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?