Tailwater fishery

Rivers that pour out of a dam are hard to characterize ecologically since their chemistries depend upon the impoundments above them. In general, they are highly productive, due to the relative constancy of environmental conditions (flow rates, annual temperature fluctuations, pH, nutrient input, etc.). Some of the world’s greatest fisheries are of this type.

Links
  http://www.tva.gov
http://www.cbr.washington.edu