EPA releases final version of “connectivity report”

The U.S. Environmental Protection Agency (EPA) recently finalized the report titled Connectivity of Streams and Wetlands to Downstream Waters: A Review and Synthesis of the Scientific Evidence. EPA indicates that the purpose of the report is “to summarize current scientific understanding about the connectivity and mechanisms by which streams and wetlands, singly or in aggregate, affect the physical, chemical, and biological integrity of downstream waters.”

The report is being used to inform a joint EPA/Army Corps of Engineers rulemaking process to clarify federal Clean Water Act (CWA) jurisdiction. The CWA authorizes federal jurisdiction over “navigable waters” broadly defined in the Act as “waters of the United States.” The Act does not, however, clearly define which rivers, streams, and wetlands are “waters of the United States,” and recent court cases have not resolved the question.

The report was prepared by staff in EPA’s Office of Research and Development. A September 2013 draft of the report was reviewed by EPA staff, a panel of the EPA’s Science Advisory Board, and the public.

Conclusions in the report include the following.

  • All streams, regardless of their size, and all wetlands and open waters in riparian areas are connected to downstream waters. 
  • Non-floodplain wetlands and open waters may be connected to downstream waters, and evaluations of connectivity may be possible on a case-by-case basis.
  • Variations in the degree of connectivity are determined by the physical, chemical and biological environment, and by human activities.
  • The contributions of individual streams and wetlands are cumulative across entire watersheds, and their effects on downstream waters should be evaluated within the context of other streams and wetlands in that watershed.

The report is available at http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=296414.