Dams and biodiversity

Posted on September 26, 2009

Dam-building typically limits the natural variations in river flow and water temperature that are important to maintain aquatic biodiversity.  Controlled releases of water from dams can help to offset the loss of physical variation to some extent, but they don’t always improve biodiversity.  Releases from Granby Reservoir on the upperColorado Riverhad little impact on low macroinvertebrate diversity in the area just below the dam, where water flows and temperatures were both regulated.  In contrast, at a site 5 km downstream of the dam, where flows were regulated but temperatures were near-natural, macroinvertebrate communities were richer and similar in structure to those above the dam.  The main message from this study is that restoring natural flows may not succeed in restoring biodiversity unless other important deficits, such as the lack of thermal variation, are also addressed.  

Reference:  Rader, R.B., Voelz, N.J.,  Ward, J.V.  2008.  Post-flood recovery of a macroinvertebrate community in a regulated river: resilience of an anthropogenically altered ecosystem.  Restoration Ecology Vol. 16 (1), 24–33.