V-/EPA
United States
Environmental Protection
Agency
Municipal Environmental Research
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-81-217 Oct. 1981
Project Summary
A Stress Function for
Evaluating Strategies for
Water Quality Management
Warren U. Brigham and Donald L. Hey
This investigation explores the
relationship between biological com-
munities and the physical and chemical
conditions in the aquatic environment.
Seasonal patterns and the duration
and probability of the occurrence of
chemical conditions and physical
events are established by means of
computer modelling. An instantaneous
measure of stress is calculated by
summing the decimal fractions of the
96-hr lethal concentrations (for blue-
gills) of each of 21 toxicants. These
data are summarized as a quasi-
continuous stress function calculated
over 1 -hr intervals. The stress function
is related to five distinct biological
communities ranging from the most to
the least tolerant of pollution.
Data from a test watershed in
northeastern Illinois yielded stress
functions as follows: 0.120 to 783.7
(mean 23.02) from a site with no fish,
0.155 to 98.47 (mean 1.038) from a
site with a carp population, and 0.005
to 0.279 (mean 0.116) from a site
with a bass population.
A hypothetical management plan to
reduce the ammonia component at
the no-fish site was incorporated into
the stress function. This plan limited
effluent ammonia concentrations to
1.5 mg/liter during summer months
and 4.0 mg/liter during the winter,
eliminated combined sewer overflows,
reduced sediment oxygen demand
levels substantially, and increased
dissolved oxygen levels moderately in
treatment plant effluents. Mean stress
was reduced from 23.02 to 2.12—
more than an order of magnitude. This
level was still significantly higher than
that of the carp site, primarily because
of residual chlorine in the effluents
from wastewater treatment plants.
These results suggest that if species
other than carp are desired in the
fishery, further control strategies
might need to be implemented.
This Project Summary was devel-
oped by EPA's Municipal Environmen-
tal Research Laboratory, Cincinnati,
OH. to announce key findings of the
research project that is fully docu-
mented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
This report introduces the concept of
the stress function as a means of
expressing the interrelationships be-
tween water quality conditions and the
aquatic biota. The study is based partly
on the bluegill toxicity index developed
by Richard E. Sparks and Kenneth S.
Lubinski of the Illinois Natural History
Survey. The toxicity index represents an
instantaneous summation of the con-
centrations of up to 21 toxicants relative
to their acute lethal effects on the
bluegill, Lepomis macrochirus. The
stress function is. a quasi-continuous
time series obtained by joining toxicity
index calculations to the output of the
Hydrocomp model. The stress function
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is constructed from the given informa-
tion regarding the physical and chemical
conditions of the stream (i.e., point
sources, nonpoint sources, and instream
physical and chemical interactions).
Thus each function represents the
signature of the stream reach and
reflects the stress that is endured by the
resident aquatic community.
Hydrocomp Nonpoint Source
Model
The Hydrocomp model was developed
as a tool for the evaluation and analysis
of nonpoint pollution problems. The
model continuously simulates hydrologic
processes (including snow accumula-
tion and melt), erosion processes, and
pollutant accumulation, generation,
and transport from the land surface.
Sediment and sediment-like materials
are used as the basic indicators of
nonpoint pollutants. These erosion
processes are simulated separately on
both pervious and impervious areas.
Pollutant loadings are determined by
multiplying the resulting sediment
discharge by potency factors represent-
ing the concentration of the pollutant in
the sediment. The model simulates the
processes that determine nonpoint
pollution and is applicable to urban,
agricultural, forested, and construction
areas.
The Hydrocomp model is composed of
three major subroutines: MAIN, LANDS,
and QUAL. MAIN, the master or execu-
tive subroutine, reads model parameters
and meteorologic data, initializes vari-
ables, monitors the passage of time,
calls the LANDS and QUALsubroutines,
and prints output summaries. LANDS,
based on the Stanford Watershed
Model, simulates the hydrologic re-
sponse of the watershed and the
process of snow accumulation and melt.
The model transforms the input data
into streamflow using a moisture-
accounting procedure. The QUAL sub-
routine simulates erosion processes,
sediment accumulation, pollutant
transport from the land surfaces, and
instream physical, chemical, and bio-
logical processes. The sources of
constituents represented in the model
are pervious surface washoff, impervious
surface washoff, groundwater, point
sources such as municipal and industrial
wastewater treatment plants, and
bottom sediments.
Toxicity Index
The toxicity index model was devel-
oped by Sparks and his associates to
demonstrate how existing water quality
monitoring data could be used to
evaluate the suitability of a lake or
stream for fish life, and if the water was
unsuitable, to determine which factors
were responsible. The bluegill sunfish
was used as the reference organism
because it is a panf ish that is common in
North America and because its sensitivity
to many chemicals has been determined
in the laboratory. The toxicity units were
therefore called bluegill toxicity units
(BGTU). For a single component, one
bluegill toxicity unit (1.0 BGTU) repre-
sents the lethal pollutant dose—or that
level of contaminant that would kill
about 50% of the fish in 4 days. A level
greater than 1.0 BGTU would kill most
fish in a shorter period of time, and a
level below 1.0 BGTU is considered
sublethal (although a value close to 1.0
might kill a few sensitive fish over a
period of days).
The water quality parameters were
divided into three categories: limiting
factors, modifying factors, and toxicants.
The limiting factors are temperature,
pH, and dissolved oxygen, which must
be within a certain range to permit fish
to survive. The model includes both a
wide range (within which bluegills can
survive for several days) and a narrower
range (within which bluegills can
survive indefinitely as well as carry on
normal functions such as growth and
reproduction). Temperature, pH, and
dissolved oxygen also are modifying
factors in that they modify the toxicity of
some chemicals by changing the chem-
ical equilibria in the water or the
sensitivity of the fish. Calcium is also a
modifying factor because the greater its
concentration in water, the less sensitive
the bluegills and other fish are to certain
toxicants such as heavy metals. Twenty
toxicants have been tested for toxic
effects on bluegills and were used in
computing toxicity indices.
The joint toxicity of all the chemicals
present at a particular water quality
sampling station at a particular sampling
time was estimated by adding the
toxicities contributed by the individual
chemicals. This estimate of the joint
toxicity is the toxicity index, and the
toxicity contributed by any particular
chemical is defined as a component
toxicity. The water quality parameters
considered are: ammonia, arsenic,
boron, cadmium, chlorine, chromium,
copper, cyanide, dissolved oxygen,
fluoride, hardness, pH, iron, LAS, lead,
manganese, mercury, nickel, nitrate
and nitrite, phenol, silver, temperature,!
and zinc.
Test Watershed
The DuPage River basin in north-
eastern Illinois was selected as the test
watershed to develop the concept of the
stress function. The drainage system
contained 30 Illinois EPA water quality
sites whose records served as sources
of water quality data. All available
information regarding the fish of the
basin is summarized in Table 1 under
the three headings (bass, carp, and no
fish) corresponding to communities
now characteristic of that reach of the
river.
Computer Simulations
To perform simulations of water
quality and to generate time series
stress functions, one representative site
at each of the three existing habitat
types was selected. Computer simula-
tion of the stress function was performed
for a 3-year period for the three study
sites. The following were included as
component toxicities in the calculation
of the total stress at each site because
these items were known to be present in
significant concentrations in at least
one of the sites: ammonia, cyanide,
lead, zinc, copper, LAS, and residual
chlorine.
Stress functions for each site and
component toxicities are given in Table
2. Inspection of the mean total stress at
each site reveals that the levels are
quite high at the no-fish site, significantly
lower at the bass site, and intermediate
at the carp site. These results are in line
with initial predictions.
The extremely high mean stress value
at the no-fish site is due to relatively
high levels of ammonia, LAS, and
residual chlorine, combined with very
low dissolved oxygen concentrations—
particularly during the summer months.
Municipal wastewater treatment plants
located upstream of the no-fish site are
the primary cause of the significant
levels of ammonia, residual chlorine,
and LAS toxicity. Because of lower
ammonia levels and improved dissolved
oxygen concentrations, the mean am-
monia stress contribution at the carp
site was substantially lower than at the
no-fish site. The bass site typically had
such higher dissolved oxygen and lower
ammonia concentrations in the summer
months, so its ammonia component
was very much lower than that of the
no-fish site. The bass site also received
a smaller contribution from the treat-
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Table 1.
Fish Known or Likely to Occur at Three Sites in the DuPage River Basin
Before 1908. Since 1950. and in 1976
Bass
Carp
No Fish
Species
Grass pickerel
Northern pike
Stoneroller
Goldfish
Carp
Hornyhead chub
Golden shiner
Emerald shiner
Striped shiner
Bigmouth shiner
Blackchin shiner
Blacknose shiner
Spotfin shiner
Sand shiner
Redfin shiner
Blunt nose minnow
Fathead minnow
Creek chub
White sucker
Creek chubsucker
Northern hog sucker
Golden redhorse
Black bullhead
Yellow bullhead
Stonecat
Tadpole madtom
Blackstripe topminnow
Starhead topminnow
Brook silverside
Rock bass
Green sunfish
Pumpkinseed
Bluegill
Smallmouth bass
Black crappie
Mud darter
Rainbow darter
Least darter
Johnny darter
Banded darter
Slenderhead darter
Total species
1908
X
X
X
-
-
X
-
X
X
-
X
X
-
-
X
X
-
X
X
X
X
X
X
X
-
X
X
X
X
X
-
-
-
X
X
X
X
X
X
X
X
31
1950
.
-
X
-
X
X
X
X
X
X
-
-
X
X
X
X
X
X
X
-
-
-
X
-
X
-
-
-
-
X
X
X
X
-
X
-
-
-
-
.
-
21
1976
-
-
X
-
X
X
X
X
X
X
-
-
X
X
-
X
X
X
X
-
-
-
X
-
-
-
-
-
-
-
X
-
X
-
X
-
-
-
-
-
-
17
1908
X
X
X
-
-
X
-
X
X
-
X
X
-
-
X
X
-
X
-
X
X
X
X
X
-
X
X
X
X
X
-
-
-
X
-
X
X
X
X
X
X
28
1950
.
-
X
X
X
-
-
-
-
X
-
-
X
X
X
X
X
-
.
-
-
-
.
-
X
-
-
-
-
X
X
X
X
-
-
-
.
-
-
-
-
14
1976
.
-
-
-
X
-
-
-
-
-
-
-
-
X
.
X
.
X
X
.
-
-
.
.
-
-
-
-
-
.
X
-
-
-
.
-
.
.
.
.
.
6
1908
-
-
X
-
-
X
-
-
X
-
-
X
-
-
-
X
-
X
-
-
-
-
X
X
-
-
X
X
-
.
-
-
-
-
-
.
.
.
X
.
.
12
1950 1976
-
-
-
-
-
-
-
-
-
-
-
-
-
-
.
-
-
-
.
-
-
-
.
-
-
-
-
-
-
.
-
-
-
-
.
-
-
.
.
-
.
0 0
component toxicities showed that
residual chlorine from the wastewater
treatment plant effluents was the
principal component of stress (1.935).
The full report was submitted in
f ulfillment of Grant No. R-805614-01-0
by the Illinois Natural History Survey
under the sponsorship of the U.S.
Environmental Protection Agency.
ment plant, so the residual chlorine and
LAS toxicities were lower as well.
After results were examined for the
basic stress function, it was tested for
sensitivity to dissolved oxygen, hard-
ness, temperature, and pH. In addition,
a hypothetical management plan to
reduce the ammonia component at the
no-fish site was developed and in-
corporated into the stress function. The
plan involved several strategies: (1)
Limit wastewater treatment plant
effluent ammonia concentrations to 1.5
mg/liter during the summer and 4.0
mg/liter during the winter, (2) eliminate
combined sewer overflows, (3) reduce
sediment oxygen demand substantially,
and (4) moderately increase dissolved
oxygen concentrations in wastewater
treatment plant effluents. Table 3
summarizes the results of this manage-
ment test. The overall mean stress was
reduced from 23.02 to 2.12 BGTU—
more than an order of magnitude.
Ammonia toxicity, which was the
principal target of the management
strategy, was reduced by nearly three
orders of magnitude. Inspection of the
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Table 2. Stress Function and Component Toxic/ties at Three Sites in the DuPage
River Basin (in Bluegill Toxicity Units/
Item
No-fish site
Carp site
Bass site
Total Stress:
Maximum
Minimum
Mean
Component toxicity:
Ammonia
Cyanide
Lead
Zinc
Copper
LAS
Residual chlorine
783.7
.120
23.024
20.18
.088
.023
.004
.020
.772
1.937
98.47
.155
1.039
.116
.081
.016
.046
.020
.107
.653
0.279
.005
.115
.014
.000
.000
.003
.008
.030
.060
Table 3. Impact of a Hypothetical
Water Quality Management
Plan on the Stress Function
at the No-Fish Site (in Blue-
gill Toxicity Units)
Item
Total stress:
Maximum
Minimum
Mean
Component
toxicity:
Ammonia
Cyanide
Lead
Zinc
Copper
LAS
Residual
chlorine
Unaltered
run
783.7
.120
23.024
20.18
.088
.023
.004
.020
.772
1.937
Altered
run
51.48
.118
2.121
.023
.079
.OOO
.003
.008
.073
1.935
Warren U. Brigham is with the Illinois Natural History Survey, Urbana, IL61801;
and Donald L. Hey is with Donald L. Hey and Associates, Chicago, IL 6O657.
James A. Heidman is the EPA Project Officer (see below).
The complete report, entitled "A Stress Function for Evaluating Strategies for
Water Quality Management." (Order No. PB 82-109 828; Cost: $11.00,
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:
Municipal Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
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