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 * __Dam! To Remove or not__**?

Dam Removal is a contentious issue around the United States. Advocates both in favor of and opposed to removal have many strongly held beliefs to defend their position. The following are two such examples:

__Removal of Dam:__ A common argument for removal of dams is to return the riverine ecosystem to its natural state of being. Specifically, this view is held amongst those who would like to see increased passage amongst favorable fish species, such as trout and salmon. This argument was illustrated by the fishing guide in the videos, who was interested in seeing more trout and salmon, high revenue fish, in order to increase his potential for drawing customers. In a study by Angela Bednarak of the University of Pennsylvania, it was found that in almost all cases the removal of the dams resulted in increased fish movement. Also, a shift from lacustrine to riverine species was often noted, which, depending on stakeholders' perspective could be perceived as a negative effect if species favoring slow moving water were desirable. Furthermore, it was seen that, in the long term, the river returned to its natural state of riffles and a gravel and cobble substrate resulting in an overall increase in biotic diversity. (pg 807-808)

__Retention of Dam:__ While most arguments against the removal of dams revolve around the financial aspects of the removal, there are some environmental concerns. Of these, the concern about dramatically increased sediment flow from the dam impoundment following removal is most often represented, especially in situations where said sediment contains potential contaminants and heavy metals. This position was taken by the stakeholder representing a mother, concerned for the well being of her children in the aftermath of removal of the dam. In a study by J.P. Giesy et. al in the August, 1994 edition of the //Archives of Environmental Contamination and Toxicology//, it was found that there were high densities of PCB's and other toxicants in fish specimens collected just above and below three dams in Michigan. While it has been proven that contaminants do accumulate in the sediments above bridges, there is yet to be much study as to the long term effects of these contaminants being washed out. However, the short term burst of PCB's is still a potential concern.

__References:__ Image: Academy of Natural Sciences website, Gallery of Small Dams. http://www.ansp.org/research/pcer/projects/small_dams/sample_dams.php

Bednarak, Angela T,. Undamming Rivers: A Review of the Ecological Impacts of Dam Removal. Environmental Management. 2001. Vol. 27, No. 6. 803-814

J. P. Giesy et al. Contaminants in fishes from Great Lakes-influenced sections and above dams of three Michigan rivers. II: Implications for health of mink. Archives of Environmental Contamination and Toxicology. 2004. Vol. 27, No. 2. 213-223.