GRAND JUNCTION, Colo. - For 50 years, humans have attempted to modify the weather for the purpose of increasing snowpack, to fill up reservoirs, reduce hail, and even prevent rain.
The scientific practice of cloud seeding has been utilized on Grand Mesa since the 1990s.
Two years ago, the Water Enhancement Authority stepped up its Grand Mesa program by doubling the number of cloud seeders to 16.
"We're trying to increase snowpack on the Mesa, to fill up the reservoirs," said Mark Ritterbush, the Grand Junction water operations supervisor and secretary for the Water Enhancement Authority (WEA).
The WEA is comprised of the City of Grand Junction, Powderhorn Ski Mountain Resort, Collbran, the Grand Mesa Water Conservancy District, and Overland Ditch and Reservoir Company. Funding for the cloud-seeding program comes from those entities, as well as Delta County, the Colorado River District, the Colorado Water Conservation Board and lower Colorado River basin states.
Meteorologists determine where to place the cloud-seeding machines on the Mesa. Oftentimes, they're located on private property where landowners are paid rent to host the machines.
In China, cloud seeders - many of them farmers - are paid to use anti-aircraft guns and rocket launchers to release pellets containing silver iodide into clouds, according to Wikipedia. Other areas disperse the precipitation-enhancing agents via airplanes.
On the Grand Mesa, cloud-seeding machines consist of tanks on the ground filled with a silver-iodide solution containing chemicals such as acetone. The solution is sprayed across a propane-fueled flame, causing the particles to drift with the wind current up into the cloud. The condensation nuclei turn into ice crystals, ride along with the cloud and fall out as a snowflake.
Silver iodide is used because its crystalline structure is almost identical to ice, Ritterbush said.
"A meteorologist (John Thompson of Montrose) watches storms as they come in," Ritterbush said. "He calls and tells (the landowners) when to turn it on. Rarely are all 16 cloud seeders running at the same time."
There is an ongoing debate regarding the effectiveness of cloud seeding versus letting nature take its course, Ritterbush said.
Ten years ago, the National Academies of Science released a report saying, that after 30 years of research, there is no convincing proof of intentional weather modification efforts.
"In nature, it's hard to set up an experiment with a control," Ritterbush said. "It's a conundrum how to compare."
Yet, studies suggest cloud seeding can increase snowpack 5 to 15 percent, which makes the program's annual cost of between $30,000 and $40,000 cost-effective when you factor in the extra water, Ritterbush said. The cost variable is due to weather conditions, how often seeding takes place, and the cost of silver, Ritterbush said.
According to the World Meteorological Policy Statement, "a well-designed, well-executed program shows demonstrative results," said Joe Busto, who runs the weather modification permitting program out of Denver for the Colorado Water Conservation Board.
The Grand Mesa has been a forum to introduce new equipment and different seeding technologies, Busto said. The topography is ideal for setting up cloud-seeding machines at a high elevation, he said.
"There's a rich history of research on the Grand Mesa, during the '70s, '80s, and '90s," Busto added.
Arlen Huggins, a semi-retired research scientist with the Desert Research Institute in Reno, Nev., is familiar with the Grand Mesa project. Huggins said there is plenty of convincing evidence that modifying weather is effective for increasing precipitation. He mentioned prior Bureau of Reclamation studies, plus a recently completed five-year experiment in Australia.
"There's a lot of evidence related to snowfall enhancement," Huggins said. "It makes it a viable option for increasing water supply."
The Water Enhancement Authority is in the process of collecting data comparing seeded areas versus non-seeded areas on the Mesa, Ritterbush said.
So, what happens when silver-iodide particles hit the ground or land in lakes or rivers? While there has been no monitoring for silver in western Colorado's environment, researchers in Australia have spent millions searching for traces of the mineral, Ritterbush said.
In Australia, where lake beds and soils have been tested, they "just don't find it near toxic levels," Busto said.
Huggins, who is considered a cloud-seeding expert, said he's often asked about potential risks of silver toxicity in the environment.
"It's a minuscule amount of silver being released," Huggins said. "The silver iodide amounts released are not harmful. (The particles) are not soluble in water. It cannot be taken up by aquatic species. It does not bio-accumulate."
There are approximately 106 cloud-seeding sites in Colorado, including Summit County, Gunnison, Telluride and the Dolores area, the West and Eastern San Juan mountains. Vail and Beaver Creek have the oldest program, having cloud-seeded for 38 years.
Most permits are issued from November through March and sometimes into mid-April, Busto said.
"We monitor snowpack, avalanche hazards, and suspend programs when needed," he said.
A 2010 statement from the American Meteorological Society states that "unintended consequences of cloud-seeding, such as changes in precipitation or other environmental impacts downwind of a target area have not been clearly demonstrated, but neither can they be ruled out. Continued effort is needed toward improved understanding of the risks and benefits of planned modification through well-designed and well-supported research programs."