Stanley, Emily H. and Martin W. Doyle. “Trading Off: The Ecological Effects of Dam Removal.” Frontiers Ecol Environ 1.1 (2003): 15-22. (reviewed by Adam Kendall)
Summary
This article focuses mostly on the ecological effects of removing and dewatering dams. Using established research and some hypotheses, the authors outline the effects (primarily when it comes to sedimentation and related problems) of dam removal on the immediate environment and on the downstream river.
Sedimentation, which is causing dams to become useless before the end of their planned lifecycle, is the cause of much concern around the discussion of dam removal. There is some speculation involved as to the effects of a sudden release of sediments into the stream following the drawdown or breaching of a dam, and conflicting research has been compiled. Some studies show that sediments contain harmful chemicals, such as were present at a dam breaching in New York State, where chemicals were released downstream into the Hudson River on two occasions, both times encouraging higher levels of concentration in fish and higher mortality rates.
Other research stipulates that particulates released into the stream can, in some cases where industrial or chemical pollution is not present, encourage growth of plants and other aquatic life downstream, by releasing vital and usually limiting elements into the stream, such as phosphorus or ammonia. The travel of sediments, however, is still much a mystery, and is different for nearly every case studied. Also, the effects of large dams (very few of which have been removed or drawn down) on river flow regimes and water quality are largely unstudied, so the removal of these types of dams (such as on the lower Snake River), as the authors state, would likely have larger and more diverse impacts on the environments, both immediate and subsidiary.
Critique
The authors of this article seem to be esteemed in the field of dam removal research. Both appear as co-authors of numerous articles on the subject, and are comfortably acquainted with the relevant research. However, their research, and the focus of the article, is on smaller dams and the effects of their removal, which may not have the most relevance to the study of dam removal in the Columbia watershed, and specifically the lower Snake River, where the dams under consideration are all considered “large dams.”
The article, still, is useful in its discussion of the principles of dam removal ecology, and the way it explains the dynamics of sediment transport, specifically following reservoir drawdown and dam breaching. It effectively portrays the process of re-channelization in the reservoir area, and how this effects the growth (or death) of both riverine and reservoir-dwelling species. While the article seems to be geared more toward outsiders, it still relies on scientific examples, including some in the Columbia Basin, to prove its points, and as such may be considered a reliable source for information on the ecological effects following dam breaching and removal.
Robert D. Clark Honors College, University of Oregon
HC 441: Science Colloquium, Columbia River Ecology
Fall term, 2005
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