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Heavy snowfall a boon to cloud seeding in Southwest Colorado – until it isn’t

Region has received so much snow that operations have ceased
Eric Hjermstad, co-owner of Western Weather Consultants, tests one of the cloud seeding generators that the company operates on Friday near County Road 220 southeast of Durango. The cloud seeding at the site ends up having effects on snow amounts near Vallecito Reservoir. Behind Hjermstad is an automated cloud seeding machine that has been tried out over the past years. (Jerry McBride/Durango Herald)

The wet, and some would argue onerously prolonged winter weather affecting the Southwest this year, has left the region in a strong position from a drought-mitigation perspective. And when it snows, it pours, thanks to Eric Hjermstad, co-owner of Western Weather Consultants.

The series of storms has meant Hjermstad has been planting snow seeds in the passing clouds. He is the operator for the San Juan Mountains weather modification program, meaning he and his employees operate 33 seeding generators across the region.

Not only is cloud seeding useful even in winters, such as this one, that bring ample snow, the program is more successful in these years, Hjermstad said, and just as necessary.

“It's important to make sure we stay on top of seeding in good years just so that you create that snowpack that really gets to soak into the mountains. ... Because that's our No. 1 storage facility,” Hjermstad said.

One good year may be a boon to reservoirs and ensure that agricultural land will be sufficiently dampened, but it is not enough to stay the West’s historic drought. The wetter the soil is heading into summer, the lower the chances of ravaging wildfires and the higher the odds of filling reservoirs next year.

“Anytime you have the opportunity to bring more water and moisture to the ground, that's good, we should do that,” said Steve Wolff, general manager of the Southwest Water Conservation District. “In those dry years, it just doesn't work. But to be sure, there are criteria (which dictate that) in really, really wet years, that if we're getting too much snow it causes problems, we do turn the seeding off.”

In fact, when data collected at SNOTEL sites indicated the region’s basins had accumulated more than 140% of the median snow-water equivalent over the last 30 years, Hjermstad shut off the generators for the season. The San Juan Basin has 185% of its median snow-water equivalent and the Upper Colorado-Dolores is at 203%.

As futuristic as weather modification may sound, cloud seeding is not so complex.

As a cold, wet storm approaches, Hjermstad’s team turns on the appropriate generators, depending on the storm’s path. He runs between 10 and 18 generators per storm, depending on its path and the area they intend to target.

The propane-fired canons shoot a stream of silver iodide – a nontoxic compound – into the atmosphere. The compound acts as the nuclei for snowflakes, which grow around it before falling back to earth.

The San Juan Mountains on Friday sit covered with above-average snowpack. Western Weather Consultants operates 33 seeding generators across the region that contributes to that snowpack. (Jerry McBride/Durango)

“It’s like we’re using a shotgun versus a rifle,” Hjermstad said of shooting the material 10,000-13,000 feet in the air and predicting where the snow will fall. Their efforts are generally accurate, he said.

Hjermstad is permitted to seed storms from Nov. 1 through April 15.

As far as selection criteria, Hjermstad said he looks for storms ranging from 5 degrees to 23 degrees Fahrenheitat the 10,000-foot elevation level. A storm is worthwhile for seeding if it would naturally produce at least a tenth of an inch of water over a 24-hour period.

Despite the “triple dip La Nina,” which led experts to predict that this winter would be drier and warmer, Wolf and Hjermstad said the season has been extremely productive. Seeding efforts have yielded between 8% and 13% more snow from each passing storm, Hjermstad said.

The tactic works best in moist, cold storms because they provide both the material and temperature conditions necessary to foster the growth of snowflakes.

“It’s been a good year for cloud seeding,” Wolff said.

The San Juan Mountains Weather Modification project, which is one of seven permitted projects in the state, has an annual budget of about $200,000.

The SWCD matches funding from smaller conservation districts, ski areas and even a handful of lower basin states that stand to benefit from any increase in water flow. Earlier this month, the Bureau of Reclamation granted the Southern Nevada Water Authority $2.4 million for cloud seeding on the Colorado River. Wolff called the lower basin states’ contributions “significant.”

Although negotiations addressing how to parse out rights to the dwindling supply of water in the Colorado River Basin have been tense, Wolff said the question of whether cloud seeding is “stealing” moisture from downwind basins has not been an issue.

“It's certainly been a topic in a lot of different places,” he said. “ But the two big studies that have been done ... have really shown that any storm event with seeding is only taking a small percentage of moisture out of the atmosphere. There's always plenty to move on. So it's been proven that's just not a valid argument.”


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