There are two kinds of rivers. One meanders over a broad course, navigable by boats and barges. Rivers like this run slow and long, like the ones that surround my home town, Pittsburgh. The Allegheny totals 325 miles, the Monongahela, 128. The Ohio rambles a thousand miles before it finds the Mississippi.
The other type of river tumbles down steep hills. Icy, swift, and relatively short, with headwaters high in the mountains, traffic on this kind of river is limited to white water rafting.
Fast or slow, short or long, almost every large river in the U.S. is dammed. Seventy-five thousand large dams (higher than 6 feet), and many thousand smaller dams interrupt our country’s rivers and streams. Dams alter water temperatures, reduce water levels, and change the flow of rivers, causing coastal erosion. Some block fish from migrating. Today, many dams are old and unsafe, or no longer serve their original purposes. Only three percent now generate electricity.
With more miles of rivers and streams than any state in the continental U.S., Pennsylvania features 3,200 dams. Many were built more than 100 years ago to supply power for grain mills. Others provided water for drinking and irrigation, flood protection, and hydroelectric power. In 2010, thirty dams were removed in Pennsylvania, more than in any other state.
A national dam removal movement is gaining momentum. Benefits of dam removal include restoring river health and clean water, revitalizing fish and wildlife, and improving public safety and recreation. Currently in the U.S., more dams are being removed than built. By the end of this year, 1000 dams will have been removed in the U.S.
News from the Olympic Peninsula of Washington State, where I grew up, landed on the front page of national newspapers last month. The Elwha River, which supplies water to the region, is the site of the largest dam removal project in North America. After two years of preparation, contractors started the three-year process of simultaneously removing two huge dams (210 and 108 feet tall), which will open 70 miles of wild salmon habitat in pristine Olympic National Park. These dams were erected in 1913 and 1927, without fish ladders, so for 100 years the ecosystem of the largest watershed in the Park has lacked fish life. Hiking beside the river, you might not notice anything missing. But without fish, the river contains no food for native black bear or bald eagles.
Prior to construction of the dams, which were erected to supply power to timber and paper industries, the National Park Service estimates that 400,000 salmon migrated annually up the 45-mile river that links the Olympic Mountains to the Juan de Fuca Strait and the Pacific Ocean. The Elwha River currently supports only about 3,000 salmon, confined to five miles of habitat below the lower dam.