Adopt Narrative Biological Criteria
Building off the data base and biological assessment methods, EPA
recommends that States and Tribes incorporate into their water quality
standards narrative expressions describing the reference biological
condition of aquatic communities inhabiting waters assigned a given
designated aquatic life use. These narrative expressions may stand
separately from or be included as part of the existing narrative
water quality criteria or "free forms" already included
in State and Tribal standards. These expressions may also take the
form of refined and expanded aquatic life use descriptions referencing
expected aquatic communities associated with attainable aquatic
life uses.
Steps in adopting narrative biological criteria:
- Perform bioassessments on all surface waters
- Determine appropriateness of designated aquatic life uses and
refine as necessary
- Determine temporal variability of reference sites
- Ensure adequacy of programs to preserver exceptional waters
- Begin implementing management practices to restore degraded
waters and to identify and address the causes of degradation
Example - Arkansas Adopts Narrative Biological Criteria
Arkansas adopted narrative biological criteria
into it's water quality standards that formerly establishes how
its use classification scheme for aquatic life is operationally
defined (".. must demonstrate aquatic life communities which
are similar in variety and abundance to least-disturbed waters within
the same ecoregion and with similar hydrologic conditions.").
The narrative further specifies that the measurements of the aquatic
community should include fish community structure and other types
of aquatic life such as benthic macroinvertebrates. Detrimental
changes to the aquatic community will be determined by statistically
significant differences in results from reference conditions and
the waters under evaluation.
Arkansas's narrative biological criteria establishes a basic framework
for development of numeric biological criteria:
- Explains how the designated aquatic life uses will be refined
(least impaired bioregional reference conditions)
- Explains how the biological community will be measured (community
metrics for fish and other assemblages)
- Explains how detrimental changes to the biological community
will be evaluated (statistically significant differences between
reference conditions and test sites).
The State's narrative biological criteria are currently based on
fish community structure such as taxonomic group dominance, functional
groups, key species, and sensitive species. For example in the Arkansas
use class Typical Gulf Coastal Ecoregion (i.e., South Central Plains)
the narrative criterion reads:
"Streams supporting diverse communities of indigenous
or adapted species of fish and other forms of aquatic life. Fish
communities are characterized by a limited proportion of sensitive
species; sunfishes are distinctly dominant, followed by darters
and minnows. The community may be generally characterized by the
following fishes: Key Species-Redfin shiner, Spotted sucker, Yellow
bullhead, Flier, Slough darter, Grass pickerel; Indicator Species-Pirate
perch, Warmouth, Spotted sunfish, Dusky darter, Creek chubsucker,
Banded pygmy sunfish".
Assessments of designated aquatic life use support have utilized
relative abundance comparison of all species, numeric indicators,
and multi-metric scoring techniques. The assessed waterbody is compared
to least disturbed ecoregion reference data and/or to data from
a local reference stream. Future plans are to incorporate more recently
developed data on fish and physical habitat into the reference data
base and to expand the data base to include information on the benthic
macroinvertebrate community.
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