SKI AREAS HAVE A BIG THIRST

Fresh white powder glistened on the slopes of the Sugarbush mountains in Vermont all winter, ever ready for eager skiers. To produce each one-foot-deep acre of snow, snowmaking machines used 150,000 gallons of water.

A large ski area such as the Sugarbush Resort in Warren, Vt., with 250 acres of trails, uses 380 million gallons of water annually for snow production. "Without a doubt, snowmaking is the life blood of the ski industry," says Robert Apple, director of planning and development at Sugarbush. "We could not exist without it."

Local rivers and streams often provide the water. As ski areas seek to expand and their use of water from the streams increases, so do the concerns about environmental damage.

"The issues center on reduction of stream flow and reduction in habitat during the most critical time of the year for the fish," says Joseph McKeon, fisheries biologist for the United States Fish and Wildlife Service in Laconia, N.H.

"The flow is naturally lowest during the months of January and February," says Rod Wentworth, impact assessment specialist for the Vermont Fish and Wildlife Department. Heavy water demands for snowmaking, combined with low flow, can stress aquatic life through ice buildups, which can freeze incubating fish eggs and invertebrates or create ice dams that can dry up a stream.

Government agencies determine the exact amount of water that can be withdrawn from a river by using historical flow data, and more recently, computer modeling that simulates worse-case scenarios for the specific site, says Mr. McKeon.

The water returns to the stream during the spring melt. Although few studies show the effects of snowmaking on aquatic life, Mr. Wentworth says, "We have to apply a little bit of conservatism based on what we know happens under natural conditions."