TECHNICAL INVESTIGATIONS BRANCH
SURVEILLANCE AND ANALYSIS DIVISION
U. S. ENVIRONMENTAL PROTECTION AGENCY
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THE EFFECT OF POINT-SOURCE DISCHARGES ON
THE DIVERSITY OF BENTHIC INVERTEBRATES OF THE
YAMPA RIVER, STEAMBOAT SPRINGS TO HAYDEN, COLORADO
SEPTEMBER - 1975
by
Ronald M. Eddy
Aquatic Biologist
TECHNICAL INVESTIGATIONS BRANCH
SURVEILLANCE AND ANALYSIS DIVISION
U. S. ENVIRONMENTAL PROTECTION AGENCY
REGION VIII
Document is available to the public from the U.S. Environmental Protection
Agency, Region VIII, Denver, CO 80203
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DISCLAIMER
This report has been reviewed by the Surveillance and Analysis Division,
U.S. Enivronmental Protection Agency, Region VIII, and approved for publication.
Mention of trade names or commercial products does not constitute endorsement
or recommendation for use.
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TABLE OF CONTENTS
Pa^e
ABSTRACT ii
LIST OF FIGURES iii
LIST OF TABLES iv
INTRODUCTION 1
SUMMARY AND CONCLUSIONS 2
RESULTS OF STUDY 3
Study Area 3
Methods and Materials 3
Results and Discussion 11
REFERENCES 19
APPENDIX A A-l
APPENDIX B B-l
APPENDIX C C-l
APPENDIX D D-l
i
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A survey was conducted by the U.S. Environmental Protection Agency
during September, 1975 to determine the effect of known point-source
discharges on the benthic invertebrates of the Yampa River, Steamboat
Springs to Hayden, Colorado, a distance of approximately 61 km (38 mi).
Using modified surber samples, three samples were collected at each of
17 sampling locations. Mean diversity (d) and equitability (e) were
computed at each sampling location. Mean diversity and equitability
decreased immediately downstream of known point-source discharges. With
increasing downstream distance from the discharge, mean diversity and
equitability gradually increased.
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LIST OF FIGURES
Page
1. SAMPLING STATION LOCATIONS ON THE YAMPA RIVER, 4
STEAMBOAT SPRINGS TO HAYDEN, COLORADO
2. MEAN TOTAL NUMBER OF ORGANISMS PER SQUARE METER 12
AND MEAN NUMBER OF GENERA COLLECTED AT EACH SAMPLING
LOCATION ON THE YAMPA RIVER, STEAMBOAT SPRINGS TO
HAYDEN, COLORADO
3. EQUITABILITY (e) AND MEAN DIVERSITY (d) OF BENTHIC 14
INVERTEBRATES COLLECTED AT EACH SAMPLING STATION
ON THE YAMPA RIVER, STEAMBOAT SPRINGS TO HAYDEN,
COLORADO
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LIST OF TABLES
Page
1. STATION DESIGNATIONS AND DESCRIPTIONS FOR YAMPA 5
RIVER STUDY, STEAMBOAT SPRINGS TO HAYDEN, COLORADO
2. MEAN DIVERSITY (d") AND EQUITABILITY (e) OF BENTHIC 13
INVERTEBRATES COLLECTED AT EACH SAMPLING STATION
3. TWO SAMPLE T-TEST COMPARISON OF THE MEAN DIVERSITY 16
OF CONTROL STATION WITH THE MEAN DIVERSITY OF EACH
DOWNSTREAM STATION
iv
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INTRODUCTION
With development of coal mining in northwestern Colorado, many
towns located in surrounding areas will be markedly impacted by accel-
erated growth. The town of Steamboat Springs, Colorado, is projected
to increase in resident population from 6,000 to 10,000 in the next ten
years with seasonal peaks growing from 13,305 to 19,500 within the same
time period (EPA, 1976).
The town of Steamboat Springs, Colorado and associated housing
developments and trailer parks on its periphery presently discharge
varying quantities and qualities of treated sewage effluent to the Yampa
River. A cooperative effort between the Environmental Protection Agency
(EPA) Region VIII, and the U.S. Geologic Survey (USGS), Colorado District,
was initiated to determine the effect of known point-source discharges on
the Yampa River. Personnel from the USGS modeled the waste assimilative
capacity of the Yampa River while personnel from the EPA determined the
effect of point-source discharges on the benthic communities within the
study area. Samples for both benthic and chemical analysis were collected
during the latter part of September, 1975.
The following report states the findings of the EPA study. The
complete results of the modeling effort by the USGS are described by
Bauer, Steele, and Anderson (1976). The data presented from both studies
will be useful in formulating growth development plans for Steamboat
Springs, Colorado and the surrounding area.
1
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SUMMARY AND CONCLUSIONS
In September, 1975, as part of a cooperative effort between the
U.S. Geologic Survey, Colorado District and the U.S. Environmental
Protection Agency, Region VIII, a survey was conducted by EPA to
determine the effect of known point-source discharges on the benthic
invertebrates in the Yampa River, Steamboat Springs to Hayden, Colorado.
Three Surber samples were collected at each of 17 stations on the
mainstem Yampa River from upstream £f Steamboat Springs to downstream from
Hayden, Colorado. Mean diversity (d) and equitability (e) were computed
for each sample at each station. The respective values for each parameter
were then averaged for each station.
Although extremely low mean diversities were not observed (i.e. <1.00),
the diversity of benthic invertebrates in the study area, on the basis
of the data presented here, is markedly affected by known point-source
discharges. Mean diversity and equitability at stations immediately
downstream of known point-source discharges were usually significantly
lower than the diversity of the control station. With increasing down-
stream distance from the area of major point-source discharges, the diversity
gradually increased. The lowest mean diversity (2.097) was observed
immediately downstream from the Steamboat Springs Sewage Treatment Plant
(STP), the KOA Campgrounds, and the Sleepy Bear Trailer Park.
Seasonal sampling would be required to determine the extent of
changes in the benthic diversity during different times of the year.
2
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RESULTS OF STUDY
I. Study Area
The Yampa River lies in the northwestern portion of Colorado,
with the headwaters located upstream of Stillwater Reservoir. A tributary
of the Green River, the Yampa River flows through Routt and Moffat Counties
passing the towns of Yampa, Phippsburg, Oak Creek, Steamboat Springs,
Milner, Hayden, Craig, Maybell, and Sunbeam. The confluence of the two
rivers is located in Echo Park, Dinosaur National Monument, Colorado.
Approximately 61 km (38 mi) of the Yampa River were included in the
study area with benthic samples collected at 17 mainstem stations, from
approximately 6.4 km (4 mi) upstream from Steamboat Springs to approximately
0.8 km (2 mi) downstream from Hayden, Colorado (Figure 1). Mainstem
sampling stations, tributary inflows, and known point-source discharges
are listed in their respective downstream order in Table 1.
The river bed within the study area was consistently composed of small
to medium sized rubble throughout the study area. The top layer of substrate
was composed of rocks averaging 15 to 25 cm (5.9 to 9.6 in) in diameter
with the spaces between the larger rubble filled with smaller stones and
coarse gravel.
II. Methods and Materials
Samples of benthic invertebrates were collected at each of the 17
mainstem sampling sites- using both artificial substrates and Surber samplers.
Artificial substrates were placed on August 19-21, 1975. All samples were
collected during the period, September 22-26, 1975.
All Surber samples were taken with modified Surber samplers. The
samplers were modified by replacing the standard mesh bag with a 1.2 m
(4 ft) long bag constructed of 207 micrometer mesh Nitex net. A large
piece of naugahyde was sewn to the bottom of the bag to prevent abrasion by
the substrate. The longer length of the bag effectively reduced any backwash
incurred due to the smaller mesh size.
At the time of sampling, the substrate enclosed within the square
foot bottom of the Surber frame was removed from the stream and placed
in a large bucket partially filled with water. Each rock was then cleaned
using a soft bristle brush and the bag of the Surber sampler inverted
and cleaned in the bucket. The contents of the bucket were then poured
into a #60 mesh (250 micrometers) sieve. The collected samples were then
placed into pint jars, preserved with 80% ET0H, and returned to the laboratory
for sorting and identification.
3
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¦E
a
>
e
at o
2 ®
• <
oc
o
-J
o
o
Figure 1. Sampling station locations on the Yampa River, Steamboat
Springs to Hayden, Colorado.
(Adapted from Steele, Bauer, Wentz, and Warner, 1976.)
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TABLE 1
STATION DESIGNATIONS AND DESCRIPTIONS FOR YAMPA RIVER STUDY
STEAMBOAT SPRINGS TO HAYDEN, COLORADO*
Station
Designation^
YM-0 402544
106493600
YT-1 402508
106493800
YT-2 402700
106485400
YM-0-1
YE -1
YT-3 402759
106493100
YT-4 402857
106494000
YM-1 09239500
402901
106495400
YT-5 402944
106495900
YT-6 402920
106505400
YM-2 402934
106505400
YE-3
Station Description
T/R-S^ (Intervening Tributaries and Point-Discharges)
6/84-32 Yampa River downstream from Oak Creek
near Steamboat Springs- 6.4 km (4 mi)
south of the city of Steamboat Springs.
Agate Creek
Walton Creek
Yampa River upstream from Mt. Werner
Sewage Disposal Ponds.
Mt. Werner Sewage Disposal Ponds
Fish Creek
Spring Creek
6/84-17 Yampa River at Steamboat Springs-
bridge at southeast end of town, at
gaging station.
Butcherknife Creek (Pole Bear Ranch)
Soda Creek (Whitman School)
6/84-7 Yampa River upstream from Steamboat
Springs STP, downstream from Steamboat
Springs- bridge south of cemetery just
downstream from camp.
Steamboat Springs Sewage Treatment
PI ant
5
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Table 1 - continued
Station
Designation T/R-S
YM-3 402958 6/85-1
106515200
YE-4
YT-7 403022
106524000
YE-5
YM-4 403017 6/85-2
106525800
YE-6
YM-5 403002 6/85-3
106545500
YM-6 402932 6/85-8
106568900
YT-8 402913
106580400
YT-9 402903
106584100
YM-7 402902 6/85-18
106580000
Station Description
(Intervening Tributaries and Point-Discharges)
Yampa River downstream from treatment
plant downstream from Steamboat Springs-
access downstream from treatment facility.
K0A Campground package plant
Slate Creek
Sleepy Bear Park package plant
Yampa River downstream from camp-
grounds near Steamboat Springs (cross-
section, access just downstream from
YE-5).
Steamboat II treatment plant
Yampa River downstream from Steamboat II
near Steamboat Springs (cross-section
downstream from treatment plant,
upstream from gravel pit).
Yampa River upstream from Elk River
confluence near Milner (WQ Recon. Y-63)
(bridge crossing, approx 1.6 km (1 mi)
upstream from Elk River).
Elk River
W. Fork Elk River
Yampa River downstream from Elk River
confluence near Milner (cross-section,
access from Elk River just upstream).
6
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Table 1 - continued
Station
Designation
YM-8 402840
107004200
YT-10 402816
107003800
Station Description
T/R-S (Intervening Tributaries and Point-Discharges)
6/86-15 Yampa River at Milner (Colo. Health
Dept. Station 000038) (Bridge, upstream
from Trout Creek).
Trout Creek
YT-11 402908
107014000
YM-9 402854 6/86-16
107020500
YT-12 402908
107025100
YM-10 402902 6/86-18
107043600
YT-13 402832
107080200
YT-14 402856
107085800
YM-11 09244410 6/87-9
402918
107093300
YT-15 402918
107094400
YT-16 403123
107115500
Cheney Creek
Yampa River downstream from Trout Creek
confluence near Milner (WQ Recon Y-50)
(bridge southwest of Milner).
Tow Creek
Yampa River at Tow Creek Oil Field
(foot bridge 2.4 km (1^ mi) downstream
from Tow Creek).
Wolf Creek
Grassy Creek
Yampa River downstream from Diversion
near Hayden (WQ Recon Y-47) (U.S. 40 Hwy
bridge, approx. .2 km (0.1 mi) upstream
from Sage Creek).
Sage Creek (Hayden Power Plant)
(WQ Recon. Y-46).
Morgan Creek
7
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Table 1 - continued
Station
Desi gnation T/R-S
YM-12 403051 7/88-36
107124500
YM-13 403006 6/88-4
107154800
YT-1 7 402952
107161600
Station Description
(Intervening Tributaries and Point-Discharges)
Yampa River downstream from Morgan
Creek confluence near Hayden (cross-
section, access by farm road on north
side of river).
Yampa River at Hayden (WQ Recon Y-45)
(bridge, north of town, 1.6 km (1 mi)
upstream from Dry Creek).
Dry Creek (Hayden treatment plant).
YM-14-1
YM-14 402930 6/88-8
1071 74200
Yampa River downstream from Dry Creek.
Yampa River downstream from Hayden
(WQ Recon Y-44) (U.S. 40 Hwy bridge
west of Hayden).
1 Adapted from Steele, Bauer, Wentz, and Warner, (1976), Table 3.
2 YM- Sampling stations on the Yampa River
YT- Tributary of the Yampa River
YE- Point-source discharge to Yampa River
Numbers adjacent to Station Designation indicate USCS station numbers,
either 15 digit latitude-longitude number and/or 8 digit downstream
order number
^ T/R-S Township, range, and section
8
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Prior to collection of each sample, the water velocity was determined
with a Marsh-McBurnay, electro-magnetic, direct readout current meter.
An attempt was made to collect all Surber samples at similar velocities to
reduce any variability in benthic community composition due to water velocity.
All Surber samples were taken in riffle areas.
Three Surber samples were collected at each sampling station. The
contents of each sample were individually processed and the results from
each sample reported separately.
Cylindrical barbeque baskets 16.5 cm (6.5 in) in diameter and 25.4 cm
(10 in) in length filled with rocks taken from the river were used as
artificial substrates. A large piece of plastic sheeting was attached
to each basket. The plastic would be used to enclose the baskets during
removal to restrict water flow through the baskets and prevent loss of
invertebrates. All rocks placed in a basket were first scrubbed with
a brush to remove any attached invertebrates. After a basket was filled
a hole slightly larger than the artificial substrate was excavated in
the stream bottom. Using a facemask and snorkel to allow good visual
inspection, the basket was then placed in the excavated hole. When the
basket was placed in the excavated hole, the attached plastic was rolled
to the sides of the basket and secured with rocks.
Following placement of the artificial substrate in the excavated
hole, the rocks were rearranged around the basket so that the top layer
of rocks within the basket were at the same level as the river bed.
All substrates were placed in riffle areas with predetermined water
velocities. Two artificial substrates were placed at each sampling
station.
After approximately 5^ weeks exposure, the artificial substrates
were removed. During removal, rocks surrounding the baskets were carefully
moved to allow enclosure of the baskets with the attached plastic sheet.
The baskets were then lifted into a Surber net and removed from the river.
The rocks were removed from the basket and placed in a bucket partially
filled with water and cleaned with a small brush. The contents of the
bucket were then poured into a #60 mesh sieve and the retained material
placed in pint jars, preserved with 80% ETOH, and returned to the
laboratory for examination.
All samples were sorted following procedures outlined by EPA
Biological Field and Laboratory Methods (1973). All organisms were
identified to the lowest taxonomic level possible using available
taxonomic texts (Pennak, 1953; Usinger, 1968; Johannsen, 1969; EPA, 1973;
Ross, 1944; Hilsenhoff, 1975; Needham, Traver and Hsu, 1935; Gaufin,
et. al, 1972). The extremely small size of many of the invertebrates
collected, due to the time of year of sampling, precluded identification
to the species level.
9
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Chemical data were collected by the USGS for use in the waste assimi-
lative capacity model. The chemical data collected for sampling stations
on the mainstem of the Yampa River are shown in Appendix 1. A complete
listing of all chemical parameters collected by the USGS is given by Bauer,
Steele, and Anderson (1976).
Periphyton biomass determinations, both dry weight and ash weight,
were determined by the USGS.
Mean diversity of collected benthic invertebrates was computed using
the machine formula of the Shannon-Weaver function (Lloyd, Zar, and Karr,
1968) as outlined in the Biological and Laboratory Methods Manual (1973).
The formula used for computation of mean diversity is as follows:
d = £ (N log-jQ N - 2nn- log10 n-j)
N i
where; d = mean diversity
C = 3.321928 (converts base 10 log to base 2)
N = total number of individuals
n-j = total number of individuals in the ith species
s = total number of taxa
Equitability of collected benthic invertebrates was computed following
the methods proposed by Lloyd and Ghelardi (1964) as outlined in the
Environmental Protection Agency, Biological and Laboratory Methods Manual
(1973). The formula used for computation of equitability is as follows:
where; s = the number of taxa in the sample
s' = the number of expected taxa, a tabulated value from
Lloyd and Gherlardi (1964)
10
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RESULTS AND DISCUSSION
Water velocities measured at the point where each Surber sample
was collected averaged 45.1 cm/sec (1.48 ft/sec) and ranged from 24.4 to
73.2 cm/sec (0.8 to 2.3 ft/sec). The reported values are within the
range reported by Stanford and Reed (1974) for effective use of a Surber
sampler.
The total number of organisms, kinds of organisms, and the number
of genera found in each sample at every station in both Surber samples and
artificial substrates are shown in Appendix A and B, respectively. Only
data obtained from the Surber samples will be discussed as a large number
(approx. 30%) of the artificial substrates were not recovered. The data
obtained from the remaining substrates, however, are included for use in
comparison with the Surber sample data.
Figure 2 shows the average total number of organisms and the average
number of genera collected at each of the sampling stations. Hydrophysche sp.
and Chuematophysche sp. were the predominate caddisflies (Tricoptera)
collected at all stations while the major stonefly (Plecoptera) was
A1loperlla sp.. Ephemerella sp. and Orthocladius sp. were consistently
the most abundant mayfly (Ephemoptera) and midge (Chironominea), respectively,
collected in the study area. The total number of organisms and the number
of genera collected in each sample and the standard deviation of samples
collected at each station are listed in Appendix C. No relationship
between either number of genera and point-source discharge or total number
of organisms and point-source discharges was observed.
The diversity of the benthic communities sampled, on the basis of
the Surber samples collected, were found to be closely related to the
known point-source discharges. Mean diversity decreased immediately
downstream from point-source discharges throughout the entire study area.
With increasing downstream distance from a point-source discharge,
the mean diversity gradually increased until introduction of another
effluent. Figure 3 shows the change in mean diversity and equitability
in relation to known point-source discharges and tributary inflows to
the Yampa River. The values plotted are the average values of the three
Surber samples collected at each station (Table 2, Appendix 4).
As can be seen from Figure 3 and Table 2, the mean diversity at the
control station YM-0 was 3.42. After introduction of effluent from the
Mt. Werner Sewage Disposal Ponds (YE-1) diversity declined to 2.68 at
Station YM-1. The mean diversity at Station YM-2 rose slightly to 2.99.
However, following introduction of effluent from the Steamboat Springs STP,
the mean diversity again declined. With additional effluents from the
KOA Campground package plant (YE-4), Sleepy Bear Park package plant (YE-5),
11
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Figure 2. Mean total number of organisms per square meter and mean number of genera collected
at each sampling location on the Yampa River, Steamboat Springs to Hayden, Colorado.
>
Z
Z 35
c
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m
33
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3 20
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33
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10
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ORGANISMS
GENERA
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-W
STATIONS
30
25
20
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TRIBUTARIES
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EFFLUENTS
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TABLE 2
MEAN DIVERSITY (d) AND EQUITABILITY (e) OF
BENTHIC INVERTEBRATES COLLECTED AT EACH SAMPLING STATION
Station
Mean Diversity* Equitability*
(d) (e)
1
0 3.38 0.62
0-1 3.16 0.54
1 2.66 0.46
2 2.92 0.58
3 2.60 0.43
4 2.49 0.34
5 2.09 0.30
6 2.50 0.35
7 2.88 0.49
8 2.67 0.36
9 2.96 0.38
10 3.01 0.48
11 3.19 0.74
12 3.13 0.49
13 .62 0.65
14-1 2.27 0.29
14 2.69 0.33
Values shown are averages of three samples collected at each station.
13
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0.70
0.60
0.50
m
O
c
H
~D
= 0.40
-<
0.30
0.20
0.00
d
e
0 0/1
sL
I
7 8
STATIONS
9 10 11
T?
B
4i-
14/1
it U S&
+
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TRIBUTARIES
M 12 four's
¦fr
EFFLUENTS
14
2
m
J>
z
5.00 2
<
m
sj
_
H
4.00 ^
Q-l
3.00
2.00
Figure 3.
Equitability (e) and mean diversity (cT) of benthic invertebrates collected at each
sampling station on the Yampa River, Steamboat Springs to Hayden, Colorado (Values
shown are averages of three samples collected at each station).
-------
and Steamboat II treatment plant (YE-6), the mean diversity continued to
decrease with Station YM-5 having the lowest mean diversity recorded during
the study (2.09). From Station YM-5 to Station YM-13, the mean diversity
gradually increased to a high of 3.61 at Station YM-13. Dry Creek, which
contains the effluent from the town of Hayden STP, entered the Yampa River
between Stations YM-13 and YM-14-1. A subsequent decrease in mean diversity
from 3.61 at YM-13 to 2.28 at YM-14-1 was observed. Mean diversity then
increased from 2.28 at YM-14-1 to 2.61 at Station YM-14. The mean diversity
at YM-13 is higher than the control Station YM-0. The exact reason for
this phenomenon is not known.
As shown in Figure 3, the computed equitabilities followed a trend sim-
ilar to the mean diversity. Equitabilities were found to decrease
immediately downstream from known point-source discharges. With increasing
downstream distance from the effluent, equitability would gradually rise
until introduction of another point-source discharge.
The extremely high equitability reported at Station YM-11 is felt
due to a non-representative sample. Station YM-11 was dissimilar
from the other stations sampled in that no shallow riffle area could
be located for sampling. Collection of the Surber samples in deeper
water than was desired resulted in the lowest total number of organisms
and the least number of taxa collected at any station.
Various researchers have attempted to correlate mean diversity
and equitability with the state of degradation of the receiving body
of water. Wilhm (1970) reported that mean diversity generally ranged
between 3 and 4 in unpolluted water, whereas mean diversity in polluted waters
was generally less than 1. EPA Biological Field and Laboratory Methods
(1973) reported that equitability in streams unaffected by oxygen demanding
wastes generally ranged between 0.6 and 0.8. Even slight levels of
pollution were reported to reduce equitability below_0.5 and often to
levels from 0.0 to 0.3. Values for mean diversity (d) and equitability (e)
reported here for stations upstream and downstream from known point-source
discharges (Table 2) agree, in general, with the range of respective
values reported by both EPA Biological Field and Methods Manual (1973)
and Wilhm (1970) for waters affected and unaffected by organic pollutions.
Although large decreases in diversity were not noted during the study,
the correlation established between known point-source discharges and changes
in benthic diversity at sampling sites along the mainstem of the Yampa River
is felt to be significant.
Using a two sample t-test, the average mean diversity of the control
Station (YM-0) was compared with the average mean diversity of each of the
downstream sampling stations. Table 3 shows the results of each of the t-test
comparisons. Stations YM-1, 3, 4, 5, 6, 8, 14-1, and 14 were found to be
statistically lower than the control Station (YM-0) at the 0.05 level, while
Stations YM-5, 6, and 14-1 were found to be statistically lower than the control
Station at the 0.025 level. Station 5 was the only station whose average mean
diversity was statistically lower than the control Station at the 0.005 level
of significance.
15
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TABLE 3
TWO SAMPLE ONE-TAILED T-TEST COMPARISON OF THE MEAN DIVERSITY
OF CONTROL STATION WITH THE MEAN DIVERSITY OF EACH DOWNSTREAM STATION
Degrees of
Freedom Calculated
Hypothesis Tested
df
t-val lie
Conclusion
Ho: yo = yc-l
Ha: ^o > vo-1
4
0.805
Accept at
- = 0.05
^o • uo ~ ^1
Ha: m0 > ^1
4
2.640
Reject at
« = 0.05
H0: u0 = u2
Ha: y0 > 4
4
1.677
Accept at
- = 0.05
Ho: yo = ^3
Ha: yo > v3
4
2.753
Reject at
« = 0.05
^o* yo ~ u4
"a: ^o > ^4
4
2.584
Reject at
- = 0.05
^o ¦ ^o ~ ^5
Ha: yo > p5
4
5.155
Reject at
« = 0.05
- = 0.025
- = 0.005
H«: \in = c
u°. o 6
a* po 6
4
3.412
Reject at
« = 0.05
- = 0.025
[|o: ^o=7
Ha: uo > 7
4
1.858
Accept at
« = 0.05
So: yo ; s
a" Mo > 8
4
2.884
Reject at
« = 0.05
^o: ^o 9
^a' ^o > 9
4
1.344
Accept at
cc = 0.05
[|o: wo 10
Ha: yo > 10
4
1.149
Accept at
- = 0.05
Ho: ^o = 11
Ha: yo > 11
2
0.779
Accept at
a = 0.05
16
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Table 3 - continued
Degrees of
Freedom Calculated
Hypothesis Tested df t-value Conclusion
H0: M0 = yi? 4 0.913 Accept at
Ha: >v<12 a = °'05
Hn: = wi-j 4 0.965 Accept at
H°: u° > U13 « = °-05
H0: u0 = m14_-, 4 3.789 Reje^nf
Ha: v0 > mi4-1 « = 0-05
u\l « = 0.05
17
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It is recognized that the benthic samples were not collected during
an optimal time of the year. Many of the invertebrates collected were
early instars, making identification difficult and tedious. The selection
of the sampling dates, however, was a result of coordination efforts with
the USGS waste assimilative capacity study of the Yampa River during low
flow conditions (Bauer, Steele, and Anderson, 1976).
The diversities reported here may fluctuate, both in absolute and
relative terms, during the year. High flows and subsequent greater dilution
of domestic waste effluents in the Yampa River may result in higher diver-
sities than reported here. Also, different species of benthic invertebrates
may be collected during sampling periods conducted during different times
of the year. Many of the genera of Plecoptera reported by Obi ad (1969)
were not observed during this study. Conversely, diversity values reported
here may be higher than expected during periods of extreme low flow and
associated increases in concentration of domestic waste effluent immediately
downstream from point-source discharges. Further sampling is necessary
to establish seasonal trends and reach profile trends in diversity.
18
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REFERENCES CITED
Bauer, D.P., T.D. Steele, and R.D. Anderson. 1976 (Draft), Waste-load
Assimilative - Capacity Analysis of the Yampa River, Steamboat Springs
to Hayden, Routt County, Colorado: U.S. Geol. Survey Water - Resources
Investigations - 76, 87 pp.
Environmental Protection Agency. 1973. Biological Field and Laboratory
Methods for Measuring the Quality of Surface Waters and Effluents.
Cincinnati, Ohio EPA-670/4-73-001.
Environmental Protection Agency. 1973(a). An Introduction to the Identi-
fication of Chironomid Larvae. U.S. EPA. Cincinnati, Ohio.
Environmental Protection Agency. 1976 (Draft), Steamboat Springs Regional
Service Authority - 201 Wastewater Facilities Plan: Report to EPA
by Weiner and Associates, Inc., Denver, Colo., 153 pp. + maps.
Gaufin, A.R., W.E. Ricker, M. Miner, P. Milam, and R.A. Haus. 1972.
The Stoneflies (Plecoptera) of Montana. Trans. Am. Ent. Soc.
Vol. 98:1-161.
Hilsenhoff, W.L.. 1975. Aquatic Insects of Wisconsin. Technical Bulletin
No. 89, Dept. of Nat. Res., Madison, Wisconsin.
Johannsen, O.A.. 1969. Aquatic Diptera: Eggs, Larvae, Pupae of Aquatic
Flies. Entomological Reprint Specialists, Los Angeles, California.
Lloyd, M., J.H. Zar, and J.R. Karr. 1968. On the Calculation of Infor-
mation - Theoretical Measures of Diversity. Am. Mid. Nat. 79(2):
257-272.
Lloyd, M., and R.J. Ghelardi. 1964. A Table for Calculating the "Equitabil-
ity" Component of Species Diversity. J. Anim. Ecol. 33:217-225.
Needham, J.G., J.R. Traver, and Yin-chi Hsu. 1935. The Biology of Mayflies.
Entomological Reprint Specialist, Los Angeles, California.
Oblad, B.R.. 1969. A Study of the Stoneflies (Plecoptera) of the Yampa
River Drainage System Moffat and Routt Co., Colorado. M.A. Thesis,
University of Montana, Missoula.
Pennak, R.W. 1953. Freshwater Invertebrates of the United States. Ronald
Press Co., New York, 769 pp.
Ross, H.H.. 1944. The Caddis Flies, or Trichoptera, of Illinois. Entomo-
logical Reprint Specialists, Los Angeles, California.
19
-------
Stanford, J.A., and E.B. Reed. 1974. A Basket Sampling Technique for
Quantifying Riverine Macrobenthos. Water Resources Bulletin
Vol. 10(3).
Steele, T.D., D.P. Bauer, P.A. Wentz, and J.W. Warner. 1976. An Environ-
mental Assessment of Impacts of Coal Development on the Water Resources
of the Yampa River Basin, Colorado and Wyoming -- Phase - I Work Plan:
U.S. Geol. Survey Open-File Report 76 - 367, May 1976, 17 pp.
Usinger, R.L. 1971. Aquatic Insects of California. University of
California Press, Berkeley, Los Angeles, London.
Wilhm, J.L. 1970. Range of Diversity Index in Benthic Macroinvertebrate
Populations. JWPCF, 42(5):R221-R224.
20
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APPENDIX A
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APPENDIX B
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DIGI
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APPENDIX C
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TABLE C-l
Mean Total Number of Organisms and Standard Deviation Computed
From Three Surber Samples Collected at Every Station on the
Yampa River, Steamboat Springs to Hayden, Colorado
Station
Sample
1 2 3
Mean*
Y
Standard De
s
0
10652 8866 9393
9637
918
0-1
17819 7467 14418
13235
5276
1
15086 4562 9706
9784
5262
2
3250 3389 4013
3551
407
3
17844 3874 5886
9218
7581
4
34636 22843 19981
25820
7768
5
9329 8586 9824
9246
623
6
19196 20089 8231
15839
6603
7
5391 8156 4896
6148
1757
8
16344 7102 10878
11441
343
9
10394 8877 9415
9562
769
10
12944 22445 4638
13342
8911
11
2443 1119 1571
1711
673
12
2787 4842 5681
4437
1489
13
12127 4412 1 3988
10175
5078
14-1
26082 11384 9770
15745
8988
14
25049 33367 33743
30727
4914
*Mean of standard deviation rounded to nearest whole number.
C-l
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TABLE C-2
Mean Number of Genera and Standard Deviation Computed From
Three Surber Samples Collected at Every Station on the
Yampa River, Steamboat Springs to Hayden, Colorado
Number of Genera/
Station
Sample
Mean
Standard De
1
2
3
X
s
0
25
25
25
25.00
0
0-1
26
20
25
23.67
3.215
1
23
16
19
19.33
3.512
2
20
16
20
18.67
2.309
3
28
15
18
20.33
6.807
4
26
23
21
23.33
2.517
5
20
23
16
19.67
3.512
6
21
29
19
23.00
5.292
7
21
25
18
21.33
3.512
8
30
28
19
25.67
5.859
9
29
32
27
29.33
2.517
10
28
26
18
24.00
5.292
11
20
17
16
17.67
2.082
12
21
28
27
25.33
3.786
13
32
24
29
28.33
4.041
14-1
27
21
21
23.00
3.464
14
30
28
28
28.67
1.155
C-2
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APPENDIX D
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TABLE D-l
Mean Equitability and Standard Deviation Computed From
Three Surber Samples Collected at Every Station on the
Yampa River, Steamboat Springs to Hayden, Colorado
Equitabil ity
Station
/Sample
Mean
Standard De'
1
2
3
e
s
0
0.737
0.689
0.418
0.614
0.173
0-1
0.444
0.566
0.620
0.542
0.091
1
0.360
0.481
0.552
0.464
0.097
2
0.569
0.750
0.432
0.584
0.159
3
0.362
0.554
0.383
0.433
0.105
4
0.425
0.290
0.291
0.335
0.078
5
0.271
0.234
0.386
0.297
0.079
6
0.420
0.241
0.391
0.351
0.096
7
0.535
0.450
0.482
0.489
0.043
8
0.307
0.289
0.475
0.357
0.103
9
0.309
0.450
0.380
0.380
0.071
10
o
00
•
o
0.505
0.458
0.481
0.024
11
0.653
0.754
0.818
0.742
0.082
12
0.490
0.500
0.491
0.494
0.006
13
0.547
0.710
0.683
0.647
0.087
14-1
0.206
0.279
0.391
0.292
0.093
14
0.310
0.274
0.407
0.330
0.069
D-l
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TABLE D-2
Average Mean Diversity and Standard Deviation Computed From
Three Surber Samples Collected at Every Station on the
Yampa River, Steamboat Springs to Hayden, Colorado
Station
Mean Diversity (d)
/Sample
1 2 3
Ave. Mean
Diversity
d
Standard Deviation
s
0
3.672
3.578
2.900
3.383
0.421
0-1
3.035
3.006
3.434
3.158
0.239
1
2.592
2.493
2.904
2.663
0.215
2
3.014
3.087
2.645
2.915
0.237
3
2.859
2.594
2.349
2.598
0.251
4
2.977
2.306
2.191
2.491
0.425
5
2.036
2.028
2.212
2.092
0.104
6
2.674
2.371
2.447
2.497
0.158
7
2.997
3.000
2.653
2.883
0.199
8
2.731
2.561
2.705
2.666
0.092
9
2.697
3.334
2.875
2.969
0.329
10
3.241
3.209
2.584
3.011
0.370
11
3.201
3.176
3.204
3.194
0.015
12
2.879
3.296
3.222
3.132
0.222
13
3.600
3.564
3.700
3.621
0.071
14-1
2.065
2.135
2.597
2.265
0.288
14
2.701
2.489
2.893
2.694
0.207
D-2
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1 REPORT NO 2
EPA-908/2-76-001
3 RECIPIENT'S ACCESSION-NO
4 TITLE AND SUBTITLE
The Effect Of Point-Source Discharges on the Diversity
of Benthic Invertebrates of the Yampa River, Steamboat
Springs to Hayden, Colorado, September-1975.
5 REPORT DATE
October, 1975
6 PERFORMING ORGANIZATION CODE
7 AUTHOR(S)
8 PERFORMING ORGANIZATION REPORT NO
S&A/TIB-30
9 PERFORMING ORGANIZATION NAME AND ADDRESS
Technical Investigations Branch
Surveillance & Analysis Division
U.S. Environmental Protection Agency, Region VIII
Denver, Colorado 80203
10 PROGRAM ELEMENT NO
11 CONTRACT/GRANT NO
12 SPONSORING AGENCY NAME AND ADDRESS
13 TYPE OF REPORT AND PERIOD COVERED
September, 1975
14 SPONSORING AGENCY CODE
15 SUPPLEMENTARY NOTES
16 ABSTRACT
A survey was conducted by the U.S. Environmental Protection Agency
during September, 1975 to determine the effect of known point-source
discharges on the benthic invertebrates of the Yampa River, Steamboat
Springs to Hayden, Colorado, a distance of approximately 61 km (38 mi).
Using modified surber samples, three samples were collected at each of
17 sampling locations. Mean diversity (a) and equitability (e) were
computed at each sampling location. Mean diversity and equitability
decrease ! immediately downstream of known point-source discharges. With
increas "g downstream distance from the discharge, mean diversity and
equitab'iity gradually increased.
17 KEY WORDS AND DOCUMENT ANALYSIS
a DESCRIPTORS
b IDENTIFIERS/OPEN ENDED TERMS
c cosati Field/Group
18 DISTRIBUTION STATEMENT
Release to the Public
19 SECURITY CLASS (This Report)
unclassified
21 NO OF PAGES
43
20 SECURITY CLASS (This page)
unciassified
22 PRICE
EPA Form 2220-1 (9-73) GPO 837 -8 17
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