For Americans, this year's winter has been an interesting dichotomy. While the eastern part of the country has been inundated with snow, the west has seen very little precipitation. One of the most affected is the State of California, which according to experts may be facing its worst drought since record-keeping began, about a century ago.
Therefore in an effort to squeeze out every last drop of moisture from the clouds, water managers, utilities and ski-resort operators are now turning to a scientific method called 'cloud seeding'. Introduced in 1946 by self-taught chemist Vincent Schaefer, who made 'snow' by dumping six pounds of dry ice onto the clouds over the Berkshire Mountains in Massachusetts, it is a technique that helps clouds release the millions of water droplets it contains. While cloud seeding has come a long way since then, and now includes many different kinds, the principle behind causing the moisture to shed, remains the same.
According to researcher Jeff Tilley, who runs the cloud seeding program at the Desert Research Institute in Reno, Nevada, the zillions of water droplets need some substance to condense upon. Dust normally does the trick. However when there is not enough available, they become static dead clouds that simply move right through the area without shedding any 'tears'.
In order to assist them, companies specializing in cloud seeding release tiny particles of silver iodide either from permanent machines that are situated atop ski summits like the one in California's Alpine Meadows or in real dire situations such as the one the State is currently facing, by locating promising-looking clouds and flying pilots to sprinkle the 'magical dust' over them. Silver iodide is the ideal choice because it provides a crystal for the moisture to condense upon and is also the perfect size and shape to help it form snowflakes. The technique of course works only if there are suitable clouds to seed and the temperature is below 20°F.
Cloud seeding is not cheap. It is estimated that California water agencies spend between $3-$5 mm USD each year to squeeze out about 4% extra water - And those numbers are just estimates, since it is almost impossible to calculate the exact amount. This has led many to argue that cloud seeding is not worth the cost. But for states like California that need all they can get, it is the only viable solution, especially given that alternatives like desalination are prohibitively expensive.
There have also been some concerns about the negative impact of silver iodide on the environment, especially since the compound does not dissolve in water. However, experts maintain that the amounts are too minuscule to cause any harm, a fact that was confirmed by a 2008 study done by the Weather Modification Association.
California is not the only US state to have a cloud seeding programs in place. Arizona, Colorado, Idaho, Nevada, Utah and Wyoming frequently utilize this technique to increase their snow pack. Kansas and Texas use it to induce rain. North Dakota also uses it not because it needs extra rain, but to ensure that the moisture in the clouds is released as rain not hail, which causes damage to the crops.