BioEd Online

The 2006 winter Olympics is highlighting winter-sport enthusiasts' growing reliance on man-made snow, and the toll that this addiction could take on the environment.

All competitive ski and snowboarding events now take place largely on man-made snow. Unlike its natural counterpart, the machine-made white stuff can be carefully tweaked to make a more durable and consistent surface: one perfect for record-breaking attempts.

The Olympic ski resorts outside Turin, Italy, have extensive snow-making facilities and several new reservoirs were built for the games to supply water for snowmakers. In recent weeks they have been piling on man-made snow, as the natural stuff has proven rather thin on the ground in the Turin area this season.

Snow-making equipment is viewed as essential in most ski areas to guarantee coverage throughout the season. Nowadays, "natural snow is a bonus," says Rich Brown of snow-making technology company York Snow in Victor, New York, whose systems were used in the 2002 winter Olympics in Salt Lake City, Utah, and previous games.

Nature's copycats

The snow 'cannons' or 'guns' that manufacture snow mimic the natural formation of snowflakes. Snow machines typically force pressurized water through a nozzle, breaking it into a mist of tiny droplets, and then use compressed air or fans to blast them into the air. As the droplets cool, the molecules align and crystallize into ice particles.

The art to snow-making is adjusting the water and air to ensure that the water drops are small enough and sent far enough that they will freeze before they hit the ground. If the air temperature is quite high, for example, dropping the water content and upping the air would create smaller particles that are more likely to freeze.

Snow-making machines also frequently incorporate nucleating agents in the water: small quantities of materials such as bacterial protein, on to which the water molecules attach and freeze. By triggering freezing, these agents raise the temperature at which snow can be made.

Many resorts now use sophisticated computer systems that automatically adjust the air and water output from snow machines based on air temperature, humidity and wind, says Brown.

Skiing on ice

For race courses, experts adjust man-made snow to create a tough, fast and icy course rather than a powdery one. A ski course is also heavily groomed and often intentionally flooded to create patches of ice; these factors generally determine the speed of a race.

There are other reasons for snow manufacturing to be in demand, beyond the benefits of having a snow whose properties can be ordered up. Some predict that the need for snow will rocket with the warming effects of climate change, which are already pushing snow lines up the Alps.

But this comes with environmental costs, says Michel Revaz, of the International Commission for Protection of the Alps (CIPRA), a conservation group in Schaan, Liechtenstein. Making snow chews up energy and water, and can rob rivers and creeks in the surrounding ecosystems.

One way to conserve the mountain environment, Revaz says, would be to reuse winter sports competition facilities rather than building new ones. "It's not clever to build a new piste every four years," he says. "It's time to say stop."