What are the environmental pros and cons of damming rivers for hydropower?

What are the environmental pros and cons of damming rivers for hydropower?

—Kartikeya Singh, Greenville, SC

Hydropower—electricity generated from turbines churning in dammed rivers—has been part of America’s energy mix since the 1880s when the world’s first hydroelectric plant began operation on the Fox River in Appleton, Wisconsin. By the 1940s, hydropower accounted for about 40 percent of America’s energy needs.

Hydropower today accounts for only about 10 percent of electricity generation in the U.S., but it plays a crucial role in keeping regional economies afloat, such as in parts of the Pacific Northwest where dammed rivers provide 80 percent of the electricity needed by area residents and businesses.

Many environmentalists still cheer hydropower as the only major source of electricity that is renewable and non-polluting. Unlike energy generated from fossil fuels, hydropower plants do not emit the waste heat and gases that are major contributors to air pollution, global warming and acid rain. Nor do they require the environmentally destructive mining and drilling needed to acquire coal, natural gas and oil.

Another environmental benefit of hydropower is its ability to help control otherwise wide fluctuations in water flow in and around rivers. By increasing water flow during dry months and reducing flow during periods of heavy run-off, hydropower projects help to enhance aquatic habitats while preventing damage to vegetation and wildlife along stream banks.

Despite the benefits, however, hydropower does have its environmental costs. In general, damming rivers and installing hydropower turbines permanently alters the environment and disrupts naturally functioning ecosystems. For example, populations of wild salmon and trout—which migrate back and forth between upstream spawning grounds and the ocean—have fallen off by as much as 90 percent in parts of the U.S. due to the damming of major coastal area rivers for hydropower.

Last year, one of Maine’s major utilities agreed to remove three dams on the Penobscot River and its tributaries in order to restore declining populations of wild Atlantic salmon. Environmentalists are calling for similar measures in the Pacific Northwest to save dwindling populations of Coho and Chinook salmon.

As more harmless forms of renewable energy such as solar, wind and hydrogen become more economically viable, hydropower will likely play an increasingly smaller role in America’s energy mix. Indeed, only time will tell whether these more efficient sources of renewable energy might finally end the need for hydropower while making fossil fuels obsolete as well.

CONTACTS: American Rivers, (202) 347-7550, www.americanrivers.org; U.S. Army Corps of Engineers” Hydropower Page, www.corpsresults.us/hydro/default.htm; National Hydropower Association, www.hydro.org.