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Reservoir and Dam Removal. Orrin Babcock. Outline. Purpose of Dams Number of Dams in America Dam affect on the environment Selected publication Conclusion. Purpose of Dams. A barrier constructed across a waterway to control the flow or raise the level of water. - PowerPoint PPT Presentation
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Reservoir and Dam Removal
Orrin Babcock
Outline
• Purpose of Dams• Number of Dams in America• Dam affect on the environment• Selected publication• Conclusion
Purpose of Dams
• A barrier constructed across a waterway to control the flow or raise the level of water.
• freshwater reservoirs, fish hatcheries, hydropower, recreation, irrigation, navigation, and flood control
In the United States there are 84,134 dams
Environmental Effects
• River’s natural course and flow– Limits species present
• Water temperatures in the stream
Environmental Effects
• Redirect river channels– Tennessee Valley Authority (TVA) regulates the
Ocoee River• • Disrupt river continuity– Fish ladders
Environmental Effects
• Transform floodplains
• Sediment Buildup
Selected Publication
• “Trading off: the ecological effects of dam removal” by Emily H Stanley and Martin W Doyle 2003
• Study looked at dam removal in the state of Wisconsin
• Size and geographic limitations can be ignored; results should apply for all sizes and areas.
Dam Removal
• Species change within two years– Reservoir to riverine species– Less Common Carp, more bass and darters
Export of Sediments
• http://video.nationalgeographic.com/video/player/news/environment-news/us-condit-dam-breach-vin.html
Elevated levels of sediment can last from days to months depending on the size of the reservoir
Export of Sediments
• Fort Edwards Dam– 1st portion removed in 1973
• Led to elevated levels of polychlorinated biphenyls (PCBs) and oils
• Clogged Hudson River• 2nd portion removed in 1991– PCB’s doubled in striped bass
Export of Sediments
• Sediments can be nutrient enriched due to agriculture
• Sedimentation can have affects as far as 12km downstream
Removal is a Trade-off
• Dams separate wild and farm raised fish– Keeps the gene pools clean
• Removal restores the stream to its original state
• It also increases the sediment load and can scour parts of the bank
• Best to remove them before they fail– Save human lives
Conclusion
• Recent survey of 10 000 flood control dams, over 2200 sites were in need of maintenance
• The best case scenario for dams that generate limited revenue is to remove them, rather than spend the money to rebuild or repair them.
Personal Conclusion
• Respect Nature, If we didn’t have the desire to live so close to rivers we would have no need to dam them for flood control.
Questions?