Western US wilderness under siege. Beauty of Rocky Mountain rivers: their beauty belies `heavy metal' contamination. Mining residues pollute runoff on both sides of the Continental Divide

The peaks high above this mountain change color this time of year as immense snowfields vanish in the wake of rising temperatures. Brooks, ponds, and waterfalls appear almost overnight, and the valley's two rivers - the Crystal and the Roaring Fork - swell and pick up speed. The beauty of the spring thaw, however, belies the quality of the water it releases. High concentrations of lead, copper, and cadmium from abandoned mining sites pollute the Roaring Fork almost from its source; the same ``heavy metals,'' along with zinc and mercury, contaminate the Crystal, which empties into the Roaring Fork and then, 10 miles downstream, into the Colorado River.

On the other side of the Continental Divide, the situation is even worse. Where the Roaring Fork heads west, tributaries of the Arkansas River head east. By the time they descend the few miles to the mining town of Leadville, the streams have picked up enough iron, zinc, manganese, cadmium, sulfate, and lead to harm aquatic life for more than 100 miles downstream.

Despite the popular image of Colorado's Rocky Mountains as a pristine wilderness, the sullying of high-country water has proceeded virtually unchecked for more than a century, since miners first flocked to the region in search of gold, silver, and other ores. The more than 10,000 mines they opened and the mill tailings they left behind are washed continually by melting snow and rain. Particles of exposed metals mix with the water and flow into rivers, subterranean ground water, and pasture lands.

Many officials are expressing increasing concern this spring about the extent and severity of the pollution.

``The question of water quality and quantity has become one of the hottest political issues in the state,'' says Sen. Tim Wirth (D) of Colorado, who serves on the Energy and Natural Resources Committee of the United States Senate. ``It is no longer possible to exploit and use up this resource.''

In compliance with provisions added to the the federal Clean Water Act last year, the Colorado Department of Health last month released a comprehensive study on surface water quality in the state. The study identifies heavy-metals pollution as the most serious ecological threat to mountain water systems.

``The primary concern resulting from metals concentrations is the chronic or toxic effect on aquatic organisms. The bioaccumulation of these toxic substances in aquatic organisms may also affect higher organisms in the food chain,'' the report states.

Fish and other wildlife have disappeared from numerous mountain streams and rivers. Health officials stress that scientists have established no definitive link between this pollution and public health problems, but they suspect that contaminated water may be the source of potentially toxic levels of lead found in the blood of children living in Leadville and Telluride, a mining community-turned-ski resort.

``The types of health problems that we've looked at ... entail problems principally from lead, which can cause neurologic system disorders, learning disorders, and, in really excessive levels, other types of disorders including birth defects,'' says Thomas Looby, assistant director of the Health Department.

Concern has also been galvanized by a new documentary film, ``Downwind/Downstream,'' shown throughout the state last month by its writer and director, Christopher McLeod. The award-winning film, viewed at the Health Department, the Colorado legislature, and the regional office of the US Environmental Protection Agency (EPA), discusses heavy-metal contamination as well as the effects of acid rain and snow.

The film emphasizes the state's unique responsibility to prevent pollution, with more than 10 million people throughout the West depending on water from the Arkansas, Rio Grande, South Platte, and Colorado Rivers, all of which have their headwaters in the Colorado Rockies.

``We've found that there are heavy-metal mines and other sources of pollution at the headwaters of all of the major rivers coming out of the mountains - water that goes as far away as New Orleans and Los Angeles. We may be the first civilization to be systematically poisoning itself at its source,'' says Hunter Lovins, president of the Rocky Mountain Institute, a nonprofit foundation specializing in resource and security issues.

All major cities in the West have sophisticated water-treatment facilities to remove heavy metals and other toxins from rivers and reservoirs used for drinking water. Hence, health officials are more concerned about subterranean ground water, which can absorb heavy metals and, when tapped by wells, endanger public health. More than three-fourths of the state's public water system and about 150,000 private wells draw on ground water.

Since much of the heavy-metal pollution has existed for decades, the cleanup debate has centered on who should take responsibility for past mistakes. Max Dodson, the EPA's director of water management in the six-state region including Colorado, acknowledges weaknesses in federal legislation on mining wastes.

``We're at the top of the watershed, and whatever we do up here has a lot of impact,'' he says. ``It's now time for EPA, the state, industry, professional groups, and elected officials to really be innovative in solving this problem.''