Adverse effects of dams on river and stream ecosystems have been well documented (Petts 1980, Cushman 1985, Bain et al. 1988, Ward and Stanford 1989, Benke 1990, Doppelt et al. 1993, Ligon et al. 1995, Shuman 1995). For example, water quality may decline in impounded streams when excessive nutrients, sediments and aquatic plants accumulate in an impoundment. Flow patterns reflecting normal high and low water conditions may also be fundamentally altered, affecting stream channel configuration, wildlife habitat, and many other physical and biological processes. Dams also limit normal movement of aquatic organisms and organic material.

Additionally, improper maintenance can increase the risk of failure during flood events, resulting in fish kills, habitat destruction, and release of large amounts of sediment that may contain toxic contaminants. The MDEQ has inventoried 2,503 dams across the State, ranging in size and function from large actively generating hydropower dams to small earthen dams. Approximately 70% of Michigan's inventoried dams are small, privately owned, non-power-generating dams. Of the inventoried dams, more than 50% are more than 50 years old, or past the average life expectancy of a dam (American Rivers et al. 1999). As evidenced by dam safety reports, many older dams are deteriorating due to age, erosion, poor maintenance, flood damage, ice damage and poor design. Dams such as these are at significant risk of failure, particularly during high flow events. Dams that no longer serve any useful purpose should be removed to avoid catastrophic failure, eliminate dam maintenance and liability costs, and restore natural river functions. Adverse effects of dams on the health and viability of rivers and streams can be reversed with dam removal.

Conservation Needs to Address Dam Threats:

Land, Water & Species Management

• Review any new dam recommendations for societal benefits and ecological effects
  
  
• Implement dam operation recommendations that mimic natural riverine conditions and temperatures, protect and maintain desired aquatic communities, protect recreational uses, and, where possible, rehabilitate natural resources degraded by the dam
  
  
• Schedule impoundment drawdowns to minimize adverse effects to wildlife species that use impoundment areas

Law & Policy

• Seek modification or voluntary removal of dams when natural resources have been affected, but can be mitigated through modification
  
  
• Seek removal of dams where they serve little or no purpose and there is a reasonable expectation that removal will benefit the environment and aquatic resources

Research, Surveys & Monitoring

• Continue to develop and test dam operations that best mimic natural riverine conditions and temperatures, protect and maintain desired aquatic communities, and protect recreational uses
  
  
• Conduct research on the effects of timing and extent of impoundment drawdowns to help minimize adverse effects to wildlife species that use impoundment areas
  
  
• Track dam location and function for use in providing recommendations for dam retention or removal