We're getting really excited for winter over here at Snowboard Colorado, but there really isn't much we can do besides wait for snow. When it comes to snowfall, some resorts choose to take matters into their own hands through a process called cloud seeding. To learn more about cloud seeding one of our writers dug deep to get the inside scoop. Originally published January 2012.
By: Tim Wegner
Picture this: It is puking snow outside. The cloud cover looks about normal for an average
snowstorm, but it looks as if the mountains are getting covered with more powder than seems normal. You are standing outside watching this phenomenon and already eyeing down your lines for the next morning, when you notice that the roads look clear heading that direction and the storm is focused on adding powder to the ski hill. You check again an hour later and notice the same thing. Dumping on the mountain and clear everywhere else. While this might seem like an act of God, it is actually the hand of man messing with the physics of nature.
Cloud seeding is a practice of weather modification performed by many ski resorts across the world. To get the scientific terminology out of the way here, I’ll go ahead and give a brief description of how cloud seeding works for those who are new to the term. By pumping the clouds in a certain area full of silver iodide and solid carbon dioxide (dry ice), a cloud can be “supercooled,” thus causing ice particles to grow at rapid rates and become dense enough to fall from the cloud as precipitation (in our case snow). “Silver iodide once burned is hexagonal and has water attracting and bonding properties and is therefore perfect for vapor to convert to snowflakes,” says Joe Busto, of the Colorado Water Conservation Board.
Joe is Colorado’s ‘kingpin of cloud seeding.’ “Cloud seeding is not the answer to any one problem, but is a little bit helpful each year,” he says. Joe is in charge of issuing the permits that allow a person or group to legally perform cloud seeding, as well as administering a grant program for winter cloud seeding operations. For everything from getting the low-down on which ski areas use cloud seeding, when they are allowed to seed clouds, and how they go about doing it, Joe is the man with the master plan.
Cloud seeding has been a bit of a controversial subject, so I decided to take a look into the matter and get some facts. The perceived problem with cloud seeding, as a lot of naturalists see it, is that we are effectively “altering” the weather, causing a small percentage of extra precipitation in a designated area than would have otherwise occurred. There is also speculation that adding extra precipitation to one area is taking away from the moisture in another. A lot of people also question whether or not cloud seeding actually works. “From my perspective, not my agency’s, I believe cloud seeding is controversial because people either over or under estimate its effectiveness,” Joe says. “It is not the reason there is 12 feet in the back bowls of Vail nor is it the reason that the Eastern Plains of Colorado (have been) dry the last few years. They also don’t understand the science very well. It is basically the stimulation of natural processes by giving more particles for water vapor to bond to.” In many cases, the everyday boarder won’t even notice that cloud seeding is taking place. “Well designed and executed programs will make up about 10% more snow in your target area, that is all,” he says.
“...CLOUD SEEDING IS CONTROVERSIAL BECAUSE PEOPLE EITHER OVER OR UNDER ESTIMATE ITS EFFECTIVENESS.”
As stated above, Joe feels strongly that cloud seeding is a practical way for us to help generate more precipitation where needed, but is not the cure all for droughts or other natural phenomenon. “You can’t cloud seed in a drought as you need the clouds with water vapor in them to work with,” he says. “Therein lies a problem- you can work in an average year to make it a little better than average or a wet year to make it a more wet year but you can do very little for a drought. It should be considered a small snow and water resource augmentation program only.”
Another main concern with cloud seeding is how it affects the surrounding wildlife. “Programs are monitored by the state and thresholds are set on snowpack to suspend operations based on the natural variability of the local climate,” says Joe. There has been speculation as to whether the silver that is pumped into the clouds is harmful to plants and animals.
During a study conducted in Australia and published in 2009 entitled An Assessment of the Environmental Toxicity of Silver Iodide, cloud seeding experiments were tested to determine the amount of silver iodide absorbed in water, snow, plants and animals. The research project was titled the Snowy Precipitation Enhancement Research Project. “Mean silver concentrations have all been shown to be well below the GTV for all matrices, at all locations and for periods of sampling during the SPERP,” Williams and Denholm.
The study also concluded that silver iodide is not harmful to living creatures, as some other forms of silver can be. “Insoluble or complexed silver compounds were found to be much less toxic or essentially non-toxic to a range of terrestrial and aquatic vertebrates,” Williams and Denholm, pg. 2.
“As far as negative impacts from the use of silver iodide, there aren’t any documented impacts to date,” Joe says. “It is basically inert and bonds with water but is used in very small quantities and doesn’t bio accumulate in plants, animals, or fish.”
This doesn’t necessarily mean that the extra snow can’t endanger wildlife, however. “In 2008 snowpack was well over 160% in late January and the DOW was doing hay drops to feed deer because there was so much mid elevation snow where there normally would not be as much snow,” Joe says.
“IT IS A WAY TO HELP WITH POWDER IN AREAS YOU CAN’T REACH WITH SNOW GUNS”
Not all ski resorts in Colorado practice cloud seeding or have anything to do with it, but many of the major resorts are a part of some kind of cloud seeding program- Winter Park, Keystone, Arapahoe Basin, Breckenridge, Vail, Beaver Creek, Powder Horn, Telluride and Purgatory. “It is a way to help with powder in areas you can’t reach with snow guns,” says Joe. “The primary goals of Vail and Winter Park are to target cloud seeding for the back bowls where their Forest Service permits do not allow for snowmaking equipment.”
“It is all about snowpack augmentation,” says Doug Laraby, Director of Mountain Planning at Winter Park Resort. “We’ve got two remote generators, and they are up high. We can take advantage of the conditions to augment our snowpack.” The remote generators are operated from Nevada under close supervision.
Ski areas aren’t the only places that are down with the extra wet cloud; several water districts across the state pitch in with funding as well, bringing the total to around 40 entities that participate, according to Joe. Because cloud seeding programs are under strict watch, the plug can be pulled if the snowpack becomes too much of a problem. “This criteria or thresholds works pretty well as we suspended the programs in Gunnison for the rest of the year that year. It was a joint decision between the CWCB, County, and contractor. But it was the right decision.”
At this point, we have a basic idea of what cloud seeding does and why people may be for or against it. So now let’s go over how it works and what it takes to get started.
Before getting started with a cloud seeding program, a ski area must get a permit. The state has a permitting program that ensures each cloud seeding operation is run by people who know what they are doing and that liability insurance is carried in case of a lawsuit. “No lawsuits have ever been paid out, but it’s best to ensure that project sponsors are covered for this activity,” says Joe.
“NOT ALL STORMS CAN BE SEEDED,” JOE SAYS. “YOU MUST KEEP IN MIND THAT SILVER IODIDE, THE SOLUTION USED IN CLOUD SEEDING, IS ONLY ACTIVE AT CERTAIN THRESHOLDS SO STORMS CAN BE TOO WARM, TOO DRY, TOO COLD TO USE THE CHEMICALS.”
So what does it take to get a permit? “You have to advertise in the papers, submit an application to the state, and defend and present the details of your application at a public hearing,” says Joe. The public also has the opportunity to express concern before a permit is granted. “The state believes you should give the public proper notice and an opportunity to be heard. The state uses that information and develops a record of decision to approve, deny, or approve with special terms and conditions. It is not a forum to vote programs up or down but legitimate concerns should be addressed.”
North American Weather Consultants from Utah and Western Weather Consultants in Durango are the two main places to go through to get started. The Winter Park Ski Area and Denver Water went through WWC and paid $107,000 to use ten generators for three months. “I have been partnering with Winter Park to have the Desert Research Institute in Reno, Nevada operate two specialized high output high elevation cloud seeding machines and they are about $60,000 for five months for two of them,” says Joe. “We really focused on getting those machines at about 9500 and 8900 feet elevation on Denver Water and USFS land to ensure our seeding solution was regularly getting in cloud.” They are also focusing on getting newer and more efficient machines to do the job. Where the old machines average 6-8 grams of silver iodide/hour, the more modern ones will average around 27 grams per hour.
The actual process of cloud seeding is quicker than you might think, as long as the generators are in the right spot. “Generators can be 5-20 miles upwind of the target area and depending on winds it could be 10–30 minutes before this starts to take effect,” says Joe.
“Not all storms can be seeded,” Joe says. “You must keep in mind that silver iodide, the solution used in cloud seeding, is only active at certain thresholds, so storms can be too warm, too dry, too cold to use the chemicals.”
THE ACTUAL PROCESS OF CLOUD SEEDING IS QUICKER THAN YOU MIGHT THINK, AS LONG AS THE GENERATORS ARE IN THE RIGHT SPOT. “GENERATORS CAN BE 5-20 MILES UPWIND OF THE TARGET AREA AND DEPENDING ON WINDS IT COULD BE 10 – 30 MINUTES BEFORE THIS STARTS TO TAKE EFFECT,” SAYS JOE.
When deciding whether or not to seed a storm, scientists also take into consideration the ‘robbing Peter to pay Paul’ argument. “In that argument we ignore the massive mountain barrier in our state and the orographic lift of our terrain,” Joe says. “Simply put, the mountains force cold air to rise and this increases the effectiveness of precipitations processes. Similarly, air will warm and descend on the downwind side of mountain ranges and that is a natural phenomenon as well.”
The Colorado Water Conservation Board has put over $1 million into locally sponsored cloud seeding programs in Colorado since 2004, according to Joe. What is more interesting is that other states that depend heavily on water from here in Colorado have been throwing down the dollars as well. “Since 2007 downstream water users Southern Nevada Water Authority, Central Arizona Water Conservation District, and the California Six Agency Committee have put $1 million towards Colorado cloud seeding,” says Joe.
“In the Colorado River Basin we have agreed to collaborate on this science to help meet our water needs. I try and balance it as grants to existing programs, modernizing existing programs with new equipment, and importing and deploying new equipment to do good evaluations. You can’t run models or do simulations without good inputs so I am at square one collecting good data,” Joe says.
“IT IS TIGHTER THAN PEOPLE THINK AND WATER RESOURCES WILL STRUGGLE TO KEEP UP WITH POPULATION GROWTH IN COLORADO
From many points, the issue with cloud seeding doesn’t have so much to do with the ski industry in Colorado, but with everyone that uses water that comes from Colorado. While Joe is an avid snowboarder, himself and everyone at the CWCB have to also make sure that the water that needs to get to Nevada, Arizona and California is actually getting there. “Few people realize our compact obligations and look at a stream and say 25% of that water is ours and the rest goes downstream. We see that at my agency. We have to. It is tighter than people think and water resources will struggle to keep up with population growth in Colorado and the Southwestern U.S.,” he says.
The least that we can hope for is that the people who are making the extra snow that we ride on every day are doing a good job and being environmentally responsible. “We don’t want to get in a position where we are seeding and hoping we are doing a good job. Those questions can be answered by good science that involves plume modeling, air flow measurements, high resolution precipitation gauges, silver in snow analysis, weather stations with icing sensors that catalog data. Contractors don’t like those ideas as they take money out of their pockets. But, we must insist on them for the long term viability of the field,” Joe says. “The focus of my agency’s effort has been to ensure programs are well conducted, executed and evaluated.”
1. Williams, Bruce D. and Denholm, John A. An Assessment of the Environmental Toxicity of Silver Iodide- With Reference to a Cloud Seeding Trial in the Snowy Mountains of Australia. April 2009.
2. FINAL CLOUD SEEDING SUMMARY REPORT 2010-11, Central Colorado Mountains Vail/BC
3. Busto, Joe. 4th Weather Modification: The Colorado Experience and Application in the White Mountain of Arizona.”