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National Pollutant Discharge Elimination System (NPDES)

Permit Limits-Watershed-based Permitting

Watershed-based permitting is a process that emphasizes addressing all stressors within a hydrologically defined drainage basin, rather than individual pollutant sources on a discharge-by-discharge basis. Watershed-based permitting can encompass a variety of activities ranging from synchronizing permits within a basin to developing water quality-based effluent limits using a multiple discharger modeling analysis.

The type of permitting activity will vary depending on the unique characteristics of the watershed and the sources of pollution affecting it. The ultimate goal of this effort is to develop and issue NPDES permits that optimally protect entire watersheds. EPA's Water Quality Trading Policy describes flexible approaches to meeting water quality requirements.


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Case Studies

To promote the innovative watershed-based permitting approach, EPA has generated a case study fact sheet series that presents an overview of watershed-based permitting efforts.

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