Laserfiche WebLink
<br />" <br /> <br /> <br />FAQs about Cloud Seeding to Augment Mountain Snowpack <br /> <br />Q, Why do we need to augment snow pack? <br />A. Snowmelt contributes 50-80% of Western reservoir water storage. Western snowpack has been declining <br />over the last 50 years. There is' a growing body of evidence that air pollution is contributing to this decline. <br />Winter cloud seeding offers a means to compensate for this trend. <br /> <br />Q, Does cloud seeding for snowpack augmentation really work? <br />A. Yes! The Weather Modification Association, World Meteorological Organization, American Meteorological <br />Society and the National Academy of Sciences Report all state that there is strong evidence for seasonal <br />precipitation increases over natural precipitation on the order of 10%. To achieve such increases, well-designed <br />projects must be operated on a long-term and continuing basis, not just during droughts. Such projects will help <br />fill reservoirs for use during times of greater need, such as droughts. <br /> <br />Q, What are the environmental and health effects of seeding material and its effect on clouds and <br />precipitation? <br />A. Minimal. The most common seeding material, silver iodide, is used in very small amounts. The typical <br />concentration of silver in rainwater or snow from a seeded cloud is less than one 0.1 microgram per litre (one <br />part in 10,000,000,000). This is well below the acceptable concentration of 50 micrograms per litre, set by the <br />U. S. Public Health Service Many regions have much higher concentrations of silver in the soil than are found in <br />precipitation from seeded clouds. The concentration of iodine in iodized salt used on food is far above the <br />concentration found in precipitation from a seeded storm, An alternative seeding technology is the expansion of <br />liquid propane gas to freeze water in clouds; the amounts of this gas are also very minute. National <br />Environmental Policy Act compliance for all cloud seeding environmental impacts has been demonstrated by <br />past studies. <br /> <br />Q, Does cloud seeding decrease precipitation downwind, i,e" "rob Peter to pay Paul?" <br />A. No. The idea that rainfall increases in one area must be offset by decreases elsewhere is a misconception. <br />The amount of atmospheric moisture passing over a mountain barrier that is converted to precipitation is usually <br />10% or less. If this natural precipitation is increased by 10% by cloud seeding, only 1 % of the original <br />atmospheric moisture supply is depleted. Moreover, winter cloud seeding is done on clouds on the upwind side <br />of mountain ranges. These clouds usually dissipate on the downwind or lee side of the range, via a natural <br />process called the "rain shadow." This is the reason that lee side areas like the Colorado Front Range and <br />Nevada are much drier than on the upwind side of the mountains. So the atmospheric moisture supply on the lee <br />side of the mountain range will not likely precipitate anyway. Finally, precipitation data from a number of long- <br />term cloud seeding projects have been examined in detail for evidence of "extra-area" effects. There have been <br />no significant indications of precipitation decreases downwind from any of these projects, in consonance with <br />what we would expect from the rain shadow effect. <br /> <br />Q, How much does cloud seeding cost? <br />A. The cost of cloud seeding programs are on the order of $10 per acre-foot of water, varying slightly with the <br />value of water and the uses to which it is put. This cost makes it an attractive alternative to desalinization and <br />construction of new reservoirs. Given typical costs of water for agricultural purposes, cloud seeding achieves <br />benefit-to-cost ratios approaching 40 to 1. <br /> <br />Adapted in part from the Weather Modification Association's Facts Brochure, <br />htto:/ /weathermodification.org/facts.htm <br />