To cover several ski trails with manmade snow, you need a lot of water. According to SMI Snow Makers, it takes about 75,000 gallons (285,000 liters) of water to create a 6-inch blanket of snow covering a 200x200-foot area (61x61 meters). The system in a good-sized ski slope can convert 5,000 to 10,000 gallons (18,927 to 37,854 liters) of water to snow every minute!
Water is not a huge expense for ski resorts, however; and pumping this much water isn't incredibly bad for the environment. Most resorts pump water from one or more reservoirs located in low-lying areas. The run-off water from the slopes feeds back into these reservoirs, so the resort can actually use the same water over and over again. Moving this water around can have some negative effects on plant and animal life, though, so ski slopes must work hard to keep water levels fairly balanced.
A significant environmental concern, and one of a resort's biggest expenses, is power consumption. If a slope uses compressed air in its snow guns, it has to provide a lot of energy to run the large air-compressing pumps. It also needs a pump system to provide the water to the snow makers. These pumps are often run by diesel engines, which expel a high level of air pollution.
Ski resorts that use airless snow guns also need a good amount of power to run the machines' fans. These types of snow guns consume a lot less energy for every foot of snow they produce, but they are still major power draws. For most ski resorts, power consumption is the second biggest operating expense, just behind labor costs (snow-making alone requires a lot of manpower). No matter what sort of technology a resort uses, snow-making accounts for a high percentage of this power use.
Because of the expense of making snow, ski resorts have to develop a good strategy for when and where they are going to use their machines. A lot of the work involved in snow-making is the task of balancing the cost of running the machines with the benefits of extending the ski season. Efficient snow-makers make sure they don't waste power making snow where it won't do any good, and they are very careful to make snow only when it will stick around.
As we've seen, snow-makers have to take many variables into account to cover a slope with ideal skiing snow. The idea behind manmade snow is extremely simple; but actually getting it to work effectively is quite a feat. Many snow-makers describe the job as a challenging marriage of science and art -- the basic elements are precise weather measurements and expensive machinery, but you need instinct, improvisation and creativity to get it exactly right.
For more information on snow-making and related topics, check out the links on the next page.