After reviewing nominations submitted by grass-roots organizations, American Rivers ranks the rivers based on threats they face and whether a public policy decision is pending that will magnify or eliminate these threats. The report discusses how traditional methods of producing and consuming energy affects rivers. More than half of the nation's electricity is still generated by coal-fired power plants, which have scarred nearly 2.5 million acres of land in the United States and release harmful pollution into the atmosphere. That pollution often finds its way into rivers through acid rain and snowmelt, where it can kill and contaminate wildlife. Hydroelectric dams, which produce less than 10 percent of the nation's energy, can transform a river as profoundly as clear-cutting a forest, American Rivers contends.
Dams wash out important wildlife habitat and block migratory fish from their spawning grounds.
Conservation groups claim that the complex system of hydrolelectric dams in the Pacific Northwest has reduced the number of returning salmon in the region from about 16 million to less than 300,000. Often left out of the environmental debate surrounding oil drilling is the impact that it can have on rivers. Heavy drilling equipment can reduce water flows and disturb wildlife habitat in riparian areas. Most of the 14,000 oil spills that occur each year in the United States end up in freshwater bodies, the report finds. Natural gas consumption can harm rivers by withdrawing massive amounts of water to power steam turbines.