To many, run-of-the-river dams, of which there are over 67,000 greater than 25 feet high in this county, appear environmentally benign. Indeed, hydroelectric dams are often praised as the least environmentally damaging of traditional energy sources. However, in addition to environmental problems stemming from dam construction, such as flooding, destruction of fish and wildlife habitat, and loss of natural river flows, the operation of dams, especially large impoundments such as hydroelectric projects, can create significant water quality problems. Water stored in reservoirs loses oxygen and can gain higher concentrations of dissolved metals and harmful chemicals. Water spilled over dams of substantial height often acquires high levels of suspended gases. Dam-engendered changes in the temperature and chemical content of river water can be harmful to aquatic life and have occasionally resulted in large fish kills.¹ Such problems can be controlled for the most part by careful control of certain aspects of dam operation. But, while construction damages have been minimized as a result of planning and regulation under the Federal Water Pollution Control Act (FWPCA)² and other federal statutes, much of the water pollution resulting from dam operations remains essentially unregulated.³

The FWPCA does not directly address the question whether dams are to be regulated as point sources under the national pollutant discharge elimination system (NPDES). Since it is undisputed that many dams contain discharge outlets that are "discernible, confined, and discrete conveyances" they seem to satisfy the §502(14) definition of a point source.⁴ Nonetheless, the Environmental Protection Agency (EPA) generally treats them as nonpoint sources because under EPA's interpretation of the Act, dams do not "discharge pollutants" within the meaning of §§502(12) and 502(14).⁵ The Agency contends that dam-induced changes in water quality do not constitute a discharge since arguably dams do not add anything to the waters they impound. Consequently, NPDES permits have, with few exceptions, not been required for dam operation.⁶