United States
             Environmental
             Protection Agency
 Office of Research
 and Development
 Washington, DC 20460
National Health & Environmental
Effects Research Laboratory
EPA/600/F-09/008
     June 2010
                                   Western Ecology Division
                    Non-Navigable  Streams & Wetlands
      Research on Non-Navigable Streams and Wetlands
                         is a Critical Need
 In 2006, the US Supreme Court
 addressed jurisdiction of non-
 navigable waters and adjacent
 wetlands (NSW) under the
 Clean Water Act (CWA).  The
 Rapanos decision resulted in two
 criteria for determining CWA
 jurisdiction of NSWs: their hy-
 drological permanence and
 whether they have a "significant
 nexus" (contribute to the func-
 tional integrity of navigable
 waters).
above: Project member Joe Ebersole in-
vestigating NSW contributions to criti-
cal coW water habitats for native fish in
Oregon's upper Grande Ronde River.
In 2008, scientists from EPA's West-
ern Ecology Division (WED) and
colleagues published a paper propos-
ing an approach for examining some
of the scientific issues raised by the
Rapanos decision. WED's NSW Pro-
ject is using this approach to develop
information and methods that could
help assess hydrologic permanence
and significant nexus.
The Project's research includes:
• Field testing of the Oregon
Streamflow Duration Assessment
Method. This method, which was
jointly developed by EPA's Region
10/Oregon Operations Office and
Office of Wetlands, Oceans and
Watersheds, and the Army Corps
of Engineers (Portland District),
assesses over 20 environmental fac-
tors in the field to distinguish be-
tween ephemeral, intermittent and
perennial streams. In partnership
with EPA's Region 10/Oregon Op-
erations Office, the NSW Project is
conducting a two-year study to test
and improve the method at over 170
sites across Oregon during wet and
dry conditions.
             An intermittent stream in John Day,
             Oregon
             (See: http://yosemite.epa.gov/R10/
             ecocomm.nsf/wetlands/
             oregonstreamflow)
             • Development of a map of Hydro-
             logic Landscape Regions (HLRs)
             for Oregon that will form part of a
             system for classifying the effects of
             NSWs on navigable waters. A
             classification system will provide
             context for  considering the aggre-
             gate function of NSWs. The HER
             maps could also inform a number
             of other applications that require a
             broadscale hydrologic perspective.
             • Other components of the Project
             examine the connectivity, or
             "significant nexus," of NSWs with
             respect to fish habitat, nitrogen
             removal, and water source.
                 Figure, left, shows the following:
                       Navigable water
                       Non-navigable stream
                       Adjacent wetland
                       Perennial streamflow
                       Intermittent streamflow
                       Ephemeral streamflow
           Such information should help EPA staff identify waters subject
           to CWA regulatory jurisdiction in light of the Rapanos decision,
           and could inform future policies and legislation.
                    Project Lead Dr. Jim Wigington (541) 754-4341
                     Western Ecology Division, NHEERL USEPA
                        200 SW 35th St. Corvallis, OR 97333
                              http://www.epa.gov/wed

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