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GREEN MOUNTAIN RESERVOIR - LOWER BLUE RIVER STUDY
COLORADO
SEPTEMBER, 1976
TECHNICAL INVESTIGATIONS BRANCH
SURVEILLANCE AMD ANALYSIS DIVISION
U.S. ENVIRONMENTAL PROTECTION AGENCY
REGION VIII
AUGUST, 1977
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GREEN MOUNTAIN RESERVOIR - LOWER BLUE RIVER STUDY
COLORADO
SEPTEMBER, 1976
by
Ronald M. Eddy
and
Robert L. Fox
TECHNICAL INVESTIGATIONS BRANCH
SURVEILLANCE AND ANALYSIS DIVISION
U. S. ENVIRONMENTAL PROTECTION AGENCY
REGION VIII
AUGUST, 1977
Document 1s available to the public from the National Technical Information
Service, U. S. Dept. of Commerce, Springfield, VA 22161
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DISCLAIMER
This report has been reviewed by the Surveillance and Analysis
Division, U.S. Environmental Protection Agency, Region VIII, and approved
for publication. Mention of trade names or commercial products does not
constitute endorsement or recommendation for use.
ii
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ACKNOWLEDGEMENTS
The authors wish to acknowledge the efforts of the Laboratory
Services Section of the Technical Investigations Branch, EPA, Region VIII,
in providing analytical chemistry support for this project. Additional
analytical support was provided by the regional microbiology staff, whose
efforts are also acknowledged.
The project was conducted under the supervision and direction of
C.E. Runas, Chief, Water Quality Investigations Section, EPA, Region VIII.
Field work was conducted by C.E. Runas, W.A. Warner, T.E. Braidech,
D.R. McDonough, and R.L. Fox. The algal assay was conducted by R.M. Eddy.
111
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TABLE OF CONTENTS
Page
ABSTRACT v
LIST OF FIGURES vi
LIST OF TABLES vii
CONVERSION FACTORS viii
INTRODUCTION 1
SUMMARY AND CONCLUSIONS 2
DESCRIPTION OF STUDY AREA 4
METHODS AND MATERIALS 7
General 7
Algal Assay 19
RESULTS AND DISCUSSION 11
Reservoir - Physical and Chemical Characteristics 11
Tributary - Physical, Chemical, and Microbiological 19
Characteristics
Algal Growth Potential 33
REFERENCES 45
APPENDICES
APPENDIX A - Chemical data - Green Mountain Reservoir 47
APPENDIX B - Bottom Depth Profiles - Green Mountain Reservoir . . 69
APPENDIX C - Tributary and STP Data - Lower Blue River 76
Drainage
iv
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ABSTRACT
During September, 1976, a study was conducted by the Environmental
Protection Aqency, Region VIII, to determine existing nutrient and organic
loadings to Green Mountain Reservoir, present trophic status of the
reservoir, and possible effects of increased nutrient addition on algal
growth potential. Sampling was conducted during a four day period, with
additional samples collected in November, 1976.
Samples in Green Mountain Reservoir were collected at quarter points
along six transects, three depths per sampling site. Samples were also
collected from the Dillon-Silverthorne STP, the mainstem Blue River,
and eight tributaries in the lower Blue River drainage.
Of the computed total phosphorus and total nitrogen loadings to
the reservoir, 12.8% and 7.0%, respectively, were attributable to the
Dillon-Silverthorne STP. Non-point loadings from the lower Blue River
drainage (omitting the discharge from Dillon Reservoir) comprised
51.1% of the total phosphorus and 36.4% of the total nitrogen entering
Green Mountain Reservoir. Results of the laboratory algal assays indi-
cated phosphorus limitation at all stations with micronutrient limitation
also evident at stations 3b and 6b. On the basis of chlorophyll a_and
primary productivity values, Green Mountain Reservoir, at the time of
sampling, was oligotrophic. Dry weight yields in the algal assays indicated
that potential primary productivity was moderate at the time of sampling.
v
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LIST OF FIGURES
Figure Page
1 Sampling station locations in the lower Blue River drainage,
Colorado 5
2 Sampling transect locations on Green Mountain Reservoir,
Colorado 6
3 Temperature profiles recorded at transects 1 and 2, Green
Mountain Reservoir, Colorado 12
4 Temperature profiles recorded at transects 3 and 4, Green
Mountain Reservoir, Colorado 13
5 Temperature profiles recorded at transects 5 and 6, Green
Mountain Reservoir, Colorado 14
6 The effects of phosphorus, nitrogen, and phosphorus plus
nitrogen, both singly and in combination with EDTA, as
compared to the control samples on the growth of Selenastrum
capricornutum in autoclaved and filtered water from Green
Mountain Reservoir, station lb 35
7 The effects of phosphorus, nitrogen, and phosphorus plus
nitrogen, both singly and in combination with EDTA, as
compared to the control samples on the growth of Selenastrum
capricornutum in autoclaved and filtered water from Green
Mountain Reservoir, station 3b 36
8 The effects of phosphorus, nitrogen, and phosphorus plus
nitrogen, both singly and in combination with EDTA, as
compared to the control samples on the growth of Selenastrum
capricornutum in autoclaved and filtered water from Green
Mountain Reservoir, station 6b 37
9 Changes in mean cell volume of Selenastrum capricornutum as
a function of time in algal assays conducted with water
from station 3b, Green Mountain Reservoir, Colorado 38
10 Changes in mean cell volume of Selenastrum capricornutum as
a function of time in algal assays conducted with water
from station 6b Green Mountain Reservoir, Colorado 39
vi
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LIST OF TABLES
Table Page
1 Description of sampling station locations in the lower Blue
River drainage, Colorado 8
2 Chlorophyll ^ and phaeophytin £ concentration of samples collected
from Green Mountain Reservoir, September and November, 1976 16
3 Comparison of primary productivity values obtained during the
September, 1976 survey with values reported by Nelson (1971)
for Green Mountain Reservoir, August, 1963 18
4 List of alga taxa recorded at stations lb, 3b, and 6b, Green
Mountain Reservoir, November, 1976 19
5 Summary of water quality data collected in the lower Blue River
drainage 20
6 Flow comparisons in the lower Blue River drainage 22
7 Water quality criteria and standards 25
8 Total phsophorus loadings in the lower Blue River drainage,
Colorado 26
9 Nutrient sources in the lower Blue River drainage, Colorado 27
10 Total phosphorus export in several subdrainages in the lower
Blue River drainage, Colorado 29
11 Comparison of total phosphorus loadings to Green Mountain
Reservoir, Colorado, present and NES study 30
12 Total nitrogen loadings in the lower Blue River drainage, Colorado ... 31
13 Comparison of total nitrogen loadings to Green Mountain Reservoir,
Colorado, present and NES study 32
14 Nutrient concentrations in euphotic zone composite samples - pre-
served, filtered only, and autoclaved and filtered, collected from
Green Mountain Reservoir, stations lb, 3b, and 6b, November, 1976 ... 34
15 Two sample two-tailed student's t-test of dry weight yields at
different nutrient spike levels in water collected from
stations lb, 3b, and 6b, Green Mountain Reservoir, Colorado 41
16 Comparison of actual vs. theoretical dry weight yields of
Selenastrum capricornutum in algal assays performed with water
collected from Green Mountain Reservoir, November, 1976 42
v 11
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CONVERSION FACTORS
Kilometers x 0.6214 = miles
Meters x 3.281 = feet
Cubic meters/sec x 35.315 = cubic feet/sec
(cms) (cfs)
Square kilometers x 0.3861 = square miles
Kilograms/square kilometer x 8.923 x 10"^ = pounds/acre
Kilograms x 2.205 = pounds
Centimeters x 0.3937 = inches
Liters x 0.946 = quarts
m3/s x mg/1 x 86.4 = Kg/day
viii
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INTRODUCTION
In 1974, a study of Dillon Reservoir and the upper Blue River drainage
was conducted to assess the trophic status of the reservoir and determine
the possible effects of nutrient addition (EPA, 1974). The study was in
partial fulfillment of a commitment by the Environmental Protection Agency,
Region VIII, to study the entire Blue River Basin. The present study of
Green Mountain Reservoir and the lower Blue River drainage, a project
similar in scope to the Dillon Reservoir study, fulfills that commitment.
The investigation was conducted over a four day period in September,
1976, with additional samples collected during November, 1976. The study
objectives for the Green Mountain study were similar to those of the Dillon
study:
1. Determine the existing nutrient levels in Green Mountain Reservoir,
2. determine the organic and nutrient loadings from the major tribu-
taries in the lower Blue River drainage,
3. determine the organic and nutrient loadings from municipal waste-
water treatment facilities discharging into the lower Blue River
drainage, and
4. determine the probable consequences of increased nutrient concen-
trations on algal growth potential.
1
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SUMMARY AND CONCLUSIONS
A water quality study was conducted by the Environmental Protection
Agency during September and November, 1976 in the lower Blue River drainage,
including Green Mountain Reservoir, in order to assess the trophic status
of the lake and the possible effects of nutrient addition on algal growth
potential. Water samples were collected from eight tributaries to the Blue
River, the Dillon-Silverthorne Sewage Treatment Plant (STP), four mainstem
Blue River locations, and along six transects of the reservoir.
The Dillon-Silverthorne STP and each stream location was sampled three
times during a four day period for 19 water quality parameters. Measure-
ments for several common parameters (temperature, pH, D.O., conductivity,
BOD5 and TSS) were generally indicative of high quality water in the lower
Blue River drainage. Evidence of possible microbiological pollution, as
indicated by fecal coliform measurements, was found in Otter Creek (597 FC/
100 ml). Runoff from livestock grazing areas is considered the likely cause
for the high coliform counts in Otter Creek. Metals data indicated that
concentrations of total molybdenum, iron, and zinc exceeded recommended
EPA criteria and/or proposed Colorado water quality standards. The
molybdenum criterion of 10 yg/1 was exceeded by a factor of 10 in the Blue
River, while the proposed total iron and zinc standards (500 ug/1 and
50 ug/1, respectively) were only slightly exceeded.
Measurements of total nitrogen (T-N) and total phosphorus (T-P)
indicated the following:
1. The only point source in the lower Blue River drainage, the Dillon-
Silverthorne STP, contributed 7.0% of the T-N and 12.8% of the T-P
entering Green Mountain Reservoir during the study period. The
phosphorus load of 0.78 kg/day (1.73 lb/day) was substantially
less than the wasteload allocation of 1.42 kg/day (3.13 lb/day).
2. The nonpoint nutrient load from the lower Blue River drainage
(excluding the contribution from Dillon Reservoir) comprised 36.4%
of the T-N and 51.1% of the T-P entering Green Mountain Reservoir.
3. The discharge from Dillon Reservoir comprised 56.6% of the T-N
and 36.1% of the T-P entering Green Mountain Reservoir.
4. Nutrient measurements obtained during this study were generally
in agreement with the results obtained during the 1974-1975 EPA
National Eutrophication Survey on Green Mountain Reservoir.
5. The Black Creek and Otter Creek drainages had the highest total
phosphorus export rates (approximately 5 and 6 kg/km*/yr, respect-
ively) .
2
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On the basis of chlorophyll a. concentrations, primary productivity
values, and plankton cell counts, Green Mountain Reservoir, at
the time of sampling, was oligotrophia
Algal assay results indicated that phosphorus was the limiting
nutrient in Green Mountain Reservoir. A concurrent micronutrient
limitation was also noted for samples collected from stations 3b
and 6b.
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DESCRIPTION OF STUDY AREA
Located west of the Continental Divide, Green Mountain Reservoir is
an impoundment of the Blue River situated 40.2 km (25 mi) downstream from
Dillon Reservoir and 24.1 km (15 mi) upstream from the town of Kremmling,
Colorado (Figure 1). Approximately 48.3 km (30 mi) downstream from the
dam, the Blue River joins the Colorado River.
Green Mountain Reservoir was the initial feature of the Bureau of
Reclamation's Colorado-Big Thompson Project, a trans-mountain diversion
project to supply water from the Colorado River on the western slope of the
Divide to the eastern slope for multiple purpose usage. The reservoir,
which was created mainly for replacement of project-induced water shortages,
also has power production capabilities. Completed in the Spring of 1943,
Green Mountain Dam created a reservoir of 191 x 106 rrr* (154,645 acre-feet)
total capacity of which 64 x 10^ (52.000 acre-feet) are reserved exclus-
ively for replacement while 117 x 10° m3 (94,888 acre-feet) are for power
production. Inactive storage (dead storage) is 10 x 106 m^ (7,757 acre-
feet) (U.S.B.R., 1957).
The Blue River is the major tributary of Green Mountain Reservoir,
comprising approximately 70% of incoming flows (EPA, 1976b). Flow in the
Blue River is, for the most part, regulated upstream by Dillon Dam.
Between Dillon and Green Mountain Reservoirs, the Blue River flows through
an area comprised of several different types of land uses. These types
include mountainous forest lands, open meadows utilized for livestock
grazing, light agricultural lands (hay fields), scattered vacation and/or
retirement homes, and light residential/commercial lands. Because of the
area's highly desirable natural setting and its proximity to several major
skiing areas, the Blue River basin is the focus of considerable debate
concerning future growth patterns.
4
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Green Mountain
\ Reservoir
iitwtliorne
SO
Dillon
Figure 1. Sampling station locations 1n the lower Blue River drainage,
Colorado, September, 1976 (adapted from EPA, 1976b),
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2
N
i
a\
0
H"
2
-L.
3 Km
-*-1
2 Mi
A.
Figure 2. Sampling transect locations on Green Mountain Reservoir, Colorado, September, 1976.
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METHODS AND MATERIALS
GENERAL
Water quality sampling during the September, 1976 survey consisted of
two major parts: (1) the main body of the reservoir and (2) the tributaries
and associated sewage treatment plant. Six transects were established on
Green Mountain Reservoir with samples collected at quarter points on each
transect (Figure 2). At each sampling location on each transect, water
was collected one meter below the surface, at the thermoclirie (plane of
maximum temperature gradient) and approximately 2 meters above the bottom.
In the event that the water depth at any sampling location was less than
the mid-channel thermocline depth, samples were collected only at the
surface and the bottom. Sampling stations were also located on nine tribu-
taries in the lower Blue River drainage- Blue River, Cataract Creek, Otter
Creek, Black Creek, Slate Creek, Boulder Creek, Rock Creek, Willow Creek,
and Straight Creek (Table 1). Samples were also collected from the Dillon-
Silverthorne Sewage Treatment Plant (STP). Figure 1 shows the respective
locations of the tributary sampling stations.
All water samples collected were "grab" type samples. Samples from
the reservoir were taken with a polypropylene Kemmerer water bottle. Samples
for nutrient (TKN, NH3, NO2 + NO3, T-P, ortho-P) and metal (total and dis-
solved Si, Mo, Fe, Zn, Cu) analysis were placed in plastic cubitainers and
preserved with 4 ml HgCl2 per liter and 5 ml HNO3 per liter, respectively.
Aliquots for dissolved metals were field filtered with a 0.45y filter
prior to preservation. In addition to collection of metal and nutrient
samples, field determinations for temperature, pH, dissolved oxygen, and
conductivity were made. Also, at all tributary sampling stations and the
Dlllon-Silverthorne STP, samples were collected for 5-day biochemical oxygen
demand (BOD5), total suspended solids (TSS), and total and fecal coliform.
All total and fecal coliform analyses were conducted by Membrane Filter
(MF) technique unless the Most Probable Number (MPN) value is shown, indi-
cating the alternate technique was used. Where possible, Instantaneous
stream flow measurents were also made using an electromagnetic current
meter.
Temperature and depth profiles were recorded at each lake transect.
A direct read-out thermistor-thermometer equipped with a 62 m (200 ft)
cable was used to establish the temperature gradients. Depth profiles
were determined using Sonar.
A submarine photometer was used to determine the depth of the euphotlc
zone (U level of light penetration) at transect mid-points. Determination
of the euphotlc zone was necessary prior to collection of euphotlc zone
composite samples for algal assays and collection Of samples for primary
productivity studies (C14). Methodology employed In determining the algal
growth potential of the reservoir water 1s discussed lit detail 1n a separate
section.
7
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Table 1. Description of sampling station locations in the lower Blue River drainage, Colorado.
River River
Station No. Kilometer Mile Description
CO
BR-1 63.1 39.2 Blue River immediately downstream from Dillon Reservoir at USGS
gaging station
SC-1 62.9 39.1 Straight Creek at mouth
WC-1 59.7 37.1 Willow Creek at Highway 9 Crossing
DS-STP 57.6 35.8 Dilion-Silverthorne Sewage Treatment Plant effluent
BR-2 52.5 32.6 Blue River at point where river bends close to Highway 9,
approximately 2.6 km (1.6 mi) upstream from Rock Creek
RC-1 49.9 31.0 Rock Creek at Highway 9 crossing
BC-1 47.6 29.6 Boulder Creek at Boulder Creek Picnic Ground
SLC-1 40.9 25.4 Slate Creek at mouth
BR-3 35.1 21.8 Blue River at Highway 9 crossing at upstream end of Green
Mountain Reservoir
BLC-1 - - Black Creek at Heeney Road crossing
0C-1 - - Otter Creek at Heeney Road crossing
CC-1 - - Cataract Creek at Heeney Road crossing
BR-4 22.5 14.0 Blue River immediately downstream from Green Mountain Reservoir
at USGS gaging station
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Primary productivity was estimated by measuring the uptake of radio-
active carbon (C'4) by the indigenous phytoplankton. The methodology
employed was that outlined in Standard Methods, 14th Edition, 1975.
Estimates of primary productivity were made in duplicate at three depths
at stations lb, 3b, and 6b. Samples were collected at three-meter intervals
from the surface to the lower level of the euphotic zone. Light energy
during the incubation period and daily photoperiods were measured with a
pyroheliometer, with values reported in gram calories per cm2 per day.
Water samples for the C14 study were collected at 3 depths with a
polypropylene Kemmerer water bottle and placed in 300 ml BOD bottles.
At each depth two of the bottles were unaltered for use as light bottles
while light penetration was eliminated from the two remaining bottles.
Five microcuries of C14 as sodium carbonate in solution were added to each
bottle. After inoculation, the bottles were suspended at the original
depth of collection and incubated four to six hours. Following incubation
300 ml were filtered through 0.45y membrane filters which were then
stored in a desiccator.
Upon arrival at the laboratory, the filters were dissolved in 2 ml
of dimethyl-foramide in a liquid scintillation counting vial and filled with
Cab-0-Sil. The Cab-0-Sil was then dissolved with 15 ml of liquid
scintillation counting media (Permafluor). Samples were counted for
20 minutes by a Packard liquid scintillation counter Model 3390. Counting
efficiency was determined by measuring a standard C'4 solution.
Carbon assimilation was determined using the following formula:
„ , ,#J 1.06 (A/t - B) C•D•E•103
C mg/nrVday s
2.22 F-G-H-J x 106
nig Carbon/m3/day x euphotic zone depth (m) ¦ mg C/m2/day
Where:
1.06 = Ratio of C12/C14 uptake rates
A * Total counts of sample
t » Counting.time In minutes
B ¦ Instrument background 1n counts per minute
C ¦ Volume Inoculated 1n C-T4
0 ¦ Carbon-12 concentration 1n sample media, mg/1
E ¦ Total photic period
103 * Conversion of liters to cubic meters ;
2.22 » Conversion factor for disintegration per m1n. to pCi
F> Counting efficiency, counts per min./disintegration per m1n.
G - Volume of sampled filtered (300 ml)
H - Amount of C*14 added to jsaniple, yC1
J « Incubation period 1n same units as photic period
10® * Conversion of pC1 to uC1
9
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Chlorophyll concentrations were determined for individual depth
samples and for each euphotic zone composite sample (see Methods and
Materials - Algal Assay). The methodology employed was the trichrometric
procedure as outlined in the EPA Biological Methods Manual (1973).
Phaeophytin ^concentrations were also determined.
Phytoplankton concentrations were determined for an aliquot of each
euphotic zone sample collected only during November. Samples were placed
in cubitainers, preserved with formalin, and stored in the dark until analysis.
Phytoplankton were enumerated following the general sedimentation procedures
outlined in Schwoerbel (1970) and Vollenweider (1969) for inverted microscopes.
Phytoplankton were identified to the lowest taxonomic level possible using
the keys of Smith (1950), Patrick and Reimer (1966), Ward and Wipple (1959),
and Weber (1971).
ALGAL ASSAY
Water was collected from three locations on Green Mountain Reservoir,
(stations lb, 3b, and 6b) on November 17, 1976 (Figure 2). A euphotic zone
composite sample was collected for use as the algal assay test water. At
each station, equal-volume water samples were collected at two-meter intervals
in the euphotic zone and composited in a 3.78 liters carboy (pre-washed with
10% HCL). Aliquots of the composite sample were withdrawn and preserved
for nutrient and metal analysis (4 ml HgClg per liter and 5 ml HNO3 per
liter, respectively). Separate aliquots were also taken for chlorophyll
analysis and phytoplankton counts. In addition to the composite sample,
water for nutrient determinations was collected at a depth of one meter,
at the mid-depth of the water column and at two meters above the bottom
at all three sampling stations. Temperature, dissolved oxygen concentration,
pH and conductivity were also recorded at each sampling location and depth.
After compositing the euphotic zone samples, the algal assay test water
was refrigerated and transported to the laboratory.
Upon arrival, the test water was transferred to glass media bottles
and autoclaved for 30 minutes at 121 C. After cooling, the test waters were
carbonated with a mixture of 1% CO? in air until the original pH was
obtained. The samples were then filtered through a 0.45y Millipore filter
to remove any particulate matter which would interfere with the electronic
particle counter (Coulter Model ZBI). An additional aliquot of the auto-
claved and filtered composite samples was then removed for nutrient analysis
to note any changes in chemical composition of the test water.
All algal assays were conducted following the procedures outlined in
the Algal Assay Procedure, Bottle Test (EPA, 1971). Selenastrum capricornuturn
Printz was used as the test alga. Assays were conducted in triplicate using
250 ml wide mouth Erlenmeyer flasks, each flask containing 100 ml total
volume of culture. Each test flask was inoculated from a 7-day old stock
culture to yield a starting concentration of 1 x 10^ cell/ml. All flasks
were then incubated for 14 days in a Psycotherm Incubator at 24 i 0.5 C.
All flasks were continuously illuminated with cool-white fluorescent lighting
of 400 ft-c (4303 lux).
10
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RESULTS AND DISCUSSION
RESERVOIR - PHYSICAL AND CHEMICAL CHARACTERISTICS
The complete tabulation of results of physical and chemical parameters
sampled at each depth at each station in Green Mountain Reservoir is given
in Appendix A.
Temperature
Figures 3-5 and Appendix B show the thermal and depth profiles deter-
mined at each of the sampling tansects during the September, 1976 survey,
respectively. In general, temperature gradients were similar at all stations.
Surface temperatures ranged from 15-18 C (mean - ca. 16 C), while the
temperatures at 15 meters (49 ft) and 30 meters (98 ft) ranged from 14 to
15.3 C and from 12 to 13 C, respectively. At 45 meters (148 ft) temperatures
ranged from 9.5 to 10 C and averaged 9.8 C. During the November sampling,
Green Mountain Reservoir was essentially isothermal. Surface temperatures
were 7 C while temperatures at 45 meters (143 ft) were 6.5 C.
In general, these findings are in agreement with previous studies
(Nelson, 1955 and 1971). Nelson (1955) reported that during 1949 and 1950,
thermal stratification existed in Green Mountain Reservoir from June through
August. Maximum temperature gradients, however, rarely exceeded 1.0 C per
meter (2.75 F per 5 ft). Thermal conditions in the upper end of the reservoir
were reported to have reflected the thermal characteristics of the incoming
Blue River.
fiH
During the September survey, pH values were generally uniform through-
out the reservoir. Values for pH for all sampling stations at surface, mid,
and bottom depths ranged from 6.5 to 7.6, 6.4 to 7.3, and 6.3 to 7.3, respect-
ively. The mode pH at surface, mid, and bottom depths was 7.3, 7.2, and
7.1, respectively, while median pH for surface, mid, and bottom depths was
7.2, 7.0, and 6.9, respectively. During November, pH values at all stations
and depths sampled were slightly higher than recorded 1n September.
Dissolved Oxygen Concentration
During the September survey, dissolved oxygen concentrations of surface
samples (1 m depth) were similar throughout the reservoir, ranging from 6.9
to 7.6 mg/1 O2 and averaging 7.1 mg/1 02. In general, dissolved oxygen
concentrations decreased with depth at all sampling stations except along
transect 6, the furthest upstream transect. Samples collected along
transects 1, 2, and 3 in the downstream half of the reservoir showed lower
concentrations of dissolved oxygen than did samples collected at similar depths
along transects 4, 5, and 6, a condition likely indicative of the influence
11
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Figure 3. Temperature
Reservoir, Colorado.
profiles recorded at transects
1 and
2, Green Mountain
11/17/76
9/13/76
Station 1-b
25
10
50
75
Q.
01
O
100
-^20
a.
v
3
30
Station 2-b
9/13/76
125
150
40
50
12
5
10
Temperature (C)
15
20
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Figure 4. Temperature profiles recorded at transects 3 and 4, Green Mountain
Reservoir, Colorado.
0
25
50
^ 7t
Q.
CU
Q 100
125
150
10
20
e
xz
4->
Q.
® 30
Q
40
50
Station 3-b
9/13/76
10
15
20
5
a
6
25
50
75
100
125
150
or
13
10
20
E
JZ
4->
a.
* 30
40
50*
0
Station 4-b
9/13/76
10
Temperature (°C)
15
20
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Figure 5. Temperature profiles recorded at transects 5 and 6, Green Mountain
Reservoir, Colorado.
50
7o
o.
01
° TOO
125
1 bO
10
sz
Q-
41 -sri
o 30
40
50
Station 5-b
9-13-76
¦4-
JLip
10
15
J
20
4->
<4-
a.
O)
-a
2j
JO
76
100
10
S" 20
30
Station 6-b
9-13-76
10
15
20
14
Temperature (°C)
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by the Blue River. The lowest dissolved oxygen levels recorded (4.0 and
4.1 mg/1) were from bottom samples at stations lb and 2b (67 and 58 m depth,
respectively).
Nutrients
Ammonia concentrations were, in general, low throughout the reservoir.
The highest concentration recorded during the September survey was 0.033
mg/1, while values of less than 0.005 mg/1 were reported frequently. No
correlation between ammonia and depth or ammonia and station location was
evident. Ammonia concentrations recorded in November were similar to those
found during the September study.
Total Kjeldahl nitrogen (TKN) concentrations ranged from 0.04 to 0.38
mg/1 N. The 96 samples collected were distributed accordingly: 0.00-0.10
mg/1, 24%; 0.11-0.20 mg/1, 33%; 0.21-0.30 mg/1, 30%; 0.31-0.40 mg/1, 9%;
and greater than 0.41 mg/1, 3%. TKN concentrations were not correctable to
either depth or sampling station location.
Of all the nutrient parameters sampled during the September survey,
nitrite plus nitrate (N0o + N03) concentration was the only one showing
disttnt chemical stratification. At all stations sampled, NO2 + NO3
concentrations increased with depth. Surface concentrations ranged from
less than 0.005 to 0.012 mg/1 N with a median of 0.006 mg/1 N, while
samples collected from 16 to 40 m ranged from 0.210 to 0.142 mg/1 N. The
two highest NO2 + NO3 concentrations recorded (0.260 and 0.223 mg/1) were
collected at station 2b at a depth of 58 m.
The NO? + NO3 stratification observed during the September survey
was not evident during November sampling. As expected, in view of the
isothermal state of the reservoir in November, concentrations were similar
at all depths and stations sampled, with concentrations averaging 0.055 mg/1 N.
Total phosphorus and ortho-phosphorus concentrations were consistently
low at all depths and stations sampled during the September survey. Ortho-
phosphorus concentrations were consistently less than 0.005 mg/1 P while
total phosphorus concentrations were consistently less than 0.010 mg/1 P.
Rejecting the total phosphorus value of 0.14 mg/1 P collected from station 2b
at 58 m as an outlier, the highest total phosphorus value recorded was
0.024 mg/1 P at station lb at 67 m. Neither ortho-phosphorus nor total
phosphorus concentrations exhibited any trends with respect to depth or
station location.
Chlorophyll a
Table 2 shows the chlorophyll 4 concentrations of samples collected
at depths of 1» 3, and 5 meters at Ttatlons lb, 3b, and 6b. Also shown are
the chlorophyll a concentrations of allquots of the composite samples
collected from tWe above stations during the September survey. As shown
1n Table 2* during the November sampling, chlorophyll a. concentrations were
determined only for the composite samples.
ID
-------
Table 2. Chlorophyll a^ and phaeophytin a. concentration of samples collected
from Green Mountain Reservoir, September and November, 1976.
Date Station - Dffh Chlorophyll a Phaeophytin a tetfo1
(m) vg/1 pg/1
9/13-17/76
11/17/76
lb
-
composite
3.12
1.56
1.47
lb
-
1
3.56
1.42
1.50
lb
-
3
3.56
1.11
1.53
lb
-
5
4.30
-
-
3b
_
composite
2.67
1.07
1.50
3b
-
1
3.12
3.43
1.33
3b
-
3
4.01
1.91
1.47
3b
-
5
3.56
0.80
1.57
6b
_
composi te
2.67
1.07
1.50
6b
-
1
-
-
-
6b
-
3
3.18
-
-
6b
-
5
3.56
2.67
1.40
lb
.
composite
2.14
0.11
1.67
3b
-
composite
2.14
0.11
1.67,
6b
-
composite
2.67
0.05
1.71'
1 0D663 ratio = 0P663 bef°re acidification
0Dg63 after acidification
A solution of pure chlorophyll would yield an 0Dgg3 ratio of 1.70. Conversely,
a solution containing phaeophytin a. but no chlorophyll would yield an
0Dgg3 ratio of 1.0.
2 Theoretical maximum is 1.70. Error is likely analytical.
16
-------
Algal biomass determinations based solely on chlorophyll admeasure-
ments are imprecise due to the possible fluctuation in concentration
resulting from physical and nutritional conditions which do not necessarily
affect the standing crop similarly. However, chlorophyll ^concentrations can
lend some insight into the relative amount of the standing crop. Greene,
et al, (1975) showed very high correlation between chlorophyll ^concen-
trations and maximum control yields in algal assays performed with Sele-
nastrum capricornutum. Strong correlation between chlorophyll a_ and
indigenous alga cell volumes was also reported.
During the September survey, chlorophyll a_ concentrations were similar
at all station locations. Maximum concentrations were recorded from
3-5 meters. Chlorophyll a concentrations recorded for November composite
samples were only slightly lower than values recorded for similar samples
taken during September. November samples, however, did display a markedly
higher OD533 ratio (OD = optical density).
The chlorophyll ^concentrations reported from both the September and
November sampling were very similar to the values reported by EPA (1975)
for samples collected from Green Mountain Reservoir during October,1975.
Although sufficient data are not available for regression analyses similar
to that reported by Greene, et al, (1975), the data is presented for
possible use with additional data collected in the future.
C™
As can be seen from Table 3, primary productivity, as measured using
methodology, was low at all sampling stations. The maximum one meter
C mg/m^/day value was recorded at station lb (8.88) while the minimum one
meter value was obtained at station 6b (4.13). On the basis of the data
collected, primary productivity increased with downstream progression
in the reservoir. The data, however, is obviously very limited. Additional
data collected during different times of the year is needed to substantiate
the possible downstream trend in productivity.
Nelson (1971) reported that Green Mountain Reservoir had the lowest
primary productivity values recorded during a study of seven reservoirs
associated with the Colorado-Big Thompson Project. Nelson also reported
that a well defined peak of maximum productivity was not observed. The
primary productivity values reported here for the September, 1976 survey
were also low and did not exhibit a defined depth of maximum productivity.
The values reported here, however, are consistently lower than the levels
reported by Nelson (1971) for similar incubation depths. Variations
between the two studies may be due, 1n part, to the difference in the time
of year of the respective studies (I.e., September, 1976 vs. AugustJ963)
and/or light conditions during Incubation, or both. During the September
1976 survey, Illumination was less than optimal as skies were consistently
overcast during at least a portion of the Incubation periods. Additional
samples are needed to determine maximum primary productivity during more
optimal light conditions.
17
-------
Table 3. Comparison of primary productivity values obtained during the September, 1976 survey with values
reported by Nelson (1971) for Green Mountain Reservoir, August,1963.
EPA (1976) Nelson (1971)
Date
Station
U
Illumination
Depth
(m)
Sampl e
Depth
(m)
C mg/m3/dayV
U
Illumination Sample
Depth Depth
Date (m) (m)
C mg/m^/day^Z
9/16/76
lb
5.5
1.0
8.88
8/1/63 7.5 0.10
10.8
lb
3.0
7.79
0.10
18.9
lb
5.4
1.65
1.00
18.0
1.50
27.0
3b
5.0
1.0
6.15
3.00
18.0
3b
3.0
7.83
6.00
9.0
3b
4.5
5.16
9.00
0.9
9/17/76
3b
4.7
1.0
5.78
3b
2.7
4.93
3b
4.5
2.61
6b
5.0
1.0
4.13
6b
2.7
4.04
6b
4.8
1.49
1 Primary productivity values were not converted to C mg/m^/day because the entire euphotic zone was not
adequately defined by the collected samples.
^ Values shown are estimates taken from Figure 12 (Nelson, 1971).
-------
Ph.ytoplankton
Algal counts from aliquots of the November euphotic zone composite
samples were extremely low at all stations. Individual genus counts were
usually less than 10 cells per ml while total cell counts were less than
100 per ml. Nitzschia sp., Asterionella formosa, Fragilaria crotonensis.
and Stephanidiscus astrea were the most abundant species. Table 4 shows
the composite list of species found at stations lb, 3b, and 6b. The very
low cell counts may be a result of both time of year sampled and the dilution
effect of the composite sample. The cell concentrations reported here
should not be construed to be indicative of concentrations at specific
depths or during different times of the year. Future sampling should
include both individual depth samples and composite samples.
Table 4. List of alga taxa recorded at stations lb, 3b, and 6b,
Green Mountain Reservoir, November, 1976.
Bacillariophyta
Achnanthes sp.
Asterionella formosa
Cocooneis sp.
Cymbella prostrata
Diatoma hiemale
Fraqilaria crotonensis
Gomphonema" sp.
Gyrosioma sp.
Navicula sp.
Nitzschia sp.
Nitzschia dissipata
Nitzschia" sigmoidea
Pinnularia sp.
Rhoicospenia curvata
Stephanod-ficus astrea
Svnedra sp.
Tabellaria fenestrata
Chlorophyta
Closterium sp.
Cosmarium sp.
Crucegenia sp.
Elakatothrix viridis
Q8c,ystis sp.
Schroderia setigera
TRIBUTARY - PHYSICAL, CHEMICAL, AND MICROBIOLOGICAL CHARACTERISTICS
The complete tabulation of results of physical, chemical, and
microbiological parameters collected at each sampling station 1s given
in Appendix C. This data has been summarized 1n Table 5 showing the
3-day average value for each parameter.
19
-------
Table 5. Suwoary of water quality data collected in the lower Blue River drainage.
Parameter1
Units
BR-1
SC-1
WC-1
OS-STP
BR-2
RC-1
BC-1
SLC-1
BR-3
BLC-1
0C-1
CC-1
BR-4
Temp
C
7.0
8.5
10.5
12.5
10.5
9.5
10.0
9.5
8.5
10.5
9.5
10.5
12.0
P« ,
Flow2
S.U.(median)
wr/s
6.9
7.0
6.6
6.6
6.7
6.7
6.8
6.8
6.7
6.7
6.8
6.5
6.4
4.30
0.221
0.161
0.022
4.59
0.331
0.221
0.357
6.57
0.65
0.045
0.161
18.97
Cond
wnhos/cm
170
110
70
390
180
60
60
60
150
<50
130
120
170
00
mg/1
9.9
8.4
8.0
-
8.6
8.5
8.3
8.1
9.0
8.3
8.3
8.2
5.8
BOOg
mg/1
<1.0
<1.0
<1.0
2.2
<1.0
1.0
<1.0
<1.0
1.0
<1.0
1.1
<1.0
<1.0
TSS
mg/1 .
<1.0
6.5
<1.1
7.9
<1.5
1.4
<1.1
1.7
2.1
<2.5
4.7
1.7
2.3
T-Coli
HF#/100ml(Geom Mean)
<2
284
118
949
23
23
12
43
351
193
871
37
18
F-Coli
MF#/100ml(Geo» Mean)
<1
64
22
42
11
6
5
32
29
85
597
20
1
51
»g/l
2.35
4.10
3.02
5.27
2.70
2.42
1.57
1.45
2.85
1.00
6.97
1.30
2.67
T-Mo
"g/1
165
<15
<10
60
135
10
<10
<10
100
<10
<10
<10
85
D-No
ug/l
165
15
<10
50
125
<10
<10
<10
100
<10
<10
<10
80
T-Fe
ug/l
40
510
130
100
100
180
200
330
160
180
1020
220
90
0-fe
ug/l
15
125
70
15
50
90
90
170
40
60
580,
150
40
T-Zn
ug/l
75
20
35
75
45
<10
15
20
65
35
15
25
35-5
D-Zn
ug/l
35
10
10
50
30
<10
10
10
25
10
10
20
50J
T-Cu
ug/l
<5
<5
5
5
5
<5
<10
<10
<10
<10
5
<5
53
D-Cu
ug/l
<5
<5
<5
5
<5
5
<5
<5
<10
<5
<5
<5
103
T-Coli
MPN/100m1(Geom Mean)
2027
F-Coli
MPH/100ml(Get» Mean)
63
*A11 values are 3-day arithmetic averages unless otherwise noted.
2 See the footnotes in Table 8 for an explanation of the computation of mean flows.
' These dissolved zinc and copper concentrations are thought to be excessive because of sample contamination.
* This value omits one excessively high concentration of 325 ug/l measured on 9/15/76.
-------
Flow
Flow rates measured during this study averaged slightly less than the
5-year average of the mean September flows at all sampling stations
(Table 6). Tributaries to the Blue River contributed 17.3% of the total
flow entering Green Mountain Reservoir while direct tributary flow to the
reservoir via Black, Otter, and Cataract Creeks comprised only 11.1% of
the total. During the National Eutrophication Survey (NES) of Green
Mountain Reservoir in 1974-1975 (EPA, 1976b), the above tributaries contrib-
uted 20.5% and 13.7% of the total annual flow, respectively. Significant
flow variations were observed during the 4-day study period, including a
51% increase in flow from Dillon Reservoir (via the Blue River) and an
approximate 50% increase in tributary flow due to sporadic rainfall occurring
throughout the study reach. These flow increases made it difficult to
calculate representative nutrient loadings, especially since individual
stations were sampled on only three out of the four sampling days. The
only point discharge in the study area was the Dillon-Silverthorne STP,
which discharged at a rate of 0.022 m3/s during this study. During the
September,1975 portion of the NES study (EPA, 1976b) the STP had averaged
0.020 m3/s (0.71 cfs). Outflow from Green Mountain Reservoir averaged
18.97 m3/s (670 cfs) during this study, while total inflow was only
7.39 m3/s (258 cfs).
General Parameters
Water temperatures measured during this study varied as much as 5 C
depending on the time of measurement, but most streams averaged between
8.5 C and 10.5 C. The'coldest water was the outflow from Dillon Reservoir
(7.0 C) while the warmest water was the outflow from Green Mountain Reservoir
(12.0 C).
pH measurements were consistently below 7.0, with median values
ranging from 6.4 at the outflow from Green Mountain Reservoir to 7.0 in
Straight Creek.
As shown 1n Table 5, measurements for specific conductance (conductivity)
were lower in the tributary streams than 1n the Blue River Itself. The
outflow from both Dillon and Green Mountain Reservoirs averaged 170 pmhos/cm.
Mean dissolved oxygen (D.Q.) measurements ranged between 8.0 and
9,0 mg/1 at all stream stations except Immediately below the two reservoirs.
The highest mean D.0. concentration recorded was 9.9 mg/1 below Dillon
Reservoir (BR-1) while the lowest mean D.0. recorded was 5.8 mg/1 below
Green Mountain Reservoir (BR-4). This relatively Tow D.0. was likely due
to water withdrawal from the lower depths of Green Mountain Reservoir.
Measurements for BOD5 averaged consistently less than 1.0 mg/1 in all
streams except Otter Creek (1.1 mg/1). The D1llon-S1lverthorne STP (DS-STP)
discharge contained only 2.2 mg/1 BOD5.
21
-------
Table 6. Flow comparisons in the lower Blue River drainage.
INS
ro
Station
BR-1
DS-STP
SC-1
WC-1
RC-1
BC-1
SLC-1
BR-3
BLC-1
OC-1
CC-1
BR-4
Mean Flow* During
9/13-16/76 Study
4.30
0.022
0.215
0.161
0.348 ) 1.276
0.215
0.337
6.57
0.629
0.045
0.147
18.97
Five-Year Average of
the Mean Sept. Flows
1
Mean Flows from NES Report (EPA, 1976b)
4.50
0.379
0.260
0.413
9.403
0.631
0.244
13.85
Sept. 1974
1
2.94
0.020
~ 0.6514
5.38
0.210
0.028
0.059
18.07
9/74-8/75
6.402
0.026
Adjusted to 2.290
to balance inflow
with outflow in
Green Mt. Reservoir
9.64
0.862
0.131
0.537
13.46
4,5
~All flow rates are in m^/s.
1 From USGS Water Resource Reports for Colorado for the years 1970-1974.
2 This value represents mean annual outflow from Dillon Reservoir as stated in the NES Report (EPA, 1976a).
3 Based on data from 1970 and 1971 only.
4 These values include "minor tributaries and immediate drainage" as shown in the NES Report (EPA, 1976b).
5 This annual flow was adjusted to make total annual inflow to Green Mountain Reservoir equal to total
annual outflow.
-------
Several streams contributed concentrations of total suspended solids
(TSS) in excess of concentrations measured in the mainstem Blue River.
Straight Creek (6.5 mg/1) was the most notable contributor, while the
DS-STP also contributed significant concentrations (7.9 mg/1).
Microbiological Parameters
The summary data in Table 5 shows that geometric mean concentrations
of total coliforms in the Blue River increased from <2 per 100 ml to
351 per 100 ml in the 28 km stream reach between Dillon Dam and the
upstream end of Green Mountain Reservoir. In this same reach, fecal coli-
forms increased from <1 per 100 ml to 29 per 100 ml. The major source of
this increase (in terms of concentration) appeared to be the Dillon-Silver-
thorne STP (T-Coli of 949 and F-Coli of 42 per 100 ml, respectively) but
several tributary streams (including Straight, Willow and Slate Creeks)
also contributed significant concentrations of total and fecal coliforms.
It should be pointed out that most probable number (MPN) concentrations of
total and fecal coliforms in the DS-STP effluent averaged approximately
50% and 100% higher, respectively, than the membrane filter (MF) concentra-
tions. Such a difference in results between the membrane filter (MF) and
most probable number (MPN) methods of coliform analysis is not unusual
since MPN results will commonly be from 10% to 40% higher than MF results,
and occassionally as much as 100% higher. The largest measured source of
total and fecal coliforms entering Green Mountain Reservoir directly was
Otter Creek (geometric mean of 871 total and 597 fecal coliforms per 100 ml,
respectively). Coltform die-off was almost complete in Green Mountain
Reservoir, as evidenced by concentrations of total and fecal coliform in
the outflow of only 18 and 1 per 100 ml, respectively.
Metal and Other Parameters
Average concentrations of molybdenum, iron, zinc, copper, and silica
are shown in Table 5 for each sampling location. Concentrations of
molybdenum and zinc tended to decrease in the stream reach from Dillon
Reservoir to Green Mountain Reservoir, whereas iron (and to a slight extent,
copper) concentrations increased in the downstream direction. Average
concentrations of molybdenum and zfnc 1n the tributary streams were all
less than concentrations measured in the Blue River Itself, whereas tributary
concentrations of Iron were all greater than values measured 1n the Blue
River. Copper concentrations did not reflect any difference between
tributary and mainstem sampling locations. Of the three tributary streams
enterfng directly Into Green Mountain Reservoir, Otter Creek exhibited
concentrations of Iron approximately 5 times greater than concentrations
measured 1n Black Creek and Cataract Creek. There were no appreciable
differences 1n molybdenum, zinc, and copper concentrations among these
three streams. Silica concentrations in all streams were observed to vary
directly with the concentrations of total suspended solids.
Table 5 shows both total and dissolved metal concentrations, and it 1s
evident that dissolved Iron and zinc averaged consistently less than total
23
-------
concentrations of these metals. There were no significant differences
between toal and dissolved concentrations of molybdenum and copper. Sample
contamination on 9/14/76 is thought to be the reason for average dissolved
zinc and copper concentrations being higher than total concentrations at BR-4.
Comparison of the metals data with recommended EPA water quality criteria
(EPA, 1976c) and proposed Colorado water quality standards (Colorado Depart-
ment of Health, 1976) (Table 7) indicate that concentrations of total molyb-
denum, iron, and zinc exceeded one or more of the criteria and/or standards.
The recommended criterion of 10 yg/1 total molybdenum for use in crop irriga-
tion was exceeded by a factor of 10 in the Blue River at all sampling locations
between Dillon and Green Mountain Reservoirs and also in Straight Creek and
the Dillon-Silverthorne STP effluent. The likely cause of molybdenum concen-
trations of this magnitude is the large-scale molybdenum mining operation
conducted in the Ten Mile Creek drainage, which drains into Dillon Reservoir.
A previous study of Dillon Reservoir (EPA, 1974) identified molybdenum concen-
trations in the reservoir ranging from 205 yg/1 to 465 yg/1. Total iron
concentrations also exceeded the proposed Colorado standard of 500 yg/1 in
Straight Creek (510 yg/1) and Otter Creek (1020 yg/1). Since water hardness
in the lower Blue River drainage generally averages less than 100 mg/1 as
CaC03 (Britton, 1977), the proposed Colorado standard for total zinc would be
50 yg/1 (zinc limits fluctuate with water hardness due to inter-related tox-
icity effects). This limit was exceeded at two mainstem Blue River locations
(immediately below Dillon Reservoir - 75 yg/1, and immediately above Green
Mountain Reservoir - 65 yg/1) and in the Dillon-Silverthorne STP effluent
(75 yg/1). Both iron and zinc concentrations are considered to be related
to natural hydrochemical stream characteristics.
Total Phosphorus Loadings
Computed total phosphorus loadings from both point and non-point sources
measured during the September, 1976 survey are shown in Tables 8 and 9.
1. Point Source - The Dillon-Silverthorne STP - the only identified
point discharge in the lower Blue River drainage - contributed
12.8% (0.78 kg/day or 1.72 lb/day) of the total phosphorus load
entering Green Mountain Reservoir (Tables 8 and 9). This loading
compares with the wasteload allocation of 1.42 kg/day (3.13 lb/day)
and the average dally 'load of 0.89 kg/day (1.96 lb/day) determined
during the year-long NES Study (EPA, 1976b). Comparison with the
NES data in Table 10 shows that the DS-STP contributed a larger
percentage of the total phosphorus load during this study, probably
due to reduced flows (and related loads) from Dillon Reservoir and
all of the tributaries.
2. Non-po1nt Sources - Non-po1nt sources accounted for 87.2% of the
total phosphorus entering Green Mountain Reservoir during this
study perlQd. As shown In Table 9 this loading consisted of the
following contributions: tributaries to the lower Blue River - 15.9%;
tributaries to the Reservoir1 Itself - 18.6%; unmeasured non-point
sources between Dillon and Green Mountain Reservoirs - 16.6%;
and the outflow from Dillon Reservoir - 36.1%. If the Dillon
24
-------
Table 7. Water quality criteria and standards.
Recommended EPA
Proposed Colorado
Parameter
Units
Criteria (1976c)
Standards (1976)c
Temperature
C
6.5-9.0
20
pH
S.U.
6.5-9.0
D.O.
mg/1
-
7.0
BOD5
T-Molybdenum
mg/1
Mg/1
10(NAS,1973)
5.0
D-Molybdenum
vjg/1
-
-
T-Iron
yg/i
1000
500
D-Iron
pg/i
300
"u
T-Zinc
ug/l
a
50
D-Zinc
yg/i
-
"*u
T-Copper
Mg/l
a
10b
D-Copper
Mg/i
-
-
T-Coliform
MF#/100ml
-
-
F-Coliform
MF#/100ml
-
200
T-Phosphorus
mg/1 as P
0.1
0.1
a A 96-hr LC50 bioassay test is recommended in order to establish a limit for
the particular water body in question.
b Proposed standards vary according to water hardness. The limit for soft water
(<100 mg/1 total hardness as CaC03) is shown.
c The proposed Colorado standards are only preliminary values which may undergo
change during future intensive public review. They are shown for comparison
purposes only.
25
-------
Table 8. Total phosphorus loadings in the lower 31ue River drainage, Colorado.
Station
9/13/76
9/14/76
9/15/76
9/16/76
Ave.
T-P Load
kq/day
Percent
of
Total
Flow*
T-P
mq/1
T-P
Flow*
T-P
T-P
Flow*
T-P
T-P
Flow*
T-P
T-P
m3/s
kg/day
m3/s
mq/1
kg/day
ffl3/S
mq/1
kg/day
rt^/s
mg/1
kq/ day
BR-1
3.09
0.009
2.40
4.16
<0.005
<1.80
4.67
0.006
2.42
5.27
-
<2.20
36.1
5C-13
(0.195)
0.017
0.29
0.2181
0.008
0.15
(0.252)
0.012
0.26
-
-
-
0.23
3.3
WC-13
(0.142)
0.008
0.10
0.15S1
<0.005
<0.07
(0.184)
0.005
0.03
-
-
-
<0.08
'1.3
OS-STP
-
-
0.784
0.022
0.46
0.87
0.021
0.40
0.72
0.022
0.40
0.76
0.78
12.8
3R-25
(3.40)
0.008
2.35
4.581
0.0942
37.20
-
-
-
(5.80)
0.009
4.51
-
-
RC-1
0.258
0.013
0.29
0.311
<0.005
<0.14
0.40
-
-
0.42
0.009
0.33
<0.25
<4.1
BC-1
0.204
0.011
0.20
0.204
0.005
0.09
0.221
-
0.252
0.098
2.13
0.146
2.3
SLC-1
0.273
0.008
. 0.20
0.280
-
-
0.31
0.009
0.24
0.48
0.009
0.37
0.27
4.4
BR-35
4.671
0.008
3.23
-
-
-
(7.05)
0.009
5.48
(7.96)
0.009
6.18
4.96
BLC-1
0.538
0.021
0.98
0.57
-
-
0.65
0.009
0.51
0.76
0.007
0.46
0.65
10.7
OC-13
-
-
-
0.0401
0.093
0.32
(0.045)
0.102
0.40
(0.054)
0.079
0.37
0.36
5,9
ec-i
0.105
-
-
0.136
<0.005
0.06
0.161
0.005
0.07
0.184
0.015
0.24
0.12
2.0
BR-4
19.14
-
-
19.08
0.008
13.18
19.14
0.006
9.91
18.46
<0.005
<7.97
<10.35
-
Total (BR-3,
BLC-1, 0C-
¦1, CC-1)
6.39
33.47
* All flows are preliminary mean daily values obtained from the USGS, unless otherwise noted.
^ Instantaneous flow measurement made by EPA.
2 The concentration of T-P at BR-2 on 9/14/76 was influenced by upstream construction activity and should not be considered a typical value.
3 In order to obtain additional flow data to supplement the single EPA flow measurement in Straight, Willow, and Otter Creeks, the average percent change
in all USGS-measured tributary flows in the Blue River drainage was calculated each day and the EPA flows adjusted accordingly (as shown in parenthesis;.
4 Value shown is the average of the three following days.
® Except for the one flow measurement made by EPA at BR-2 and BR-3, flows at these stations were estimated (see figures in parenthesis) by adjusting the
EPA flow in proportion to the daily change in flow observed at the upstream Blue River station (BR-1).
® This average load omits the anomolously high value of 0.098 mg/1 on 9/1E/76.
' The 16.6% of the total load not accounted for may be partly due to lack of data, but it also reflects the unmeasured non-point T-P loading oce-ir'HHg
between Dillon and Green Mountain Reservoirs.
-------
Table 9. Nutrient sources in the lower Blue River drainage, Colorado.
Source*
Dillon Reservoir
Tributaries to Lower
Blue River
Dillon-Silverthorne STP
Sub-total
T-N Load
kg/day
137
30.5
17.0
184
Percent
of Total
56.6
12.6
7.0
T-P Load
kg/day***
2.20
0.97
0.78
3.95
Percent
of Total
36.1
15.9
12.8
Blue River at inlet to 217
Green Mt. Reservoir
Difference in Blue River** 33
Drainage Contributions
Direct Tributaries to 25.2
Green Mt. Reservoir
13.5
10.3
4.96
1.01
1.13
16.6
18.6
Total Entering
Green Mt. Reservoir
242
100.0
6.09
100.0
* This table presents only the data actually measured during this study - it
does not utilize NES data (EPA, 1976b) for nutrient contributions from septic
tanks or direct precipitation, nor does it consider the Portion of the
DUlon Reservoir nutrient load due to STP discharges within the Dillon Reservoir
drainage as point loadings to the lower Blue River drainage.
** This difference may be partly due to a lack of data, but 1t also reflects the
unmeasured non-po1rit nutrient loading occurring between Dillon and Green
Mountain Reservoirs.
*** T^e "less than" syirfools (<) shown for average T-P loads in Table 8 are not
Included 1n thls table ln order to facilitate the presentation. The values as
shown may be slightly higher than the actual values.
27
-------
Reservoir load is omitted from the total, the total phosphorus
load from non-point sources in the lower Blue River drainage
comprises 51.1% of the total entering Green Mountain Reservoir.
A tabulation of the total phosphorus loads originating from
several of the subdrainage areas is presented in Table 10. Black
Creek and Otter Creek had the highest total phosphorus export
rates. It should be emphasized that the annual surface loading rates
(kg P/km^/yr) are based on only three days of sampling in the Fall
and therefore, are representative of seasonal loads only. The values
in Table 10 compare to reported annual T-P loadings from well managed
pastures and forested lands of 3 to 4 kg P/km'/yr (Kilmer, undated).
Results of this study have been compared to results of the NES study
(EPA, 1976b) in Table 11. It appears that the decreased flow leaving Dillon
Reservoir during this study resulted in a lower percentage contribution of
total phosphorus from Dillon Reservoir and therefore, higher percentage
contributions from most other sources. The large outflow, 18.97 nvtys (670 cfs),
from Green Mountain Reservoir at the time of this study, in combination with
a relatively small inflow, 7.39 m3/s (261 cfs), resulted in a net loss of
3.84 kg/day (8.45 lb/day) total phosphorus out of the reservoir.
Total Nitrogen Loadings
Total nitrogen loadings from both point and non-point sources measured
during the September 1976 survey are shown in Tables 9 and 12.
1. Point Sources - The only identified point discharge in the study
area was the Dillon-Silverthorne STP (DS-STP) which contributed
7.0% (17.0 kg/day or 37.4 lb/day) of the total nitrogen load entering
Green Mountain Reservoir during the study period (Tables 9 and 12).
2. Non-point Sources - The total nitrogen contribution from non-point
sources accounted for 93% of the total nitrogen entering Green
Mountain Reservoir during the study period (Table 9). Of this total,
12.6% was from tributaries to the lower Blue River (Straight, Willow,
Rock, Boulder, and Slate Creeks), 13.5% was due to unidentified
sources (including groundwater recharge) in the same reach of the
Blue River, 10.3% was from direct tributaries to Green Mountain
Reservoir (Black, Otter, and Cataract Creeks), and 56.6% was
contributed by the flow from Dillon Reservoir. The actual non-
point loading from the lower Blue River drainage itself (omitting the
load from Dillon Reservoir) amounted to 36.4% (88.0 kg/day or
194 lb/day) of the total nitrogen entering Green Mountain Reservoir.
A comparison of nitrogen loadings determined during this study
with the loadings determined during the 1974-1975 NES study (EPA,
1975b) is presented in Table 13. For comparison purposes the loadings
were tabulated in the same format, which resulted in substantial
agreement in percentage contributions from the various sources.
This surprisingly good correlation occurred despite the disparity
in study durations - the NES study covered a one year period while
the present study covered only a one week period. Due to the
28
-------
Table 10. Total phosphorus export In several subdrainages in the lower Blue
River drainage, Colorado.
Drainage Area^ Ave. Flow Ave. T-P Cone.
Stream km? rc3/s mg/1 kg P/km2/yr
BR-l 868 4.30 0.007 1.09
RC-1 40.9 0.348 0.009 2.42
BR-3 1323 6.57 0.009 1.41
BLC-1 47.9 0.629 0.012 4.97
CC-1 36.3 0.147 0.008 1.02
0C-1 21.8 0.045 0.091 5.92
^ Values were taken from EPA, 1976b and USGS, 1971.
29
-------
Table 11. Comparison of total phosphorus loadings to Green Mountain Reservoir, Colorado, present and
NES study.
1. Inputs
Source
a. Tributaries (non-point load)
Blue River* (DR-3)
Black Cr. (BLC-1)
Otter Cr. (0C-1)
Cataract Cr. (CC-1)
b. Tributaries to Blue River
(non-point load)
¦ c. DS-STP
Indirect load from STP discharges
into Dillon Reservoir drainages**
d. Septic Tanks
e. Direct Precipitation
Total
2. Outputs (kg/day)
Reservoir Outlet (BR-4)
3. Net T-P accumulation (kg/day)
Present Study Percent of Total Load
kg/day Present Study NLS Stu'dy(EPA, 1976b)
2.54 39.0 58.1
0.65 10.0 5.7
0.36 5.5 5.2
0.12 1.8 3.1
0.97 15.0 12.1
0.78 12.0 4.9
0.66 10.1 8.5
0.03*** 0.5 0.2
0.40*** 6.1 2.2
6.51 100.0 100.0
10.35 17.51
-3.84 +0.52
where A = non-point load contributed by the Blue River itself (2.54 kg/day)
B = total load entering Green Mountain Reservoir at BR-3 (4.96 kg/day)
C = non-point load from tributaries to the Blue River (u.y'j kg/day;
D = point load from DS-STP (0,78 kg/day).
E = indirect point loai from STP discharges into Dillon "eservoir drainage (0.66 kg/day)
** E = F x G
where E is defined as before
F * load leaving Dillon Reservoir as measured at BR-1 (2.20 kg/day)
G = .301 = 30.1% = the percentage of T-P entering Dillon Reservoir from STP discharges(EPA, 19761
*** These values are the estimates shown in the NES Report (EPA, 1976b).
They are included only for the purpose of making valid comparisons between the two studies.
30
-------
Tai)
-------
Table 13. Comparison of total nitrogen loadings to Green Mountain Reservoir, Colorado, present and
NES study.
1. Inputs
Source
a. Tributaries (non-point load)
Blue River* (BR-3)
Black Creek (BLC-1)
Otter Creek (OC-1)
Cataract Creek (CC-1)
b. Tributaries to Blue River
(non-point load)
c. DS-STP
Indirect load from STP discharges
into Dillon Reservoir drainages**
d. Septic Tanks
e. Direct Precipitation
2. Outputs (kg/day)
Reservoir Outlet (BR-4)
3. Net T-N accumulation (kg/day)
Total
Present Study
kg/day
159
18.9
1.9
4.4
30.5
17.0
10.3
Percent of Total Load
Present Study NES Study(EPA, 1976b)
1.1***
24.2***
267
492
-225
59.6
7.1
0.7
1.6
11.4
6.4
3.8
100.0
59.2
6.1
1.2
3.2
12.2
6.1
6.7
0.2
5.1
100.0
1018
* A = B-C-D-E
where A = non-point load contributed by the Blue River itself ( 159 kg/day )
B = total load entering Green Mountain Reservoir at BR-3 (217 kg/day)
C = non-point load from tributaries to the Blue River (30.5 kg/day)
D = point load froiii UU-STP (17.0 kg/day)
E = Indirect point load from STP discharges into Dillon Reservoir drainage (10.3 kg/day)
** E = F x G
where E is defined as before
F = load leaving Dillon Reservoir as measured at BR-1 (137 kg/day)
G = 0.075 = 7.5% = the percentage of T-N entering Dillon Reservoir from STP discharges (EPA, 1976a«
*** These values are the estimates presented in the NES Report (EPA, 1976b).
They are included only for the purpose of making comparisons between the two studies.
32
-------
relatively large outflow from Green Mountain Reservoir during this
study (18.97 nvfys or 670 cfs) and the small inflow (7.39 m3/s or
261 cfs) there was a net reduction in total nitrogen in the reservoir
of 225 kg/day (496 lb/day).
ALGAL GROWTH POTENTIAL
In order to determine the nutrient limiting algal growth in Green
Mountain Reservoir and to assess the possible impact of nutrient addition
to the reservoir, laboratory algal assays were performed with euphotic zone
composite samples.
Table 14 shows the nutrient concentrations reported for the composite
samples (preserved, filtered, and autoclaved and filtered) collected from each
sampling location on Green Mountain Reservoir. Increases in total soluble
inorganic nitrogen after autoclaving and filtration ranged from 0.009 to
0.017 mg/1 N while orthophosphate concentrations changed only slightly.
Figure 6 shows the results of the algal assay performed with autoclaved
and filtered water collected from station lb, Green Mountain Reservoir.
Additions of nitrogen, singly (0.32 mg/1 dry weight yield) or in combination
with EDTA (0.30 mg/1 dry weight yield), did not markedly increase dry weight
yields from the control level (0.33 mg/1 dry weight yield). Additions of
phosphorus and phosphorus plus EDTA, however, resulted in significantly larger
maximum dry weight yields (1.14 and 1.14 mg/1, respectively).
As can be seen from Figure 6, the largest dry weight yield occurred
in the combined phosphorus and nitrogen plus EDTA spike (5.70 mg/1). The
dry weight yield of the combined nitrogen and phosphorus spike without EDTA
was only 1.85 mg/1. The large observed increase in dry weight with addition •
of EDTA may be indicative of metal toxicity or secondary micronutrient limita-
tion. Additional algal assays would be required to determine which, if either,
of the above hypotheses is correct.
An algal assay with water from station 3b was conducted simultaneously
with the algal assay for station lb. In direct contrast to the responses
observed for station lb, little or no Increase 1n dry weight yield was observed
at any of the nutrient spike levels with water from station 3b. Both assays
were terminated on day 14. Due to the low dry weight yields at all nutrient .
spike levels, another algal assay with water from station 3b was conducted,
with an assay with water from station 6b conducted simultaneously. After
14 days of Incubation under test conditions, little or no increase 1n growth
from the control level was observed for either station 3b or 6b (Figures 7
and 8, first bar of each couplet). Although cell count 1n the phosphorus -
associated spikes had gradually Increased during Incubation period, the mean
cell volume after the first 3-5 days of Incubation had remained very low 1n
comparison to the mean cell volumes 1n the other spikes (Figures 9 and 10).
Micronutrient limitation was suspected. Rather than terminate the algal
assays on day 14 as planned, each flask was Inoculated with 1.0 mg/1 of the
33
-------
Table 14. Nutrient concentstions in euphotic zone composite samples - preserved, filtered only, and auto-
claved and filtered, collected from Green Mountain Reservoir, stations lb, 3b, and 6b, November, 1976.
Parameter
Preserved Only
Filtered Only
Autoclaved and
Filtered
lb
3b
6b
lb
3b
6b
lb
3b
6b
nh3
0.011
0.007
0.005
0.011
0.015
0.006
0.012
0.013
0.011
no2 + no3
0.058
0.058
0.053
0.058
0.061
0.061
0.066
0.067
0.064
TKN
0.15
0.12
0.15
0.10
0.12
0.12
0.13
0.11
0.12
TP
0.006
0.006
0.006
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
o-po4
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
o-po4*
0.001
0.001
0.004
0.001
0.001
0.002
0.003
0.003
0.003
* Actual ortho-phosphate values recorded. However, values recorded from 0.00 to 0.004 mg/1 P are reported
as <0.005 mg/1 due to variable precision near the lower limits of detection.
-------
Figure 6. The effects of phosphorus, nitrogen, and phosphorus plus
nitrogen, both singly and In combination with EDTA, as compared to the
control samples on the growth of Selenastrum caprlcornutum 1n autoclaved
and filtered water from Green MountaIn ReservoIr, sta't?on 1 b.
35
-------
lu
<
I—
1—
o
+
a.
a,
E
•M
C)
O)
s.
n>
CJ)
E
CNJ
o
n-~
o
o
s-
+J
•M
c
CI
o
o
<_>
o
CD
o
+
Q_
+
en
+
£X
cn
C\J
o
o
<
I
+
r—
Q
CM
+->
C
O
c
o
•
o
o
o
o
OJ
r—
CL
E
(T3
aj
UO
r—
CL
O
E
ro
(/)
1
O
—
l
+
c
C
H-
o
O
l-J
UJ
C
+
+
h—¦
Q
LjJ
—
--
+
CD
Cp
Q.
E
Er.
+
O
O
•
•
T1
i—
i—
Figure 7. The effects of phosphorus, nitrogen, and phosphorus plus nitrogen, both singly
and in combination with EDTA, as compared to the control samples on the growth of Selenastrui
capricornutum in autoclaved and filtered water from Green Mountain Reservoir, station 3b.
The first bar indicates dry weight yield at the end of 14 days incubation. (The second bar
indicates dry weight yield after micronutrient (MN) addition on day 14 and an additional
two week incubation.)
3 C
-------
Figure 8. The-effects of nitrogen, phosphorus, and phosphorus plus nitrogen, both singly
and in combination with EDTA, as compared to the control samples, on the growth of
Selenastrum capricornutum in autoclaved and filtered water from Green Mountain Reservoir,
"station 6b. (Tne first bar indicates dry weight yield at the end of 14 days of incubation.
The second bar Indicates dry weight yield after micronutrient (MN) addition on day 14 and
an additional two week incubation.)
37
-------
CO
CO
110
100
CO
E
p.
90
0)
§ 80
- 70
OJ
cj
S 60
50
40
1
O Control
~ P - P + EDTA
O N - N + EDTA
£ N+P-N+P+ EDTA
_L
±
>
i
10
12
14 16
Days
18
20
22
24
26
28
Figure 9. Changes in mean cell volume of Selenastrum capricornutum as a function of time in aloal
assays conducted with water from station 3b, Green Mountain Reservoir, Colorado. (Data points
shown are averages of each spike levels, singly and in combination with EDTA.)
-------
u>
vo
110
100
fO
E
3-
a>
E
Z3
90
80
o
Z 70
a>
o
c
to
aj
60
50
40
X
o
Control
~
P - P +
EDTA
o
N - N +
EDTA
A
N + P -
N + P + EDTA
r
I
10
12
14 16
Days
18
20
22
24
26
28
Figure 10. Changes in mean cell volume of Selenastrum capricornutum as a function of time in algal
assays conducted with water from station 6b, Green Mountain Reservoir, Colorado. (Data points shown
are averages of spike levels singly and in combination with EDTA.)
-------
micronutrient stock solution outlined in the Algal Assay Procedure:
bottle test (1371). The test flasks were then incubated for an additional
14 days with growth monitored five times during the additional incubation
period. If the algal growth in the test waters was limited by micro-
nutrient concentrations a marked increase in growth would theoretically
be observed during the additional incubation period.
As can be seen in Figures 7 and 8, algal growth in the water collected
from stations 3b and 6b was limited by micronutrient concentration. It
is difficult to determine if the micronutrient concentration was the major
limiting factor or if a dual limitation of micronutrients and phosphorus
existed. Addition of micronutrients to the control and the control plus
EDTA resulted in a slight increase in maximum dry weight yield. The small
increase in dry weight may represent the growth response to the micro-
nutrient addition and subsequent secondary limitation by phosphorus, or may
be solely a result of the additional 14 day incubation. Regardless of
whether the micronutrient concentration was the primary limiting factor
or a co-limiting factor, both spikes (micronutrient and phosphorus) were
required to markedly stimulate algal growth in the test water. Additions
of micronutrients to those flasks previously spiked with phosphorus resulted
in significant increases in dry weight yield from the levels of the controls.
On day 28 of the incubation period (14 days after micronutrient addition)
maximum dry weight yields in the control flasks for stations 3b and 6b
were 0.33 and 0.33 mg/1, respectively, while maximum dry weight yields in
the nitrogen and phosphorus plus EDTA were 6.37 and 12.77 mg/1, respectively.
On the basis of the algal assay results, both micronutrient and phosphorus
concentrations were limiting algal growth potential at stations 3b and 6b
at the time of sampling.
In summary, phosphorus significantly limited potential algal growth
at all stations at the time of sampling. In addition, micronutrient
concentration also limited algal growth'in water collected at stations 3b
and 6b. Table 15 shows the t-values for a two-tailed student's t-test of
the hypothesis of equal dry weight yields at various spike levels.
After extensive research using S. capricornutum cultured in algal
assay media (AAM), Shiroyama, Miller, and Greene (1975) reported that
maximum dry weight yields of Selenastrum capricornutum could be predicted
if the concentrations of nitrogen and phosphorus are known, all other essential
nutrients are present, and toxicants are absent. Water containing greater
than 0.010 mg/1 ortho-P can yield 0.43 mg/1 dry weight of test alga per
0.001 mg/1 phosphorus while 0.001 mg/1 TSIN (total soluble inorganic nitrogen)
cati yield 0.038 mg/1 dry weight of the test alga. In water containing
greater than 0.000 mg/1 but less than 0.010 mg/1 ortho-P, dry weight yields
per 0.001 mg/1 phosphorus addition will range from 0.1 - 0.43 mg/1
(personal communication - William Miller, NERC, Corvallis, Oregon).
Table 16 shows both the actual dry weight yield and the yields predicted
on the basis of the reported nutrient concentrations. Although maximum
dry weight yields for the phosphorus and phosphorus plus nitrogen were
40
-------
Table 15. Two sample b«Q-ta11ed student's t-test of dry *eignt yields at different nutrient spike levels
1n water collected front stations lb, 3b, and ob, Sreen Mountain Reservoir, Colorado.
lb
Control
0.02 P
1.0 1
N * P
EDTA +
Control
EDTA +
0.02 P
EOTA *
1.0 '1
EOTA «¦
N •* '
Control
33.56*
0.73
31.10*
1.11
58.15*
2.57
•12.95*
0.02 P
33 . 56*
40.28
13.96*
35.43*
0.16
41.59*
26.Zl*
1.0 N
0.73
40.28*
32.46*
0.80
172.53*
= .66*
43.25*
N ~ P
31.10*
13.96*
32.46*
31.73*
15.20*
33.02*
28.96'
EDTA ~
Control
1.11
35.43
0.80
31.73
66.01
1.34
43.16
EDTA *
0.02 P
53.45*
0.16
172.53*
15.20*
66.01*
178.19*
36.72*
EOTA *
1.0 N
2.57
41.59
5.56
33.02
1.34
178.19
43.43
EDTA +
N + P
42 .95*
36.24*
43.26*
23.96*
43.16*
36.72*
43.43*
3b
Control
0.02 P
1.0 N
>1 + P
EDTA +
Control
EOTA +
0.02 P
EOTA *
1.0 N
EDTA ~
N v P
Control
27.16*
2.41
20.35*
0.21
64.65*
1
13.70*
0.02 ?
27.16*
27.41*
1.21
27.16*
0.97
1
3.C9
1.0 N
2.41
27.41*
20.56*
2.30
65.06*
1
13.SO*
N + P
20.35*
1.21
20.56*
20.35*
0.57
\
o
i/>
ai
|
3.66
E3TA +
Control
0.21
27.16*
2.80
20.35*
64.93*
13.70*
EOTA +
0.02 P
' 64.6:*
0.97
65.C6*
64,93*
i
3.57
EDTA *
1.0 N
t
i
<
EDTA t
N + P
13.70*
3.00
13.30*
3.56
13.70*
3.57
i
Sb
Control
0.02 P
1.0 N
« » p
EDTA +
Control
EDTA +
0.02 P
EOTA +
1.0 N
EOTA +
N * P
Control
4.10**
2.29
75.59*
1.34
13.29*
3.25
14.28*
0.02 P
*». 10*-
4,04**
7.70*
4.08**
0.07
4.03**
7.34*
1.0 N
2.29
4.40**
74.81*
1.79
13.06*
0.36
14.23*
N + P
75.69*
7.70
74.ai*
75.71*
23.04*
75.00*
3.65
EOTA *
Control
1.34
4.08**
1.79
75.71*
13.24*
2.77
14.27*
EDTA *
0.02 P
13.29*
0.07
13.06*
23.04*
13.24*
13,06*
10,32*
EDTA ~
1.0 N
3.25
4.03**
0.36
75.00*
2.77
13.06*
14.22*
EDTA ~
14.28*
7.94*
14.23*
3.S5
14.27*
10.32*
14.22*
N + P
• Significant at « ¦ 0,01
** Significant at • • 0,02
V'^o * U1
Vo * *1
wh«rt:
•4q ¦ »n« l«v#l
ui ¦ any nutrient spike level otfttr thin u9
-------
Table 16. Comparison of actual vs. theoretical dry weight yields of Selenastrum capricornutum in algal assays performed with water collected fror
Green Mountain Reservoir, November, 1976.
Actual and Theoretical Dry Weight Yields in mg/1^
EDTA + EDTA + EDTA + EDTA +
Day Control 0.02 P 1.0 N N + P Control 0.02 P 1.0 N + P
3b
6b
lb 14 0.33(0.30-1.29) 1.14(2.96) 0.32(0.30-1.29) 1.85(9.89) 0.31(0.30-1.29) 1.14(2.96) 0.30(0.30-1.29) 5.7;:3.89)
14 0.17(0.30-1.29) 0.19(3.04) 0.17(0.30-1.29) 0.18(9.89) 0.18(0.30-1.29) 0.26(3.04) No Sample 0.55(3.89)
28 0.33(0.30-1.29) 4.76(3.04) 0.28(0.30-1.29) 4.45(9.89) 0.33(0.30-1.29) 4.59(3.04) No Sample 6.18(9.89)
14 0.23(0.30-1.29) 0.34(2.85) 0.20(0.30-1.29) 0.31(9.89) 0.21(0.30-1.29) 0.36(2.85) 0.21(0.30-1.29) ".33:9.89)
28 0.33(0.30-1.29) 3.13(2.85) 0.36(0.30-1.29) 8.46(9.89) 0.34(0.30-1.29) 3.08(2.85) 0.37(0.30-1.29) 11.£9(3.89)
^ The first number in each grouping is the actual dry weight yield. Those numbers enclosed with parentheses are the theoretical yields based the
reported available nutrients.
-------
significantly greater than the control, the actual dry weight yields of
S. capricornutum in test water from station lb were less than the predicted
yields. In view of the growth response after micronutrient addition to
samples from station 2b and 6b, however, it is felt that the difference
between actual and theoretical yield for station lb is likely due to second-
ary micronutrient limitation.
Dry weight yields for station 3b, after micronutrient addition and
an additional 14 day incubation period were, in general, similar to the
predicted values. However, dry weight yields for the phosphorus spikes,
both singly and in combination with EDTA, were consistently higher than
the predicted levels, possibly indicative of a TSIN concentration higher
than reported. Also, yields from nitrogen plus phosphorus addition, both
singly and in combination with EDTA, did not reach the predicted level,
a condition indicative of secondary limitation other than phosphorus,
nitrogen, or micronutrient concentration. As stated previously, algal
growth in test water from station 3b was primarily limited by phosphorus
and micronutrient concentration at the time of sampling.
Dry weight yields for station 6b were very similar to the predicted
values. Both actual and predicted dry weight yields indicated strong phos-
phorus limitation. As previously mentioned, station 6b was also micro-
nutrient limited.
Miller, Maloney, and Greene (1974) defined four productivity groups
based on dry weight yields in the control samples of algal assay conducted
for 49 lakes; (1) low productivity- 0.00-0.10 mg dry wt. per liter,
(2) moderate productivity- 0.11-0.80 mg dry wt. per liter, (3) moderately
high productivity- 0.81-6.00 mg dry wt. per liter, and (4) high productivity-
6.10-20.00 mg dry wt. per liter. As reported by the above authors, the
productivity values reported reflect only the nutrient content of the water
sample at the time of assay and not the entire body of water. The above
productivity groupings do, however, allow for comparison of algal assay
results from different bodies of water. On the basis of the dry weight
yields in the control samples for stations lb, 3b, and 6b in Green Mountain
Reservoir, potential primary productivity was moderate at all stations
sampled.
Phosphorus limitation of potential algal growth at all sampling stations
is further substantiated by the corresponding N:P ratios reported (TSIN:0-P0/).
Theoretically, water exhibiting a N:P ratio greater than 11.3:1 (38/430)
would likely be phosphorus limited, while waters containing a N:P ratio less
than 11.3:1 would be nitrogen limited (Shiroyama, et al, 1975; Greene,
Soltero, Miller, Gasperino, and Shiroyama, 1975). The N:P ratios of the
preserved lake water composite samples from statlonslb, 3b, and 6b (using
recorded values of O-PO4) were 69:1, 65:1, and 14.5:1, respectively. When
the reported values (i.e., >0.005 mg/1 P) rather than the recorded values of
ortho-phosphate are used in computation (Table 14) the N:P ratio still
indicate phosphorus limitation at all stations (14:1, 13:1, and 12:1 for
stations lb, 3b, and 6b, respectively).
43
-------
As can be seen above, N:P ratios are a useful tool in determining
the nutrient limiting algal growth in a body of water. However, limiting
nutrient assessment based solely on N:P ratios may be of questionable value.
In waters of low nutrient content, the N:P ratio may vary greatly with minor
changes in reported nutrient concentrations due solely to analytical precision
of nutrient analysis (i.e. TSIN = 0.040 mg/1 N, O-PO4 = 0.002 mg/1 P,
N:P = 20:1 = phosphorus limitation; TSIN - 0.040 mg/1 N, O-PO4 r 0.004 mg/1
P, N:P = 10:1 = possible nitrogen limitation). For waters of low nutrient
content, N:P ratios must be used in conjunction with other supportive data
(i.e. algal assays). Also, N:P ratios obviously do not reflect the possible
algal growth potential limitation by factors other than nitrogen or phos-
phorus.
The results of the algal assays reported here are in agreement with the
findings of the Environmental Protection Agency's National Eutrophication
Survey (NES) study (EPA, 1976b). Using a depth integrated sample composited
from three sampling locations on Green Mountain Reservoir, NES reported that
phosphorus was the primary limiting nutrient. The NES report did not mention
any possible nutrient limitation other than phosphorus. Secondary micro-
nutrient limitation, however, may have been present,as reported dry weight
yields for all spike levels are less than predicted on the basis of the
reported nutrient concentrations. The exact reason for the smaller dry
weight yields, however, can not be stated on the basis of the available
information.
44
-------
REFERENCES
American Public Health Association. 1975. Standard method for the examina-
tion of water and wastewater. 14th ed. A.P.M.A. 1193 pp.
Britton, L.J. 1977. A water quality inventory of surface waters in Lagle,
GranJ, Jackson, Pitkin, Routt, and Summit Counties, Colorado. U.S.
Geological Survey, in cooperation with the Northwest Colorado Council
of Governments. (In press.)
Bureau of Reclamation. 1957. Colorado Big Thompson Project. Technical
record of design and construction. Vol I. U.S. Gov't. Printing
Office, Wash., D.C.
Colorado Dept. of Health. August, 1976. Proposed water quality standards
for Colorado. Water Quality Control Commission, Denver, Colorado.
Environmental Protection Agency. 1971. Algal assay procedure: bottle
test. Nat' 1. Eutrophication Research Program, Corvallis, Oregon.
82 pp.
1973. Biological field and laboratory
methods for measuring the quality of surface waters and effluents.
Cincinnati, Ohio. EPA-670/4-73-001.
1974. Dillon Reservoir - Blue River Study.
U.S. EPA, Denver, Colorado. S&A/TIB-28.
1976a. Preliminary report on Dillon
Reservoir, 1974-1975, National Eutrophication Survey. U.S. EPA,
Corvallis, Oregon.
1976b. Preliminary report on Green
Mountain Reservoir, 1974-1975, National Eutrophication Survey.
U.S. EPA, Wash., D.C.
1976c. Quality criteria for water.
U.S. EPA, Wash., D.C.
Greene, J.C., R.A. Soltero, W.E. Miller, A.F. Gasperino, and T. Shiroyama.
1975. The relationship of laboratory algal assays to measurements of
indigenous phytoplankton 1n Long Lake, Washington. Proc. biostimulatlon
and nutrient assessment. September 10-12, 1975. Utah State University,
Logan, Utah. PRWG 168-1.
Hook, R.K. 1974. Water quality management plan, Blue River hydrologlc
basin. R. Keith Hook and Associates, Colorado Springs, Colorado.
45
-------
Kilmer, V.J. (Undated manuscript.) Nutrient losses through leaching and
runoff. Tennessee Valley Authority. Muscle Shoals, Alabama, as
referenced by McElroy, et al, 1976. Loading functions for assessment
of water pollution from nonpoint sources. EPA-600/2-76-1G1.
Wash., D.C.
Miller, W.E., T.E. Maloney, and J.C. Greene. 1974, Algal productivity in
49 lake waters as determined by algal assays. Water Research,
3:667-679.
National Academy of Sciences - National Academy of Engineering. 1973.
Water quality critiera, 1972. EPA-R3-73-033. Wash., D.C.
Nelson, W.C. 1955. Green Mountain Reservoir studies, 1949-1950. Colorado
Department of Game and Fish. Ft. Collins, Colorado.
1971. Comparative limnology of Colorado - Big Thompson Project
reservoirs and lakes. Colorado Game, Fish & Parks Dept. F-25-R-1 to 4.
Ft. Collins, Colorado.
Patrick, R. and C.W. Reimer. 1966. The diatoms of the United States,
Vol. I. Acad. Natural Sci., Philadelphia, Penn. 638 pp.
Schwoerbel, J. 1970. Methods of hydrobiology (freshwater biology).
Pergamon Press, New York, N.Y. 200 pp.
Shiroyama, T., W.E. Miller, and J.C. Greene, 1975. The effects of nitrogen
and phosphorus on the growth of Selenastrum capricornutum Printz.
Proc. biostimulation - nutrient assessment workshop, October 16-18,
1973. U.S. EPA, Corvallis, Oregon. EPA-606/3-75-034.
Smith, G.M. 1950. The fresh-water algae of the United States. McGraw-
Hill Publishing Col, New York, N.Y. 719 pp.
Vollenweider, R.A. 1969. A manual on methods for measuring primary
production in aquatic environments. Int'l Biol. Programme Handb. 12,
Oxford and Edinburgh, Blackwell Sci. Pub. 213 pp.
Ward, H.B. and G.C. Whipple. 1959. Freshwater biology. John Wiley and
Sons, Inc. New York - London. 1248 pp.
Weber, C.I. 1971. A guide to the common diatoms at water pollution sur-
veillance system stations. Environmental Protection Agency. Nat'l.
Environmental Research Center, Cincinnati, Ohio. 101 pp.
46
-------
APPENDIX A
CHEMICAL DATA - GREEN MOUNTAIN RESERVOIR
47
-------
Station: 1-a Transect 1, South 1/4 point
Date
Mo/Da.y/Yr
9/13/76
9/15/76
9/13/76
9/15/76
9/13/76
9/15/76
Time
Mtly
1400
1735
1455
1732
1350
1730
Depth
Meters
1
1
20
20
27
27
Temperature
Cent.
14.5
13.5
12.5
12.0
12.0
11.5
pH
SU
6.8
7.4
6.6
7.2
6.7
7.3
DO
mg/£
7.6
7.1
5.0
5.2
5.6
5.2
Conductivity
umbos/cm
170
170
165
170
165
170
NH3 - N
mg/Ji
0.005
0.007
0.009
<0.005
0.005
<0.005
TKN - N
mg/£
0.13
0.14
0.16
0.10
0.06
0.12
no2 + no3 - n
mg/£
<0.005
<0.005
0.100
0.097
0.102
0.101
Ortho - P
mg/£
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
Total - P
mg /i
<0.005
0.009
<0.005*
<0.005
0.007
0.005
* Average of duplicate analyses
-------
Station: 1-b Transect 1, Mid-channel
Date
Mo/Day/Yr
9/13/76
9/15/76
9/13/76
9/15/76
9/13/76
9/15/76
Time
Htly
1330
1710
1320
1705
1310
1700
Depth
Meters
1
1
20
20
67
64
Temperature
Cent.
14.5
13.5
13.0
12.0
8.5
8.0
pH
SU
6.55
7.4
6.4
7.1
6.3
7.1
DO
mg/£
7.2
7.1
5.0
5.6
4.0
4.25
Conductivity
ymhos/cm
165
165
165
170
190
180
NH3 - N
mg/Jl
<0.005
<0.005
<0.005
<0.005
0.011
0.018
TKN - N
mg/A
0.12
0.12
0.13
0.38
0.16
0.12
N02 + N03 - N
mg/A
<0.005*
<0.005
0.099
0.078
0.199
0.093
Ortho - P
mg/A
0.010*
<0.005
<0.005
<0.005
0.017
0.010
Total - P
mg/A
0.014*
0.006
0.006
<0.005
0.024
0.016
* Average of duplicate analyses
-------
Station: 1-b Transect 1, Mid-channel (continued)
Date
Mo/Day/Yr
11/17/76
11/17/76
11/17/76
Time
Mtly
1000
1020
1040
Depth
Meters
1
12
33
Temperature
Cent.
7.0
7.0
6.5
pH
SU
8.2
8.2
7.7
DO
mg/£
8.6
8.4
8.5
Conductivity
umhos/cm
165
175
175
NH3 - N
mg/i
<0.005
0.005
0.008
TKN - N
mg/£
0.11
0.12
0.20
NO2 + NO3 - N
mg/£
0.034
0.061
0 .057
Ortho - P
mg/£
<0.005
<0.005
<0.005
Total - P
mg/£
0.005
0.007
0.008
-------
Station: 1-c Transect 1, North 1/4 point
Date
Mo/Day/Yr
9/13/76
9/15/76
9/13/76
9/15/76
9/13/76
9/15/76
Time
Mtly
1420
1718
1418
1720
1415
1715
Depth
Meters
1
1
20
20
27
27
Temperature
Cent.
14.5
13.5
12.0
12.0
11.5
11.5
PH
SU
6.9
7.3
6.8
7.25
6.7
7.2
DO
mg/fc
7.6
7.2
5.1
5.4
5.3
5.4
Conducti vi ty
ymhos/cm
165
165
170
170
170
170
NH3 - N
mg/£
0.006
<0.005
<0.005
0.033
0.006
<0.005
TKN - N
mg/fc
0.08
0.20
0.22
0.07
-
0.10
nq2 + no3 -n
mg/£
0.005
<0.005
0.100
0.090
0.099
<0.005
Ortho - P
mg/fc
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
Total - P
mg/£
0.006
0.008*
<0.005
0.005
<0.005
0.006
* Average of duplicate analyses
-------
Station: 2-a Transect 2, South 1/4 point
Date
Mo/Day/Yr
9/13/76
9/17/76
9/13/76
9/17/76
9/13/76
9/17/76
Time
Mtly
1555
1255
1550
1253
1545
1250
Depth
Meters
1
1
17
17
30
30
Temperature
Cent.
15.0
14.5
12.5
13.5
11.0
12.0
PH
SU
7.0
7.3
6.8
7.2
6.8
7.2
DO
mg/n
7.4
7.2
5.3
6.1
5.5
5.2
Conductivity
umhos/cm
170
160
170
160
175
165
NH3 - N
mg/£
0.008
0.005
<0.005
0.006
0.009
<0.005
TKN - N
mg/£
0.05
0.16*
0.09
0.66
0.04
0.24
N02 + NO3 - N
mg/£
<0.005
0.006
0.095
0.054
0.110
0.124*
Ortho - P
mg/£
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005*
Total - P
mg/£
<0.005
0.009
<0.005
0.005
<0.005
<0.005*
* Average of duplicate analyses
-------
Station: 2-b Transect 2, Mid-channel
Date
Mo/Day/Yr
9/13/76
9/17/76
9/13/76
9/17/76
9/13/76
9/17/76
Time
Mtly
1540
1230
1535
1225
1530
1220
Depth
Meters
1
1
17
17
58
58
Temperature
Cent.
15.0
14.5
12.5
13.0
8.5
9.0
pH
SU
6.85
7.1
6.6
6.9
6.6
6.9
DO
mg/J.
7.5
7.2
5.3
6.1
4.1
4.2
Conductivity
ymhos/cm
170
165
170
160
180
180
NH3 - N
mg /«.
<0.005
<0.005
<0.005
-
0.014
0.006
1
i
mg/*
0.17
0.22*
0.06
-
0.09
0.21
no2 + no3 - n
mg fi
<0.005
0.006
0.087
-
0.223
0.260
Ortho - P
mg/*.
<0.005
<0.005
<0.005
-
0.011
0.010
Total - P
mg/£
0.005
0.007
0.007
-
0.14*
0.014
* Average of duplicate analyses
-------
Station: 2-c Transect 2, North 1/4 point
Date
Mo/Day/Yr
9/13/76
9/17/76
9/13/76
9/17/76
9/13/76
9/17/76
CI
Time
Mtly
1610
1241
Depth
Meters
1
1
Temperature
Cent.
15.0
14.5
5
PH
SU
7.3
7.1
o
r—
DO
mg/z
7.5
7.1
-C
CO
o
Conductivity
umhos/cm
170
160
0
\-
1
NH3 - N
mg/£
<0.005
0.008
Q_
E
TKN - N
mg/«.
0.28
0.24*
tQ
OO
no2 + no3 - n
mg/£
<0.005
0.005
O
z
Ortho - P
mg/£
0.005
<0.005
Total - P
mg/Ji
0.006
0.008
5
o
03
_C
oo
o
o
I
0)
r—
Q.
E
to
in
1605
14
14.0
7.1
7.6
170
<0.005
0.36
<0.005
<0.005
0.007
1237
12
14.0
7.3
6.8
165
<0.005
0.17
0.007
<0.005
0.010
* Average of duplicate analyses
-------
Station: 3-a Transect 3, South 1/4 point
Date
Mo/Day/Yr
9/13/76
9/15/76
9/13/76
9/16/76
9/13/76
9/16/76
Time
Mtly
1705
1012
1700
1010
1655
1005
Depth
Meters
1
1
17
17
26
26
Temperature
Cent.
15.0
13.0
12.5
12.5
12.5
11.5
PH
SU
7.35
7.5
7.2
7.1
7.2
7.1
DO
mg /i
7.5
7.1
5.3
5.7
5.5
5.4
Conductivity
pmhos/cm
170
170
175
170
170
170
NH3 - N
mg/Ji
<0.005
0.014
<0.005
<0.005
<0.005
<0.005
TKN - N
mg/1
0.31
0.27
0.26
0.30
0.06
0.34
no2 + no3 - n
mg/«.
<0.005
0.008
0.087
0.075
0.009
0.105
Ortho - P
mg/I
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
Total - P
mg/£
0.007
0.008
0.005
<0.005
<0.005
<0.005
-------
Station: 3-b Transect 3, Mid-channel
Date
Mo/Day/Yr
9/13/76
9/16/76
9/13/76
9/16/76
9/13/76
9/16/76
Time
Mtly
1650
0940
1645
0955
1640
0950
Depth
Meters
1
1
17
17
50
50
Temperature
_ Cent.
15.0
12.5
13.0
12.0
9.0
8.5
PH
SU
7.25
6.5
7.2
6.7
7.2
6.5
DO
mg/s.
7.3
7.1
5.7
5.7
4.5
4.65
Conductivity
ymhos/cm
170
165
170
170
180
180
NH3 - N
mg/£
<0.005
0.009
0.008
<0.005
<0.005
<0.005
TKN - N
mg/£
0.18
0.41
0.05
0.26*
0.04
0.15
no2 + no3 - n
mg ! i
<0.005
0.009
0.072
0.081
0.194
0.210
Ortho - P
mg/£
<0.005
<0.005
<0.005
<0.005
0.006
0.008
Total - P
mg/£
<0.005
0.009
<0.005
0.005
0.009
0.015
* Average of duplicate analyses
-------
Station: 3-b Transect 3, Mid-channel (continued)
Date Mo/Day/Yr 11/17/76 11/17/76 11/17/76
Time
Mtly
1115
1135
1155
Depth
Meters
1
12
39
Temperature
Cent.
7.0
7 .0
6.75
PH
SU
7.7
7.4
7.9
DO
mg/i.
8.7
8.45
8.4
Conductivity
ymhos/cm
200
220
165
NH3 - N
mg/«,
0.010
0.006
0.006
TKN - N
mg/ii
0.13
0.12
0.15
N02 + N03 - N
mg/£
0.057
0.057
0.057
Ortho - P
mg/£
<0.005
<0.005
<0.005
Total - P
mg/a,
0.006
0.006
0.007
-------
Station: 3-c Transect 3, North 1/4 point
Date
Mo/Day/Yr
9/15/76
9/16/76
9/15/76
9/16/76
9/15/76
9/16/76
Time
Mtly
0935
1050
0920
1040
Depth
Meters
1
1
9
9
Temperature
/
Cent.
12.5
13.0
5
Q
X
O
12.0
13.0
PH
SU
6.6
6.5
r—
6.5
6.4
DO
mg/£
7.0
7.1
(0
_c
_C=
C/-)
7.1
7.1
Conductivity
vimhos/cm
175
165
0
0
I—
0
0
h-
220
165
NH3 - N
mg/£
<0.005
0.015
-------
Station: 4-a Transect 4, South 1/4 point
Date
Mo/Day/Yr
9/15/76
9/17/76
9/15/76
9/17/76
9/15/76
9/17/76
Time
Mtly
1032
1150
1030
1148
1025
1145
Depth
Meters
1
1
18
18
26
26
Temperature
Cent.
13.0
14.0
12.0
13.0
11.0
12.0
PH
SU
7.3
7.2
7.1
7.3
6.9
7.1
DO
mg/£
7.1
7.0
5.8
6.2
5.3
5.2
Conductivity
umhos/cm
170
160
170
160
180
170
NH3 - N
mg /i
<0.005
<0.005
0.013
0.012
<0.005
<0.005
TKN - N
mg/£
0.10
0.22
0.08
0.14*
0.15
0.08
no2 + no3 - n
mg/£
<0.005
0.007
0.064
0.037
0.103
0.112*
Ortho - P
mg/£
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005*
Total - P
mg/5.
0.011
0.010
0.006
0.009
<0.005
<0.006*
~Average of duplicate analyses
-------
Station: 4-b Transect 4, Mid-channel
Date
Mo/Day/Yr
9/15/76
9/17/76
9/15/76
9/17/76
9/15/76
9/17/76
Time
Mtly
1017
1105
1010
1125
1005
1120
Depth
Meters
1
1
18
18
40
40
Temperature
Cent.
13.0
14.0
12.5
13.0
11.0
11.0
PH
SU
7.0
6.6
7.2
6.9
6.75
6.7
DO
mg/i.
6.9
7.4
6.4
6.1
5.4
5.5
Conductivity
ymhos/cm
170
180
170
160
170
160
NH3 - N
mg/£
0.009
<0.005
<0.005
0.013
<0.005
0.007
TKN - N
mg/ £
0.21
0.21
0.12
0.19
0.08
0.23
no2 + no3 - n
mg/£
0.006*
0.007
0.035
0.055
0.108
0.142
Ortho - P
mg/z
<0.005*
<0.005
<0.005
<0.005
<0.005
<0.005
Total - P
mg/1
0.010
0.008
0.007
0.007
0.005
0.008
* Average of duplicate analyses
-------
Station: 4-c Transect 4, North 1/4 point
Date
Mo/Day/Yr
9/15/76
9/17/76
9/15/76
9/17/76
9/15/76
9/17/76
Time
Mtly
1050
1128
1045
1125
1040
1130
Depth
Meters
1
1
18
18
26
26
Temperature
Cent.
13.0
14.0
12.5
13.0
11.0
12.0
PH
SU
7.1
7.3
7.0
7.0
7.0
6.8
DO
mg/s.
7.0
7.0
6.2
6.5
5.4
5.7
Conductivity
ymhos/cm
165
160
170
160
180
160
NH3 - N
mg/s.
0.005
0.005
0.006
<0.005
<0.005
<0.005
TKN - N
mg/fc
0.11
0.34*
0.19
0.22*
0.11
0.13*
N02 + N03 - N
mg/fc
0.008
0.006
0.048
0.042
0.0961
0.108*
Ortho - P
mg/£
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005*
Total - P
mg/a
0.011
0.009
0.007
0.007
<0.005
0.006*
* Average of duplicate analyses
-------
Station: 5-a Transect 5, South 1/4 point
Date
Mo/Day/Yr
9/15/76
9/16/76
9/15/76
9/16/76
9/15/76
9/16/76
Time
Mtly
1150
1558
1145
Depth
Meters
1
1
12
Temperature
Cent.
13.5
14.5
S-
o
*
o
13.0
pH
SU
7.4
7.2
(0
.c
sz
7.4
CO
CO
DO
mgM
6.9
7.2
o
o
o
o
7.1
1—
t—
Conductivity
umhos/cm
160
160
1
1
170
a>
CD
NH3 - N
mg/£
0.015
<0.005
Q.
E
O.
E
<0.005
fO
rC
TKN - N
mg/£
0.20
0.27
GO
o
CO
Q
0.11
2T
no2 + no3 - n
mg/£
0.006
0.006
0.006
Ortho - P
mgM
<0.005
<0.005
<0.005
Total - P
mg /i
0.007
0.007
0.010
1555
12
14.0
7.2
6.9
160
0.027
0.25
0.008
<0.005
0.008
-------
Station: 5-b Transect 5, Mid-channel
Date
MO/Day/Yr
9/15/76
9/16/76
9/15/76
9/16/76
9/15/76
9/16/76
Time
Mtly
1120
1530
1118
1525
1115
1520
Depth
Meters
1
1
18
18
34
34
Temperature
Cent.
13.5
14.0
12.5
13.0
11.0
12.0
pH
SU
7.3
6.9
7.15
6.5
7.1
6.3
DO
mg/£
7.0
7.0
6.6
6.6
5.2
5.8
Conductivity
ymhos/cm
165
160
170
170
175
170
NH3 - N
mg/£
<0.005
0.022
0.021
0.023
<0.005
0.009
TKN - N
mg/S-
0.23
0.27
0.22
0.33
0.07
0.28
N02 + N03 - N
mg/«.
0.007*
0.007
0.034
0.035
0.118*
0.086
Ortho - P
mg/£
<0.005*
<0.005
<0.005
<0.005
<0.005
<0.005
Total - P
mg/£
0.006
0.012
0.010
0.008
0.006
0.007
* Average of duplicate analyses
-------
Station: 5-c Transect 5, North 1/4 point
Date
Mo/Day/Yr
9/15/76
9/16/76
9/15/76
9/16/76
9/15/76
9/16/76
Time
Mtly
1135
1545
1130
1543
1125
1540
Depth
Meters
1
1
18
18
26
26
Temperature
Cent.
13.0
14.0
12.5
13.0
11.5
13.0
PH
SU
7.3
6.8
7.1
7.0
7.3
6.6
DO
mgM
6.9
7.0
6.4
6.9
5.7
5.9
Conductivity
ymhos/cm
170
160
170
165
170
165
NH3 - N
mg/£
0.007
<0.005
0.011
0.018
0.018
0.022
TKN - N
mg/«.
0.25
0.24
0.10
0.47
0.13
0.30
no2 + no3 - n
mg/£
0.012
0.007
0.035
0.021
0.082
0.080
Ortho - P
mg/s,
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
Total - P
mg/Ji
0.006
0.009
0.008
0.008
0.006
0.007
-------
Station: 6-a Transect 6, South 1/4 point
Date
Mo/Day/Yr
9/15/76
9/16/76
9/15/76
9/16/76
9/15/76
9/16/76
Time
Mtly
1625
1445
1620
1440
Depth
Meters
1
1
7
7
Temperature
Cent.
13.0
14.5
5
O
r—
5
O
13.0
14.0
PH
SU
7.3
7.5
ro
_C
to
to
-C
-------
Station: 6-b Transect 6, Mid-channel
Date
Mo/Day/Yr
9/15/76
9/16/76
9/15/76
9/16/76
9/15/76
9/16/76
Time
Mtly
1550
1422
1540
1420
1545
1410
Depth
Meters
1
1
21
21
24
23
Temperature
Cent.
13.0
14.0
11.5
12.5
11.0
12.0
PH
SU
7.2
7.3
7.2
6.7
7.1
6.6
DO
mg/Ji
6.9
6.9
7.0
6.9
6.9
6.9
Conductivity
ymhos/cm
165
165
170
170
180
170
NH3 - N
mg/x.
0.010
<0.005
0.005
0.011
0.007
<0.005
TKN - N
mg/£
0.10
0.18
0.19
0.23
0.13
0.14
no2 + no3 - n
mg/s,
<0.005
0.009
0.031
0.023*
0.046
0.035
Ortho - P
mg/A
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
Total - P
mg/£
0.007
0.007
0.008
0.010
0.014
0.010
*Average of duplicate analyses
-------
Station: 6-b Transect 6, Mid-channel (continued)
Date
Mo/Day/Yr
11/17/76
11/17/76
Time
Mtly
1215
1250
Depth
Meters
1
6
Temperature
Cent.
7.0
7.0
pH
SU
7.8
7.9
DO
mg/£
9.2
9.2
Conductivity
ymhos/cm
195
180
NH3 - N
mg/s-
0.008
<0.005
TKN - N
mg/£
0.16
0.18
no2 + no3 - n
mg/£
0.054
0.061
Ortho - P
mg/Ji
<0.005
<0.005
Total - P
mg/£
0.006
0.008
-------
Station: 6-c Transect 6, North 1/4 point
Date
Mo/Day/Yr
9/15/76
9/16/76
9/15/76
9/16/76
9/15/76
9/16/76
Time
Mtly
1600
1435
1615
1430
Depth
Meters
1
1
6
6
Temperature
Cent.
12.5
14.5
2
o
*
o
13.0
13.5
PH
SU
7.3
7.0
*n3
-C
1 /s
JZ
f /¦%
7.2
6.7
DO
mg/Ji
7.2
6.9
o
1/ }
a
7.1
6.9
Conducti vi ty
ymhos/cm
170
160
0
1—
1
0
h-
1
170
165
NH3 - N
mg/J>
<0.005
0.008
CD
Q.
B
to
CL)
Q_
E
fO
0.008
0.017
TKN - N
mg/1
0.10
0.38
C/)
C/")
0.10
0.29
no2 + no3 - n
mg/£
0.009
0.006
o
z
o
z
0.010
0.010
Ortho - P
mg/£
<0.005
<0.005
<0.005
<0.005
Total - P
mg/£
0.010
0.005
0.008
0.009
-------
Appendix b
BOTTOM DEPTH PROFILES - GREEN MOUNTAIN RESERVOIR
69
-------
f
0.1
I
600
800
i
1000
1200
I
Feet
0.2
0.3
0.4
i | Kilometers
CD
S-
o
O
-------
0
r
1000
2000
I
Q.
-------
0
20
40
60
80
100
120
140
160
180
200
100C
2000
Feet
3000
4000
I
5030
6000
0.5
Kilometers
1.0
1.5
—r—
QJ
S-
o
CD
S-
o
sz
CO
O
cn
S-
o
Transect 3
-------
ZL
Depth, Feet
ro —1 —' —1 —1 —1
O QO CT> -P» ro O CO (Ti 4» PO
ooooooooo oo
r i i i i i i i i i |
Depth, Meters
South Shore
cn
o
o
o
o
o
o
3
n>
c+
0>
s
(/)
cn
o
o
no
O
o
o
ro
cn
o
O
North Shore
CO
o
o
o
-------
0
1
5r 20
a> 30
Transect 5
Feet
1000
i
1500
2000
I
2500
Kilometers
0.3 9.4
0.7
3.3
1
CD
S-
o
-C
00
s-
o
-------
0
r
s-
a>
+¦»
a>
5:
+->
o.
a>
o
Transect 6
50 ¦"
Feet
1500 2000 2500 3000
Ki1ometers
0.4 0.5
0.6
0.7
0.8
0.9
—|
-------
APPENDIX C
TRIBUTARY AND STP DATA - LOWER BLUE RIVER DRAINAGE
76
-------
Station BR-1 Blue River
Date
Mo/Day/Yr
9/13/76
9/14/76
9/15/76
Time
Mtly
1420
1250
1235
Temp
°C
7.5
6.5
6.5
PH
su
6.85
7.0
6.8
Flow*
m^/s
3.09
4.16
4.67
Cond
vtmhos/cm
180
180
160
DO
ng/1
10
9.8
9.8
BOOS-
mg/1
<1.0
1 .0
<1.0
TS S
mg/1
<1
<1
<1.0
T-Coli
#/100ml
<1
<1
8
F-Coli
#/100ml
<1
<1
<1
TKN
mg/1
0.10
0.29
0.26
N02+N03-N
mg/1
0.140
0.163
0.201
NH,-N
mg/1
<0.005
<0.005
0.007
T-P
mg/1
0.009
<0.005
0.006
0-P
mg/1
<0.005
<0.005
<0.005
Si
mg/1
2.40
2.30
2.35
T-Mo
ng/1
165
170
155
D-Mo
ug/l
145
185
170
T-Fe
ug/l
40
50
30
D-Fe
ug/l
20
20
10
T-Zn
ug/l
50
60
115
D-Zn
pg/i
25
35
40
T-Cu
yg/l
<5
<5
<5
D-Cu
ug/l
<5
5
5
* Preliminary data from USGS
77
-------
Station SC-1 Straight Creek
Date
Mo/Day/Yr
9/13/76
9/14/76
9/15/76
Time
Mtly
1405
0840
0835
Temp
°C
12.0
7.0
6.0
PH
su
nr/s
6.8
7.0
7.0
Flow
-
0.218
-
Cond
Mmhos/cm
110
110
110
DO
mg/1
7.7
8.7
8.9
B0D5
mg/1
<1.0
1.0
<1.0
TSS
mg/1
9.0
6.0
4.4
T-Coli
#/100ml
180
510
250
F-Coli
#/100ml
34
160
48
TKN
mg/1
0.12
0.32
0.29
NO2+NO3-N
mg/1
0.103
0.120
0.144
NH3-N
mg/1
<0.005
0.007
<0.005
T-P
mg/1
0.017
0.008
0.012
0-P
mg/1
<0.005
<0.005
<0.005
Si
mg/1
4.30
4.00
4.00
T-Mo
M9/1
20
10
10
D-Mo
yg/l
<10
<10
15
T-Fe
pg/i
600
530
400
D-Fe
ng/i
120
110
140
T-Zn
yg/l
30
20
5
D-Zn
pg/i
10
10
10
T-Cu
Mg/1
<5
<5
<5
D-Cu
yg/l
<5
5
5
70
-------
Station WC-1 Willow Creek
Date
Mo/Day/Yr
9/13/76
9/14/76
9/15/76
Time
Mtly
1345
1240
1220
Temp
°C
11.5
11.0
9.0
PH
su
6.5
7.1
6.6
Flow
m3/s
-
0.158
-
Cond
umhos/cm
75
70
70
DO
mg/1
7.9
7.8
8.4
B0D5
mg/1
<1.0
<1.0
<1.0
TSS
mg/1
1.2
<1.0
<1.0
T-Coli
#/l 00ml
56
44
660
F-Coli
#/ 100ml
10
4
260
TKN
mg/1
0.05
0.22
0.19
no2+no3-n
mg/1
0.013
0.050
0.045
NH-j-N
mg/1
<0.005
0.007
0.010
T-P
mg/1
0.008
<0.005
0.005
0-P
mg/1
<0.005
<0.005
<0.005
Si
mg/1
3.15
2.90
3.00
T-Mo
ug/1
10
<10
<10
D-Mo
Mg/1
<10
<10
<10
T-Fe
ug/1
140
120
130
D-Fe
ug/1
70
60
80
T-Zn
ug/1
20
15
75
D-Zn
ug/1
10
10
5
T-Cu
ug/1
5
5
5
D-Cu
ug/i
<5
5
<5
79
-------
Station DS-STP Pi 1 Ion-Si 1verthorne Wastewater Treatment Plant Discharge
Date
Mo/Day/Yr
9/14/76
9/15/76
9/16/76
Time
Mtly
0905
0900
0855
Temp
°C
14.4
11.5
11.5
PH
SU
6.6
6.6
6.5
Flow
nrVs
0,022
0.021
0.022
Cond
ymhos/cm
400
360
410
DO
mg/1
-
-
-
bod5
mg/1
1.8
3.5
1.2
TSS
mg/1
7.6
9.0
7.0
T-Coli
#/100ml
-
1000
900
F-Coli
#/l 00ml
-
28
64
TKN
mg/1
1 .96
1.58
1.36
NOp+NOq-N
mg/1
7.84
6.86
7.66
NHo-N
mg/1
1 .37
1.01
0.94
T-P
mg/1
0.46
0.40
0.40
0-P
mg/1
0.34
0.29
0.28
Si
mg/1
5.65
5.05
5.10
T-Mo
yg/1
50
65
70
D-Mo
ug/l
40
55
50
T-Fe
yg/1
90
140
70
D-Fe
Mg/i
10
20
20
T-Zn
Mg/l
25
135
60
D-Zn
Mg/1
35
35
75
T-Cu
Mg/1
5
10
5
D-Cu
Mg/1
5
<5
10
T-Coli
MPN/100ml
1400
3500
1700
F-Coli
MPN/100ml
49
79
64
30
-------
Station BR-2 Blue River
Date
Mo/Day/Yr
9/13/76
9/14/76
9/16/76
Time
Mtly
1300
1200
1230
Temp
°C
11.5
9.5
10.0
PH
SU
6.3
6.9
6.7
Flow
m3/s
-
4.59
-
Cond
umhos/cm
180
180
170
DO
mg/1
8.4
8.8
8.7
B0D5
mg/1
<1.0
<1.0
<1 .0
TSS
mg/1
<1.0
2.0
1.6
T-Coli
#/100ml
20
26
24
F-Coli
#/l 00ml
10
8
16
TKN
mg/1
0.16
0.37
0.29
N02+N03-N
mg/1
0.134
3.26
0.178
NH3-N
mg/1
0.009
0.028
<0.005
T-P
mg/1
0.008
0.094
0.009
0-P
mg/1
0.006
0.065
<0.005
Si
mg/1
2.85
2.60
2.65
T-Mo
vg/1
125
145
140
D-Mo
yg/1
110
130
135
T-Fe
yg/l
60
90
160
D-Fe
yg/l
80
20
40
T-Zn
ng/i
30
50
60
D-Zn
yg/l
40
20
25
T-Cu
yg/l
5
5
5
D-Cu
ug/1
5
<5
5
81
-------
Station RC-1 Rock Creek
Da te
Mo/Day/Yr
9/13/76
9/14/76
9/16/76
Time
Mtly
1245
1145
1215
Temp
°C
10.0
10.0
9.0
PH
SU
6.3
6.95
6.7
Flow*
m3/s
0.258
0.311
0.425
Cond
umhos/cm
60
60
60
DO
mg/1
8.4
8.4
8.7
B0D5
mg/1
<1.0
<1.0
<1.0
TSS
mg/1
1.2
1.6
1.4
T-Coli
#/100ml
12
24
40
F-Coli
#/l00ml
4
4
16
TKN
mg/1
0.06
0.17
0.24
NOo+NOo-N
mg/1
0.048
0.088
0.112
NH-j-N
mg/1
<0.005
<0.005
<0.005
T-P
mg/1
0.013
<0.005
0.009
0-P
mg/1
0.012
<0.005
<0.005
Si
mg/1
2.60
2.45
2.20
T-Mo
ug/l
10
15
10
D-Mo
ug/l
<10
<10
15
T-Fe
Mg/1
170
180
180
D-Fe
ug/1
110
90
70
T-Zn
ug/l
<5
10
15
D-Zn
ug/1
10
5
10
T-Cu
ug/l
<5
<5
<5
D-Cu
ug/l
5
5
5
* Preliminary data from USGS
82
-------
Station BC-1 Boulder Creek
Date
Mo/Day/Yr
9/13/76
9/14/76
9/16/76
Time
Mtly
1210
1135
1200
Temp
°C
10.5
10.5
9.0
pH
SU
6.2
6.8
6.8
Flow*
nrVs
0.204
0.204
0.252
Cond
umhos/cm
60
60
60
DO
mg/1
8.2
8.2
8.4
B0D5
mg/1
<1.0
<1.0
<1.0
TSS
mg/1
<1.0
<1.0
1.2
T-Coli
#/100ml
12
16
8
F-Coli
#/100ml
2
12
4
TKN
mg/1
0.20
0.18
0.25
NO2+NO3-N
mg/1
0.028
0.056
0.088
NH3-N
mg/1
<0.005
<0.005
<0.005
T-P
mg/1
0.011
0.005
0.098
O-P
mg/1
0.008
0.005
0.094
Si
mg/1
1.60
1.50
1.60
T-Mo
ug/1
<10
10
<10
D-Mo
ug/1
<10
<10
10
T-Fe
yg/1
210
220
160
D-Fe
ug/l
70
90
120
T-Zn
ug/1
10
<5
25
D-Zn
ug/1
10
5
10
T-Cu
ug/1
5
<5
10
D-Cu
ug/1
5
<5
5
* Preliminary data from USGS
83
-------
Station SLC-1 Slate Creek
Date
Mo/Day/Yr
9/13/76
9/15/76
9/16/76
Time
Mtly
1150
1130
1145
Temp
°C
11.0
9.0
9.0
pH
sy
6.8
6.8
6.3
Flow*
nvVs
0.278
0.311
0.481
Cond
ymhos/cm
70
60
60
DO
mg/1
7.75
8.2
8.4
bod5
mg/1
<1.0
<1.0
1.0
TSS
mg/1
1.2
1.6
2.4
T-Coli
#/100ml
22
34
110
F-Coli
#/l 00ml
14
28
80
TKN
mg/1
0.08
0.17
0.24
NOo+NOo-N
mg/1
0.017
0.056
0.138
NHo-N
mg/1
<0.005
0.006
<0.005
T-P
mg/1
0.008
0.009
0.009
0-P
mg/1
<0.005
<0.005
<0.005
Si
mg/1
1.60
1.40
1.35
T-Mo
yg/1
<10
<10
<10
D-Mo
yg/1
<10
<10
<10
T-Fe
yg/1
370
310
320
D-Fe
yg/1
170
170
170
T-Zn
yg/1
10
30
25
D-Zn
yg/i
15
10
10
T-Cu
yg/l
<5
10
10
D-Cu
yg/i
<5
<5
<5
* Preliminary data from USGS
84
-------
Station BR-3 Blue River
Date
Mo/Day/Yr
9/13/76
9/15/76
9/16/76
Time
Mtly
1100
1110
1125
Temp
°C
9.5
8.0
8.5
pH
SU
6.0
6.7
6.8
Flow
nrVs
4.67
-
-
Cond
ymhos/cm
140
180
140
DO
mg/1
8.8
9.1
9.1
BOD5
mg/1
1.0
1.0
1.0
TSS
mg/1
1.6
1.2
3.4
T-Coli
#/100ml
270
240
670
F-Coli
#/100ml
12
75
28
TKN
mg/1
0.16
0.24
0.13
NO0+NO0-N
mg/1
0.106
0.271
0.209
NHo-N
mg/1
0.007
0.018
0.005
T-P
mg/1
0.008
0.009
0.009
0-P
mg/1
<0.005
<0.005
<0.005
Si
mg/1
3.00
2.75
2.80
T-Mo
yg/1
90
100
100
D-Mo
Mg/1
85
120
100
T-Fe
yg/1
140
150
180
D-Fe
yg/1
40
40
40
T-Zn
Mg/1
25
115
55
D-Zn
Mg/1
20
20
30
T-Cu
Mg/l
<5
10
5
D-Cu
Mg/1
5
5
10
85
-------
Station BLC-1 Black Creek
Date
Mo/Day/Yr
9/13/76
9/15/76
9/16/76
Time
Mtly
1015
1100
1110
Temp
°C
10.5
10.5
11.0
PH
SU
6.2
6.8
6.7
Flow*
m3/s
0.54
0.65
0.76
Cond
umbos/cm
<50
50
<50
DO
mg/1
8.4
8.2
8.3
BOD5
mg/1
<1.0
<1.0
1.0
TSS
mg/1
2.2
<1.0
4.4
T-Coli
#/100ml
250
100
290
F-Coli
#/l 00ml
78
60
130
TKN
mg/1
0.10
0.32
0.30
NO0+NO3-N
mg/1
0.060
0.066
0.115
NH3-N
mg/1
<0.005
0.008
<0.005
T-P
mg/1
0.021
0.009
0.007
0-P
mg/1
0.008
<0.005
<0.005
Si
mg/1
1.10
0.90
1.00
T-Mo
pg/i
<10
<10
<10
D-Mo
ug/i
<10
10
<10
T-Fe
yg/i
220
120
210
D-Fe
pg/l
50
60
70
T-Zn
pg/i
10
65
35
D-Zn
yg/l
15
5
10
T-Cu
ug/l
<5
10
10
D-Cu
yg/l
<5
<5
5
* Preliminary data from USGS
86
-------
Station OC-1
Otter Creek
Da te
Mo/Day/Yr
9/14/76
9/15/76
9/16/76
Time
Mtly
1050
1045
1100
Temp
°C
11.0
9.0
8.0
pH
su
6.8
6.3
6.9
F1 ow
nrVs
0.040
-
-
Cond
ymhos/cm
130
140
130
DO
mg/1
7.9
8.4
8.7
B0D5
mg/1
1.1
1.3
1 .0
TSS
mg/1
4.8
3.6
5.6
T-Coli
#/100ml
1100
1000
600
F-Coli
#/100ml
800
720
370
TKN
mg/1
0.46
0.32
0.36
NO2+NO3-N
mg/1
0.162
0.042
0.116
NH3-N
mg/1
0.005
<0.005
0.012
T-P
mg/1
0.093
0.102
0.079
0-P
mg/1
0.078
0.084
0.063
Si
mg/1
7.00
7.30
6.60
T-Mo
yg/l
<10
<10
<10
D-Mo
yg/l
<10
<10
<10
T-Fe
yg/1
1200
950
900
D-Fe
yg/1
600
620
530
T-Zn
yg/1
15
325*
20
D-Zn
yg/l
5
10
10
T-Cu
yg/l
5
10
5
D-Cu
yg/1
<5
<5
<5
* This value appears to be an outlier.
87
-------
Station CC-1
Cataract Creek
Da te
Mo/Day/Yr
9/14/76
9/15/76
9/16/76
Time
Mtly
1035
1030
1045
Temp
°C
12.0
10.0
9.5
pH
SU
6.8
6.5
6.5
Flow*
nrVs
0.136
0.164
0.184
Cond
ymhos/cm
120
120
120
DO
mg/1
7.9
8.3
8.4
B0D5
mg/1
<1.0
<1.0
<1.0
TSS
mg/1
2.0
1.2
1.8
T-Coli
#/100ml
36
56
26
F-Coli
#/100ml
16
28
18
TKN
mg/1
0.30
0.35
0.16
NO0+NO0-N
mg/1
0.041
0.053
0.071
NHo-N
mg/1
<0.005
<0.005
0.006
T-P
mg/1
<0.005
0.005
0.015
0-P
mg/1
<0.005
<0.005
0.011
Si
mg/1
1 .30
1.30
1.30
T-Mo
yg/i
15
<10
<10
D-Mo
yg/1
<10
15
<10
T-Fe
yg/i
230
210
210
D-Fe
yg/i
220
120
120
T-Zn
yg/l
20
15
35
D-Zn
yg/i
40
5
10
T-Cu
yg/1
<5
5
5
D-Cu
yg/i
10
<5
<5
* Preliminary data from USGS
88
-------
Station BR-4 Blue River
Date
Mo/Day/Yr
9/14/76
9/15/76
9/16/76
Time
Mtly
1015
1010
1025
Temp
°C
12.0
12.5
12.0
PH
su
6.6
6.3
6.4
Flow*
m3/s
19.08
19.14
18.46
Cond
umhos/cm
170
160
180
DO
mg/1
5.7
5.8
5.8
BOD5
mg/1
<1.0
<1.0
<1.0
TSS
mg/1
2.0
2.4
2.6
T-Coli
#/100ml
8
6
120
F-Coli
#/l 00ml
<1
2
<1
TKN
mg/1
0.06
0.17
0.22
NO2+NO1-N
mg/1
0.146
0.154
0.156
NH3-N
mg/1
<§.005
0.005
<0.005
T-P
mg/1
0.008
0.006
<0.005
0-P
mg/1
<0.005
<0.005
<0.005
Si
mg/1
2.60
2.70
2.70
T-Mo
yg/1
95
80
85
D-Mo
yg/1
75
80
85
T-Fe
ug/1
110
100
60
D-Fe
ug/1
70
20
40
T-Zn
wg/1
15
65
20
D-Zn
ug/i
120**
10
20
T-Cu
yg/i
5
10
<5
D-Cu
wg/i
25**
5
<5
* Preliminary data from USGS
** The only plausible explanation for these high concentrations of dissolved zinc
and copper 1s that the sample may have inadvertently been contaminated during
sampling.
89
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO. 2.
EPA-908/2-77-003
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
Green Mountain Reservoir - Lower Blue River Study,
Colorado, September, 1976
5. REPORT DATE
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Ronald M. Eddy, Robert L. Fox
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 80295
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
13. TYPE OF REPORT AND PERIOD COVERED
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
i6.abstract September, 1976, a study was conducted by the Environmental Protec-
tion Agency, Region VIII, to determine existing nutrient and organic loadings to Green
Mountain Reservoir, present trophic status of the reservoir, and possible effects of
increased nutrient addition on algal growth potential. Sampling was conducted during
a four day period,with additional samples collected in November*1976.
Samples in Green Mountain Reservoir were collected at quarter points along six
transects, three depths per sampling site. Samples were also collected from the
Dillon-SiIverthorne STP, the mainstem Blue River, and eight tributaries in the lower
Blue River drainage.
Of the computed total phosphorus and total nitrogen loadings to the reservoir,
12.8% and 7.0%, respectively, were attributable to the Dillon-Silverthorne STP. Non-
point loadings from the lower Blue River drainage (omitting the discharge from Dillon
Reservoir) comprised 51.1% of the total phosphorus and 36.4% of the total nitrogen
entering Green Mountain Reservoir. Results of the laboratory algal assays indicated
phosphorus limitation at all stations with micronutrient limitation also evident at
stations 3b and 6b. On the basis of chlorophyll a and primary productivity values,
Green Mountain Reservoir, at the time of sampling was oligotropnic. Dry weight
yields in the algal assays indicated that potential primary productivity was
moderate at the time of sampling.
17. KEY WORDS AND DOCUMENT ANALYSIS
a. DESCRIPTORS
b. IDENTIFIERS/OPEN ENOED TERMS
c. COSATI Field/Group
18. DISTRIBUTION STATEMENT
Release to the Public
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
39
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
CPA Form 2220-1 (»-73)
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Dillon Reservoir - Slue River Study. Colorado
June, July, August 1973. 1974.
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Green Mountain Reservoir - Lower Blue River Study
September 1976", 1977.
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