From the Watch (Stephen Elliott):
[Andy VanDenBerg] is one cog in a regional cloud seeding program that purports to increase wintertime snowfall over Telluride by as much as 15 percent; he’s one of the dozen or so landowners from Dolores to the southwest to Disappointment Creek and Saltado Creek further north who have allowed Durango-based Western Weather Consultants to install cloud-seeding generators on their properties, and are paid to operate them when a promising storm system moves into the area.
“It doesn’t make much money. It’s kind of a waste of time and an inconvenience,” VanDenBerg said. “But there’s a chance it works.”
It’s difficult — nearly impossible — to prove wintertime cloud seeding’s efficacy, but that hasn’t stopped the Telluride Ski & Golf Company, Dolores Water Conservancy District, Southwestern Water Conservation Board, Colorado Water Conservation Board, California Six Agency Committee, Central Arizona Water Conservation District, Southern Nevada Water Authority and Metropolitan Water District of Southern California from funding cloud seeding in the Upper San Miguel Drainage Basin, specifically on the Telluride Ski Resort.
“We’re in a 15-year drought and reservoirs are down, so we’re trying to help prevent them from going down further, and maybe bring them back up a little bit,” said Bill Hasencamp, Colorado River Resources Manager for the Metropolitan Water District around Los Angeles.
Hasencamp, like VanDenBerg, can’t be sure cloud seeding works (or at least how well it works), but his agency still enthusiastically funds the program. “There’s a general feeling that it increases snow, but no absolute proof. That’s the tough part: It’s very difficult to tell exactly,” he said.
All of the water managers involved in the Colorado cloud seeding program cite a study from Wyoming when discussing the effectiveness of cloud seeding. The study, conducted by the National Center for Atmospheric Research and several other organizations, was completed in 2014 and compared two mountain ranges in the state: the Medicine Bow and the Sierra Madre. For 10 years, researchers randomly seeded storms in one of the ranges, but not the other, in an attempt to discover if cloud seeding increased snowfall.
That study indicated a 5-15 percent snowfall increase, presumably due to cloud seeding.
“There’s not really any downside to [cloud seeding],” said Joe Busto, cloud seeding program manager with the CWCB. “It doesn’t do a lot, just a few inches more here and there. It can’t replace dams or conservation; it’s just a thing we do every year and we get a little more and that’s all it is.”
[…]
Water managers could conceivably seed clouds anywhere along the Colorado River Basin but have decided to partner with ski areas to boost recreational economies and take advantage of the funding those ski areas are willing to put up for the program.
“Although the state supports [cloud seeding], it’s not just because we want to support all the ski areas. This is a new water source, but it has the great benefit of helping out our recreational economy in Colorado,” said April Montgomery, a San Miguel County-based representative on the CWCB. “This is also a huge benefit to Norwood and the West End. We’re producing more water for our Telluride headwater reservoir, and that’s all going down to the lower ends of the San Miguel, into the Dolores, into the Colorado.”
As reservoirs along the Colorado River, including Lake Powell and Lake Mead, have dried up during the past few years, water managers downstream have turned to more experimental ways to keep them full, or at least less empty. Busto at the CWCB said the out-of-state agencies have contributed nearly $2 million to the Colorado cloud seeding program since 2007.
“The reason why the state is involved in cloud seeding is because it’s the cheapest form of new water. If you look at other ways of creating new water sources, you’re looking at desalinization or you’re looking at giant reservoir systems and new diversion systems. That costs so much money,” Montgomery said. “Our snowpack is the largest reservoir we have and if we can increase our snowpack, we are basically creating this giant reservoir that we can use later.”
[…]
But cloud seeding raises questions. Does silver iodide negatively impact the watershed once it falls out of the clouds? If we coax precipitation from clouds over Telluride, does that mean less will fall on other communities?
Cloud seeding proponents answer a resounding “No” to both questions.
The Wyoming study found silver concentrations in the water after cloud seeding in the parts per trillion range, and in the parts per billion range in soil, “about three orders of magnitude less than values considered hazardous to environmental system or human health.”
“Silver iodide doesn’t dissolve into the water,” Montgomery said. “One reason I’ve been able to embrace this technology is, as we improve and we’re being more efficient and effective with it, we’re not just throwing this up into the atmosphere.”
“This is something that doesn’t bioaccumulate,” Busto added. “When a chemical gets in the fish, then the eagles get it… That’s bioaccumulation. It’s a concern, but [silver iodide] won’t do that.”
As for cloud seeding’s effect on nearby areas, Western Weather’s founder Larry Hjermstad, who has been working in weather modification for four decades, said seeding merely takes advantage of an opportunity in a storm.
“One of the big concerns is, if we’re putting more precipitation in one area, it’s at the expense of another area. The answer is no; we’re creating a slightly better storm system,” he said.
Busto added that winter storms are typically large, often 200 miles long or more, and contain huge amounts of moisture, only a small amount of which will ever fall as precipitation. So when cloud seeding urges slightly more of that moisture out of the clouds, the vast majority of a storm’s moisture remains to fall elsewhere or stick around in the cloud.
“To say you took all the water out of a system that was 200 miles long is really a stretch,” Busto said. “Did you steal that [precipitation] from someone else? No, I don’t think so.”
The Wyoming study concurred, finding that the “downshadow effect,” or the impact of cloud seeding on areas outside the seeded area, was negligible.