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New National Network of Reference Watersheds Increases Access to Information
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Do you need reference watershed information for your data analysis project? Check out the
National Network of Reference Watersheds (NNRW), a new Web-based resource developed
by the National Water Quality Monitoring Council (NWQMC), in cooperation with the
U.S. Geological Survey (USGS) and the U.S. Environmental Protection Agency (EPA). The
NNRW provides quality-assured data and information for minimally disturbed watersheds (refer-
ence watersheds) and freshwater stream monitoring sites across the continental United States. The
website allows users to search the NNRW database of reference watersheds, identify watersheds of
interest, and download watershed information and water quality data.
What is a Reference Watershed?
The NNRW defines reference watersheds as those minimally disturbed by human activity,
and preferably in an area protected from human-induced changes. The EPA refers to these as
healthy watersheds. The database includes many types of reference watersheds; some are consid-
ered to be reference watersheds based on any number of characteristics, such as low hydrologic
disturbance, limited land use disturbance, water quality, stream
* .'+ watersheds can be used to measure changes in soil chemistry,
V it . j* vegetation, water quality and biology through time, as well as to
- " "compare to disturbed watersheds. The NNRW currently con-
tains information on almost 2,500 reference watersheds across
* - the United States (Figure 1).
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Core Sites: 504
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Figure 1. The National Network of Reference Watersheds
currently includes 2,474 minimally disturbed reference
watershed sites (top map) and 504 pristine core watershed
sites (lower map). New sites will be added as the network
expands.
A subset of the reference watersheds, referred to as the "core
watersheds," includes those watersheds that have stream dis-
charge data available and are considered the most pristine, based
on specific land use criteria. The NNRW currently contains
information for more than 500 core watersheds (see Figure 1).
To be considered a core watershed, the drainage area must have:
* Low hydrologic disturbance (dams, water withdrawal, pollut-
ant discharge, etc.).
* No row crops present.
* Less than 5 percent of land in pasture.
* No medium or high impact development (areas with a mixture
of constructed materials and vegetation, where impervious
surfaces account for 50-79 percent or 80-100 percent of total
cover, respectively).
* Less than 10 percent total development.
* More than 75 percent of land covered by natural vegetation or
is barren (bare rock or other earthen material).
Users may search the database of reference watersheds by defining watershed characteristics; data
will be queried and accessed through the NWQMC's Water Quality Portal (see box, next page).
At present, the majority of the reference watersheds provided on the NNRW are from the USGS'
GAGESII dataset. Several hundred EPA watersheds are also included; additional watersheds will
be added as other federal, state, tribal, interstate, academic, local and private sector organizations
choose to participate in the network.
"Anyone can submit a site to the network," explains Mike McHale, Research Hydrologist with
the USGS. "We have a template of information that must be supplied for the site to be search-
able, and a shapefile is necessary for us to calculate all of the watershed land use characteristics.
The only requirement for the general NNRW database is that the person or agency submitting
the watershed justify why they consider it a reference watershed. For the core watershed section of
JANUARY 2016, ISSUE #99 NONPOINT SOURCE NEWS-NOTES 3
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NONPOINT SOURCE NEWS-NOTES 3
JANUARY 2016, ISSUE #99
