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The Science of Snow: The Art of Making Snow Work

From snowmaking on ski slopes to cloud seeding for water, snow doesn't just have to fall

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Water rules the West—it's not a groundbreaking statement, just a simple matter of fact since humans first started settling in the often dry expanses of the region. And since that time, man has sought to harness water in all its forms.

Whether digging canals to irrigate crops in the desert or building dams to control the flow and location of water, mankind has never been satisfied letting Mother Nature run the entire show.

We're still trying to stack the deck any way we can, especially when it comes to snow. Where summer rains are scarce, winter snowpack is the ultimate deciding factor between a good year and a bad year for an array of Idaho businesses, from farmers and fishing guides to firefighters and utility companies.

"Snow is really important here in Idaho," said Jay Breidenbach, warning coordination meteorologist with the National Weather Service. "It's one of the most important predictions we can make."

There's a science to snow, and those who can predict it or manipulate it are often the ones who come out ahead.

The Natural Resources Conservation Service has been carefully watching the West's snowpack for nearly 100 years. It started with a water dispute near Lake Tahoe when agriculture, mining and logging interests butted heads about how much water should be used for what. The dispute led to the realization that scientists could predict the next year's water runoff by studying the snowpack.

The research spread through the country and in the 1930s, the Soil Conservation Program organized a snow survey with standardized measurements and methods. Since then, the snowpack science has continued to grow and now, researchers have access to hour-by-hour data from automated sites in key locations across the West.

In the Boise area the majority of snow runoff comes from elevations of 6,000-8,000 feet. Ron Abramovich, water supply specialist for the NRCS, said 75 percent of the area's annual precipitation comes in the form of snow, making monitoring snowpack critical.

"We get a lot of users looking at that data," Abramovich said, naming not only hydropower providers but also highway departments concerned with public safety and road maintenance, school districts that use it to determine snow days, farmers and ranchers who plan their years by the data, and public land mangers who watch for conditions that could lead to wildfires, flash floods or mudslides, as well as recreationists who want to get outside whether on the snow or the water.

The economic ties to snowfall are vast.

"If you have a business and your business relies on tourists coming to town, you've learned to look at the weather," Abramovich said. "Depending on how the snow falls, you may make a slightly different decision."

"We've become snow farmers in the winter," said Jack Sibbach, director of marketing and PR at Sun Valley Resort.

The ski industry was an early adopter of the idea of making snow work for it rather than simply relying on Mother Nature to kindly leave a solid base and several inches of fresh powder every day. Instead, most ski areas make their own snow to some degree, and Sun Valley is a devout practitioner.

The resort started snowmaking in the 1970s, but the technology wasn't very efficient at that time. It began using the current system in 1982 and has expanded and improved it since then. Now, roughly 80 percent of the groomed runs on Bald Mountain have snowmaking capability, and nearly all of Dollar Mountain is covered as well. The resort also makes extensive use of its snowmaking abilities to shape and maintain its terrain park at Dollar, including a 22-foot super pipe.

Between making snow and grooming it, Sibbach said the resort works on its snow 24 hours a day during the season.

But making snow doesn't just allow for good conditions on the slope; it has become essential for achieving the much-sought-after Thanksgiving opening and the absolutely necessary Christmas holiday opening.

"Being open on Thanksgiving is not as [financially] important as the perception that you're open," Sibbach said. "As a destination resort, it's very important to be off to a good start."

He added that in eight out of 10 years, it would be impossible to be open on Thanksgiving without snowmaking.

"The goal is to be able to be open from top to bottom on Thanksgiving, and we're nearly always able to do that," Sibbach said. "Last year, we wouldn't have been open for Thanksgiving or Christmas without snowmaking."

In a resort economy like Sun Valley's, having good snow isn't just of concern to the ski area. The entire community depends on skiers and boarders heading to the resort for getaways, where hotel stays and dining out support the local economy.

"Having good snow is extremely important to the economics of the [Wood River] valley," Sibbach said.

Sun Valley Resort started making snow in earnest for this season Oct. 21 and has already announced its Thanksgiving opening day of Thursday, Nov. 22.

Of course, some years Mother Nature feels like helping out more than others, and last season was not one in which she was feeling particularly generous.

According to the National Ski Areas Association, skier count last season was down industrywide by about 15.8 percent from the 2010-2011 season, the largest year-over-year decline since the 1980-1981 season. Nationally, snowfall was down 42 percent compared to the previous season, making it the biggest year-over-year decline in 20 years.

Sun Valley was down in terms of skier visits as well but only by about 6 percent, according to Sibbach. The resort had roughly 6,000 skiers per day during the all-important week of the Christmas holiday, although some years more than 8,000 skiers per day pack the slopes.

"After last year, [the snowmaking system] again proved itself," he said. "It's part of an insurance policy and part of a plan to have a good product."

Bogus Basin Mountain Recreation Area wasn't so lucky. Without any snowmaking capabilities, Bogus was unable to open until Jan. 19, the latest opening date ever. The previous record had been Jan. 6, 1970.

"We've been fairly consistent in our ability to open between Thanksgiving and the first week of December, but this last year was so far off the charts that it doesn't even bear discussion," said Alan Moore, general manager at Bogus Basin.

Ski area officials have looked into the possibility of snowmaking, but the location of the ski hill rules it out.

"Bogus Basin being literally at the top of a mountain, we don't have much water," Moore said. "Even if we wanted to take the risk of using water, using electricity and pumping the water up the slopes ... you also have the temperature issue in the early season. Bogus doesn't have the temperatures."

Last season Bogus Basin was down about $2 million in revenue because of missing the holiday opening.

"Those two weeks around Christmas are so important to us. In a good holiday week, we can do $1 million."

For the previous three to four years prior the 2011-2012 season, the area had seen roughly 350,000 skier visits per year. Last year there were only 235,000 skier visits, Moore said.

It was an economic wallop that stung even more because the ski area had just replaced the Superior chairlift with a new high-speed quad lift with a price tag of $5 million.

"As our historian put it, there's a curse of Bogus Basin: When you build something new, there's a difficult snow year," Moore joked.

But it wasn't just Bogus that was affected. The roughly 700 seasonal employees who man the hill during the winter weren't working either, and even many of the 35 full-time employees had to be furloughed until the snow fell.

Still, Moore said he's willing to bet just about anything that Bogus will make the holiday opening this season. Rather than major improvement projects, the ski area focused on smaller maintenance projects like repainting buildings at the base of the hill, resurfacing the No. 1 parking lot, and skiers purchasing a new shuttle bus for that lot.

"We've not spent a lot of money, but we've done a lot of projects," Moore said. "Bogus Basin will look a lot shinier."

He's also optimistic when he looks at long-range forecasts which call for an average winter.

"We love average," Moore said.

Average isn't bad for the folks at Idaho Power, but average can always be improved upon. In fact, Idaho Power has been trying to go above average since it started a regular cloud-seeding program in 2003.

By introducing silver iodide into the clouds of passing storm systems, the utility is attempting to improve the snowpack in key areas, thereby creating more runoff and more water to generate electricity in the company's hydroelectric dams.

"The more snowpack we have, especially in the higher elevations ... it's really valuable to the company," said Derek Blestrud, meteorologist with Idaho Power.

The cloud-seeding program began in the winter of 1996-1997, but because it was a heavy snow year, it only operated for one month. It wasn't until February 2003 that Idaho Power had the funding in place to start it up again.

Efforts are now focused on two areas: the Payette River Basin and the Upper Snake River Basin.

Idaho Power's program started in the Payette River Basin, where the company now has 17 remotely operated ground generators. The generators are spread in a horseshoe across the basin from the northwest to the south roughly seven miles apart to allow for targeted seeding. The company occasionally uses a plane to do the seeding when conditions are more appropriate for it.

Idaho Power also teamed up with several communities in the Upper Snake River area that had been using cloud seeding since the 1990s for irrigation. The partnership started in 2008 and it has allowed the program to grow to include 18 generators with plans for a 19th, as well as an additional 25 manual generators.

There have been a few studies on the effectiveness of cloud seeding and Idaho Power cites studies that show a roughly 5-15 percent increase in snowpack in the Payette River Basin, with an average of a 13 percent increase.

Studies on the effectiveness of the Upper Snake River program are still in the works, although there is an ongoing $13 million research project in Wyoming looking to better quantify the effects across three mountain ranges there.

Last winter Idaho Power spent roughly $1 million on the cloud-seeding program, and while that may sound like a lot to invest, Blestrud said the cost-benefit ratio is between 3-1 and 4-1, adding that company estimates show that the program adds roughly 200,000 acre feet of water to the system. That amount can generate roughly 100,000 megawatts of electricity, enough to power an estimated 7,900 homes.

Cloud seeding is not snow making, Blestrud cautioned; it's working with what nature already provides.

When a storm system comes across Idaho and into the West Central Mountains, Idaho Power meteorologists look to see if it meets the criteria they're looking for, then they target the layers of super-cooled water within the clouds.

The generators or plane then introduce silver iodide to super-cooled water--liquid water that is between -5 and -15 degrees Celsius--to encourage it to start freezing and drop out of the cloud as snow.

When cloud seeding started, dry ice was originally used to start the freezing process. Then scientists discovered that on a molecular level, silver iodide actually looks like an ice particle and makes a good seeding agent. These days, there are four different types of cloud seeding: winter, like what Idaho Power is doing; hail suppression, which is used most commonly in the Plains; rain enhancement, which is a byproduct of hail suppression; and fog suppression, commonly used at airports to improve visibility.

Idaho Power is one of only a few power companies utilizing cloud seeding as a tool. In fact, according to the National Oceanic and Atmospheric Administration, in 2001 only 66 cloud-seeding projects were operating in the West.

Idaho Power officials are quick to point out that increased snowpack not only benefits the utility company, but it means there's more water for all water users, be they irrigators, recreationists or fish and wildlife.

Idaho Power started its annual program Nov. 1 and will run it through the end of April 2013, depending on what Mother Nature adds to the mix.

But Blestrud is careful to add that snow doesn't come from every storm--it has to be the right storm.

"When it's a thick, deep storm and it's cooler, we can do a lot with that," he said. "[Cloud seeding] can't offset a drought--we can't seed if the clouds aren't there."

Forecasting what nature is going to do is the purview of the National Weather Service. Each day, the Boise office releases a weather balloon to get a better picture of what's happening above the surface. Combine that info with numerical weather prediction models and it helps meteorologists understand the larger patterns.

Breidenbach said that while the most accurate predictions are only a few days out, longer-range predictions look at weather on a seasonal level.

This year has kept officials on their toes. A few months ago all, indicators pointed toward an El Nino winter, when warmer equatorial ocean conditions lead to a drier, warmer winter in Idaho. But over the last several weeks, it appears as if the ocean isn't going to warm as much as expected, keeping water temperatures near normal and creating what is called a neutral year.

"The dice are equally weighted at this point," Breidenbach said.

If it is in fact a normal winter, Boise could receive roughly 20 inches of snowfall over the season.

Of course, what is considered normal is changing this year. Percent of normal is measured in comparison to the past 30 years--but that 30-year period changes every 10 years. This year marks just such a shift, meaning the snowpack will be compared to the snowfall between 1981 and 2010 rather than 1971 to 2000, as it was last year.

Abramovich said that means the relatively wet 1970s will no longer be used as a comparison but the dry 2000s will, which affects the percent of normal statistic. For example, the Bigwood Basin finished the 2011-2012 winter with slightly below normal snowpack, but that same snowfall would be considered slightly above average this winter.

October's early snowfall was welcome by more than just ski areas. Abramovich said record-low rainfall in August and September makes a good snowpack even more important.

"After the long, dry summer, there's a big deficit in the soil moisture," he said. "Fall rain helps fill the void and prime the soil for next year's runoff."

Abramovich and the NRCS crew will be carefully watching the snowpack monitoring sites--known as SnoTel sites--measuring snow not only in inches but in snow water content, or the amount of water in the snow that will melt into runoff. In a typical year, Bogus Basin receives roughly 260 inches of snow and has a 10 percent water density, which means all that snow melts down to 26 inches of snow water.

The higher the elevation, the more precipitation and the colder the temperatures (roughly 3 degrees per 1,000 feet), meaning that a location like nearby Trinity Mountain, which sits at 7,700 feet, compared to Bogus Basin's 6,340 feet, gets roughly 380 inches of snow a year.

While reservoirs were drained to meet irrigation demands because of the extremely dry summer, Breidenbach said normal snowpack would be enough to refill the area's reservoirs. That is, as long as the snowpack doesn't melt as fast as it did last spring when sudden warm temperatures meant so much runoff water hit at once that reservoirs had to release some of it.

"That's why we depend so much on our winter snowfall," Abramovich said.

But when it all comes down to daily life, most skiers are simply hoping that they can make the snow work for them this winter by taking advantage of a long ski season. For them, Abramovich suggests a new favorite number: 41.

"Forty-one is the key number in Boise," he said. "It has to be at least 41 degrees in Boise to snow at Bogus."





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