Biggest storms came after the silver-iodide burners shut down for the year
By Summit Voice
SUMMIT COUNTY — Colorado’s cloud-seeding program for the central mountains ended April 10, just as a series of strong spring storms rolled into the area.
While the winter’s biggest snow totals came after the end of this year’s program, the seeding operations may have helped bring near-average snowfall to area in February and March, according to the operators, who are now measuring their efforts under a “target and control” evaluation that will be submitted to the Colorado Water Conservation Board for review.
Durango-based Western Weather Consultants, which seeds the central mountains, was able to extend operations into early April and use all its allotted operational days, said Larry Hjermstad.
During the 2012-2013 season, the central mountains program cost $293,600 and targeted an area of about 1,668 square miles of the Upper Colorado River Basin, generally above elevation 8,500 feet, in parts of Pitkin, Eagle, Summit, and Grand counties. Front Range water providers and ski areas, along with other partners, help fund the program, aimed at enhancing water supplies and boosting ski conditions at A-Basin, Breckenridge, Keystone and Winter Park, all included in the target area
Cloud seeding in Colorado involves burning silver iodide in ground-based generators to inject tiny particles of the material into approaching weather systems. The silver iodide provides nucleii for crystal formation and growth, helping to wring a bit of additional moisture from the clouds.
In places like North Dakota, cloud seeding is done in summer, with airplanes targeting developing thunderclouds with silver iodide to spur more rainfall.
This winter’s operations got off to a slow start, with only one seeding opportunity in November, according to Hjermstad.
“I would say December turned out to be OK. All the ski areas had sufficient snow … January was a little slow again, but February and March picked up, but we sure could use more normal-type winters,” Hjermstad said.
In past seasons, Hjermstad estimated that cloud-seeding may have boosted snowfall by as much as 15 percent in targeted areas.
Cloud-seeding efforts in Colorado have a long, on-and-off history dating back to the 1970s, when the federal Bureau of Reclamation was active in the southwestern mountains, said state climatologist Nolan Doesken, who acknowledged that there is still a debate about the effectiveness of cloud-seeding.
Doesken said that there is good evidence that cloud-seeding can work in the right conditions, with very specific requirements as to wind direction, moisture and temperatures. Outside that range, the results are less clear.
Funding comes from the Front Range Water Council including Aurora Water, Denver Water, Colorado Springs Utilities, Northern Colorado Water Conservancy District, Twin Lakes Reservoir & Canal Company, Southeastern Colorado Water Conservancy District, and Pueblo Board of Water Works. The Colorado River Water Conservation District, A-Basin, Keystone, Breckenridge, and Winter Park also participate.
The Colorado Water Conservation Board and the Lower Basin States, including the Southern Nevada Water Authority, Central Arizona Water Conservation District, and California Six Agency Committee also help fund the cloud-seeding, but don’t directly participate in the program, said program manager Maria Pastore, of Glenwood Springs-based Grand River Consulting.
As part of the state-authorized weather modification plan, operators of cloud-seeding operations are required to complete annual “target versus control” analyses, comparing snowfall in target areas against similar non-targeted control areas.
“This method is credible and develops relationships between snow data and tracks precipitation totals over time in both seeded areas and non-seeded areas to help track the efficacy of the program,” Pastore said in a previous interview.