Across the United States, 2.5 million dams of all sizes block and harness rivers; of those, 80,000 dams are great than 6 feet high and store a combined total of approximately 1 billion acre-feet - the equivalent to one year's runoff (Graf, 1999). Dams serve a wide range of purposes such as hydroelectric power, water supply and irrigation, recreation, shipping, and flood control; they have become integral to the identity of some communities. The Huron River Watershed alone has no fewer than 98 dams, but a comprehensive inventory likely would increase the tally.

Dams have severe negative impacts on rivers as they alter chemical, physical and biology processes. Downstream environmental costs of dams have only recently captured scientific attention as the negative impacts became obvious in the past two decades.

• Dams block free-flowing river systems and impede a river's flushing function that enables sediment and nutrients to be transported downstream. Instead, sediment builds up behind the dam.
• Dams fragment rivers and block movement of fish, mussels and other species.
• Dams have been a contributing factor (or the sole cause) of many species to become threatened, endangered, extirpated, or extinct; in part because they are located on prime spawning habitat. Many fish species require high gradient, well-oxygenated water and gravelly streambeds for spawning, which are the same parameters that provide a favorable dam site.
• Dams alter water temperatures, dissolved oxygen levels, turbidity and salinity, both upstream and downstream of the structure.

The Huron River system is typical of Great Lakes Basin river in that this formerly free-flowing river is interrupted by dams on its tributaries and mainstem. Unique to the Huron River is the opportunity to:

• restore more than 100 miles of a freshwater ecosystem,
• expand viable habitat for sensitive fish, mussel and benthic macroinvertebrate species, and
• capture important data during all phases of restoration in order to benefit future dam removals.

As more dams age, what to do about a dam is a question that will face increasing numbers of communities, dam owners and government agencies. Finding funds to cover costs for the studies, engineering and restoration of dam removals likely will grow in difficulty as more dams are slated for removal. Dam removal experts suggest tying dam removal to community redevelopment, as river restoration generally increases property values in the community. Whichever tools are used, success in restoring the Huron River and improving the communities through which it flows is more likely in the context of strong, comprehensive state and national programs.

Last Updated: February 2006