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Silver iodide has proven to be ideal. It is a safe, inert salt, and it very closely resembles minute ice crystals. '~is im- possible to detect the cIifferenc:e be- tween snow crystals grown on silver iodide and natural ice crystals, " according to Larry Hjermstad, the President of Western Weather Consultants. Larry Hjermstad has studied cloud seeding since 1965, when he was at Colorado State University working towards his Master's Degree in At- mospheric Science. He was on the csu faculty until 1971, when he became director of a Bureau of Reclamation 'Weather Modification Project" based COlOllAOO CClllNYn' UR - JANUARY 1_ ~ -J~~ _ ~~_~~~~_~~~_~___ in Durango. When that experimental program ended in 1975, he formed Western Weather Consultants to put his experience into commercial prac- tice. His firm holds the only two cloud seeding contracts for which permits were issued this year in Colorado. "Experience shows cloud seeding can actually increase snowfall by anywhere from 10% to 25%. For an area such as Vail, that means an extra 20 to 50 inches of snow," says Hjerm- stad. With an annual snowfall of 200 inches, does Vail really need more snow? According to Vail's Joe Macy, "Early in the season, the extra snow from cloud seeding is very' important to us." The greatest effect of cloud seeding is on the upper slopes of the mountains, exactly where artificial snowmaking is least cost-effective. "Experienced skiers judge a ski slope, more than anything else, by the powder of its upper slopes." 'Rlere is, of course, a certain amount of tImtroversy associated with cloud seeding. One obvious fear is that by in- ducing more snowfall in the Vail area, for example, the snowfall will be reduced farther to the east. "That has simply not been proven to be true," says Larry Hjermstad. "Gouds nor- mally carry much more moisture than they drop to the earth-a cloud usually drops less than 5 % of the moisture contained in it. Ooud seeding will in- duce perhaps another 15 % of that meager 5 % to fall to earth. It is doubt- ful that that noticeably affects precipitation farther downwind." Ap- parently little, if any, opposition to cloud seeding has actually come from people concerned about losing precipitation. What opposition there has been in the past has mostly come from local ranchers, farmers, and drivers con- cerned about adding to the snowfall they consider to be more than plentiful already. Winter travel in the moun- tains is often hazardous, and the ad- ditional snoWfall certainly does not help the situation. And what about the rancher worried about his cattle being caught in a blizzard? These concerns have been aired at the hearings that are held each year prior to the Colorado Department of Natural Resources' is- suing of annual weather modification licenses. Both Larry Hjermstad and Joe Macy are aware of the concerns. 'We do everything possible to make the snowmaldng as accurate as pouible," ....._~.....-.- ~~ says Hjermstad. "Cloud seeding is necessarily a shotgun mel~hod; we just cannot pinpoint exactly where the ex- tra snow will fall. But we can come very close by analyzing the weather patterns, wind speed and direction, and cloud composition." Western Weather operates a complete weather data gathering service, and they com- municate up-t~the-minute instructions to the operators of the propane generators. Additional measures, such as suspending operations entirely dur- ing 'dangeroUs storms' and when mountain travel is severely hampered, are taken when the situatiion warrants. " Avalanche danger is always taken in- to consideration," adds Hjermstad. The annual permit granted by the state also specifies exact snow levels at which cloud seeding must be suspend- ed entirely. According to Vail's Macy, if for example" total snowfall exceeds 150% of normal in October, cloud seeding must cease. The percentage of excess snowfall that triggers a suspen- sion of cloud seeding de<<:reases as the winter progresses. "The c:Ioud seeding is to malce sure we have adequate snow cover, not excessive snow cover. Our aim is not to place any urtdue burdens on ranchers or drivE!rs, just to guarantee a good ski l;eason," em- phasizes Macy. Interestingly, this year'li public hear- ings a~no opposition at all. Ac- cording to Barbara Welles, the Direc- tor of Weather Modification Programs at the State Department of Natural Resources, ''The permits appear to have evolved so that they adequately address the concerns of th.e public. The permits issued have COIl'le to contain quite a few specific restrictions and safeguards. " Everyone concerned with cloud seeding, or "weather modification" as it is technically referred tiC), agrees that it works. At the same time, it is also clear that cloud seeding can only play a marginal role in bringirlg more snow to our sId areas. It cannot create snow out of thin air, and the most it can do is to get heavy moisture-.laden clouds to drop just a little mOl'e snow than they would normally drop anyway. '~.._ Expensive 'artificial' '1Inowmaking '-.,' ~..dpment wtll have to continue to handle.tnost m the job of supplement- ing nature. But at the S21D\e time, the statement attributed to Will Rogers that "everyone talks about the weather but no one does anything about it" is no longer entirely 'true. 0 11