Last week, I posted about seeking a Clean Bill of Health. I sent the link to this post to many of my caregivers at the CET Cancer Center at Alta Bates Summit Hospital in Oakland. So after my last treatment, Alfred Jamison, one of the many skilled folks assisting me through through the rigorous morning routine, engaged me in a conversation about, of all subjects, water supplies in California. Alfred wondered why the State water managers don't engage in the practice of cloud seeding to increase the amount of rain that falls from the skies in the watersheds with near empty reservoirs. This is certainly not on the list reported by the media of forthcoming solutions to California's water woes. Things are pretty serious though, when the Peripheral Canal is actually being discussed again and was to be included as a bond election in November.
Alfred's question set off my memories of when the Santa Clara Valley Water District performed cloud seeding in a program that was intended to be as scientific and as liability-free as possible. In 1973, when I took my seat as an elected member of the District's Board of Directors, an engineer named Dan Kriege managed this program and reported his procedures and results to us during the time that the operations unit of the agency conducted this activity.
In 1952, the first cloud seeding began in an effort to increase the average rainfall in the valley. Silver iodide crystals were shot from the ground into the clouds. According to the water history available at the Water District's website, in 1992 the cloud seeding program switched to airplanes flying into clouds with canisters of silver iodide crystals sprayed from the wings of the aircraft in order to increase the density of the water droplets and "squeeze more water out of the clouds." It also states that the "Cloud seeding remains a drought fighting strategy of the District."
I could swear that the Board ended the use of cloud seeding for a variety of reasons long before I left the Board in 1995. I will ask the Clerk to survey the Board's minutes to see when it was last discussed. I seem to remember that the District may have done an Environmental Impact Report on the program. This may be when they decided to eliminate the risks to the environment from spraying silver, which is a toxic heavy metal, into the watershed to fall with the induced raindrops.
There was also the aspect of determining the efficacy of the program. Each storm that was seeded had to be classified as a seedable event by the official weather watcher agencies. After that, there was kind of a lottery where as Seed or No Seed determination was made by flip of the coin or some other means. This was supposed to give more statistical relevance to the overall measurement of water added to the watershed by virtue of the cloud seeding. But during times of extended drought like we experienced in 1976-78, we abandoned the lottery and seeded every storm to try to get more local rainfall.
A Google search of Cloud Seeding shows that 12 States including Utah, Nevada, Idaho, Kansas, North Dakota, Texas, Wyoming, Washington, Oregon, Georgia, Colorado and California, operate ongoing cloud seeding programs. Kansas and North Dakota use cloud seeding for hail suppression, while Washington, Oregon and Georgia use it for fog dispersal.The remaining states use it to increase precipitation, with California with the most activities, according to a 1996 publication of the Weather Modification Association.
Although the American Meteorological Society says some studies have shown a 10 percent increase in rain volume, the National Academy of Sciences has said there is no conclusive evidence that cloud seeding works.
It's not the initial cloud-seeding equation that is in doubt: Silver iodide does produce ice crystals in clouds. "You can see on a radar how it grows to larger particles," says Dan Breed, a project scientist with the National Center for Atmospheric Research. "But the chain of events between that and precipitation hitting the ground is much more complicated."
Some clouds, it turns out, are less complicated than others. Winter orographic clouds, which form over mountains in winter, are simpler to work with than convective clouds, which cause thunderstorms. Orographic clouds occur almost every day in the Western mountains, where shortages of winter snowpack (needed to fill lakes, rivers and reservoirs in the spring) mean extra precipitation is most often needed.
Glaciogenic seeding, using silver iodide -- its structure mimics that of ice crystals -- is most commonly used in cloud seeding. It is also used for hail suppression; by providing many ice particles for hail to form around, it prevents very large hail from developing. But hailstorms are extremely complicated, Breed says, and experiments with hailstorms are risky. "You do a project or experiment and you can end up with insurance claims or crop damage," he says.
Other countries that practice cloud seeding include Japan, Australia, Russia and China. China spends $90 million per year on cloud seeding, and made an extraordinary effort to seed storms to try to wash some of the pollution from the air before the Olympics began this week. Reports on the air quality by the media indicate that the results were less than noticeable.
In June of this year, The Russians tried to seed a storm to prevent it from raining in Moscow on June 12, Russian Day. The Russian Air Force, for some reason, was using a some packages of cement as condensation nuclei. When the cement failed to disperse, it fell straight to earth, and put a 3 ft. hole in the roof of a suburban homeowner, who is now suing the government for "moral suffering." Guess Russia also has too many lawyers.
Beyond using cloud seeding for solving local weather shortcomings, some researchers are looking at using similar physics to mitigate the global warming process brought on by increased CO2 concentration in the atmosphere. Click here to view a 10 minute video on this subject.
If this account was not as entertaining as you'd prefer, please click on the this YouTube link for a funny episode on a Canadian show featuring cloud seeding. And if you don't have a sense of humor, I hope you get one soon.Never Thirst!