United States
Environmental Protection
Agency
Environmental Research
Laboratory
Corvallis, OR 97333
Research and Development
EPA/600/S3-87/025 August 1988
&EPA Project Summary
The Ohio Stream
Regionalization Project: A
Compendium of Results
Thomas R. Whittier, David P. Larsen, Robert M. Hughes, Christina M. Rohm,
Alisa L Gallant, and James M. Omernik
Regional patterns in terrestrial
characteristics can be used as a
framework to monitor, assess and
report the health of aquatic
ecosystems. In Ohio, five ecological
regions were delineated using spatial
patterns in land-surface form, land
use, soil and potential natural
vegetation. We evaluated this
framework by studying the water
quality, physical habitat, and fish and
macroinvertebrate assemblages of
109 minimally impacted repre-
sentative streams. Water quality and
fish assemblages showed clear
regional differences. The highest
quality water and fish assemblages
were consistently found in the
southeast ecoregion and the lowest
quality in the northwest ecoregion.
We found no clear regional patterns
in macroinvertebrate assemblages
and limited regional patterns in
physical habitat
This Profect Summary was
developed by EPA's Environmental
Research Laboratory, Corvallis, OR, to
announce key findings of the
research project that is fully
documented in a separate report of
the same title (see Project Report
ordering Information at back).
Introduction
To implement the mandates of the
Clean Water Act of 1977 (CWA), many
state environmental protection agencies
have relied on statewide chemical criteria
that presumably protect fish, shellfish,
and wildlife. These agencies increasingly
face a need to address the goals of the
CWA more directly, through regional
chemical and biological objectives for
water quality management.
The Ohio Environmental Protection
Agency (OEPA) saw a need to determine
what was reasonably attainable in Ohio
streams. OEPA also recognized
differences in streams in various parts of
the state. These concerns led to
cooperative research between OEPA and
the USEPA to evaluate a land
classification for identifying regional
patterns in aquatic ecosystems and
attainable physical, chemical and
biological conditions within them.
Ecoregion Concept
An important premise in our work is
that streams reflect the characteristics of
the land they drain. Streams in areas of
relatively homogeneous land should be
relatively similar to each other. Thus,
regional patterns in terrestrial
characteristics can be used as a
framework for studying aquatic
ecosystems. In Ohio, five ecological
regions were delineated using spatial
patterns in land-surface form, land use,
soil, and potential natural vegetation.
Sampling sites were chosen at 109
locations throughout Ohio that met three
criteria: 1) The watersheds and streams
were minimally impacted by human
activity, 2) The streams, watersheds and
sites were representative of their regions,
and 3) The watersheds above the
sampling site were wholly contained
within one ecoregion (some cross-
regional boundary sites were also
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studied). This sampling scheme helps
assure that data from these sites
represent attainable conditions for each
region. The OEPA sampled these sites in
1983-84 for fish, macroinvertebrates,
water quality, and physical habitat.
Regional Patterns
The clearest regional patterns were
found in the fish assemblages and the
water quality attributes. The Index of
Biotic Integrity (IBI) which expresses
ecological health by assessing fish
assemblages, was highest in southeast
Ohio (particularly in the Western
Allegheny Plateau). The lowest values
were in northwest Ohio (mostly in the
Huron/Erie Lake Plain), Figure I. These
two regions also have the most distinctly
different landscapes; the northwest is flat
and predominantly used for row crop
agriculture, the southeast is a dissected
plateau consisting of woodland mixed
with some cropland and pasture. The
other (transitional) regions had generally
intermediate IBI values. This pattern was
found for several other measures
generally considered indicative of the
quality of fish assemblages, e.g. species
richness, diversity, and number of
species and proportion of fish intolerant
of siltation and low dissolved oxygen.
Similar patterns in water quality
occurred. The highest quality was in
southeast Ohio and the lowest in the
northwest. The streams in the Huron/Erie
Lake Plain were nutrient and mineral rich.
Figure 2 summarizes the relationship
between water quality of the sites and
their regions.
There were only slight regional
patterns in the physical habitat attributes.
Streams in the southeast portion of Ohio
tended to have more instream cover for
fish (logs, boulders, undercut banks) and
coarser substrate materials (cobbles,
rocks and boulders), than the other
regions. Macroinvertebrate assemblages
showed almost no regional pattern.
Conclusions
There are clear regional patterns in
Ohio's stream ecosystems. While the
ecoregion classification does not fit
perfectly for any single component of
aquatic ecosystems, it does provide a
useful geographic framework to monitor,
assess, and report on the status of
aquatic resources. The regions,
combined with the sampling strategy
outlined here, can be used to determine
a range of reasonable regional
expectations for attainable water quality
and biological communities.
Ohio's current, highly-detailed
stream standards based on several
categories of biological uses and
biological criteria are being revised by
the OEPA based on reasonably
attainable conditions. The OEPA is
combining the data and methods of this
study with their extensive knowledge of
Ohio stream conditions to determine
regional background water quality. For
example, based on these results,
attainable phosphorus levels for the
Western Allegheny Plateau could be
<0.05 mg/l; in the Huron/Erie Lake Plain
a more realistic goal might be <0.15
mg/l. These levels are based on this
study only and will be subject to
revision.
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Ecoregion
IP
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Figure 1.
Relationship between the Index of Biotic Integrity and ecoregions in Ohio. Each
boxplot includes: median {the circle), interquartile range (height of the wide box).
10 and 90 percentiles (height of the narrow box), relative sample size (width
of the box), and range.
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Figure 2.
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Nutrient Richness (PCA 1)
Regional patterns in nutrient richness and ionic strength variables indicated by
principal component axis I scores for each. Areas enclosed indicate hypothesized
attainable water quality for each region.
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Thomas R. Whittier, Robert M. Hughes, Christina M. Rohm, and Alisa L Gallant
are with Northrop Services, Inc., Corvallis, OR 97333. The EPA authors David
P. Larsen (also the EPA Project Officer) and James M. Omernik are with the
Environmental Research Laboratory, Corvallis, OR 97333.
The complete report, entitled "The Ohio Stream Regionalization Project: A
Compendium of Results," (Order No. PB 88-204 2271 AS; Cost: $14.95,
subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Environmental Research Laboratory
U.S. Environmental Protection Agency
Corvallis, OR 97333
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
EPA/600/S3-87/025
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