U.S. Department of the Interior

U.S. Geological Survey

Water Quality of Rob Roy Reservoir and 

Lake Owen, Albany County, and Granite 

Springs and Crystal Lake Reservoirs, 

Laramie County, Wyoming, 1997-98

By Kathy Muller Ogle1, David A. Peterson1, Bud Spillman2, and Rosie Padilla2

Water-Resources Investigations Report 99-4220

Prepared in cooperation with the 

Cheyenne Board of Public Utilities

1U.S. Geological Survey

2Cheyenne Board of Public Utilities

Cheyenne, Wyoming

1999
U.S. Department of the Interior

Bruce Babbitt, Secretary

U.S. Geological Survey

Charles G. Groat, Director

Any use of trade, product, or firm names in this publication is for 

descriptive purposes only and does not imply endorsement by the 

U.S. Government

For additional information write to:

District Chief

U.S. Geological Survey, WRD

2617 E. Lincolnway, Suite B

Cheyenne, Wyoming 82001-5662

Copies of this report can be purchased from:

U.S. Geological Survey

Branch of Information Services

Box 25286, Denver Federal Center

Denver, Colorado 80225

Information regarding the programs of the Wyoming District is available on the Internet via the World Wide Web. You 

may connect to the Wyoming District Home Page using the Universal Resource Locator (URL): 

http://wy.water.usgs.gov
CONTENTS iii

CONTENTS

Page

Abstract ............................................................................................................................................................................... 1

Introduction......................................................................................................................................................................... 1

Purpose and scope ................................................................................................................................................... 3

Description of water system .................................................................................................................................... 3

Description of area................................................................................................................................................... 3

Acknowledgments ................................................................................................................................................... 3

Data Collection ................................................................................................................................................................... 6

Water Quality ...................................................................................................................................................................... 7

Rob Roy Reservoir ................................................................................................................................................. 7

Profiles ......................................................................................................................................................... 13

Phytoplankton .............................................................................................................................................. 13

Chemical quality .......................................................................................................................................... 16

Bottom sediment .......................................................................................................................................... 16

Lake Owen .............................................................................................................................................................. 22

Profiles ......................................................................................................................................................... 22

Phytoplankton .............................................................................................................................................. 24

Chemical quality .......................................................................................................................................... 25

Bottom sediment .......................................................................................................................................... 26

Granite Springs Reservoir ...................................................................................................................................... 27

Profiles ......................................................................................................................................................... 27

Phytoplankton .............................................................................................................................................. 29

Chemical quality .......................................................................................................................................... 31

Bottom sediment .......................................................................................................................................... 31

Crystal Lake Reservoir ........................................................................................................................................... 34

Profiles ......................................................................................................................................................... 34

Phytoplankton .............................................................................................................................................. 38

Chemical quality .......................................................................................................................................... 39

Bottom sediment .......................................................................................................................................... 40

Comparison among reservoirs................................................................................................................................. 44

Profiles ......................................................................................................................................................... 44

Phytoplankton .............................................................................................................................................. 44

Chemical quality .......................................................................................................................................... 47

Bottom sediment .......................................................................................................................................... 47

Summary ............................................................................................................................................................................. 48

References cited .................................................................................................................................................................. 50

Appendix A--Profile data 

Profile data for Rob Roy Reservoir ......................................................................................................................... A1

Profile data for Lake Owen ..................................................................................................................................... A12

Profile data for Granite Springs............................................................................................................................... A24

Profile data for Crystal Lake Reservoir................................................................................................................... A40

Appendix B--Phytoplankton data

Table B1. Phytoplankton density and biomass, Rob Roy Reservoir ...................................................................... B1

Table B2. Phytoplankton density and biomass, Lake Owen .................................................................................. B4

Table B3. Phytoplankton density and biomass, Granite Springs Reservoir ........................................................... B8

Table B4. Phytoplankton density and biomass, Crystal Lake Reservoir................................................................ B12
iv WATER QUALITY OF FOUR RESERVOIRS 

FIGURES

Page

1. Map showing location of Rob Roy Reservoir and Lake Owen, Albany County, and Granite Springs and 

Crystal Lake Reservoirs, Laramie County, Wyoming .................................................................................... 2

2. Maps showing location of sampling sites in Rob Roy Reservoir and Lake Owen, Albany County, and 

Granite Springs and Crystal Lake Reservoirs, Laramie County, Wyoming ................................................... 4

3-7. Graphs showing:

3. Temperature, dissolved oxygen, specific conductance and pH profiles of Rob Roy Reservoir, 

Albany County, Wyoming..................................................................................................................... 14

4. Secchi disk transparency depths in 1998 for Rob Roy Reservoir and Lake Owen, Albany County,

and Granite Springs and Crystal Lake Reservoirs, Laramie County, Wyoming................................... 15

5. Temporal variation of temperature with depth in Rob Roy Reservoir, Albany County, 

Wyoming in summer and fall, 1998...................................................................................................... 16

6. Phytoplankton biomass changes over time in Rob Roy Reservoir, Albany County, Wyoming ............... 17

7. Dissolved-solids concentrations in water samples collected in 1997 from Rob Roy 

Reservoir and Lake Owen, Albany County, and Granite Springs and Crystal Lake Reservoirs, 

Laramie County, Wyoming ................................................................................................................... 22

8. Pie diagrams showing the percentage of major ions in water samples collected in 1997 from Rob Roy 

Reservoir and Lake Owen, Albany County, and Granite Springs and Crystal Lake Reservoirs, 

Laramie County, Wyoming ............................................................................................................................. 23

9-24. Graphs showing:

9. Dissolved-silica concentrations in water samples collected in 1997 from Rob Roy Reservoir 

and Lake Owen, Albany County, and Granite Springs and Crystal Lake Reservoirs, 

Laramie County, Wyoming ................................................................................................................... 24

10. Dissolved-iron concentrations in water samples collected in 1997 from Rob Roy 

Reservoir and Lake Owen, Albany County, and Granite Springs and Crystal Lake 

Reservoirs, Laramie County, Wyoming................................................................................................ 25

11. Dissolved-manganese concentrations in water samples collected in 1997 from Rob Roy 

Reservoir and Lake Owen, Albany County, and Granite Springs and Crystal Lake 

Reservoirs, Laramie County, Wyoming................................................................................................ 26

12. Concentrations of selected constituents in bottom-sediment samples collected from Rob Roy 

Reservoir and Lake Owen, Albany County, and Granite Springs and Crystal Lake 

Reservoirs, Laramie County, Wyoming................................................................................................ 27

13. Temperature, dissolved oxygen, specific conductance and pH profiles of Lake Owen, Albany 

County, Wyoming ................................................................................................................................. 28

14. Temporal variation of temperature with depth in Lake Owen, Albany County, Wyoming 

in summer and fall of 1998 ................................................................................................................... 29

15. Phytoplankton biomass changes over time in Lake Owen, Albany County, Wyoming ........................... 30

16. Temperature, dissolved oxygen, specific conductance and pH profiles for Granite Springs 

Reservoir, Laramie County, Wyoming.................................................................................................. 32

17. Temporal variation of temperature with depth in Granite Springs Reservoir, Laramie County, 

Wyoming, 1998..................................................................................................................................... 34

18. Phytoplankton biomass changes over time in Granite Springs Reservoir, Laramie 

County, Wyoming ................................................................................................................................. 35

19. Temperature, dissolved oxygen, specific conductance and pH profiles of Crystal Lake Reservoir, 

Laramie County, Wyoming ................................................................................................................... 36

20. Temporal variation of temperature with depth in Crystal Lake Reservoir, Laramie County, 

Wyoming, 1998..................................................................................................................................... 39

21. Temporal variation of dissolved oxygen with depth in Crystal Lake Reservoir, Laramie County, 

Wyoming, 1998..................................................................................................................................... 40

22. Phytoplankton biomass changes over time in Crystal Lake Reservoir, Laramie County, Wyoming........ 41
CONTENTS v

FIGURES--Continued

Page

9-24. Graphs showing--Continued

23. Phytoplankton biomass and density in Rob Roy Reservoir and Lake Owen, Albany County, and

Granite Springs and Crystal Lake Reservoirs, Laramie County, Wyoming ......................................... 45

24. Comparison of the concentrations of major ions in the surface samples collected in the fall of 1997

at Rob Roy Reservoir and Lake Owen, Albany County, and Granite Springs and Crystal Lake 

Reservoirs, Laramie County, Wyoming ................................................................................................ 48

TABLES 

1. Selected reservoir characteristics for Rob Roy Reservoir and Lake Owen, Albany County, and Granite 

Springs and Crystal Lake Reservoirs, Laramie County, Wyoming ................................................................ 6

2. Chemical analyses and physical properties of water samples collected in 1997 from Rob Roy 

Reservoir and Lake Owen, Albany County, and Granite Springs and Crystal Lake Reservoirs, 

Laramie County, Wyoming............................................................................................................................. 8

3. Chemical analyses of composite samples of bottom sediment collected in 1998 from Rob Roy Reservoir 

and Lake Owen, Albany County, and Granite Springs and Crystal Lake Reservoirs, Laramie 

County, Wyoming ........................................................................................................................................... 11

 4. Phytoplankton taxa list for Rob Roy Reservoir and Lake Owen, Albany County, and Granite Springs

 and Crystal Lake Reservoirs, Laramie County, Wyoming ............................................................................ 18

5. Microscopic particulate analyses of water samples collected in the fall of 1997 at Rob Roy Reservoir

and Lake Owen, Albany County, and Granite Springs and Crystal Lake Reservoirs, Laramie County, 

Wyoming......................................................................................................................................................... 21

6. Concentrations of selected radionuclide activities and organic compounds in water samples collected 

September 4, 1997, at Crystal Lake Reservoir, Laramie County, Wyoming .................................................. 42
vi WATER QUALITY OF FOUR RESERVOIRS 

CONVERSION FACTORS 

Multiply By To obtain

acre 43,560 square foot (ft2)

4,047 square meter

0.001562 square mile

cubic foot per second (ft3

/s) 0.02832 cubic meter per second

foot (ft) 0.3048 meter

gallon per day (gal/d) 3.785 liter per day

inch (in.) 25.4 millimeter

mile (mi) 1.609 kilometer

million gallons per day (Mgal/d) 1.121 thousand acre-feet per year

0.001547 thousand cubic feet per second

0.6944 thousand gallons per minute

0.003785 million cubic meters per day

1.3815 million cubic meters per year

square mile (mi2) 2.590 square kilometer

thousand acre-feet per year 0.8921 million gallons per day

0.001380 thousand cubic feet per second

0.6195 thousand gallons per minute

0.003377 million cubic meters per day

Some other water relations in inch-pounds units are listed below:

1 gallon = 8.34 pounds

1 million gallons = 3.07 acre-feet

1 cubic foot = 62.4 pounds

= 7.48 gallons

1 acre-foot (acre-ft) = 325,851 gallons

= 43,560 cubic feet

1 inch of rain = 17.4 million gallons per square mile

= 27,200 gallons per acre

= 100 tons per acre

Temperatures can be converted to degrees Fahrenheit (°F) or degrees Celsius (°C) by using the following equations:

 °F = 9/5(°C)+32

°C = 5/9(°F-32)

Sea level: In this report “sea level” refers to the National Geodetic Vertical Datum of 1929 (NGVD of 1929)—a geodetic datum derived 

from a general adjustment of the first-order level nets of both the United States and Canada, formerly called Sea Level Datum of 1929.
ABSTRACT 1

ABSTRACT

The water quality of four reservoirs was 

assessed during 1997 and 1998 as a cooperative 

project between the Cheyenne Board of Public 

Utilities and the U. S. Geological Survey. The four 

reservoirs, Rob Roy, Lake Owen, Granite Springs, 

and Crystal Lake, provide approximately 75 percent of the public water supply for Cheyenne, 

Wyoming. Samples of water and bottom sediment 

were collected and analyzed for selected physical, 

chemical, and biological characteristics to provide 

data about the reservoirs. Water flows between the 

reservoirs through a series of pipelines and stream 

channels. The reservoirs differ in physical characteristics such as elevation, volume, and depth.

Profiles of temperature, dissolved oxygen, 

specific conductance, and pH were examined. 

Three of the four reservoirs exhibited stratification 

during the summer. The profiles indicate that stratification develops in all reservoirs except Lake 

Owen. Stratification developed in Rob Roy, Granite Springs, and Crystal Lake Reservoirs by midJuly in 1998 and continued until September, with 

the thickness of the epilimnion increasing during 

that time. Secchi disk readings indicated Rob Roy 

Reservoir had the clearest water of the four reservoirs studied.

The composition of the phytoplankton community was different in the upper two reservoirs 

from that in the lower two reservoirs. Many of the 

species found in Rob Roy Reservoir and Lake 

Owen are associated with oligotrophic, nutrientpoor conditions. In contrast, many of the species 

found in Granite Springs and Crystal Lake Reservoirs are associated with mesotrophic or eutrophic 

conditions. The total number of taxa identified also 

increased downstream. 

The chemical water type in the reservoirs 

was similar, but dissolved-solids concentrations 

were greater in the downstream reservoirs. Water in 

all four reservoirs was a calcium-bicarbonate type. 

In the fall of 1997, Rob Roy Reservoir had the lowest dissolved-solids concentration (19 milligrams 

per liter), whereas Crystal Lake Reservoir had the 

highest concentration (63 milligrams per liter). 

Relatively little differences in the concentrations of 

major-ion species were noted between samples collected near the surface and near the bottom of the 

same reservoir. In contrast, iron and manganese 

concentrations generally were higher in samples 

collected near the bottom of a reservoir than in nearsurface samples collected from the same reservoir. 

Composite bottom-sediment samples from 

all four reservoirs contained similar concentrations 

of bulk constituents such as aluminum, iron, phosphorus and titanium, but varied in concentrations of 

trace elements. Trace-element concentrations in 

Rob Roy Reservoir and Lake Owen were similar to 

the crustal average, whereas in Granite Springs and 

Crystal Lake Reservoirs the concentrations were 

similar to granitic rocks.

INTRODUCTION

Surface water contributes approximately 75 percent of the City of Cheyenne’s public water supply. The 

water is collected from the Douglas Creek and Crow 

Creek drainage areas. Most of the water is stored in four 

reservoirs located in southeastern Wyoming—Rob Roy, 

Lake Owen, Granite Springs, and Crystal Lake (fig. 1). 

Water flows through the reservoir system via a series of 

pipelines and stream channels. At Crystal Lake Reservoir, the water is diverted into pipelines and routed to the 

public water-treatment facilities. The entire water collection, treatment, and distribution system is operated by 

the Cheyenne Board of Public Utilities (BOPU).

Water Quality of Rob Roy Reservoir and Lake Owen, 

Albany County, and Granite Springs and Crystal Lake 

Reservoirs, Laramie County, Wyoming, 1997-98

By Kathy Muller Ogle, David A. Peterson, Bud Spillman, and Rosie Padilla
2 WATER QUALITY OF FOUR RESERVOIRS 
INTRODUCTION 3

Although extensive water-quality data have been 

collected for the treated water, relatively limited data 

are available for the raw-water quality within the storage reservoirs. Data on the water quality in the reservoirs are needed to assist BOPU managers for future 

planning of the Cheyenne water system. In order to 

meet those needs, a study was conducted during 1997-

98 by the BOPU and the U.S. Geological Survey 

(USGS). Data on the reservoir water quality collected 

during the study will assist the BOPU in evaluating reservoir and watershed management options in conjunction with treatment options. 

Purpose and Scope

This report provides baseline water-quality data 

for four reservoirs—Rob Roy, Lake Owen, Granite 

Springs, and Crystal Lake. Specifically this report summarizes phytoplankton and profile data collected at a 

selected monitoring site in each reservoir over a summer season, selected physical, chemical and biological 

constituents for a single sample collected from the water 

column during the summer of 1997, and selected chemical constituents in composite samples of bottom sediment from each reservoir. The report is limited to the 

four reservoirs and to a general description of the water 

quality of the reservoirs. Lake processes are not examined. Due to unexpected opportunities, the project team 

was able to add winter, spring, and summer profiles for 

Granite Springs and Crystal Lake Reservoirs.

Description of the Water System

Surface water for the City of Cheyenne’s publicwater system is collected in reservoirs, two of which—

Rob Roy and Lake Owen—are about 80 miles west of 

Cheyenne (fig. 1). Most diversion facilities and a delivery pipeline were constructed in the 1960s. These facilities were designed and constructed to divert water from 

the Douglas Creek drainage (fig. 2A) to provide Cheyenne with a long-term surface-water supply. The original construction was referred to as Stage I. Stage II was 

constructed in 1985 and consisted of improvements to 

the dams as well as construction of a parallel pipeline 

from Rob Roy Reservoir to Crystal Lake Reservoir. 

The Cheyenne water-treatment facilities receive 

raw water directly from Crystal Lake Reservoir, located 

in the Middle Crow Creek drainage (fig. 2D). The average annual yield from Middle Crow Creek drainage, 

which includes Granite Springs and Crystal Lake, is 

estimated to be about 1.23 billion gallons. The 1998 

annual treated-water demand was approximately 

4.5 billion gallons. Of this total, about 1 billion gallons 

of treated water is supplied by ground water and the 

remainder is supplied by surface water. To meet the current and future treated-water demands of the community, yield from the Stage I and Stage II projects is 

required. This will include the average annual divertable flow from the Douglas Creek drainage of about 

6.8 billion gallons. 

Description of Area

The study area (fig. 1) is the four reservoirs—Rob 

Roy, Lake Owen, Granite Springs, and Crystal Lake. 

The reservoir system begins with Rob Roy Reservoir 

located in the Douglas Creek drainage. Runoff is collected and stored in Rob Roy Reservoir (fig. 2A). 

BOPU diverts stored water from Rob Roy by a pipeline 

to Lake Owen (fig. 2B). From Lake Owen, water is 

transported, again by pipeline to the Middle Crow 

Creek drainage (fig. 2C).

Within the Middle Crow Creek drainage, water is 

stored in two reservoirs—Granite Springs and Crystal 

Lake. Granite Springs provides 1.7 billion gallons of 

storage and Crystal Lake provides 1.1 billion gallons. 

Water within the Middle Crow Creek drainage is routed 

from Granite Springs down Middle Crow Creek and 

also by pipeline to Crystal Lake. From Crystal Lake, 

water is transported by pipelines and Middle Crow 

Creek to the water treatment facilities. Selected characteristics of the four reservoirs are summarized in table 1.

Acknowledgments

The Cheyenne BOPU and many BOPU employees have contributed to making this project a success. 

The sampling assistance of Kay Knott, Marv Tripp, 

Jason Haughton, and Deb Streetman is gratefully 

acknowledged. Tim Wilson’s continuing support and 

Herman Noe’s help in collecting information about the 

reservoirs are appreciated. Jerry Mark and 

Jack Carroccia were instrumental in initiating the study.
4 WATER QUALITY OF FOUR RESERVOIRS 
INTRODUCTION 5
6 WATER QUALITY OF FOUR RESERVOIRS 

DATA COLLECTION

The sampling sites in each reservoir were located 

at or near the deepest point, to reflect integrated water 

quality to the extent possible (fig. 2A, B, C, D). Three 

types of sampling were completed at each reservoir: 

(1) depth profiles of temperature, dissolved oxygen, specific conductance, and pH, and sampling of phytoplankton, (2) a one-time sampling for chemical quality, and 

(3) a composite bottom-sediment sample. Profile measurements and phytoplankton samples were collected 

once in the late summer of 1997 and approximately 

every two weeks in the summer of 1998 at all four reservoirs. 

The reservoirs were vertically profiled from about 

1 foot below the water surface to the bottom of the lake 

in a location estimated to have the greatest depth, based 

on examination of maps and initial sounding of depths. 

During late summer of 1997, all four reservoirs were profiled. Granite Springs and Crystal Lake Reservoirs also 

were profiled in February 1998. Rob Roy Reservoir and 

Lake Owen were not profiled in the winter due to accessibility problems and dangerous ice conditions. Profile 

data for Granite Springs and Crystal Lake Reservoirs 

were collected from mid-May until mid-July of 1998. 

Beginning in mid-July, profiles were completed at all 

four reservoirs until late summer of 1998. The data were 

measured with HydroLab Scout II and YSI 6920 multiparameter probes. Data collected were temperature, dissolved oxygen, specific conductance, and pH. Individual probes were calibrated before profiling, and the two 

multiparameter-probes were compared to each other in 

the field at random times. Readings of the two instruments were comparable with temperature differences 

Table 1. Selected reservoir characteristics for Rob Roy 

Reservoir and Lake Owen, Albany County, and Granite 

Springs and Crystal Lake Reservoirs, Laramie County, 

Wyoming

[Elevation and storage data provided by Cheyenne Board of Public 

Utilities]

Reservoir

Approximate

elevation

(feet above 

sea level)

Approximate

storage 

(billions of 

gallons)

Approximate

depth at 

profiling site 

(feet)

Percent 

of

system

storage

Rob Roy 9,470 11.4 80 79

Lake Owen 8,955 .2 10 1

Granite Springs 7,210 1.7 60 12

Crystal Lake 6,969 1.1 65 8

between 0.1 and 0.15 degrees, dissolved-oxygen differences between 0.02 and 0.5 mg/L (milligrams per liter), 

and pH differences from 0.06 to 0.2. Specific conductance had the largest differences between probes varying 

from 2.6 μS/cm (microsiemens per centimeter at 25oC) 

to 22.5 μS/cm. The same profile pattern was obtained 

with both instruments. No adjustments were made to the 

data. Secchi disk transparencies were collected at each 

reservoir.

At the same time as profiling, a sample was collected at a depth of 1 foot below the water surface (hereafter referred to as the surface sample) at each water 

sampling site for identification and enumeration of phytoplankton. During the sampling for chemical quality in 

the late summer of 1997, a bottom sample of phytoplankton also was collected at 3 ft (feet) above the reservoir 

bottom (hereafter referred to as the bottom sample) at 

Rob Roy, Granite Springs and Crystal Lake Reservoirs. 

Due to its shallow depth, only a surface sample was collected at Lake Owen. The same nomenclature for surface and bottom samples is used throughout this report 

for both phytoplankton and chemical-quality samples. 

The four reservoirs were sampled once in the fall 

of 1997 between August 28 and September 11 for chemical analysis of organic and inorganic constituents. Reservoirs were sampled at the same location where the 

profiles were measured. At each sampling site, waterquality samples were collected at two depths, using a 

Kemmerer bottle. As described for phytoplankton sampling, a surface sample was collected at a depth of 1 ft 

below the water surface in the epilimnion. A bottom 

sample was collected from about 3 ft above the reservoir 

bottom. Likewise, at Lake Owen, due to its shallow 

depth and the lack of variability in the profile data, a single surface sample was collected. A third sample was 

collected at Crystal Lake at 30 ft below the reservoir surface. This depth was estimated to correlate to the pipeline intake level for the water treatment plant. The 

constituent list included phytoplankton, nutrients, major 

ions, trace elements, and microscopic particulate analysis (MPA). Additional analyses for selected radiochemical and pesticide compounds were completed in 

samples collected from Crystal Lake Reservoir because 

it is the direct source of the water to the treatment plant. 

Nutrients, major ions, and trace elements were analyzed 

at the USGS National Water Quality Laboratory in 

Arvada, Colorado. The MPA samples were collected by 

BOPU using the procedure recommended by the U.S. 

Environmental Protection Agency (1996); the procedure 

specifies a total collection time of 24 hours from filter 
WATER QUALITY 7

installation. The phytoplankton and MPA analyses were 

performed by CH Diagnostic in Loveland, Colorado. 

Phytoplankton biomass was calculated from phytoplankton biovolume, assuming a density of one gram per cubic 

centimeter. Chemical analyses and physical properties 

of the water samples collected from the four reservoirs 

are listed in table 2.

Samples of the bottom sediment were collected at 

five sites in each reservoir (fig. 2) using a Ponar grab 

sampler. One of the five sites in each reservoir also was 

the sampling site for profiles, phytoplankton, and chemical quality. Each sample was subsampled to obtain 

material that had not been in contact with the sides of the 

sampler. The five samples then were composited into a 

single sample for each reservoir. If needed, the sample 

was sieved through a 63-um (micrometer) sieve in preparation for trace-element analysis. Sediment samples 

were analyzed for trace elements and nutrients at the 

USGS, Branch of Geochemistry Analytical Services 

Group Laboratory, Denver, Colorado. 

A second sample for replicate phytoplankton analysis was collected from Crystal Lake Reservoir on September 7, 1997. Comparison of the two samples 

indicated the difference was less than 30 percent for phytoplankton biomass, density, and number of taxa identified. No adjustments were made to the phytoplankton 

data based on the quality-control sample. 

A duplicate sample for chemical analysis was collected when the surface sample was collected at Crystal 

Lake. Major-ion concentrations agreed closely. Differences in the individual ion concentration between the 

two samples were less than 0.1 mg/L, except for alkalinity, which varied by 1 mg/L.

WATER QUALITY

Water in reservoirs often becomes stratified. This 

zonation of lakes is a reflection of the differences in 

water density with the warmer, less dense water at the 

top; a cold dense layer at the bottom; and a zone of rapidly changing density between them. The three zones are 

the epilimnion (the upper, warmer water), the metalimnion (the middle zone where the rate of change in temperature is the greatest—also sometimes called the 

thermocline), and the hypolimnion (the lower, colder 

water). Powell (1964, p. 19-20) states that the metalimnion in natural lakes is often observed between 25 to 

40 ft below the surface, but may vary from that depth in 

artificial impoundments.

Profiles of temperature were examined in all four 

reservoirs for thermal stratification. As is commonly 

found in temperate lakes (Horne and Goldman, 1994, 

p. 53-65), three vertical zones were identified in Rob 

Roy, Granite Springs, and Crystal Lake Reservoirs at 

selected times during late summer. Lake Owen’s shallow depth precluded such stratification. Temperatures in 

the reservoirs in this study are influenced by both natural 

lake processes and pipeline inflow and outflow. That 

stratification impacts the quality of the impounded water 

(McGauhey, 1968, p. 92).

Surface-water quality in an impoundment is 

highly variable on both short and long term cycles 

(Moore, 1989, p. 30). Reservoirs are dynamic and have 

a complex interaction of chemistry and biology both seasonally and over decades. Samples collected during this 

study represent the quality of the water in the reservoirs 

at that point in time.

Sediment can act as sites for ion exchange 

between aquatic and solid phases. If elements or compounds are in large concentrations in the water, the sediments may remove them by adsorption. Conversely, if 

the concentrations are low, the elements or compounds 

may move from the sediment into the water. Thus, a 

dynamic equilibrium exists between the sediment and 

the water. Bottom-sediment samples were collected at 

all four reservoirs. The sediment-analysis results for 

each reservoir are summarized in table 3.

Sediment in reservoirs is strongly influenced by 

the geology of the watershed of the lake. Concentrations 

of selected constituents in sediment from the reservoirs 

were compared to published values for diabase (diorite), 

crustal averages, and granitic rocks (Mason, 1966) to 

give a perspective on the concentration.

Rob Roy Reservoir 

Rob Roy Reservoir is the largest, deepest, and 

highest in the series of the reservoirs (fig. 2A; table 1). It 

contains 79 percent of the storage capacity of the fourreservoir system. At the profiling site, the reservoir was 

about 80-ft deep. The spillway elevation is 9,470 ft 

above sea level (table 1). Rob Roy is located in a mountainous area surrounded by evergreen forest. The lake 

and surrounding area are the focus of recreational activities, such as boating, fishing and camping. Rob Roy is 

the only reservoir of the four that receives runoff only 

from its watershed and receives no inflow from other reservoirs.
8

WATERQUALITYOFFOURRESERVOIRS

Table 1. Chemical analyses and physical properties of water-quality samples collected in 1997 from Rob Roy Reservoir and Lake OweGranite Springs and Crystal Lake Reservoirs, Laramie County, Wyoming[QA, duplicate sample collected for quality assurance purposes; a, not measured due to the occurrence of a lightning storm; concentrations of copper, lead, boron, alumiRob Roy Reservoir and Lake Owen should be considered approximate. The initial samples were misplaced at laboratory login. Back-up samples that had been chilled μS/cm, microsiemen per centimeter at 25oC; oC, degrees Celsius; mg/L, milligram per liter; μg/L, microgram per liter]

Site 

(fig. 2)

Identification 

number

Date

sampled

Time

sampled

Specific

conductance

(μS/cm) pH

Water

temperature

(oC)

Color

(as

platinumcobalt)

Dissolved

oxygen

(mg/L)

Chemical

oxygen

demand

(mg/L)

Hardness

(mg/L)

Calcium

dissolved

(mg/L)

Rob Roy

Reservoir (top)

411153106154401 9/2/97 10:40 25 6.9 15.4 20 6.0 11 10 3.1 

Rob Roy 

Reservoir(bottom)

411153106154402 9/2/97 12:15 24 6.2 6.3 30 6.2 11 10 3.0 

Lake Owen 

(top)

410858106060901 9/2/97 15:40 30 7.2 15.6 16 6.7 11 13 3.9 

Granite Springs 

Reservoir (top)

411031105132501 8/28/97 13:40 95 8.0 19.9 22 8.0 19 40 13 

Granite Springs 

Reservoir (bottom)

411031105132502 8/28/97 15:30 101 6.7 16.0 22 6.7 13 43 14 

Crystal Lake

Reservoir (top)

410928105115201 9/4/97 9:50 108 8.4 18.5 12 6.3 15 46 15 

Crystal Lake

Reservoir(top-QA)

410928105115201 9/4/97 9:55 108 8.4 18.5 13 6.3 16 46 15 

Crystal Lake

Reservoir(middle)

410928105115203 9/11/97 13:00 a a a 12 a 15 47 15 

Crystal Lake

Reservoir(bottom)

410928105115202 9/4/97 12:00 114 6.7 16.3 13 <1 <10 48 15 
WATER QUALITY 9

Table 2. Chemical analyses and physical properties of water-quality samples collected in 1997 from Rob Roy Reservoir and Lake Owe

Granite Springs and Crystal Lake Reservoirs, Laramie County, Wyoming--Continued

Site

(fig. 2)

Sodium

(percent)

Sodium

adsorption

ratio

Potassium,

dissolved

(mg/L)

Alkalinity

as CaCO3, 

dissolved

(mg/L)

Sulfate,

dissolved

(mg/L)

Chloride,

dissolved

(mg/L)

Fluoride,

dissolved

(mg/L)

Silica

as SiO2,

dissolved

(mg/L)

Dissolved

solids,

sum of

constituents

(mg/L)

Residual

solids

(mg/L)

Rob Roy

Reservoir (top)

22 0.2 0.4 13 1.3 0.3 <0.1 4.0 19 39 

Rob Roy

Reservoir(bottom)

21 0.2 0.4 12 1.4 0.3 <0.1 6.9 22 45 

Lake Owen

(top)

19 0.2 0.3 15 1.1 0.7 <0.1 2.5 20 42 

Granite Springs 

Reservoir (top)

13 0.2 1.0 40 3.4 2.4 0.3 5.8 55 69 

Granite Springs 

Reservoir (bottom)

13 0.2 1.0 41 3.4 2.5 0.4 8.3 59 79 

Crystal Lake

Reservoir (top)

12 0.2 1.1 46 4.5 2.4 0.5 2.1 58 80 

Crystal Lake

Reservoir(top-QA)

13 0.2 1.2 46 4.4 2.6 0.5 2.1 58 91 

Crystal Lake

Reservoir(middle)

12 0.2 1.3 45 4.3 2.7 0.5 3.9 60 87 

Crystal Lake

Reservoir(bottom)

12 0.2 1.2 44 4.4 3.4 0.5 6.4 63 90 
10 WATER QUALITY OF FOUR RESERVOIRS Table 3. Chemical analyses and physical properties of water-quality samples collected in 1997 from Rob Roy Reservoir and Lake Ow

Granite Springs and Crystal Lake Reservoirs, Laramie County, Wyoming--Continued Site (fig. 2) Nitrogen, NO2 + NO3, dissolved (mg/L) Phosphorus Ortho as P, dissolved (mg/L) Oil & grease (total) (mg/L) Arsenic, dissolved (μg/L) Boron, dissolved (μg/L) Copper, dissolved (μg/L) Iron, dissolved (μg/L) Lead, dissolved (μg/L) Manganese, dissolved (μg/L) 

Rob Roy Reservoir (top) <0.05 <0.01 <1 <1 16 4 51 <1 2 Rob Roy Reservoir (bottom) 0.08 <0.01 2 <1 17 4 69 <1 69 

Lake Owen

(top)

<0.05 <0.01 <1 <1 19 4 130 2.3 8 

Granite Springs 

Reservoir (top)

<0.05 <0.01 <1 <1 14 4 7 <1 5 

Granite Springs 

Reservoir (bottom)

<0.05 <0.01 <1 <1 8.4 4 21 4.1 76 

Crystal Lake

Reservoir (top)

<0.05 <0.01 2 <1 12 2 10 <1 <1 

Crystal Lake

Reservoir(top-QA)

<0.05 <0.01 <1 <1 <16 2 13 <1 <1 

Crystal Lake

Reservoir(middle)

<0.05 <0.01 <1 <1 18 2 28 <1 2 

Crystal Lake

Reservoir(bottom)

<0.05 <0.01 <1 <1 12 7 24 <1 31 
WATER QUALITY 11

Table 4. Chemical analyses of composite samples of bottom sediment collected in 1998 from Rob Roy Reservoir and Lake Owen, Alba

Springs and Crystal Lake Reservoirs, Laramie County, Wyoming

[Except for nitrogen, all results are for sediment passing through a 63 μm sieve; μg/g, microgram per gram}

Site

(fig. 2)

Date 

sampled

Nitrogen,

as total

NO2 + NO3

(mg/kg

as N)

Aluminum

(percent)

Arsenic

(μg/g)

Barium

(μg/g)

Beryllium 

(μg/g)

Bismuth 

(μg/g)

Cadmium 

(percent)

Calcium

(percent)

Cerium

(μg/g)

Rob Roy 

Reservoir

7/23/98 9 6.9 <10 690 2 <10 <2 1.0 58 

Lake Owen 7/23/98 8 6.9 <10 520 1 <10 <2 2.2 50 Granite Springs 

Reservoir

2/5/98 <2 6.2 <10 830 2 <10 <2 .65 130 

Crystal Lake 

Reservoir

2/3/98 <2 6.8 <10 720 3 <10 <2 .90 200 

Site

(fig. 2) Date

Copper

(μg/g)

Europium

(μg/g)

Gallium 

(μg/g)

Gold

(μg/g)

Holmium

(μg/g)

Iron

(percent)

Lanthanum

(μg/g)

Lead 

(μg/g)

Lithium 

(μg/g)

Rob Roy 

Reservoir

7/23/98 43 <2 14 <8 <4 3.1 35 19 36 

Lake Owen 7/23/98 58 <2 13 <8 <4 2.7 30 16 29 Granite Springs 

Reservoir

2/5/98 77 <2 17 <8 <4 2.2 82 28 15 

Crystal Lake 

Reservoir

2/3/98 150 2 20 <8 <4 3.6 120 31 20 
12 WATER QUALITY OF FOUR RESERVOIRS Table 5. Chemical analysis of composite samples of bottom sediment collected in 1998 from Rob Roy Reservoir and Lake Owen, Alba

Springs and Crystal Lake Reservoirs, Laramie County, Wyoming--Continued Site (fig. 2) Date Mercury (μg/g) Molybdenum (μg/g) Neodymium (μg/g) Nickel (μg/g) Niobium (μg/g) Phosphorus (percent) Potassium (percent) Scandium (μg/g) Seleni

(μg/g

Rob Roy Reservoir 7/23/98 .05 <2 27 25 16 .080 1.8 10 0.4 Lake Owen 7/23/98 .04 <2 26 52 13 .050 1.3 14 0.9 Granite Springs Reservoir 2/5/98 .02 <2 63 8 22 .050 3.3 6 0.4 Crystal Lake Reservoir 2/3/98 .03 <2 93 14 29 .080 2.7 10 0.6 

Site

(fig. 2) Date

Strontium

(μg/g)

Sulfur

(μg/g)

Tantalum

(μg/g)

Thorium

(μg/g)

Tin

(μg/g)

Titanium

(percent)

Uranium 

(μg/g)

Vanadium

(μg/g)

Yttrium 

(μg/g)

Rob Roy Reservoir

7/23/98 160 .05 <40 8 <5 .32 <100 87 17 

Lake Owen 7/23/98 220 .24 <40 7 <5 .23 <100 110 16 Granite Springs Reservoir

2/5/98 130 <.05 <40 21 <5 .19 <100 29 31 

Crystal Lake Reservoir

2/3/98 120 .07 <40 31 <5 .31 <100 46 49 
WATER QUALITY 13

Profiles

Profile measurements indicated that Rob Roy 

was stratified from mid-July to late September 1998. 

Stratification is shown in a profile measured September 

2, 1997 (fig. 3A). The temperature, dissolved oxygen, 

specific conductance, and pH profiles were relatively 

constant in the epilimnion, from about 1 ft below the 

surface to about 11 ft. The temperature decreased at a 

steady rate, from about 15°C (degrees Celsius) at 11 ft, 

to about 6°C at about 65 ft below the surface. The pH 

also gradually decreased, from 6.9 at about 8 ft to 6.2 at 

about 55 ft. The Secchi disk transparency was 9.8 ft, 

which was the deepest transparency recorded during the 

summer 1997 sampling trips. In many lakes the Secchi 

depth is approximately one-third the depth of the 

euphotic zone (Horne and Goldman, 1994, p. 34); therefore, the euphotic zone was estimated to extend to about 

29 ft below the surface, which is also where dissolvedoxygen concentrations decrease about 1 mg/L.

Likewise, the July 23, 1998 profiles of Rob Roy 

(fig. 3B) show stratification of the water column in the 

reservoir. The temperature, dissolved oxygen, specific 

conductance, and pH profiles were relatively constant 

from the surface to about 13 ft. The temperature 

decreased with depth at a fairly steady rate, from about 

17°C at 13 ft, to about 8.5°C at about 27 ft in the metalimnion. Within about that same interval, dissolved oxygen increased and specific conductance decreased. The 

Secchi disk transparency on July 21 was 12.5 ft (fig. 4), 

yielding an estimated euphotic zone of about 38 ft.

The September 3, 1998 profiles of Rob Roy 

(fig. 3C) were similar to the September 2, 1997 profiles; 

however, the most noticeable change was the increased 

thickness of the epilimnion and the decreased thickness 

of the metalimnion in 1998. The temperature, dissolved 

oxygen, and specific conductance were relatively constant from the surface to about 24 ft in depth. The temperature ranged from about 15°C to 14°C in the upper 

24 ft, then sharply decreased to about 8.2°C at 29 ft. 

Temperature then gradually decreased from about 8.2 to 

6.4°C at 67 ft. The pH increased from 6.9 at the surface 

to 7.3 at 12 ft and then decreased to 6.5 at 28 ft. The pH 

remained relatively constant from 28 ft to 67 ft. 

Dissolved-oxygen concentrations varied from 7.4 mg/L 

at the surface to 5.9 mg/L at 67 ft. A zone of slightly 

lower dissolved oxygen was present from 24 to 29 ft. 

The Secchi disk transparency was 11.6 ft, with the estimated euphotic zone extending to about 35 ft. Additional profiles for 1998 are included in appendix A.

The profiles indicate that the depth of stratification in Rob Roy changed over time in 1998. When the 

seasonal variations of temperature in the summer and 

fall of 1998 are examined (fig. 5), two characteristics of 

Rob Roy are apparent. The first is that a strong stratification developed by mid-July and continued until September; by early October, the reservoir was no longer 

stratified. The second is that the zone of warming in the 

reservoir extended deeper into the reservoir from midJuly to late September 1998. The 10°C temperature 

contour line dropped from about 20 ft in mid-July to 

about 30 ft by late September. The zone continued to 

deepen after surface cooling began in early September. 

Phytoplankton

Bacillariophyta (diatoms) and Chlorophyta 

(green algae) dominated the phytoplankton community 

of Rob Roy. The diatoms, in terms of biomass (mass of 

the phytoplankton cells), dominated the samples collected during September 1997 and August 1998 (fig. 6). 

The data shown in figure 6 are from samples collected 

at a depth of 1 ft below the surface, at a site near the 

deepest part of the reservoir (fig. 2A). An abrupt shift 

in the phytoplankton community from diatoms to green 

algae was evident in the September 1998 samples. 

Other algae identified in the samples included the Cryptophyta (cryptomonads), the Pyrrophyta (dinoflagellates), and the Chrysophyta (golden-brown algae). 

Euglenophyta (euglenoids) and Cyanophyta (bluegreen algae), which are often associated with organic or 

nutrient enrichment, were absent from the samples. 

Phytoplankton taxa are listed in table 4. The complete 

phytoplankton data set for all four reservoirs are listed 

in Appendix B; data for Rob Roy are listed in table B1 

of Appendix B.

Twenty-nine taxa of algae were identified from 

the samples (table 4). Two species of diatoms, Asterionella and Fragilaria, were responsible for the predominance of diatoms in the September 1997 and August 

1998 samples. The maximum biomass of Asterionella

was 3,500 μg/L (micrograms per liter), which constituted 98 percent of the total phytoplankton biomass in 

the September 1997 sample. The corresponding density 

of Asterionella in that sample was 2,590 cells per milliliter (cells/mL). Asterionella and Fragilaria were 

codominant species during August 1998. The maximum concentration of Fragilaria was 1,700 μg/L biomass (1,550 cells/mL density) in the August 11 sample. 
14 WATER QUALITY OF FOUR RESERVOIRS 
WATER QUALITY 15

Eighteen taxa of green algae were identified. 

The genus Cosmarium was the predominant algae in 

samples collected on September 3, 17, and 22, 1998. 

Staurastrum dominated the September 10, 1998, sample. Dictyosphaerium was a codominant species in the 

September 3, 1998, sample, and Spondylosium was a 

subdominant species in the September 22, 1998, sample. The maximum biomass of green algae was 

740 μg/L of Cosmarium in the September 17 sample. 

The corresponding density of Cosmarium was 

40 cells/mL, which is a relatively low density but is 

reflective of the large size of the cells. 

One or more species of cryptomonads were 

present in most of the samples. The crytomonads typically were not dominant, with the exception of the 

July 23 sample that was dominated by Campylomonas 

rostratiformis. Other species that occurred in Rob Roy 

include Gymnodinium (dinoflagellates) and Mallomonas (golden-brown algae). 

A phytoplankton sample also was collected during September 1997 about 3 ft above the bottom of the 

reservoir. That sample contained only Asterionella, at 

a relatively low concentration. The algae likely were 

cells that had sunk from the euphotic zone. The depth 

of the euphotic zone, where sufficient light is available 

for photosynthesis, was estimated to be about 29 ft 

based on a Secchi disk transparency of 9.8 ft. 

The Secchi disk transparencies measured during 

1998 in Rob Roy ranged from 9.0 to 12.5 ft; the average 

transparency was 10.4 ft (fig. 4). The greatest transparencies were in mid-July and early September. Comparison of transparencies to the water profile data indicate 

the euphotic zone extended below the metalimnion 

when the reservoir was stratified. 

Protozoa (animal kingdom) also were noted in 

the samples from Rob Roy (Appendix B, table B1). 

Unidentified flagellates, ciliates, and ameba were 

present at densities on the order of tens to hundreds per 

milliliter; the maximum biomass was 53 μg/L. The 

distinction between protozoa and algae, especially the 

flagellated forms, can be controversial (Smith, 1950, 

p. 1-11; Reid and Wood, 1976, p. 320-330). For this 

report, the algae were distinguished from the protozoa 

by the presence of chlorophyll and other photosynthetic pigments in the algae. 
16 WATER QUALITY OF FOUR RESERVOIRS 

In Rob Roy in the fall of 1997, MPA was dominated by non-diatomaceous phytoplankton and diatoms. 

The MPA results are summarized in table 5.

Chemical Quality

Relatively little difference in water chemistry 

existed between the top and bottom of Rob Roy Reservoir (table 2). The dissolved-solids concentration was 

19 mg/L for the surface sample and 22 mg/L for the bottom sample (fig. 7). The water was a calcium bicarbonate type. The concentrations of selected major ions 

shown on the pie diagrams in figure 8 indicate no differences in the concentration of major ions between surface 

and bottom water samples. Dissolved fluoride concentrations were less than the detection level of 0.1 mg/L. 

Silica concentrations, as dissolved SiO2, increased 

slightly with depth (table 2; fig. 9). Nutrient concentrations generally were less than the detection level. An 

exception was dissolved nitrogen, as nitrite plus nitrate, 

in the bottom sample, which was 0.08 mg/L (table 2).

Some differences were detected in selected traceelement concentrations between the top and bottom 

samples collected at Rob Roy. Dissolved iron (fig. 10) 

and dissolved manganese concentrations (fig. 11) were 

higher in the bottom sample. 

Bottom Sediment

On July 23, 1998, bottom sediment samples were 

collected from five sites (fig. 2A) in Rob Roy and composited into a single sample. The composite sample was 

analyzed for selected constituents (table 3). The nitrogen concentration, reported as total nitrite plus nitrate, 

was 9 mg/kg, the highest concentration from all four reservoirs (table 3). Of the constituents analyzed, aluminum was present in the highest percentage (6.9 percent) 

and iron was next highest (3.1 percent). Most of the 
WATER QUALITY 17
18 WATER QUALITY OF FOUR RESERVOIRS 

Table 4. Phytoplankton taxa list for Rob Roy Reservoir and Lake Owen, Albany County, and Granite Springs and Crystal 

Lake Reservoirs, Laramie County, Wyoming

Phytoplankton taxa

Reservoir

Rob Roy Lake Owen Granite Springs Crystal Lake

BACILLARIOPHYTA (Diatoms)

Centrales (Centric diatoms) 

Centrales size 1 x x

Centrales size 2 x x

Centrales size 3 x x

Centrales size 4 x

Cyclotella x x

Melosira x

Melosira size 1 x

Melosira size 2 x

Melosira size 3 x

Stephanodiscus x x

Pennales (Pennate diatoms)

Achnanthes x x

Asterionella xxx

Cymbella x

Fragilaria xxxx

Nitzschia x

Pennales size 1 x

Pennales size 2 x x

Pennales size 3 x x

Synedra x

Tabellaria x

CHLOROPHYTA (Green algae)

Actinastrum x

Ankistrodesmus xxx

Chlamydomonas size 1 x

Chlamydomonas size 2 x

Chlorella xxxx

Chlorophyte size 1 x

Table 4. Phytoplankton taxa list for Rob Roy Reservoir and Lake Owen, Albany County, and Granite Springs and Crystal 

Lake Reservoirs, Laramie County, Wyoming

[x indicates taxa presence]
WATER QUALITY 19

Chlorophyte size 2 x x x x

Chlorophyte size 3 x x

Chlorophyte size 4 x x x x

Chlorophyte size 5 x

Chlorophyte size 6 x x

Chlorophyte size 7 x

Chlorococcales x

Closterium x

Coelastrum x

Cosmarium xx x

Crucigenia x

Dictyosphaerium x x

Didymocystis x

Elakatothrix x

Eudorina x

Micractinium x

Oocystis x

Oocystis size 1 x x x

Oocystis size 2 x

Pandorina x

Quadrigula xxxx

Scenedesmus x x

Schroederia x

Sphaerocystis xxxx

Spondylosium xx x

Staurastrum x x

Tetraspora x

Zygnematales x

CHRYSOPHYTA (Golden-brown algae)

Chrysophyte size 1 x

Dinobryon x x

Table 4. Phytoplankton taxa list for Rob Roy Reservoir and Lake Owen, Albany County, and Granite Springs and Crystal 

Lake Reservoirs, Laramie County, Wyoming--Continued

Phytoplankton taxa

Reservoir

Rob Roy Lake Owen Granite Springs Crystal Lake
20 WATER QUALITY OF FOUR RESERVOIRS 

Mallomonas x x

Uroglenopsis x

CRYPTOPHYTA (Cryptomonads)

Campylomonas reflexa xxxx

Campylomonas rostratiformis xxxx

Cryptomonas xx x

Cryptophyte size 1 x x x

Cryptophyte size 2 x x

Cryptophyte size 3 x x

Cryptophyte size 4 x

Katablepharis xxxx

Plagioselmis xxxx

CYANOPHYTA (Blue-green algae)

Anabaena x x

Aphanothece x x

Cyanophyte size 1 x

Gomphosphaeria x

Microcystis x

Pseudanabaena x

EUGLENOPHYTA (Euglenoids)

Euglena x

Euglenophyte size 1 x

Euglenophyte size 2 x

Trachelomonas size 1 x x

Trachelomonas size 2 x x x

PYRROPHYTA (Dinoflagellates)

Ceratium x x

Gymnodinium xxx

Table 4. Phytoplankton taxa list for Rob Roy Reservoir and Lake Owen, Albany County, and Granite Springs and Crystal 

Lake Reservoirs, Laramie County, Wyoming--Continued

Phytoplankton taxa

Reservoir

Rob Roy Lake Owen Granite Springs Crystal Lake
WATER QUALITY 21

Table 5. Microscopic particulate analyses of water samples collected in the fall of 1997 at Rob Roy Reservoir and Lake Ow

Granite Springs and Crystal Lake Reservoirs, Laramie County, Wyoming 

[ND, none detected; μm, micrometer; L, liter].

Reservoir

(fig. 2)

Date

sampled

Amorphous

clay, silt, and 

detritus - 

aggregates

(diameter,

in μm)

Nondiatomaceous 

phyto plankton 

(million 

counts/100L)

Diatoms

(million 

counts/100L)

Plant 

Debris

Rotifers

(counts/

100L) Nematodes Pollen 

Rob Roy 9/2/97 1-75 1.00 0.40 ND ND ND ND Lake Owen 9/2/97 1-100 0.40 0.03 ND 60 ND ND Granite Springs 8/28/97 1-50 0.80 8.00 ND 1,000 ND ND Crystal Lake 9/4/97 1-50 4.00 7.00 ND ND ND ND 

Reservoir

(fig. 2)

Date

sampled Ciliates

Colorless

Flagellates Crustaceans

Other

arthropods

(thousand

counts/100L) Other

Total

(million

counts/100L)

Volume of

water

filtered

(gallons)

1Giard

tota

(numb

100L

1Analyzed by method outlined by U.S. Environmental Protection Agency (1996b). All limitations stated in the method apply. 

Rob Roy 9/2/97 ND ND ND 1.00 ND 1.40 905 <11 Lake Owen 9/2/97 ND ND ND ND ND 0.43 791 3 Granite Springs 8/28/97 ND ND ND 3.00 ND 8.80 1174 19 Crystal Lake 9/4/97 ND ND ND ND ND 11.00 798 <14 
22 WATER QUALITY OF FOUR RESERVOIRS 

trace elements are present in concentrations in the 

microgram per gram range. Trace-element concentrations of arsenic, bismuth, cadmium, europium, gold, 

holmium, molybdenum, silver, tantalum, tin, and uranium were less than the detection limit. Cerium, chromium, thorium, and vanadium concentrations fit best 

with Group 1, the crustal average, rather than diabase or 

granitic rocks (fig. 12). The similarity is probably a 

reflection of the surrounding geology which is composed of sedimentary deposits (Tertiary age) and 

metasedimentary and metavolcanic rocks (Pre-Cambrian) (Love and Christiansen, 1985).

Lake Owen

Lake Owen is the shallowest and smallest in the 

series of reservoirs (fig. 2B; table 1). Its maximum 

depth is about 10 ft and it contains only about 1 percent 

of the storage capacity of the system. Although lower 

in elevation than Rob Roy Reservoir, Lake Owen is 

located in a high mountainous area and has a spillway 

elevation of 8,955 ft above sea level. The vegetation 

surrounding Lake Owen is composed of mixed evergreen and aspen areas with some open meadow. Lake 

Owen is used primarily for recreational activities such 

as boating and fishing.

Profiles

Probably due to its shallow depth, Lake Owen is 

not stratified. The September 2, 1997 profiles of Lake 

Owen (fig. 13) did not indicate stratification. The water 

temperature was about 15°C, the dissolved oxygen was 

about 6.5 mg/L, the specific conductance was about 

30 μS/cm, and the pH was about 7.2. The Secchi disk 

was still visible when resting on the reservoir bottom. 

Profile data collected September 16, 1997 indicate a 

sharp drop in water temperature. The water temperature 

was just over 11°C on September 16 (Appendix A).
WATER QUALITY 23
24 WATER QUALITY OF FOUR RESERVOIRS 

Lake Owen also was not stratified in 1998. The 

July 23, 1998 profile showed a consistent water temperature of 18.2°C, dissolved oxygen decreased from 

7.3 to 7.2 mg/L, the specific conductance was about 

57 μS/cm, and pH decreased from 7.9 to 7.8. By September 3, 1998 the temperature decreased from 16.6 to 

14.6°×C, dissolved oxygen increased from 8.2 to 

9.0 mg/L, specific conductance remained around 42 to 

43 μS/cm, and pH increased from 8.4 to 8.9.

The temperature changes probably were facilitated by Lake Owen’s high elevation, shallow depth, 

large surface-area exposure, and the seasonal climatic 

change. Temporal changes indicate that although Lake 

Owen warms by mid-July, it cools quickly in the fall 

(fig. 14). Water transparency, as measured by a Secchi 

disk, ranged from a minimum of 4.6 ft on August 10, 

1998 to 7.3 ft on July 17, 1998 (fig. 4).

Phytoplankton

The golden-brown algae (chrysophyta) dominated the phytoplankton community in Lake Owen. 

The biomass of the golden-brown algae ranged from 

about 3,500 to 7,1000 μg/L in samples collected on 

August 11 and during early to mid-September 1998 

(fig.15). The cause for the low concentration of phytoplankton on August 19, between 2 weeks of higher 

concentrations, is unknown. Green algae were present 

in nearly all of the samples, whereas the dinoflagellates 

and euglenoids appeared only in the late summer samples (fig.15).

Uroglenopsis was the dominant species of chrysophyte in the samples from Lake Owen. The maximum 

biomass of Uroglenopsis was 7,000 μg/L 

(30,500 cells/mL) in the September 3, 1998 sample 

(Appendix B, table B2). Other chrysophytes, such as 

Dinobryon and Mallomonas, were present in smaller 
WATER QUALITY 25

quantities in some samples. Green algae were the most 

diverse group of algae in Lake Owen; of the 37 taxa 

identified, 14 taxa were green algae. Cosmarium was 

the most common green algae, particularly in the samples collected on July 23 and September 22 (fig. 15). 

The green algae Quadrigula and Tetraspora were 

present at biomasses less than 100 μg/L. Other species 

of algae identified include the diatoms, Asterionella and 

Fragilaria, the euglenoids Euglena and Trachelomonas, and the dinoflagellate Gymnodinium. 

Lake Owen is the only reservoir in this study to 

have extensive macrophyte growth. This may be due in 

part to the shallow depth of Lake Owen, which allows 

sunlight to penetrate to the bottom and in turn, allows 

photosynthesis by rooted plants. On some occasions, the 

Secchi disk was still visible as it rested on the lake bottom. 

Protozoa were present in some samples, mostly at 

small concentrations. The exception was the 

September 17 sample, which contained a biomass of 

13,000 μg/L of ciliated protozoans. Biomasses of other 

protozoans in the samples typically were less than 

50 μg/L.

In Lake Owen in the fall of 1997, MPA was dominated by non-diatomaceous phytoplankton and diatoms. 

A few rotifers were detected. This rotifers group are

suspension feeders that influence algae species through 

selective feeding. The MPA results are summarized in 

table 5.

Chemical Quality

Due to the shallow depth of Lake Owen and lack 

of variability in the profile data, only a single surface 

sample was collected for water quality. Dissolved-solids
26 WATER QUALITY OF FOUR RESERVOIRS 

concentration was 20 mg/L (fig. 7). The water was a 

calcium bicarbonate type. The relative concentrations 

of major ions are shown on the pie diagram (fig. 8). 

Dissolved-fluoride concentration was less than the 

detection level of 0.1 mg/L. Silica concentration, as 

dissolved SiO2, was 2.5 mg/L (fig. 9). Nutrient concentrations were less than the detection limit.

Trace-element concentrations in samples were 

variable (table 2). Dissolved-iron concentration at 

130 μg/L was the highest in any sample collected from 

the four reservoirs (fig. 10). A possible source for this 

iron might be a magnetite gabboro (Lake Owen mafic 

complex, Precambrian) which outcrops at the reservoir. 

Houston and Orback (1976) found that unit to contain 

more than 10 percent magnetite in the gabbro and 

sparse layers of massive magnetite several inches thick. 

Dissolved-manganese concentration was slightly 

higher than surface samples collected from the other 

reservoirs.

Bottom Sediment

On July 23, 1998, bottom sediment samples were 

collected at five sites (fig. 2B) in Lake Owen and composited into a single sample. The composite sample 

was analyzed for selected constituents (table 3). The 

nitrogen concentration, reported as total nitrite plus 

nitrate, was 8 mg/kg. Of the constituents analyzed, aluminum was present at the highest concentration at 

6.9 percent, iron was 2.7 percent, and calcium was 

2.2 percent. Trace-element concentrations of arsenic, 

bismuth, cadmium, europium, gold, holmium, molybdenum, silver, tantalum, tin, and uranium were less 

than the detection limit. When thorium, vanadium, 

cerium and chromium concentrations are plotted 

(fig.12), it is apparent that the sediment concentrations 

are more like the crustal average than either diabase or 

granitic rocks. The trace-element concentrations are 

probably similar to crustal averages due to the local 

geology, which is composed of sedimentary deposits
WATER QUALITY 27

(Tertiary age) and metasedimentary and metavolcanic 

rocks (Pre-Cambrian age). Near Lake Owen, alluvium, 

gravel, colluvium, conglomerate sandstones, and shales 

occur, along with medium to coarse grained gabbros, 

and other mafic rocks.

Granite Springs Reservoir

Granite Springs Reservoir is the third reservoir in 

the series (fig. 2C) and receives water through both 

Stage I and Stage II pipelines from Lake Owen. The 

reservoir contains about 12 percent of the system storage and has a spillway elevation of 7,210 ft above sea 

level (table 1). Granite Springs is located in an area of 

mixed forest and grassland. It is an active recreational 

site with boating, fishing, and camping being the primary activities. Some houses are present in the area surrounding the reservoir.

Profiles

Profile data were collected for Granite Springs 

once during summer 1997, from mid-May through the 

first part of October in 1998, and once during winter 

1998. These profiles indicate that Granite Springs was 

stratified by early to mid-July and was unstratified in the 

winter. 

The August 28, 1997 profiles (fig. 16A) indicate 

stratification in the reservoir. Changes in the temperature, dissolved oxygen, specific conductance, and pH 

profiles indicate that the epilimnion extended from the 

surface to about 19 ft deep. In the epilimnion, the temperature decreased from 20 to 18°C, dissolved-oxygen 

concentrations were about 7 to 8 mg/L, specific conductance was about 94 to 95 μS/cm, and pH ranged from 

8.3 to 8.5. Dissolved-oxygen concentrations in the epilimnion were above saturation, probably due to photosynthetic activity by the phytoplankton. The euphotic 

zone also extended to about 19 ft, as estimated from a 

Secchi disk transparency of 6.2 ft. The metalimnion 

appeared to range from about 19 to 26 ft below the reservoir surface. Water temperature, dissolved oxygen, 

and pH decreased relatively in the metalimnion, while 

specific conductance increased slightly. In the hypolimnion, dissolved-oxygen concentrations continued to 

decrease, and were less than the 5 mg/L level suggested 
28 WATER QUALITY OF FOUR RESERVOIRS 
WATER QUALITY 29

for protection of cold-water fish. The dissolved-oxygen concentrations decreased from 73 percent of saturation at 26 ft to 38 percent of saturation at 60 ft.

The February 5, 1998 profiles of Granite Springs 

(fig. 16B) show a lack of stratification in the water column, with only slight changes in the profiles, mostly 

below about 50 ft. Water temperature was approximately 4°C. Dissolved-oxygen concentrations 

decreased from about 11 to about 8 mg/L. Specific conductance generally was less than 115 μS/cm to about 

50 ft, below which conductance increased to almost 

145 μS/cm. pH decreased from 7.7 to 6.9. 

July 21, 1998 profiles again show stratification in 

Granite Springs (fig.16C). The temperature in the epilimnion was about 22°C, dissolved-oxygen concentrations were about 8.5 mg/L, the specific conductance 

was about 128 μS/cm, and pH measured about 8.5. 

Changes in temperature and pH occurred in the metalimnion. Below 30 ft, in the hypolimnion, the temperature decreased from about 15 to about 14°C. Dissolvedoxygen concentrations remained near 4.0 mg/L to about 

38 ft, then decreased to less than 1 mg/L near the bottom. Specific conductance was about 122 μS/cm from 

about 32 ft to about 44 ft, then increased to 127 μS/cm. 

The pH gradually decreased from 7.7 to 7.4. 

The September 1, 1998 profiles (fig. 16D) continue to show strong stratification of dissolved oxygen 

and pH; both were stable to about 25 ft. The metalimnion also was defined by changes in dissolved oxygen 

and pH. Dissolved-oxygen concentrations dropped 

from 7.1 to less than 1 mg/L at 45 ft. Over the same 

interval, pH decreased from 8.1 to 7.1. Temperature 

decreased gradually from top to bottom in this profile. 

In the metalimnion and hypolimnion, specific conductance gradually increased.

Examination of the 1998, Granite Springs temperature profiles (fig. 17) shows a seasonal increase of 

the water temperature in the reservoir. The reservoir 

lacked stratification in early May and was a fairly consistent 9°C. By late May into mid June, a nearly linear 

gradation in temperature developed from about 14°C at 

the surface to slightly greater than 10°C near the bottom. During this time period, no stratification was 

present. By July, stratification began to develop in the 

reservoir (Appendix A). Stratification continued to 

develop in early August, with the epilimnion expanding 

down to about 25 ft, and the metalimnion ranged from 

about 25 to 35 ft. Stratification became less pronounced 

in mid-August, with the temperature decreasing gradually from about 20 to 14°C with depth. By midSeptember, thermostratification had ceased and the profiles indicate little change in water temperature from the 

reservoir surface to the bottom. In late September and 

early October, the reservoir cooled quickly compared to 

its rate of warming (fig. 17). It is interesting to note the 

persistence of stratification of dissolved oxygen and pH 

well after temperatures had nearly equalized throughout 

the water column.

Phytoplankton

Diatoms and blue-green algae dominated the 

phytoplankton community of Granite Springs. 

Although five other divisions of algae were present in 

the samples, their biomasses were small relative to the 

diatoms and blue-green algae (fig. 18). 

Blue-green algae, principally Anabaena, dominated the biomass of the algae in the August 28, 1997 

and July, 16, 1998 samples. The biomass of Anabaena

was 59,000 μg/L (69,100 cells/mL density) in the July 

14 sample (Appendix B, table B3). Blue green algae, 

particularly Anabaena, are known for producing algal 

blooms and creating taste and odor problems in 

temperate-zone lakes. The blooms tend to occur in late
30 WATER QUALITY OF FOUR RESERVOIRS 
WATER QUALITY 31

summer, when water temperatures are warmest and 

nutrients have been removed from the epilimnion. Many 

blue-green algae are capable of fixing atmospheric nitrogen, and therefore have a competitive advantage over 

other algae when nutrient supplies are limited. Somewhat in contrast to this general pattern for temperatezone lakes, the blue-green algae in Granite Springs 

peaked in mid-July; diatoms dominated the phytoplankton later in the summer (fig. 18). Peak concentrations of 

the diatoms were considerably smaller, however, than 

the peak concentrations of the blue-green algae. 

Both orders of diatoms, the Pennales and the Centrales, were represented in the samples. The pennate diatoms typically are elongate; cigar or boat shaped 

organisms, whereas the centric diatoms are round, pillbox-shaped organisms (Prescott, 1978, p. 241). The 

pennate diatom Fragilaria dominated the July 22 and 

September 1, 1998 samples and was a subdominant species in some of the other samples from Granite Springs. 

The peak concentration of Fragilaria was 4,200 μg/L 

(fig. 18) (3,030 cells/mL) in the July 22 sample. The 

centric diatom Cyclotella was a subdominant in the 

July 22 sample (1,700 μg/L) and the September 1 sample (1,100 μg/L). The centric diatom Stephanodiscus

dominated the August 4 sample and was a subdominant 

in the September 9 sample, but was not identified in 

other samples from Granite Springs. An unidentified 

centric diatom dominated the samples from August 10 

and 18, and September 15 and 21. Of the 41 taxa identified from Granite Springs, 15 taxa were diatoms and 

13 taxa were green algae. 

A phytoplankton sample, collected on August 28, 

1997, at 3 ft above the reservoir bottom at the same site 

as the near-surface sample, contained mostly diatoms. 

The biomass of the deep sample was 950 μg/L, considerably less than the 4,400 μg/L of the near-surface sample. The cause for the predominance of the diatoms 

Fragilaria and Melosira in the bottom sample may be 

related to the resistance of their siliceous shells. The relatively soft-bodied blue-green algae that predominated 

in the near-surface sample on the same date may have 

decomposed as they sank through the water column. 

Secchi disk transparencies from Granite Springs 

averaged 8.2 ft. A maximum transparency of 12.5 ft was 

recorded under ice cover in February; a minimum transparency of 5.1 ft was recorded July 14 and August 4, 

1998. The low transparencies on July 14 were coincident with the high phytoplankton concentration. In contrast, the phytoplankton concentration on August 4 was 

relatively low (fig. 18). Inorganic material suspended in 

the water may have contributed to the low reading on 

August 4. The depth of the euphotic zone extended 

below the thermocline when the reservoir was stratified, 

indicating adequate light for photosynthesis throughout 

the epilimnion. 

Protozoans were present in samples at concentrations of a few hundred micrograms per liter or less, with 

the exception of the July 14 sample. The concentration 

of rotifers in the July 14 sample was 5,000 μg/L biomass 

(10 organisms/mL). 

In Granite Springs in the fall of 1997, MPA was 

dominated by non-diatomaceous phytoplankton and diatoms. A few rotifers were detected. The MPA results are 

summarized in table 5.

Chemical Quality

Two samples were collected at Granite Springs 

(surface and bottom). The dissolved-solids concentrations of 55 mg/L for the surface sample and 59 mg/L for 

the bottom sample (table 2) indicated little difference in 

the dissolved solids between the two samples. The water 

was a calcium bicarbonate type. The relative concentrations of major ions shown in pie diagrams in figure 8 

indicate no differences between surface and bottom 

samples. Dissolved-fluoride concentrations were at 

0.3 mg/L in the surface sample and 0.4 mg/L in the bottom sample (table 2). Silica concentrations, as dissolved 

SiO2, increased slightly with depth (table 2; fig. 9). 

Nutrient concentrations were less than the detection 

level in both samples. An exception was dissolved nitrogen as ammonia in the surface sample, which was 

0.15 mg/L.

The concentrations of metals indicated some differences between the surface and bottom samples. Iron 

concentrations increased from 7 μg/L (surface sample) 

to 21 μg/L (bottom sample) (fig. 10). The increase in 

manganese concentration from 5 μg/L (surface sample) 

to 76 μg/L (bottom sample) was even greater (fig. 11).

Bottom Sediment

On February 5, 1998, bottom sediment samples 

were collected at five sites (fig. 2C) in Granite Springs 

and composited into a single sample. The composite 

sample was analyzed for selected constituents (table 3). 

Nitrogen concentration, reported as total nitrate plus 

nitrite, was less than the detection limit. Of the constituents analyzed, aluminum concentration was 6.2 percent, 

iron was 2.2 percent, and potassium was 3.3 percent. 
32 WATER QUALITY OF FOUR RESERVOIRS 
WATER QUALITY 33
34 WATER QUALITY OF FOUR RESERVOIRS 

Most bottom-sediment concentrations were in the 

microgram-per-gram range. Concentrations of nitrogen, 

arsenic, bismuth, cadmium, europium, gold, holmium, 

molybdenum, silver, sulfur, tantalum, tin, and uranium 

were less than the detection limit (table 3). Concentrations of thorium, vanadium, cerium, and chromium are 

plotted in figure 12. The trace-element concentrations 

fit best in Group 2—more like granitic rocks than either 

diabase or the crustal average. The similarity is most 

likely due to the sediments having been derived from the 

surrounding Sherman Granite (Precambrian).

Crystal Lake Reservoir 

Crystal Lake Reservoir is the last reservoir in the 

series (fig. 2D). During the period of this study, water 

flowed via Middle Crow Creek and a pipeline from 

Granite Springs Reservoir into Crystal Lake Reservoir. 

At 6,969 ft, Crystal Lake has the lowest spillway elevation of the four reservoirs. The reservoir contains about 

8 percent of the system storage and is about 65 ft deep 

(table 1). It is located in an open forest and grassland 

area, and is popular for recreational activities such as 

boating, fishing, and camping. 

Profiles

Profile data indicate that stratification occurs in 

Crystal Lake during the warmer months. The September 4, 1997 profiles of Crystal Lake (fig. 19A) show 

stratification of dissolved oxygen and pH in the reservoir. Water temperature, dissolved oxygen, specific 

conductance, and pH were essentially constant in the 

epilimnion. Temperature was constant to about 17 ft. 

The dissolved-oxygen concentration was 6.3 mg/L and 

86 percent of saturation at a depth of 1 ft. The 

dissolved-oxygen concentrations decreased to less than 
WATER QUALITY 35
36 WATER QUALITY OF FOUR RESERVOIRS 
WATER QUALITY 37
38 WATER QUALITY OF FOUR RESERVOIRS 

5 mg/L in the metalimnion. A minimum dissolvedoxygen concentration of 5 mg/L generally has been suggested for the protection of cold-water fish. Water temperature and pH also decreased in the metalimnion, 

which extended from about 16 ft to about 26 ft below the 

surface. The euphotic zone extended to about the bottom of the metalimnion, based on a Secchi disk transparency of 7.7 ft. In the hypolimnion, dissolved-oxygen 

concentrations continued to decrease (fig. 19A). The 

dissolved-oxygen concentration was about 1.3 mg/L at 

about 44 ft and was only 17 percent of saturation. This 

concentration was less than the concentration generally 

suggested for the protection of warm-water fish. Specific conductance increased with depth in the hypolimnion, from about 109 to 115 μS/cm. 

The February 3, 1998 winter profiles (fig. 19B) 

show a general lack of stratification of the water in 

Crystal Lake. On February 3, the reservoir was covered 

with about 1 ft of very clear ice with virtually no snow 

cover. The clear ice apparently allowed enough light for 

photosynthesis by the phytoplankton, as indicated by 

the dissolved-oxygen concentration of 14.7 mg/L, or 

134 percent of saturation, at a depth of 1 ft below the 

ice. The water temperature at 1 ft beneath the water surface was 1.0°C; below that depth the temperature, 

ranged between 3 and 4°C. This temperature pattern, 

typical of temperate lakes, was expected because water 

at its maximum density is at about 4°C. From 2 ft to 

about 50 ft below the surface, the profiles show little 

variation. Below 50 ft, small changes in pH and specific 

conductance were noted. 

The July 21, 1998 profile data indicate weak 

stratification (fig. 19C). The epilimnion extended to 

about 10 ft, the metalimnion from about 10 to 24 ft, and 

the hypolimnion from about 24 ft to the bottom. Temperatures ranged from 22 to 20°C in the epilimnion, 

decreased from 20 to 16°C through the metalimnion, 

and ranged from 16 to 14°C in the hypolimnion. 

Dissolved-oxygen concentrations were near 10 mg/L to 

a depth of about 9 ft. Concentrations then decreased to 

5.6 mg/L at about 24 ft. In the hypolimnion, dissolvedoxygen concentrations were essentially stable to about 

42 ft, then decreased to 1.9 mg/L near the bottom. 

By September 1, 1998, profiles indicate that stratification had reached much deeper into the reservoir 

with the epilimnion extending down to nearly 30 feet 

(fig. 19D). Dissolved-oxygen concentrations and pH 

showed sharp changes between about 26 ft and 31 ft. 

Dissolved oxygen ranged from 7.3 to 6.4 mg/L from the 

surface to 26 ft; concentrations then decreased to less 

than 1 mg/L by 31 ft and were less than 1 mg/L throughout the hypolimnion. The pH was fairly constant down 

to about 26 ft, about 9.0. In the metalimnion, the pH 

decreased from 8.9 to 7.3. The pH remained around 7.2 

to 7.3 throughout the hypolimnion. From about 26 ft, 

specific conductance increased in the metalimnion. 

Specific conductance continued to gradually increase 

with depth in the hypolimnion.

Temperature and dissolved oxygen in Crystal 

Lake were measured between May and October, 1998. 

In mid-May, the reservoir showed a relatively uniform 

temperature profile, ranging between 5 and 10°C 

(fig. 20). Throughout May and June, the reservoir 

warmed and began to stratify. By mid-July, the reservoir was stratified and the surface-water temperature 

was slightly higher than 20°C. The water cooled 

throughout the fall, and by early October 1998 the water 

was relatively uniform in comparison to the summer 

profiles. Dissolved-oxygen concentrations (fig. 21) 

during May and June 1998 ranged from 5 to 10 mg/L. 

However, in mid-July a zone of dissolved oxygen in the 

upper 10 ft of the lake was higher than 10 mg/L. 

From late-June until mid-September, a dissolved 

oxygen zone of less than 5 mg/L developed near the bottom of the reservoir. By August, the zone had expanded 

and concentrations were less than 1 mg/L. The multiparameter probes used in this study do not accurately measure oxygen concentrations below 

1 mg/L. By mid-August, dissolved-oxygen concentrations of 1 mg/L or less extended about 30 ft above the 

bottom of the reservoir. As oxygen concentrations 

approach zero, many trace elements become more soluble and may move into the water column from the sediment. An increase in manganese concentration is 

sometimes observed in the raw water at the water treatment facilities. A possible explanation could be anoxic 

conditions of the lower part of the reservoir, which 

allows the manganese to become more soluble.

Phytoplankton

Blue-green algae and diatoms dominated the phytoplankton community of Crystal Lake. Other divisions, such as the green algae and the cryptomonads, 

were present in the samples, but each constituted less 

than 25 percent of the total biomass (fig. 22).

Of the 42 algal taxa identified, only 5 taxa were 

blue-green algae. Nonetheless, the blue-green algae 

Anabaena dominated the phytoplankton community in 

the July 14, July 21, and August 10, 1998 samples 
WATER QUALITY 39

(Appendix B, table B4; fig. 22). Anabaena reached a 

maximum concentration of 18,000 μg/L biomass 

(29,100 cells/mL density) in the July 14 sample. Anabaena also was the most common of the blue-green 

algae present in the samples collected on September 9, 

15, and 21, 1998. Diatoms, particularly Fragilaria, 

were the dominant algae in the remainder of the samples 

(fig. 22). The peak mass of Fragilaria was 6,500 μg/L 

(4,490 cells/mL) in the September 4, 1997 sample. The 

diatoms Stephanodiscus and Cyclotella were subdominants in some of the samples; Stephanodiscus predominated in the September 9 sample. A total of 17 taxa of 

green algae were identified, but none was dominant. 

The most common taxa of green algae were Staurastrum

and Cosmarium. 

Samples were collected 1 foot below the surface 

and 3 ft above the lake bottom on September 4, 1997. 

The total phytoplankton biomass of the deep sample was 

2,000 μg/L, compared to 9,000 in the near- surface sample. The diatom Fragilaria was the predominant alga in 

both samples. A phytoplankton sample was collected at 

a depth of about 30 ft, within the metalimnion, on September 11, 1997; the diatom Fragilaria predominated in 

the sample. The total phytoplankton mass in the sample 

collected at 30 ft was 4,900 μg/L. 

The concentration of Protozoa in samples from 

Crystal Lake typically was less than 100 μg/L. Some 

samples had higher concentrations; for example, September 9 sample had a concentration of ciliates of 

670 μs/L. 

In Crystal Lake in the fall of 1997, MPA was dominated by non-diatomaceous phytoplankton and diatoms. 

MPA results are summarized in table 5.

Chemical Quality

Three samples were collected for chemical analysis at Crystal Lake: a surface sample, a sample at 30-ft 

below the lake surface, (hereafter referred to as the middle sample), and a bottom sample. The depth for the 

middle sample was selected based on the estimated pipe-
40 WATER QUALITY OF FOUR RESERVOIRS 

line intake level for the water treatment plants. The dissolved-solids concentrations of 58 mg/L for the surface 

sample, 60 mg/L for the middle sample, and 63 mg/L 

for the bottom sample (table 2; fig. 7) indicate relatively little difference between the three samples, with 

a possible slight increase toward the reservoir bottom. 

The water was a calcium-bicarbonate type. No differences were apparent in the percentages of major ions 

between samples collected from the top, middle, and 

bottom of the reservoir (fig. 8). Dissolved-fluoride 

concentrations were 0.5 mg/L in all three samples. 

Silica concentrations, as dissolved SiO2, increased 

from 2.1 to 6.4 mg/L with depth (table 2; fig. 9). Nutrient concentrations were less than the detection level in 

all samples except two. In the sample at 30 ft, dissolved nitrogen as ammonia was 0.09 mg/L, and in the 

bottom sample nitrogen as ammonia was 0.14 mg/L. 

Dissolved-iron concentrations were slightly higher in 

the middle and bottom samples than in the surface sample (fig. 10). Dissolved-manganese concentrations 

increased from <1 μg/L in the surface to 31 μg/L in the 

bottom sample (fig. 11).

Because water is diverted from Crystal Lake to 

the treatment plants, analyses also were completed for 

4 radionuclides and 48 organic compounds. Two radionuclides and two organic compounds were detected; 

all others were less than the detection limit. Alpha 

(Th-230 and beta (CS-137) emission were the radionuclides detected. Metolachlor and atrazine were 

detected, but the low concentrations were estimated. 

Metholachlor was detected only in the surface sample 

at a concentration estimated to be slightly greater than 

the detection limit. Results are summarized in table 6.

Bottom Sediment

On February 3, 1998, bottom-sediment samples 

were collected at five sites in Crystal Lake (fig. 2D). 

The samples were composited into a single sample. 

The concentrations of selected constituents analyzed in 
WATER QUALITY 41
42 WATER QUALITY OF FOUR RESERVOIRS 

Table 6. Concentrations of selected radionuclide activities and organic compounds in water-quality 

samples collected September 4, 1997, at Crystal Lake Reservoir, Laramie County, Wyoming

Parameter/compound

Surface sample

(μg/L

except

as noted)

Bottom sample

(μg/L

except

as noted)

Gross beta, dissolved as Cs-137 <4.0.pCi/L <4.0.pCi/L

Propachlor, <.007 <.007

Butylate <.002 <.002

Simazine <.005 <.005

Prometon <.018 <.018

Des-ethylatrazine, <.002 <.002

Cyanazine <.004 <.004

Fonofox <.003 <.003

Alpha, dissolved as Th-230 <3.0.pCi/L <3.0.pCi/L

Phenols, total <1 <1.

Alpha BHC <.002 <.002

p,p’ DDE <.006 <.006

Chlorpyrifos <.004 <.004

Lindane <.004 <.004

Dieldrin <.001 <.001

Metolachlor .002 est. <.002

Malathion <.005 <.005

Parathion <.004 <.004

Diazinon <.002 <.002

Atrazine .0028 est. .0029 est.

Alachlor <.002 <.002

Acetochlor <.002 <.002

Alpha, pe Th-230 .56.pCi/L .41 pCi/L

Beta, pe Cs-137 1.95.pCi/L 1.97.pCi/L

Metribuzin <.004 <.004

Table 6. Concentrations of selected radionuclide activities and organic compounds in water-quality 

samples collected September 4, 1997, at Crystal Lake Reservoir, Laramie County, Wyoming

[Surface sample collected 1 foot below reservoir surface; bottom sample collected 3 feet above reservoir bottom; est., estimated; 

pCi/L, picoCurries per liter; μg/L, microgram per liter; concentrations are dissolved unless otherwise noted]
WATER QUALITY 43

2,6-Diethylaniline <0.003 <0.003

Trifluralin <.002 <.002

Ethalfluralin <.004 <.004

Phorate <.002 <.002

Terbacil <.007 <.007

Linuron <.002 <.002

Methyl parathion <.006 <.006

EPTC <.002 <.002

Pebulate <.004 <.004

Tebuthiuron <.01 <.01

Molinate <.004 <.004

Ethoprop <.003 <.003

Benfluralin <.002 <.002

Carbofuran <.003 <.003

Terbufos <.013 <.013

Pronamide <.003 <.003

Disulfoton <.017 <.017

Triallate <.001 <.001

Propanil <.004 <.004

Carbaryl <.003 <.003

Thiobencarb <.002 <.002

DCPA <.002 <.002

Pendimethalin <.004 <.004

Napropamide <.003 <.003

Propargite <.04 <.013

Methyl azinphos <.001 <.001

cis-Permethrin <.005 <.005

Table 6. Concentrations of selected radionuclide activities and organic compounds in water-quality 

samples collected September 4, 1997, at Crystal Lake Reservoir, Laramie County, Wyoming--Continued

Parameter/compound

Surface sample

(μg/L

except

as noted)

Bottom sample

(μg/L

except

as noted)
44 WATER QUALITY OF FOUR RESERVOIRS 

in that sample are listed in table 3. Of the constituents 

analyzed, aluminum concentration was highest at 

6.8 percent, iron was 3.6 percent, and potassium was 

2.7 percent. 

Most of the trace-element concentrations are in 

the microgram-per-gram range. Concentrations of 

nitrogen, (nitrite plus nitrate), arsenic, bismuth, cadmium, gold, holmium, molybdenum, silver, tantalum, 

tin, and uranium were less than the detection limit. 

Concentrations of thorium, vanadium, cerium and 

chromium are plotted in figure 12. The trace-element 

concentrations fit best in Group 2—more like granitic 

rocks than either diabase or the crustal average. This 

similarity is probably due to the extensive exposures of 

Sherman Granite (Precambrian) within the drainage 

area of the reservoir.

Comparison among Reservoirs

All reservoirs have some distinct characteristics, 

but, in general, Rob Roy Reservoir and Lake Owen are 

unique, whereas Granite Springs and Crystal Lake Reservoirs are similar. Rob Roy is the highest in elevation, 

the largest in storage capacity, and the deepest. In contrast, Lake Owen has minimal storage capacity and is the 

shallowest of the four reservoirs. Both Rob Roy and 

Lake Owen are located in the Medicine Bow Mountains, 

Albany County; Granite Springs and Crystal Lake are 

located in the Laramie Mountains, Laramie County, 

about 45 miles to the east. Granite Springs and Crystal 

Lake are close to 7,000 ft above sea level, about 2,000 ft 

lower than Rob Roy and Lake Owen. Granite Springs 

and Crystal Lake have comparable storage capacities 

and similar depths. All four reservoirs are recreational 

areas.

Profiles

A general comparison can be made among the 

profiles measured at Rob Roy, Granite Springs, and 

Crystal Lake. Lake Owen, due to its shallow depth, is 

not very comparable to the other three reservoirs and 

will not be discussed further in this section. 

Rob Roy, Granite Springs, and Crystal Lake are 

dimictic reservoirs because they mix or “turn over” 

twice a year. In 1998, Rob Roy was always cooler, 

probably due to the high elevation, than either Granite 

Springs or Crystal Lake Reservoirs. In 1998, temperature in the hypolimnion zone in Rob Roy generally 

ranged from 5 to 10°C (fig. 5). By September 1998, the 

temperature in the hypolimnion was about 15°C in both 

Granite Springs and Crystal Lake. In 1998, the temperature in the epilimnion of Rob Roy reached a maximum 

of 16.7°C. During 1998 the maximum temperature in 

the epilimnion was 26.6°C in Granite Springs and 

21.1°C in Crystal Lake. Rob Roy retained a stronger 

stratification in mid-September, 1998, in comparison to 

Granite Springs or Crystal Lake. 

Granite Springs and Crystal Lake showed very 

similar thermal changes over time (figs. 17 and 20). 

Both reservoirs were unstratified in May, developed 

strong thermal stratification by mid-July, and stratification dissipated by early fall. It is most likely that the 

large volume of water that passes through Granite 

Springs and Crystal Lake reservoirs disrupts the more 

classic stratification pattern associated with temperate 

lakes. Whereas Rob Roy reservoir maintained temperatures below 8°C in the hypolimnion throughout the 

summer, much warmer temperatures (greater than 

10°C) were measured in the hypolimnion of Granite 

Springs and Crystal Lake reservoirs.

September 1998 profiles (fig. 3C, 16D, 19D) 

show similar patterns of higher pH in the epilimnion, 

and lower pH in the hypolimnion. The pH also was 

greater in the two lower reservoirs than in the upper reservoirs: 6.5 to 7.5 in Rob Roy; 7.0 to above 8.0 in Granite Springs; and 7.0 to 8.5 in Crystal Lake. Dissolved 

oxygen during the same period was substantially different in Rob Roy (fig. 3C) than in Granite Springs and 

Crystal Lake (figs. 16D and 19D). Dissolved-oxygen 

concentrations in Rob Roy decreased from slightly 

higher than 7 mg/L to about 5 mg/L. In contrast, concentrations in both Granite Springs and Crystal Lake 

were slightly higher than 7.5 mg/L near the surface to 

about 26 ft and decreased to less than 1mg/L in the 

hypolimnion. 

 Phytoplankton

The phytoplankton community was different in 

each reservoir. The average biomass and density of 

phytoplankton were lowest in Rob Roy, and the concentrations generally increased progressively from Lake 

Owen to Granite Springs and Crystal Lake (fig. 23A). 

The one exception to the pattern was that the average 

density was larger in Granite Springs than in Crystal 

Lake. The average concentrations are slightly skewed 

by a phytoplankton bloom in Granite Springs and to a 

lesser degree, blooms in Crystal Lake and Lake Owen 
WATER QUALITY 45
46 WATER QUALITY OF FOUR RESERVOIRS 

(fig. 23B). The phytoplankton density followed the 

seasonal pattern of the biomass, although large concentrations of relatively small-sized Chrysophyta in Lake 

Owen caused a spike in density relative to biomass, as 

did large concentrations of relatively small-sized bluegreen algae in Crystal Lake (fig. 23C). The biomass 

concentrations are considered a more reliable indicator 

of primary productivity because the size of the algae is 

not accounted for in the density estimate. 

The composition of the phytoplankton community also was different between the upper and lower 

reservoirs. Many of the species found in Rob Roy and 

Lake Owen are associated with oligotrophic, nutrientpoor conditions. In contrast, many of the species found 

in Granite Springs and Crystal Lake are associated with 

mesotrophic (between poor and rich nutrient conditions) or eutrophic (nutrient-rich) conditions. As an 

example, blue-green algae were absent from the higher 

elevation reservoirs, but dominated some of the samples from the lower reservoirs. The species Anabaena, 

which is often associated with algal blooms, was the 

predominant species of blue-green algae in the lower 

reservoirs. Green algae, diatoms, and chrysophytes 

dominated the phytoplankton samples from the higherelevation reservoirs. An abundance of desmids (a family of green algae) relative to other algae in oligotrophic lakes has been noted by Prescott (1968, 

p. 293). The desmids Cosmarium, Staurastrum, and 

Spondylosium were dominant or subdominant in some 

of the samples from Rob Roy, as described earlier in 

this report. Desmids also were present in Lake Owen 

and Crystal Lake, but at relatively smaller concentrations. Desmids typically are found sparingly in phytoplankton samples, with large numbers of species or 

individuals usually found only where the pH ranges 

from 5 to 6 (Smith, 1950, p. 310). The pH values at 

Rob Roy were the lowest of the four reservoirs studied 

and generally were less than 7. 

Nutrient concentrations could be limiting phytoplankton growth in the reservoirs, based on samples 

collected in late August and early September 1997 

(table 2). All concentrations of dissolved ortho-phosphorus were less than the reporting limit of 0.01 mg/L. 

For comparison, the U.S. Environmental Protection 

Agency (1986) recommends ortho-phosphate concentrations in lakes and reservoirs not exceed 0.025 mg/L 

for protection against aquatic nuisance algal blooms 

and to control accelerated or cultural eutrophication. 

Concentrations of dissolved nitrogen species generally 

were less than the reporting limits, particularly in the 

near-surface samples. Silica can be a limiting nutrient 

to diatoms, because they need silica to build their frustules. Concentrations of silica from the one set of surface samples collected in this study, however, were in 

the range of 2.1 to 5.8 mg/L, indicating adequate supplies of silica. Limiting concentrations of silica for certain diatoms are 0.5-0.8 mg/L (Reid and Wood, 1976, 

p. 244), and 0.5-1.0 mg/L (Prescott, 1968, p. 338). 

The total number of taxa identified also 

increased downstream in the reservoirs: Rob Roy, 

29 taxa; Lake Owen, 37 taxa; Granite Springs, 41 taxa; 

and Crystal Lake, 42 taxa. The green algae were the 

most diverse division, with a total of 34 taxa identified 

in this study. Some green algae, such as Chlorella, 

Quadrigula, and Sphaerocystis were found in all four 

reservoirs (table 4). Twenty taxa of green algae, however, were found in only one reservoir. Other taxa of 

algae found in all four reservoirs include the diatom 

Fragilaria, and the cryptomonads Campylomonas 

reflexa, Campylomonas rostratiformis, Katablepharis, 

and Plagioselmis. A total of 80 taxa were identified in 

the samples from this study. 

The phytoplankton communities and water 

chemistry of Rob Roy and Lake Owen appear to be 

somewhat similar to those of Fremont and New Fork 

Lakes, two oligotrophic lakes in western Wyoming. 

The dissolved solids and nutrient concentrations in all 

four water bodies were similar to each other, except for 

silica, which was lower in Fremont Lake (median concentration 1.4 mg/L) (Peterson and others, 1987, 

p. 36-43). The average phytoplankton density was 

4,840 cells/mL in Fremont Lake and 1,710 cells/mL in 

New Fork Lakes (Peterson and others, 1987, p. 26-29); 

this range is similar in Rob Roy and Lake Owen. Diatoms, green algae, golden-brown algae, and blue-green 

algae were common components of the phytoplankton 

community at Fremont and New Fork Lakes. In contrast, blue-green algae were not identified in Rob Roy 

or Lake Owen. 

During 1983-84 and 1989, a total of 146 species 

were identified in samples from Fremont Lake (Averett 

and others, 1993). The larger number of species identified in Fremont Lake, compared to Rob Roy and Lake 

Owen, is due, at least in part, to two factors: (1) the 

wider scope of seasons, years, and depths sampled 

from Fremont Lake, and (2) the species-level identifications, as opposed to the mostly genus-level identifications from this study. Many of the same genera of 

algae were identified from all three-water bodies. 
WATER QUALITY 47

Secchi disk transparencies indicate that Rob Roy 

had the clearest water of the four reservoirs studied 

(fig. 4). The average transparency in each reservoir 

was: 

The euphotic zone is the upper layer of the lake 

where sufficient sunlight penetrates for photosynthesis. 

The depth of the euphotic zone typically extended 

below the metalimnion when the reservoirs were stratified, indicating adequate light for photosynthesis 

throughout the epilimnion. For comparison, Secchi 

disk readings from Fremont and New Fork Lakes 

ranged from 10.5 to 49 ft (Peterson and others, 1987, 

p. 18-19). 

The phytoplankton counts in the MPA are lower 

in Rob Roy then in Granite Springs and Crystal Lake. 

Rob Roy is at an elevation of 9,470 ft. The surface of 

the reservoir is frozen and snow-covered for most of 

the year, thereby, restricting sunlight and phytoplankton growth. Water flows from Rob Roy to Lake Owen 

where the MPA indicated less algae. Several factors at 

Lake Owen could influence it’s phytoplankton counts. 

Lake Owen is shallow and vegetation is abundant. 

Also, Lake Owen contains some rotifers that may be 

consuming algae. Lake Owen may be acting as a wetland with the vegetation consuming the nutrients, 

thereby limiting the algal cell growth. The elevation of 

Crystal Lake Reservoir is 6,969 ft, allowing even more 

favorable conditions for algal growth.

Higher phytoplankton counts in the MPA are 

seen in both Granite Springs and Crystal Lake. Granite 

Springs is dominated by diatoms, whereas Crystal Lake 

had both non-diatomaceous phytoplankton and diatoms in the MPA. The warmer climate associated with 

the lower elevation of these two reservoirs, and the 

wind, which often keeps the ice from being covered

by snow, are possible reasons for the higher phytoplankton counts. Investigation of the reasons for 

these differences is beyond the scope of this study. 

 Chemical Quality

Dissolved-solids (fig. 7) concentrations were 

slightly greater with depth within Rob Roy, Granite 

Springs, and Crystal Lake Reservoirs. The pattern was 

consistent in all three reservoirs although the amount of 

increase was small. Silica, as dissolved SO2, showed a 

consistent pattern of increasing with depth in Rob Roy, 

Granite Springs, and Crystal Lake (fig. 9), as did iron 

(fig. 10) and manganese (fig. 11).

Dissolved-solids concentrations in Granite 

Springs and Crystal Lake were about double those of 

the upper two reservoirs, Rob Roy and Lake Owen 

(fig. 24). The concentrations of individual major ions 

were larger in the lower two reservoirs, but the percentages of major ions were similar (fig. 8). Thus, 

although the concentrations of individual dissolved 

constituents were larger in the two lower reservoirs, the 

major-ion concentrations occurred in about the same 

proportions.

Bottom Sediment

Composite sediment samples were collected and 

analyzed from all four reservoirs (table 3). The major 

constituents analyzed were present in similar concentrations in all four reservoirs, except for nitrogen. Rob 

Roy and Lake Owen were similar with 9 and 8 mg/kg 

of nitrogen, reported as total nitrite plus nitrate. Granite Springs and Crystal Lake both had nitrogen concentrations less than the detection limit. In all four 

reservoirs, aluminum was 6.2 to 6.9 percent of the sediment. Iron concentrations in samples from all four reservoirs ranged from 2.2 percent to 3.6 percent. 

Phosphorus and titanium were present in similar concentrations in all four reservoirs. 

Differences in bottom-sediment samples from 

the reservoirs were most apparent in the concentrations 

of trace elements. When thorium, vanadium, cerium 

and chromium concentrations were plotted (fig. 12), 

the samples fell into two groups. Sediment concentrations from Rob Roy and Lake Owen (Group l) are more 

like the crustal average than either diabase or granitic 

rocks. In contrast, the concentrations from Granite 

Springs and Crystal Lake Reservoirs (Group 2) are 

closer to concentrations present in granitic rocks.

Reservoir

Secchi disk 

transparency

(feet)

Approximate 

euphotic 

zone 

thickness

(feet)

Rob Roy 10.4 31

Lake Owen 6.6 20

Granite Springs 8.2 25

Crystal Lake 6.1 18
48 WATER QUALITY OF FOUR RESERVOIRS 

SUMMARY

Surface water contributes approximately 75 percent of the City of Cheyenne’s drinking-water supply. 

Most of that surface water is provided by four reservoirs: 

Rob Roy, Lake Owen, Granite Springs, and Crystal 

Lake. Although extensive water-quality data are collected for the treated water, limited data were available 

on the raw-water quality within the storage reservoirs. 

Rob Roy Reservoir is the largest, deepest, and 

highest in the series of the reservoirs. Profile measurements indicate that in 1998 Rob Roy was strongly stratified from mid-July into late September and by early 

October was no longer stratified. The zone of warming 

in Rob Roy extended progressively deeper into the reservoir from mid-July into September. Bacillariophyta 

(diatoms) and Chlorophyta (green algae) dominated the 

phytoplankton community of Rob Roy. Twenty-nine 

taxa of algae were identified from the samples, including 

eighteen taxa of green algae. In Rob Roy, the microscopic particulate analysis (MPA) was dominated by 

non-diatomaceous phytoplankton and diatoms. The 

water was a calcium-bicarbonate type with the lowest 

dissolved solids of the four reservoirs. Dissolved-solids 

and major-ion concentrations indicated little difference 

between the top and bottom samples of Rob Roy. Iron 

and manganese concentrations, however, were higher in 

the bottom sample. Concentrations of selected trace elements in bottom sediment from Rob Roy resemble the 

crustal average rock more than either diabase or granitic 

rocks.

Lake Owen is the shallowest and smallest of the 

series of reservoirs. It showed little stratification, probably due to its shallow depth and large surface area to 

volume ratio. Lake Owen warmed by mid-July in 1998 

and cooled quickly in the fall. The golden-brown algae 

Chrysophyte dominated the phytoplankton community; 

Uroglenopsis was the most common species in the samples. Lake Owen is the only one of the four reservoirs in 

this study to have extensive macrophyte growths. In the 

fall of 1997, MPA was dominated by non-diatomaceous 

phytoplankton and diatoms, with a few rotifers being 

detected. Analysis of a single water sample, collected 

1 foot below the reservoir surface, indicated the water 

quality was similar to that of Rob Roy, with a dissolvedsolids concentration of 20 mg/L and of a calciumbicarbonate type. Lake Owen had the largest concentration of dissolved iron of the four reservoirs. Like Rob 

Roy, bottom sediment from Lake Owen resembled 

crustal averages.
SUMMARY 49

Granite Springs Reservoir is the third reservoir in 

the series and receives water through both Stage I and 

Stage II pipelines from Lake Owen. Profiles indicate 

that Granite Springs developed stratification by early-tomid July; the reservoir was unstratified in the winter. 

The 1998 temperature profiles in Granite Springs indicate a seasonal progression of the water temperature in 

the reservoir from a uniform profile, to linear warming, 

to stratification, to a uniform profile. Diatoms and bluegreen algae dominated the phytoplankton community. 

Blue-green algae, principally Anabaena, dominated the 

biomass of the algae in the August 1997 and July 14, 

1998 samples. The two samples collected for chemical 

analysis indicated that the water was a calcium-bicarbonate type. Dissolved-solids concentration increased 

slightly with depth. Likewise, dissolved-iron and 

-manganese concentrations increased with depth. The 

MPA was dominated by non-diatomaceous phytoplankton and diatoms. A few rotifers were detected. Traceelement concentrations in bottom sediment in Granite 

Springs resemble concentrations found in granitic rocks. 

Crystal Lake Reservoir is the last reservoir in the 

series. Water flows down Middle Crow Creek and 

through a pipeline from Granite Springs into Crystal 

Lake. Profile data indicate that stratification occurred 

during the warmer months. Throughout the May and 

June period of 1998 the reservoir warmed and stratification developed. By mid-July, the reservoir was stratified 

and surface water temperature was slightly greater than 

20°C. Blue-green algae and diatom biomass dominated 

the phytoplankton community. Of the 42 algal taxa 

identified, only 5 taxa were blue-green algae. The MPA 

was dominated by non-diatomaceous phytoplankton and 

diatoms. The three samples collected for chemical analysis at Crystal Lake indicated the water was a calciumcarbonate type with dissolved-solids concentrations 

varying from 58 mg/L at the surface to 63 mg/L at the 

bottom. Concentrations of dissolved iron and manganese increased with depth in Crystal Lake. Selected 

trace-element concentrations in bottom sediment were 

more like granitic rocks than either diabase or the crustal 

average. 

A general comparison was made between the 

1998 profiles measured at Rob Roy, Granite Springs, 

and Crystal Lake Reservoirs. Rob Roy was always 

cooler, probably due to it’s higher elevation. In Rob Roy, 

the temperature in the epilimnion reached a maximum of 

16.7°C. In Granite Springs and Crystal Lake, the maximum temperature in the epilimnion was several degrees 

warmer—26.6°C in Granite Springs and 21.1°C in Crystal Lake. The hypolimnion in Rob Roy remained 

between 5 to 10°C. By September 1998, the temperature 

in the hypolimnion was greater than 15°C in both Granite Springs and Crystal Lake. This difference may be a 

result of the large inflow and outflow in Granite Springs 

and Crystal Lake caused by water-supply withdrawals. 

Granite Springs and Crystal Lake showed similar thermal changes over time. Both were unstratified in May, 

developed strong stratification by mid-July, and the 

stratification dissipated by early fall.

The phytoplankton community changed progressively downstream in the four reservoirs. The average 

biomass and density of phytoplankton were smallest in 

Rob Roy, and the concentrations generally were progressively larger in Lake Owen, Granite Springs, and Crystal 

Lake. The composition of the phytoplankton community also changed downstream. Many of the species 

found in Rob Roy and Lake Owen are associated with 

oligotrophic, nutrient-poor conditions. In contrast, 

many of the species found in Granite Springs and Crystal 

Lake are associated with mesotrophic or eutrophic conditions. The total number of taxa identified also changed 

progressively downstream: Rob Roy, 29 taxa; Lake 

Owen, 37 taxa; Granite Springs, 41 taxa; and Crystal 

Lake, 42 taxa. 

The reservoirs showed increases in concentrations 

of dissolved solids in the direction of water flow 

between the reservoirs. Dissolved-solids concentrations 

in the two lower reservoirs, Granite Springs and Crystal 

Lake, were more than twice the dissolved-solids concentrations in the upper two reservoirs, Rob Roy and Lake 

Owen. The water type in all four reservoirs was calcium 

bicarbonate. Silica, as dissolved SiO2, increased with 

depth in all four reservoirs. Major-ion concentrations 

were present in about the same proportion in all four reservoirs. Concentrations of dissolved iron and manganese were elevated in the bottom samples as compared to 

the surface samples in all three reservoirs (figs. 10 and 

11).

Bottom sediment was examined because sediment 

particles can act as sites for ion exchange between 

aquatic and solid phases. Differences in the reservoir 

sediment samples were most apparent when concentrations of trace elements were examined. Concentrations 

of selected trace elements from Rob Roy and Lake Owen 

are more like the crustal average than concentrations in 

either diabase or granitic rocks. In contrast, the concentrations from Granite Springs and Crystal Lake more 

closely resemble concentrations present in granitic 

rocks. 
50 WATER QUALITY OF FOUR RESERVOIRS 

REFERENCES CITED

Averett, R.C., Emmett, W.W., and Peterson, D.A., 1993, The 

phytoplankton of Fremont Lake, Wyoming: U.S. Geological Survey Water-Resources Investigations Report 

92-4071, 64 p.

Horne, A.J., and Goldman, C.R., 1994, Limnology (2d ed.): 

New York, McGraw-Hill, Inc., 576 p.

Houston, R.S., and Orback, C.J., 1976, Geologic Map of the 

Lake Owen Quadrangle, Albany County, Wyoming: 

U.S. Geological Survey Geologic Quadrangle 

Map GQ-1304, 1 sheet, scale 1:24,000.

Love, J.D., and Christensen, A.C., 1985, Geologic Map of 

Wyoming: U.S. Geological Survey, 3 sheets, 

scale 1:500,000.

McGauhey, P.H., 1968, Engineering Management of Water 

Quality: New York, McGraw-Hill Book Co., 295 p.

Mason, Brian, 1966, Principles of Geochemistry (3d ed.): 

New York, John Wiley & Sons, Inc., 329 p.

Moore, J.W., 1989, Balancing the Needs of Water Use: New 

York, Springer-Verlag, 267 p.

Peterson, D.A., Averett, R.C., and Mora, K.L., 1987, Water 

quality of Fremont Lake and New Fork Lakes, western 

Wyoming—A progress report: U.S. Geological Survey 

Water-Resources Investigations Report 86-4016, 55 p.

Powell, S.T., 1964, Quality of Water, in Chow, V.T. (ed.), 

Handbook of Applied Hydrology: New York, 

McGraw-Hill Book Co., Section 19, 37 p.

Prescott, G.W., 1968, The algae: A review: Boston, Mass., 

Houghton Mifflin Company, 436 p. 

_____1978, How to know the freshwater algae: Pictured key 

nature series (3d ed.): Dubuque, Iowa, Wm. C. Brown 

Company Publishers, 348 p. 

Reid, G.K., and Wood, R.D., 1976, Ecology of inland waters 

and estuaries: New York, D. Van Nostrand Company, 

485 p. 

Smith, G.M., 1950, The freshwater algae of the United 

States: New York, McGraw-Hill Book Co., 719 p. 

U.S. Environmental Protection Agency, 1986, Quality criteria for water 1986: EPA 440/5-86-001, unnumbered 

pages. 

———1996 (a), ICR Laboratory manual, EPA/600/R-95/

178.

———1996 (b), Microscopic particulate analysis (MPA) 

for filtration optimization: EPA 910-R-96-001.

———1997, The incidence and severity of sediment contamination in surface waters of the United States, 

Volume 1: National Sediment Quality Survey, Appendix D, D-19 p.
REFERENCES CITED 51

APPENDIX A—PROFILE DATA

Explanation of figure numbers. Letter indicates reservoir.

R Rob Roy Reservoir

L Lake Owen

G Granite Springs Reservoir

C Crystal Lake Reservoir

Numerals respresent date of profile. Example:

R9-2-97 Profile measured in Rob Roy Reservoir on September 2, 1997
REFERENCES CITED 52
APPENDIX A 1
2 WATER QUALITY OF FOUR RESERVOIRS 
APPENDIX A 3
4 WATER QUALITY OF FOUR RESERVOIRS 
APPENDIX A 5
6 WATER QUALITY OF FOUR RESERVOIRS 
APPENDIX A 7
8 WATER QUALITY OF FOUR RESERVOIRS 
APPENDIX A 9
10 WATER QUALITY OF FOUR RESERVOIRS 
APPENDIX A 11
12 WATER QUALITY OF FOUR RESERVOIRS 
APPENDIX A 13
14 WATER QUALITY OF FOUR RESERVOIRS 
APPENDIX A 15
16 WATER QUALITY OF FOUR RESERVOIRS 
APPENDIX A 17
18 WATER QUALITY OF FOUR RESERVOIRS 
APPENDIX A 19
20 WATER QUALITY OF FOUR RESERVOIRS 
APPENDIX A 21
22 WATER QUALITY OF FOUR RESERVOIRS 
APPENDIX A 23
24 WATER QUALITY OF FOUR RESERVOIRS 
APPENDIX A 25
26 WATER QUALITY OF FOUR RESERVOIRS 
APPENDIX A 27
28 WATER QUALITY OF FOUR RESERVOIRS 
APPENDIX A 29
30 WATER QUALITY OF FOUR RESERVOIRS 
APPENDIX A 31
32 WATER QUALITY OF FOUR RESERVOIRS 
APPENDIX A 33
34 WATER QUALITY OF FOUR RESERVOIRS 
APPENDIX A 35
36 WATER QUALITY OF FOUR RESERVOIRS 
APPENDIX A 37
38 WATER QUALITY OF FOUR RESERVOIRS 
APPENDIX A 39
40 WATER QUALITY OF FOUR RESERVOIRS 
APPENDIX A 41
42 WATER QUALITY OF FOUR RESERVOIRS 
APPENDIX A 43
44 WATER QUALITY OF FOUR RESERVOIRS 
APPENDIX A 45
46 WATER QUALITY OF FOUR RESERVOIRS 
APPENDIX A 47
48 WATER QUALITY OF FOUR RESERVOIRS 
APPENDIX A 49
50 WATER QUALITY OF FOUR RESERVOIRS 
APPENDIX A 51
52 WATER QUALITY OF FOUR RESERVOIRS 
APPENDIX A 53
54 WATER QUALITY OF FOUR RESERVOIRS 
APPENDIX A 55
56 WATER QUALITY OF FOUR RESERVOIRS 
APPENDIX A 57
 1

APPENDIX B—PHYTOPLANKTON DATA

Tables of phytoplankton density and biomass.

B1 Rob Roy Reservoir

B2 Lake Owen

B3 Granite Springs Reservoir

B4 Crystal Lake Reservoir
2 WATER QUALITY OF FOUR RESERVOIRS 
A

PPENDIXB1

Table B1. Phytoplankton density and biomass, Rob Roy Reservoir

Date

9-2-97 9-2-97 7-17-98 7-23-98 8-5-98 8-11-98 8-19-98 9-3-98 9-10-

3’ above 

bottom 1’ below surface

Chlorophyta

Ankistrodesmus density 0 20,000 0 0 10,000 0 0 0 Ankistrodesmus biomass 0 5.0 0 0 2.5 0 0 0 Chlamydomonas size 1 density 0 0 0 0 10,000 0 0 0 Chlamydomonas size 1 biomass 0 0 0 0 1.1 0 0 0 Chlamydomonas size 2 density 0 0 0 0 0 0 0 0 Chlamydomonas size 2 biomass 0 0 0 0 0 0 0 0 Chlorella density 0 0 10,000 0 0 0 0 0 Chlorella biomass 0 0 2.7 0 0 0 0 0 Chlorophyte size 2 density 0 0 0 0 0 0 20,000 0 20,00Chlorophyte size 2 biomass 0 0 0 0 0 0 16 0 1Chlorophyte size 3 density 0 10,000 0 0 0 10,000 20,000 0 Chlorophyte size 3 biomass 0 26 0 0 0 26 51 0 Chlorophyte size 4 density 0 10,000 0 10,000 0 0 0 20,000 Chlorophyte size 4 biomass 0 2.1 0 2 .1 0 0 0 4.1 Chlorophyte size 5 density 0 60,000 0 0 0 0 0 0 Chlorophyte size 5 biomass 0 0.9 0 0 0 0 0 0 Chlorophyte size 7 density 0 0 0 0 0 0 0 0 Chlorophyte size 7 biomass 0 0 0 0 0 0 0 0 Cosmarium density 0 0 0 0 0 0 0 10,000 Cosmarium biomass 0 0 0 0 0 0 0 190 Dictyosphaerium density 0 0 0 0 0 0 0 1,250,000 Dictyosphaerium biomass 0 0 0 0 0 0 0 140 Elakatothrix density 0 0 0 0 0 0 0 100,000 Elakatothrix biomass 0 0 0 0 0 0 0 15 Oocystis size 1 density 0 0 0 0 0 0 0 120,000 30,00Oocystis size 1 biomass 0 0 0 0 0 0 0 17 Quadrigula density 0 0 0 0 0 0 0 0 160,00Quadrigula biomass 0 0 0 0 0 0 0 0 6

Table B1. Phytoplankton density and biomass, Rob Roy Reservoir[Density in cells per liter, biomass in micrograms per liter]
2 WATER QUALITY OF FOUR RESERVOIRS Schroederia density 0 0 0 0 0 0 0 0 

Schroederia biomass 0 0 0 0 0 0 0 0 Sphaerocystis density 0 0 0 0 0 160,000 40,000 160,000 Sphaerocystis biomass 0 0 0 0 0 47 12 47 Spondylosium density 0 0 0 0 0 0 0 0 Spondylosium biomass 0 0 0 0 0 0 0 0 Staurastrum density 0 0 0 0 0 0 0 0 50,0Staurastrum biomass 0 0 0 0 0 0 0 0 6

Chrysophyta

Mallomonas density 0 0 0 0 0 0 0 10,000 

Mallomonas biomass 0 0 0 0 0 0 0 13 

Cryptophyta

Campylomonas reflexa density 0 0 0 10,000 0 10,000 0 10,000 60,0Campylomonas reflexa biomass 0 0 0 14 0 14 0 14 Campylomonas rostratiformis density 0 0 0 10,000 0 0 0 20,000 

Campylomonas rostratiformis biomass 0 0 0 32 0 0 0 64 

Cryptophyte size 2 density 0 20,000 0 0 0 0 0 0 Cryptophyte size 2 biomass 0 21 0 0 0 0 0 0 Cryptomonas density 0 0 0 0 0 0 10,000 10,000 Cryptomonas biomass 0 0 0 0 0 0 23 23 Katablepharis density 0 0 0 80,000 60,000 20,000 80,000 20,000 10,0Katablepharis biomass 0 0 0 14 11 3.6 14 3.6 Plagioselmis density 0 0 0 0 10,000 10,000 10,000 0 Plagioselmis biomass 0 0 0 0 1.5 1.5 1.5 0 

Bacillariophyta

Asterionella density 140,000 2,590,000 0 0 270,000 1,090,000 590,000 40,000 10,0Asterionella biomass 190 3,500 0 0 360 1,500 790 53 Fragilaria density 0 0 0 0 610,000 1,550,000 390,000 0 Fragilaria biomass 0 0 0 0 670 1,700 430 0 Nitzschia density 0 0 0 0 0 10,000 0 0 Nitzschia biomass 0 0 0 0 0 1.0 0 0 

Table B1. Phytoplankton density and biomass, Rob Roy Reservoir--Continued

Date

9-2-97 9-2-97 7-17-98 7-23-98 8-5-98 8-11-98 8-19-98 9-3-98 9-10

3’ above 

bottom 1’ below surface
APPENDIX B 3

Pyrrophyta

Gymnodinium density 0 0 0 0 0 0 0 0 Gymnodinium biomass 0 0 0 0 0 0 0 0 

Colorless Flagellates

Flagellate size 3 density 0 370,000 0 20,000 0 0 0 10,000 Flagellate size 3 biomass 0 53 0 2.9 0 0 0 1.4 Flagellate size 5 density 0 0 10,000 0 0 0 0 0 Flagellate size 5 biomass 0 0 7.0 0 0 0 0 0 Ciliate size 2 density 0 0 0 0 0 0 0 0 30,00Ciliate size 2 biomass 0 0 0 0 0 0 0 0 2

Ameba

Ameba density 0 0 0 10,000 0 0 0 0 Ameba biomass 0 0 0 26 0 0 0 0 

Table B1. Phytoplankton density and biomass, Rob Roy Reservoir--Continued

Date

9-2-97 9-2-97 7-17-98 7-23-98 8-5-98 8-11-98 8-19-98 9-3-98 9-10-

3’ above 

bottom 1’ below surface
4 WATER QUALITY OF FOUR RESERVOIRS Table B2. Phytoplankton density and biomass, Lake Owen Reservoir Date 9-2-97 9-16-97 7-17-98 7-23-98 8-5-98 8-11-98 8-19-98 9-3-98 9-10-98 

Chlorophyta Actinastrum density 0 0 5,000 0 0 0 0 0 0 

Actinastrum biomass 0 0 1.1 0 0 0 0 0 0 Ankistrodesmus density 0 0 0 0 10,000 0 0 0 0 Ankistrodesmus biomass 0 0 0 0 2.8 0 0 0 0 Chlorella density 0 2,314,000 0 10,000 0 0 0 0 0 Chlorella biomass 0 78 0 0.3 0 0 0 0 0 Chlorophyte size 2 density 70,000 0 0 10,000 0 0 0 0 0 Chlorophyte size 2 biomass 42 0 0 6.1 0 0 0 0 0 Chlorophyte size 4 density 0 0 0 0 10,000 10,000 50,000 0 0 Chlorophyte size 4 biomass 0 0 0 0 1.6 1.6 8.1 0 0 Cosmarium density 0 0 0 10,000 0 0 0 0 0 Cosmarium biomass 0 0 0 200 0 0 0 0 0 Crucigenia density 0 0 0 0 0 0 0 0 0 Crucigenia biomass 0 0 0 0 0 0 0 0 0 Oocystis density 0 0 0 10,000 0 0 0 0 0 Oocystis biomass 0 0 0 1.0 0 0 0 0 0 Quadrigula density 0 90,000 0 0 0 0 0 0 20,000 Quadrigula biomass 0 53 0 0 0 0 0 0 12 Scenedesmus density 0 0 0 0 0 0 80,000 0 0 Scenedesmus biomass 0 0 0 0 0 0 4.1 0 0 Sphaerocystis density 0 0 0 0 0 80,000 0 0 0 Sphaerocystis biomass 0 0 0 0 0 9.0 0 0 0 Spondylosium density 0 0 0 0 0 0 0 0 0 Spondylosium biomass 0 0 0 0 0 0 0 0 0 Tetraspora density 0 170,000 0 0 0 0 0 0 0 Tetraspora biomass 0 89 0 0 0 0 0 0 0 Zygnematales density 0 0 0 0 0 0 0 0 0 Zygnematales biomass 0 0 0 0 0 0 0 0 0 

Table B2. Phytoplankton density and biomass, Lake Owen Reservoir[Density in cells per liter, biomass in micrograms per liter]
APPENDIX B 5

Chrysophyta

Chrysophyte size 1 density 0 0 0 0 0 0 0 0 0 Chrysophyte size 1 biomass 0 0 0 0 0 0 0 0 0 Dinobryon density 0 0 0 0 0 50,000 0 0 0 Dinobryon biomass 0 0 0 0 0 5.4 0 0 0 Mallomonas density 0 0 0 0 0 0 0 40,000 50,000 Mallomonas biomass 0 0 0 0 0 0 0 23 29 Uroglenopsis density 0 0 0 0 0 26,236,000 0 30,503,000 19,175,000 Uroglenopsis biomass 0 0 0 0 0 6,100 0 7,000 4,400 

Cryptophyta

Campylomonas reflexa density 0 0 0 0 20,000 0 0 0 0 Campylomonas reflexa biomass 0 0 0 0 16 0 0 0 0 Campylomonas rostratiformis density 0 0 0 0 0 0 0 0 10,000 Campylomonas rostratiformis biomass 0 0 0 0 0 0 0 0 51 Cryptophyte size 1 density 0 10,000 0 0 0 0 0 0 0 Cryptophyte size 1 biomass 0 5.0 0 0 0 0 0 0 0 Cryptophyte size 2 density 0 0 0 0 0 0 0 0 0 Cryptophyte size 2 biomass 0 0 0 0 0 0 0 0 0 Cryptophyte size 3 density 0 10,000 0 0 0 0 0 0 0 Cryptophyte size 3 biomass 0 2.3 0 0 0 0 0 0 0 Cryptomonas density 0 0 0 0 0 0 0 0 20,000 Cryptomonas biomass 0 0 0 0 0 0 0 0 41 Katablepharis density 0 0 0 40,000 330,000 40,000 140,000 20,000 60,000 Katablepharis biomass 0 0 0 7.3 60 7.3 26 3.7 11 Plagioselmis density 0 0 0 30,000 0 0 0 0 0 Plagioselmis biomass 0 0 0 3.5 0 0 0 0 0 

Bacillariophyta

Achnanthes density 0 0 0 0 0 0 0 0 0 Achnanthes biomass 0 0 0 0 0 0 0 0 0 Asterionella density 0 0 0 0 0 0 0 0 30,000 Asterionella biomass 0 0 0 0 0 0 0 0 34 Fragilaria density 0 0 0 0 0 0 0 0 0 

Table B2. Phytoplankton density and biomass, Lake Owen Reservoir--Continued

Date

9-2-97 9-16-97 7-17-98 7-23-98 8-5-98 8-11-98 8-19-98 9-3-98 9-10-98 
6 WATER QUALITY OF FOUR RESERVOIRS Fragilaria biomass 0 0 0 0 0 0 0 0 0 

Pennales size 2 density 0 0 0 0 0 0 0 0 0 Pennales size 2 biomass 0 0 0 0 0 0 0 0 0 Pennales size 3 density 0 0 0 0 0 0 0 10,000 0 Pennales size 3 biomass 0 0 0 0 0 0 0 14 0 Synedra density 0 0 0 0 10,000 0 0 0 0 Synedra biomass 0 0 0 0 25 0 0 0 0 

Pyrrophyta Gymnodinium density 0 0 0 0 0 0 0 0 0 

Gymnodinium biomass 0 0 0 0 0 0 0 0 0 

Euglenophyta

Euglena density 0 0 0 0 0 0 0 0 0 Euglena biomass 0 0 0 0 0 0 0 0 0 Euglenophyte size 1 density 0 0 0 0 0 0 0 0 0 Euglenophyte size 1 biomass 0 0 0 0 0 0 0 0 0 Euglenophyte size 2 density 0 0 0 0 0 0 0 0 0 Euglenophyte size 2 biomass 0 0 0 0 0 0 0 0 0 Trachelomonas size 2 density 0 0 0 0 0 0 10,000 0 10,000 Trachelomonas size 2 biomass 0 0 0 0 0 0 58 0 58 

Colorless Flagellates

Flagellate size 3 density 0 0 5,000 40,000 0 0 80,000 30,000 0 Flagellate size 3 biomass 0 0 0.7 5.8 0 0 12 4.3 0 Salpingoeca density 0 0 0 0 0 0 0 0 60,000 Salpingoeca biomass 0 0 0 0 0 0 0 0 180 

Ciliates

Ciliate size 1 density 0 0 0 0 0 0 0 0 10,000 Ciliate size 1 biomass 0 0 0 0 0 0 0 0 14 Ciliate size 2 density 0 0 0 0 0 0 10,000 0 0 Ciliate size 2 biomass 0 0 0 0 0 0 42 0 0 Ciliate size 3 density 0 0 0 0 0 0 0 0 0 Ciliate size 3 biomass 0 0 0 0 0 0 0 0 0 Ciliate size 5 density 0 0 0 0 0 0 0 0 0 

Table B2. Phytoplankton density and biomass, Lake Owen Reservoir--Continued

Date

9-2-97 9-16-97 7-17-98 7-23-98 8-5-98 8-11-98 8-19-98 9-3-98 9-10-98 
APPENDIX B 7

Ciliate size 5 biomass 0 0 0 0 0 0 0 0 0 Ciliate size 6 density 0 0 0 20,000 0 0 0 0 0 Ciliate size 6 biomass 0 0 0 9.4 0 0 0 0 0 Rotifers 0 0 0 0 0 0 0 0 0 Ameba density 0 0 0 0 0 0 0 0 0 Ameba biomass 0 0 0 0 0 0 0 0 0 

Table B2. Phytoplankton density and biomass, Lake Owen Reservoir--Continued

Date

9-2-97 9-16-97 7-17-98 7-23-98 8-5-98 8-11-98 8-19-98 9-3-98 9-10-98 
8 WATER QUALITY OF FOUR RESERVOIRS Table B3. Phytoplankton density and biomass, Granite Springs Reservoir Date 8-28-97 8-28-97 7-14-98 7-22-98 8-4-98 8-10-98 8-18-98 9-1-98 9-9-9

3’ above bottom 1’ below surface Chlorophyta Ankistrodesmus density 0 30,000 0 0 0 0 0 0 

Ankistrodesmus biomass 0 5.0 0 0 0 0 0 0 Chlorella density 0 0 0 10,000 0 0 0 0 Chlorella biomass 0 0 0 2.7 0 0 0 0 Chlorophyte size 1 density 0 20,000 0 0 0 0 0 0 Chlorophyte size 1 biomass 0 71 0 0 0 0 0 0 Chlorophyte size 2 density 20,000 0 10,000 0 10,000 0 0 500,000 Chlorophyte size 2 biomass 18 0 9.0 0 9.0 0 0 450 Chlorophyte size 4 density 0 0 0 0 0 0 0 140,000 50,0Chlorophyte size 4 biomass 0 0 0 0 0 0 0 25 Chlorophyte size 6 density 0 0 0 0 20,000 0 0 0 Chlorophyte size 6 biomass 0 0 0 0 3.0 0 0 0 Didymocystis density 0 0 0 0 0 0 0 0 Didymocystis biomass 0 0 0 0 0 0 0 0 Eudorina density 0 0 0 0 0 240,000 0 0 Eudorina biomass 0 0 0 0 0 170 0 0 Micractinium density 0 0 0 0 0 0 0 0 Micractinium biomass 0 0 0 0 0 0 0 0 Oocystis size 1 density 0 0 0 130,000 0 0 0 0 Oocystis size 1 biomass 0 0 0 20 0 0 0 0 Quadrigula density 0 0 0 20,000 0 0 0 0 Quadrigula biomass 0 0 0 15 0 0 0 0 Scenedesmus density 0 0 40,000 0 0 0 0 0 40,0Scenedesmus biomass 0 0 12 0 0 0 0 0 Sphaerocystis density 0 0 110,000 59,000 0 0 0 0 Sphaerocystis biomass 0 0 16 8.5 0 0 0 0 

Table B3. Phytoplankton density and biomass, Granite Springs Reservoir[Density in cells per liter, biomass in micrograms per liter]
APPENDIX B 9

Chrysophyta

Dinobryon density 0 0 0 0 0 0 0 0 10,Dinobryon biomass 0 0 0 0 0 0 0 0 

Cryptophyta

Campylomonas reflexa density 0 0 30,000 30,000 20,000 10,000 0 0 Campylomonas reflexa biomass 0 0 24 24 16 8.0 0 0 Campylomonas rostratiformis density 0 0 0 10,000 0 0 0 0 Campylomonas rostratiformis biomass 0 0 0 36 0 0 0 0 Cryptophyte size 1 density 0 0 0 0 0 0 0 10,000 Cryptophyte size 1 biomass 0 0 0 0 0 0 0 11 Katablepharis density 0 0 0 0 60,000 130,000 480,000 10,000 Katablepharis biomass 0 0 0 0 9 20 72 1.5 Plagioselmis density 0 0 0 280,000 120,000 60,000 0 30,000 Plagioselmis biomass 0 0 0 41 17 8.7 0 4.4 

Cyanophyta

Anabaena density 0 3,830,000 69,127,000 0 0 0 0 40,000 Anabaena biomass 0 3,300 59,000 0 0 0 0 34 Aphanothece density 0 4,750,000 0 0 0 0 0 0 1,140,Aphanothece biomass 0 8.1 0 0 0 0 0 0 Pseudanabaena density 0 0 0 0 0 0 0 0 

Pseudanabaena biomass 0 0 0 0 0 0 0 0 

Bacillariophyta

Asterionella density 0 0 0 0 0 40,000 0 0 Asterionella biomass 0 0 0 0 0 19 0 0 Centrales size 1 density 0 70,000 150,000 0 0 1,270,000 700,000 0 Centrales size 1 biomass 0 67 140 0 0 1,200 670 0 Centrales size 2 density 0 0 0 0 0 0 0 0 Centrales size 2 biomass 0 0 0 0 0 0 0 0 Centrales size 3 density 0 0 0 30,000 0 0 0 0 Centrales size 3 biomass 0 0 0 410 0 0 0 0 

Table B3. Phytoplankton density and biomass, Granite Springs Reservoir--Continued

Date

8-28-97 8-28-97 7-14-98 7-22-98 8-4-98 8-10-98 8-18-98 9-1-98 9-9

3’ above 

bottom 1’ below surface
10 WATER QUALITY OF FOUR RESERVOIRS Centrales size 4 density 0 0 0 0 10,000 0 0 0 

Centrales size 4 biomass 0 0 0 0 60 0 0 0 Cyclotella density 0 0 0 1,170,000 0 0 0 790,000 Cyclotella biomass 0 0 0 1,700 0 0 0 1,100 Cymbella density 0 0 0 10,000 0 0 0 0 Cymbella biomass 0 0 0 4.2 0 0 0 0 Fragilaria density 140,000 660,000 630,000 3,030,000 580,000 500,000 80,000 1,230,000 720,0Fragilaria biomass 200 930 880 4,200 810 700 110 1,700 1,0Melosira size 1 density 560,000 50,000 0 0 240,000 120,000 0 0 Melosira size 1 biomass 600 53 0 0 260 130 0 0 Melosira size 2 density 0 0 0 0 0 0 0 0 Melosira size 2 biomass 0 0 0 0 0 0 0 0 Melosira size 3 density 0 0 0 0 0 0 0 0 90,0Melosira size 3 biomass 0 0 0 0 0 0 0 0 1,6Pennales size 1 density 10,000 0 0 0 0 0 0 0 Pennales size 1 biomass 2.8 0 0 0 0 0 0 0 Pennales size 2 density 110,000 0 0 0 0 0 0 0 Pennales size 2 biomass 140 0 0 0 0 0 0 0 Stephanodiscus density 0 0 0 0 1,360,000 0 0 0 960,0Stephanodiscus biomass 0 0 0 0 1,100 0 0 0 8Tabellaria density 0 0 0 0 50,000 0 0 0 Tabellaria biomass 0 0 0 0 140 0 0 0 

Pyrrophyta

Ceratium density 0 10,000 0 0 0 0 0 0 Ceratium biomass 0 0.4 0 0 0 0 0 0 Trachelomonas size density 0 0 0 10,000 0 0 10,000 0 Trachelomonas size 1 biomass 0 0 0 31 0 0 31 0 Trachelomonas size 2 density 0 0 0 0 0 30,000 0 0 10,0Trachelomonas size 2 biomass 0 0 0 0 0 110 0 0 

Table B3. Phytoplankton density and biomass, Granite Springs Reservoir--Continued

Date

8-28-97 8-28-97 7-14-98 7-22-98 8-4-98 8-10-98 8-18-98 9-1-98 9-9-9

3’ above 

bottom 1’ below surface
APPENDIX B 11

Colorless Flagellates

Flagellate size 2 density 0 170,000 0 0 0 0 0 0 Flagellate size 2 biomass 0 38 0 0 0 0 0 0 Flagellate size 3 density 0 0 0 50,000 0 0 0 0 60,0Flagellate size 3 biomass 0 0 0 5.7 0 0 0 0 Flagellate size 5 density 0 0 0 0 0 0 0 0 Flagellate size 5 biomass 0 0 0 0 0 0 0 0 

Ciliates

Ciliate size 1 density 0 0 0 0 0 0 0 0 Ciliate size 1 biomass 0 0 0 0 0 0 0 0 Ciliate size 3 density 0 0 0 0 0 10,000 0 0 Ciliate size 3 biomass 0 0 0 0 0 82 0 0 Ciliate size 4 density 0 0 0 0 20,000 0 0 10,000 Ciliate size 4 biomass 0 0 0 0 560 0 0 280 

Rotifers

Rotifer size 2 density 0 0 10,000 0 0 0 0 0 Rotifer size 2 biomass 0 0 5,000 0 0 0 0 0 

Ameba

Ameba size 1 density 0 0 0 0 0 0 40,000 10,000 Ameba size 1 biomass 0 0 0 0 0 0 28 7.0 Ameba size 2 density 0 0 0 0 0 0 0 0 Ameba size 2 biomass 0 0 0 0 0 0 0 0 

Table B3. Phytoplankton density and biomass, Granite Springs Reservoir--Continued

Date

8-28-97 8-28-97 7-14-98 7-22-98 8-4-98 8-10-98 8-18-98 9-1-98 9-9-9

3’ above 

bottom 1’ below surface
12 WATER QUALITY OF FOUR RESERVOIRS Table B4. Phytoplankton density and biomass, Crystal Lake Reservoir Date 9-4-97 9-4-97 9-4-97 9-11-97 7-14-98 7-21-98 8-4-98 8-10-98 8-18-98 9-1-98 

1’ below surface 3’ above bottom At 30’ 1' below surface Chlorophyta Chlorella density 330,000 375,000 0 1,322,000 0 0 0 0 0 0 

Chlorella biomass 4.7 5.3 0 19 0 0 0 0 0 0 Chlorophyte size 2 density 0 0 0 20,000 0 0 30,000 0 0 0 Chlorophyte size 2 biomass 0 0 0 20 0 0 31 0 0 0 Chlorophyte size 3 density 0 40,000 0 0 0 0 0 10,000 10,000 0 Chlorophyte size 3 biomass

0 100 0 0 0 0 0 26 26 0 

Chlorophyte size 4 density

350,000 300,000 0 310,000 0 0 0 0 0 0 

Chlorophyte size 4 biomass

120 100 0 110 0 0 0 0 0 0 

Chlorophyte size 6 density

0 0 0 0 0 0 0 0 0 0 

Chlorophyte size 6 biomass

0 0 0 0 0 0 0 0 0 0 

Chlorococcalesdensity

0 0 0 0 0 0 0 0 0 0 

Chlorococcales biomass

0 0 0 0 0 0 0 0 0 0 

Closterium density 0 0 0 0 0 0 0 0 0 0 Closterium biomass

0 0 0 0 0 0 0 0 0 0 

Coelastrumdensity

0 0 0 0 0 0 0 0 0 0 

Coelastrum biomass

0 0 0 0 0 0 0 0 0 0 

Cosmarium density

0 10,000 0 0 0 0 0 0 20,000 0 

Cosmarium biomass

0 150 0 0 0 0 0 0 290 0 

Dictyosphaerium density

0 0 0 0 0 0 0 0 0 0 

Dictyopshaerium biomass

0 0 0 0 0 0 0 0 0 0 

Table B4. Phytoplankton density and biomass, Crystal Lake Reservoir[Density in cells per liter, biomass in micrograms per liter]
APPENDIX B 13

Oocystis size 1 density

40,000 0 0 0 90,000 0 0 0 80,000 0 

Oocystis size 1 biomass

4.6 0 0 0 10 0 0 0 9.1 0 

Oocystis size 2 density

0 0 0 0 20,000 0 0 0 0 0 

Oocystis size 2 biomass

0 0 0 0 40 0 0 0 0 0 

Pandorina density 0 0 0 0 0 120,000 0 0 0 0 Pandorina biomass

0 0 0 0 0 14 0 0 0 0 

Quadrigula density

0 0 0 0 0 0 0 0 0 0 

Quadrigula biomass

0 0 0 0 0 0 0 0 0 0 

Sphaerocystis density

0 0 0 0 0 0 80,000 0 80,000 0 

Sphaerocystis biomass

0 0 0 0 0 0 5.2 0 5.2 0 

Spondylosium density

80,000 0 0 0 0 0 0 0 0 0 

Spondylosium biomass

170 0 0 0 0 0 0 0 0 0 

Staurastrum density

0 0 0 0 0 0 0 0 0 10,000 

Staurastrum biomass

0 0 0 0 0 0 0 0 0 390 

Cryptophyta 0 0 0 0 0 0 0 0 0 0 

Campylomonas reflexa density

0 0 0 0 0 20,000 20,000 50,000 0 10,000 

Campylomonas reflexa biomass

0 0 0 0 0 19 19 48 0 9.5 

Campylomonas rostratiformis density

0 0 0 0 0 0 0 0 0 0 

Campylomonas rostratiformis biomass

0 0 0 0 0 0 0 0 0 0 

Cryptophyte size 1 density

20,000 0 0 0 0 0 0 0 0 0 

Table B4. Phytoplankton density and biomass, Crystal Lake Reservoir--Continued

Date

9-4-97 9-4-97 9-4-97 9-11-97 7-14-98 7-21-98 8-4-98 8-10-98 8-18-98 9-1-98 

1’ below surface

3’ above 

bottom At 30’ 1' below surface
14 WATER QUALITY OF FOUR RESERVOIRS Cryptophyte size 1 biomass 13 0 0 0 0 0 0 0 0 0 

Cryptophyte size 3 density 0 0 0 0 0 0 0 0 0 0 Cryptophyte size 3 biomass 0 0 0 0 0 0 0 0 0 0 Cryptophyte size 4 density 0 0 0 10,000 0 0 0 0 0 0 Cryptophyte size 4 biomass 0 0 0 2.7 0 0 0 0 0 0 Cryptomonas density

0 0 0 0 0 0 0 0 0 30,000 

Cryptomonas biomass

0 0 0 0 0 0 0 0 0 50 

Katablepharis density

0 0 0 0 0 50,000 50,000 220,000 40,000 20,000 

Katablepharis biomass

0 0 0 0 0 8.6 8.6 38 6.9 3.4 

Plagioselmis density

0 0 0 0 0 180,000 60,000 20,000 0 10,000 

Plagioselmis biomass

0 0 0 0 0 28 9.4 3.1 0 1.6 

Cyanophyta

Anabaena density 0 0 0 0 29,127,000 16,706,000 550,000 6,300,000 0 12,000 Anabaena biomass 0 0 0 0 18,000 10,000 330 3,800 0 7.3 Aphanothece density

0 0 0 0 0 0 0 0 0 3,780,000 

Aphanothece biomass

0 0 0 0 0 0 0 0 0 5.9 

Cyanophyte size 1 density

0 0 0 0 0 0 0 0 0 0 

Cyanophyte size 1 biomass

0 0 0 0 0 0 0 0 0 0 

Gomphosphaeriadensity

0 0 0 0 0 0 1,500,000 0 0 15,020,000 

Gomphosphaeria biomass

0 0 0 0 0 0 21 0 0 210 

Microcystis density

0 0 0 0 0 0 0 0 3,313,000 0 

Table B4. Phytoplankton density and biomass, Crystal Lake Reservoir--Continued

Date

9-4-97 9-4-97 9-4-97 9-11-97 7-14-98 7-21-98 8-4-98 8-10-98 8-18-98 9-1-98 

1’ below surface

3’ above 

bottom At 30’ 1' below surface
APPENDIX B 15

Microcystis biomass

0 0 0 0 0 0 0 0 47 0 

Bacillariophyta

Achnanthes density

160,000 0 0 0 0 0 0 0 0 0 

Achnanthes biomass

64 0 0 0 0 0 0 0 0 0 

Centrales size 1 density

0 0 0 0 0 0 0 80,000 0 0 

Centrales size 1 biomass

0 0 0 0 0 0 0 92 0 0 

Centrales size 2 density

1,060,000 650,000 80,000 600,000 0 0 0 0 0 0 

Centrales size 2 biomass

2,100 1,300 160 1,200 0 0 0 0 0 0 

Centrales size 3 density

0 0 10,000 0 0 0 0 0 0 0 

Centrales size 3 biomass

0 0 170 0 0 0 0 0 0 0 

Cyclotella density 0 0 0 0 230,000 0 0 0 120,000 550,000 Cyclotella biomass 0 0 0 0 270 0 0 0 140 650 Fragilaria density 4,490,000 3,630,000 1,130,000 2,490,000 810,000 710,000 830,000 590,000 1,030,000 690,000 Fragilaria biomass

6,500 5,300 1,600 3,600 1,200 1,000 1,200 860 1,500 1,000 

Melosira density 0 0 0 0 40,000 0 110,000 0 0 0 Melosira biomass 0 0 0 0 33 0 90 0 0 0 Pennales size 3 density

0 0 10,000 0 0 0 0 0 0 0 

Pennales size 3 biomass

0 0 9.8 0 0 0 0 0 0 0 

Stephanodiscus density

0 0 0 0 0 240,000 80,000 20,000 0 0 

Stephanodiscusbiomass

0 0 0 0 0 790 260 66 0 0 

Pyrrophyta

Ceratium density 0 0 0 0 0 0 0 20,000 0 0 Ceratium biomass 0 0 0 0 0 0 0 0.8 0 0 

Euglenophyta

Table B4. Phytoplankton density and biomass, Crystal Lake Reservoir--Continued

Date

9-4-97 9-4-97 9-4-97 9-11-97 7-14-98 7-21-98 8-4-98 8-10-98 8-18-98 9-1-98 

1’ below surface

3’ above 

bottom At 30’ 1' below surface
16 WATER QUALITY OF FOUR RESERVOIRS Trachelomonas size 1 density 0 0 0 0 0 0 0 0 0 0 

Trachelomonas size 1 biomass 0 0 0 0 0 0 0 0 0 0 Trachelomonas size 2 density 0 0 0 0 0 0 0 0 0 20,000 Trachelomonas size 2 biomass 0 0 0 0 0 0 0 0 0 83 

Colorless Flagellates Flagellate size 1 density 0 0 0 0 0 60,000 0 0 0 0 

Flagellate size 1 biomass

0 0 0 0 0 9.0 0 0 0 0 

Flagellate size 2 density

0 0 0 0 0 10,000 20,000 0 0 0 

Flagellate size 2 biomass

0 0 0 0 0 4.2 8.4 0 0 0 

Flagellate size 3 density

0 0 0 0 10,000 0 0 0 1,270,000 0 

Flagellate size 3 biomass

0 0 0 0 1.1 0 0 0 140 0 

Flagellate size 4 density

0 0 0 0 0 0 0 0 0 0 

Flagellate size 4 biomass

0 0 0 0 0 0 0 0 0 0 

Flagellate size 5 density

0 0 0 0 0 0 0 0 0 0 

Flagellate size 5 biomass

0 0 0 0 0 0 0 0 0 0 

Ciliates

Ciliate size 2 density

0 0 0 0 0 0 0 10,000 0 0 

Ciliate size 2 biomass

0 0 0 0 0 0 0 42 0 0 

Ciliate size 4 density

0 0 0 0 0 0 0 0 0 10,000 

Ciliate size 4 biomass

0 0 0 0 0 0 0 0 0 210 

Ciliate size 7 density

0 0 0 0 0 0 0 0 0 0 

Table B4. Phytoplankton density and biomass, Crystal Lake Reservoir--Continued

Date

9-4-97 9-4-97 9-4-97 9-11-97 7-14-98 7-21-98 8-4-98 8-10-98 8-18-98 9-1-98 

1’ below surface

3’ above 

bottom At 30’ 1' below surface
APPENDIX B 17

Ciliate size 7 biomass

0 0 0 0 0 0 0 0 0 0 

Rotifers

rotifer size 1 density

0 0 0 0 10,000 0 0 0 0 0 

rotifer size 1 biomass

0 0 0 0 230 0 0 0 0 0 

Ameba

Ameba density 0 0 0 0 0 10,000 10,000 0 0 0 Ameba biomass 0 0 0 0 0 3.8 3.8 0 0 0 

Table B4. Phytoplankton density and biomass, Crystal Lake Reservoir--Continued

Date

9-4-97 9-4-97 9-4-97 9-11-97 7-14-98 7-21-98 8-4-98 8-10-98 8-18-98 9-1-98 

1’ below surface

3’ above 

bottom At 30’ 1' below surface