Dams
Argo Dam, in Ann Arbor, Michigan, blocks the flow of the main branch of the Huron River.
Dams
Across the United States, 2.5 million dams of all sizes block and harness rivers. Most of them are quite small. Of those 2.5 million dams, only 80,000 are more than six feet high.
Dams serve a wide range of purposes, such as providing hydroelectric power, water supply, and irrigation, supporting recreation and shipping, and managing flood control. Many dams have become integral to the identity of their communities. The Huron River Watershed alone has 97 impoundments, and a comprehensive inventory would likely increase that number.
Beneficial functions notwithstanding, dams produce severe negative impacts on the rivers they harness. Dams alter a river’s chemical, physical, and biological processes. Over the past two decades these negative impacts have become more obvious, but the environmental costs of dams have only recently captured scientific attention.
- Dams cause the build-up of sediment. They block free-flowing water and impede the river’s flushing function, as well as the transport of nutrients and sediment downstream.
- Dams fragment rivers and block the natural movement of fish and other aquatic species.
- Dams contribute to, and sometimes are the sole cause of, many species becoming threatened, endangered, or extinct. Prime dam sites often are prime fish spawning sites.
- Dams alter water temperatures, dissolve oxygen levels, and produce turbidity and salinity, both upstream and downstream of the structure.
Dams on the Huron
The Huron River system is typical of rivers and tributaries in the Great Lakes Basin. What was once a free-flowing river system is now interrupted by dams on both the main stem and the tributaries. However, dams do not have to be permanent structures, and concerned citizens can bands together to remove dams and alleviate their negative impacts. In the Huron River Watershed, we have the opportunity to
- restore more than 100 miles of a freshwater ecosystem;
- expand viable habitat for sensitive species – fish, mussels, and macro invertebrates;
- capture important data that will benefit future restoration efforts.
The removal of dams is a complex issue. The decision to remove or not to remove a dam involves many considerations, as do the decisions about what methods to use to restore the free-flowing stream. Such considerations include dam safety, environmental impact (i.e. possible toxins in the accumulated sediment), and economic issues.
As the dams along the Huron continue to age, increasing numbers of communities, dam owners, and government agencies will face decisions about dam removal. And, it will become increasingly difficult to secure the funds needed to cover the costs of dam removal studies, engineering, and restoration. Some experts recommend linking dam removal to community redevelopment, because river restoration generally increases property values. Whatever plan is chosen, success in restoring the Huron River and improving the watershed communities is more likely to be achieved through strong, comprehensive state and national programs.
For more information about Argo Dam, go here.
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