central Oklahoma we would see the banks of clouds coming in — not dust blowing off fields, but almost complete blackouts at 20,000 to 25,000 feet, a solid wall,” he remembers. That brush with the mysteries of weather drove him into a career in atmospheric science.
Serving in the Air Force during World War II, Grant received training in meteorology that he continued after the war, first with a bachelor’s degree at the University of Tulsa then with a master’s degree in atmospheric science from the California Institute of Technology in Pasadena. The summer after graduation, he and a buddy were loading their pickup for a summer adventure in Alaska when he was hired to manage a project in Arizona’s Salt River Valley. There, water users wanted to see if modifying thunderstorms during summer and mountain (orographic) clouds during winter could produce more water for their dry watersheds. He had two airplanes at his disposal. In this way, Grant began his career in 1948 as someone who tried to do more than just talk about the weather.
Soon enough, Grant decided the best shot to wring water from clouds was during winter in the mountains. To do serious research, however, he needed government money. To get those research grants, he needed to be at a university. So, in 1959, Grant joined the staff of Colorado State University.
HIS TIMING WAS RIGHT. With the drought of the mid-1950s still fresh in their minds, those who controlled federal dollars were receptive to experiments in weather modification. This interest was greatest in the West, where 80 percent of water comes from snow. With small grants initially, then larger funding, primarily from the National Science Foundation, Grant began his experiments in 1960.
The center of those experiments was Chalk Mountain, located across the highway from the Climax Mine. The site was relatively accessible and also close to the University of Colorado’s nearby high-altitude observatory and to highways that crossed nearby Vail, Hoosier, and other passes, where they could measure snow that had fallen from both seeded and non-seeded clouds.
Then, as now, clouds were seeded using somewhat primitive technology. Snowstorms naturally occur as a result of clouds containing super-cooled liquid water, i.e. water that remains liquid even though the temperatures are below freezing. When the moisture collects around dust particles, snowflakes are made. Often, there are too few natural nuclei for all the water in the clouds, hence the need for artificial nuclei.
Silver iodide, with a crystal structure nearly identical to ice, is the preferred medium. A gram of the substance can be used to create 10 quintillion (10,000,000,000,000,000) nuclei. The task is to disperse these sub-microscopic nuclei into the clouds of super-cooled liquid water.
Propane burners are used to vaporize the silver iodide, which is then quickly cooled to condense into the small particles. These are then carried with the wind rising over the mountains and into the clouds. Depending upon the lay of the land, these silver iodide generators can be located at various sites upwind of the area targeted to get snow. For the Climax experiments, generators were placed at Camp Hale, Leadville, and Ruedi Reservoir, among other sites. In this way, a combination of guesswork and empirical science, clouds are seeded. Or, if you wish, the clouds are artificially inseminated.
Key to the scientific credibility of the experiment — the reason it remains a benchmark study even now — was the process called randomization. Before storms arrived, Grant randomly picked half the storms in which clouds were to be seeded. Clouds were not seeded during the remaining storms. After the storm, new snowfall was measured along the nearby roads. This continued for five winters. After five winters of this, snowfall from the seeded storms was compared with snowfall from non-seeded storms.
The results? On average, 10 to 15 percent more snow came from the seeded storms. Results, however, depended upon cloud temperatures and other factors. In this way, Grant identified what cloud conditions were favorable for seeding.
But that was only the first half of the experiment. “In science, you like to do replication, and so in the last half of the 1960s, we did it all over again,” says Grant. This time, they stated what they expected to find. And mostly, they found it.
Grant’s team had a shack atop Chalk Mountain for measuring what was going on inside the passing clouds — to measure the supercooled water and natural ice nuclei, and also to study how efficiently the seeding nuclei were arriving in the clouds. Only by knowing how much water was in the clouds could the “efficiency” of seeding be evaluated. Like modern-day Ben Franklins Grant’s team flew large, instrument-bearing kites in the storms to measure these things. The kites were tethered to the ground by piano wire, which in turn was controlled by a huge winch. One time, after flying the kite from the afternoon onward, Grant’s crew called it quits about midnight. When trying to reel in the kite, the winch instead spun open, causing the piano wire to break. The kite dragged the untethered piano wire down the mountain and across electrical transmission lines, shorting the power to the Climax Mine, which was then the second largest consumer of electricity in Colorado. For all the grief that this caused the Climax miners, says Grant, they remained both friendly and helpful.
BUT ANOTHER INCIDENT revealed the dangers of science. To get atop Chalk Mountain for the first several years the scientists climbed it on snowshoes, itself a good test of physicality. Then, as Grant’s funding improved, his team bought a Sno-cat. After going to Leadville one day after a long stretch on the mountain, two of the researchers were returning to the mountain top in a hard-blowing storm. Stakes at 50-foot intervals guided drivers, but the blowing snow that day so reduced visibility that the driver strayed and the Sno-cat tumbled down a steep slope. One researcher died, and a second suffered a broken leg and lost an eye.
ABOUT THE SAME TIME, Grant conducted cloud seeding in the San Juan Mountains. Unlike the experiments at Climax, which were intended as pure research, the project in the San Juans was conducted under the assumption by the Colorado Legislature that cloud seeding works — or worked well enough to satisfy some of Colorado’s obligations of water to New Mexico. Colorado at the time was about 10 years behind on its delivery of water from the Rio Grande as had been specified under interstate compact. As the two states squabbled, Colorado sought to show an effort to meet its commitment. The seeding, Grant concluded, augmented snow packs about as much or even better than had occurred at Climax. Because the seeding was not controlled by randomization, however, that conclusion was less confident.
In yet a third program, Grant and his team conducted experiments during the 1970s and early 1980s near Steamboat Springs. Newer instrumentation was tenfold better than that available at Climax, allowing better understanding of how clouds form and weather can be modified. These instruments also allowed them to identify artificial sources of particulates, some from nearby coal-fired power plants at Hayden and Craig, but others that were traced to San Francisco, Los Angeles, and even copper mines in Arizona.
A stuffed magpie today stands on a counter at Grant’s home, a legacy of his work in Steamboat. Storms in early 1979 delivered a three-wire winter, as ranchers measured the snowfall along barbed-wire fences. Struggling to feed their cattle, the ranchers bitterly blamed the cloud seeding for the deep snows and hence their woes. They also noted an uncommon number of dead magpies — canaries-in-the-coal-mine evidence, they argued, of harms caused by silver iodide.
Pouring into the Routt County courthouse chambers, they angrily questioned what the silver iodide might be doing to them if it could cause magpies to die. An autopsy at the CSU pathology lab, however, revealed a different cause for the birds’ demise. Grains treated with pesticides to ward off grasshoppers had been stored in a rancher’s shed, and the birds had gotten into the supply.
But that squall in Steamboat was nothing compared to the protest in the San Luis Valley. There, Grant had been hired to seed summer clouds in a way to reduce hail. But in removing hail, said locals, the seeders were also reducing rain. Not so, said Grant and his team after analyzing precipitation data. Instead, they found greater-than-expected precipitation during the years of cloud seeding. The land was drier, they agreed, but what had caused it was the recent profusion of center-pivot irrigation systems. In drawing from the underground aquifers, the sprinklers caused the water table to drop below the root zone of the subirrigated grasses. Grant recalls explaining this at a meeting in Alamosa, but not necessarily persuading anybody. Instead, he heard tearful and angry complaints about how the cloud seeding was wrecking a valley’s way of life. “Basically it ended up in a brawl,” he recollects.
IN 1983, after the West had turned wet once more, research funding dried up again. Grant gradually turned his attention to his farm north of Fort Collins, near the town of Wellington. It is what is now called an organic farm, and it may now be the largest single-family organic vegetable farm in the country. Whereas he first put chemicals in the sky, he now avoids putting chemicals in the ground. It seems incongruous, but he disagrees.
Using pesticides, he explains, is using poisons. And if a poison can kill insects, it isn’t good for wildlife or, ultimately, people. The other end of industrial agriculture is artificial fertilizers, which operate basically by burning up the carbon in the soil that has been building for centuries. As such, fertilizers are poisons, too. Silver iodide, say microbiologists, has no adverse environmental effects, and in any event is used in very tiny amounts. Says Grant, “I don’t see them (agricultural chemicals and silver iodides) as the same at all.”
Leaving cloud seeding and Colorado State University behind, Grant has been replaced by a wave of graduate students. They continue to argue the merits of seeding winter storms — not as a way to end drought, but as a way to augment natural precipitation.
“I think there is no question that you can increase precipitation in the mountains by at least 10 to 15 percent,” says Grant. “The real potential would probably be four or five times as much if there were a good delivery system for the seeding materials. The main hang-up for achieving that potential is being able to seed the clouds at the right time, in the right amount, and in the right place. You really can’t do this from the ground, or with aircraft or rockets, and all have been tried.
“As regards summer convective clouds, I’m very negative about the potential to get more moisture. Many experiments have shown both increases and decreases in precipitation from seeding this type of clouds, and the science is not advanced enough to firmly show the condition under which one or the other of these effects occur.”
Just as droughts were key to each of Grant’s major career steps, so the recent drought signals a renewed interest in just how reliably cloud seeding can aid Colorado and other states of the West. Despite its pessimistic tone, last October’s report from the National Research Council is seen by many as a thinly concealed pitch for more funding.
The next step, says one of Grant’s former students, Arlen Huggins, associate research scientist at the Desert Research Institute in Reno, Nev., is a study that evaluates cloud seeding across a broad watershed, including not only a river but also its tributaries. Such a study could easily cost $1 million. Since the Climax experiments, there have been few opportunities for such pure, field research.
To learn more see the North American Weather Consultants website at: http://www.nawcinc.com/
Allen Best was once a snow-maker on the ground, when he worked at a resort now called SolVista Basin, but he never made snow in the clouds.