Contamination known as acid-rock drainage enters waterways, such as Summit County's Snake River, that are used for making artificial snow. When the snow melts, the water can run into streams not previously polluted, further spreading the contamination, said the research team.
CU-Boulder's Andrew Todd and Diane McKnight of the Institute of Arctic and Alpine Research and Lane Wyatt of the Northwest Council of Governments describe how past Colorado mining is adversely affecting tourism, now a $9 billion industry. The paper will be published in the Sept. 23rd issue of Eos, published by the American Geophysical Union.
They note that the problem is not limited to Colorado or to the United States. Nationwide, mine contamination affects more than 12,000 miles of rivers and streams and 180,000 acres of lakes, according to the U.S. Bureau of Mines.
In Colorado alone, roughly 7,000 abandoned mines continue to leach waste minerals into more than 1,600 miles of streams. The state's long mining history is clearly visible to motorists on Interstate 70 heading west from Denver to the ski areas of Summit County in the form of orange mine tailings, weathered structures and even in the names of some communities and ski trails.
Colorado's severe drought has made artificial snowmaking essential at many ski areas, including Keystone and Arapahoe Basin, the focus of the authors' study. The main portion of the Snake River, which is contaminated with heavy metals, has been the source of Keystone's artificial snowmaking since 1971.
Heavy metals have been detected in headwater drainages within the ski areas, according to a recent study conducted by Hydrosphere, a regional consulting firm. Resort management is seeking to more than double the amount of Snake River water it utilizes for snowmaking. Currently, at the point where river water is diverted for this purpose, concentrations of zinc, cadmium and copper occasionally exceed criteria for aquatic life, including three of the four species of trout found in state streams.
Although periodic droughts are normal in Colorado, affecting at least 5 percent of the state periodically, ski resorts also are concerned about the potential additional impact of climate change, which could add to the problem of inadequate snow. Recent studies cited by the authors suggest that warming, under even the most conservative scenarios, could shorten the ski season, shift ski areas to higher elevations and eliminate marginal areas altogether.
One method of mitigating these effects would be additional snowmaking on a large scale, wrote the authors. Another is moving to a four-season strategy, with spring, summer and fall activities focused on fishing, golfing and rafting. Many of these activities depend on clean water supplies, however, and winter snowmaking, using less abundant and contaminated water, can adversely affect these other sports.
The authors observe that, at present, there are no reliable methods of mitigating acid-rock drainage at its source, the abandoned mines that dot today's recreational areas.
Both McKnight and Todd also are affiliated with the environmental engineering program at CU-Boulder.
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