Water Quality in the

Upper Colorado River Basin

Colorado, 1996–98

U.S. Department of the Interior

U.S. Geological Survey

Circular 1214
POINTS OF CONTACT AND ADDITIONAL INFORMATION

Front cover: Maroon Creek in the Elk Mountains above Aspen, Colorado. (Photograph by Michael Collier. )

Back cover: Left, Drilling sampling well (photograph by Lori Apodaca); center, sampling the Colorado River near 

Dotsero (photograph by Norman Spahr); right, collecting invertebrate samples (photograph by Jeffrey Deacon). 

The companion Web site for NAWQA summary reports:

http://water.usgs.gov/nawqa/

Upper Colorado River Basin contact and Web site:

USGS State Representative

U.S. Geological Survey

Water Resources Division

Denver Federal Center

Building 53, MS 415

Lakewood, CO 80225

e-mail: dc_co@usgs.gov

http://co.water.usgs.gov

National NAWQA Program:

Chief, NAWQA Program

U.S. Geological Survey

Water Resources Division

12201 Sunrise Valley Drive, M.S. 413

Reston, VA 20192

http://water.usgs.gov/nawqa/

River Basin Assessments

Albemarle-Pamlico Drainage Basin (Circular 1157)

Allegheny and Monongahela River Basins (Circular 1202)

Apalachicola-Chattahoochee-Flint River Basin (Circular 1164)

Central Arizona Basins (Circular 1213)

Central Columbia Plateau (Circular 1144)

Central Nebraska Basins (Circular 1163)

Connecticut, Housatonic and Thames River Basins (Circular 1155)

Eastern Iowa Basins (Circular 1210)

Georgia-Florida Coastal Plain (Circular 1151)

Hudson River Basin (Circular 1165)

Kanawha-New River Basins (Circular 1204)

Lake Erie-Lake Saint Clair Drainages (Circular 1203)

Las Vegas Valley Area and the Carson and Truckee River Basins

(Circular 1170)

Lower Illinois River Basin (Circular 1209)

Long Island - New Jersey Coastal Drainages (Circular 1201)

Lower Susquehanna River Basin (Circular 1168)

Mississippi Embayment (Circular 1208)

Ozark Plateaus (Circular 1158)

Potomac River Basin (Circular 1166)

Puget Sound Basin (Circular 1216)

Other NAWQA summary reports

Red River of the North Basin (Circular 1169)

Rio Grande Valley (Circular 1162)

Sacramento River Basin (Circular 1215)

San Joaquin-Tulare Basins (Circular 1159)

Santee River Basin and Coastal Drainages (Circular 1206)

South-Central Texas (Circular 1212) 

South Platte River Basin (Circular 1167)

Southern Florida (Circular 1207)

Trinity River Basin (Circular 1171)

Upper Mississippi River Basin (Circular 1211)

Upper Snake River Basin (Circular 1160)

Upper Tennessee River Basin (Circular 1205)

Western Lake Michigan Drainages (Circular 1156)

White River Basin (Circular 1150)

Willamette Basin (Circular 1161)

National Assessments

The Quality of Our Nationís WatersóNutrients and Pesticides (Circular 1225)
U.S. GEOLOGICAL SURVEY CIRCULAR

Water Quality in the Upper Colorado River 

Basin, Colorado, 1996ñ98

1214

By Norman E. Spahr, Lori E. Apodaca, Jeffrey R. Deacon, Jeffrey B. Bails, 

Nancy J. Bauch, C. Michelle Smith, and Nancy E. Driver
Library of Congress Cataloging-in-Publications Data

The use of firm, trade, and brand names in this report is for identification purposes only and

does not constitute endorsement by the U.S. Government.

Free on application to the

U.S. Geological Survey

Information Services

Box 25286 Federal Center

Denver, CO 80225

Or call: 1-888-ASK-USGS

U.S. DEPARTMENT OF THE INTERIOR

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director

2000

Water quality in the Upper Colorado River Basin, Colorado, 1996–98 / by Norman E. Spahr...[et al.].

p. cm. -- (U.S. Geological Survey Circular ; 1214)

Includes bibliographical references.

ISBN 0-607-95424-8 (alk. paper)

1. Water quality--Colorado River Watershed (Colo.-Mexico) I. Spahr, Norman E. II. Geological Survey 

(U.S.) III. Series.

TD224.9 W38 2000

363.739’42’097913--dc21

00-049454
CONTENTS

Contents III

NATIONAL WATER-QUALITY ASSESSMENT PROGRAM............................................................... IV

SUMMARY OF MAJOR FINDINGS.................................................................................................... 1

Stream and river highlights ........................................................................................................... 1

Ground-water highlights................................................................................................................ 2

INTRODUCTION TO THE UPPER COLORADO RIVER BASIN ....................................................... 3

MAJOR FINDINGS ............................................................................................................................. 6

Urban Development is a Water-Quality Issue Within the Southern Rocky Mountains.................. 6

NATIONAL PERSPECTIVEóBiological measures indicate that urban sites in the UCOL

are less degraded when compared to other urban sites nationally............................................ 8

NATIONAL PERSPECTIVEóRadon concentrations in UCOL ground water were

generally higher than other areas of the Nation......................................................................... 9

The Quality of Streams and Rivers is Affected by Historical Mining Activities .............................. 11

NATIONAL PERSPECTIVEóTrace elements in streambed sediments of the UCOL

were often greater than concentrations found at other sites nationally...................................... 12

Water-Quality Characteristics of Agricultural Areas ..................................................................... 15

NATIONAL PERSPECTIVEóHerbicides commonly detected in the UCOL were also

 commonly detected in other agricultural areas nationally ......................................................... 17

NATIONAL PERSPECTIVEóNitrogen concentrations at the UCOL agricultural sites

 were greater than concentrations for many agricultural sites nationwide ................................. 18

NATIONAL PERSPECTIVEóBiological measures indicate that UCOL agricultural and

Colorado Plateau mixed land use sites rank among the more degraded sites nationally.......... 19

STUDY UNIT DESIGN ....................................................................................................................... 21

GLOSSARY ........................................................................................................................................ 23

REFERENCES ................................................................................................................................... 25

APPENDIXóWATER-QUALITY DATA FROM THE UPPER COLORADO RIVER BASIN IN A 

NATIONAL CONTEXT........................................................................................................................ 28
NATIONAL WATER-QUALITY ASSESSMENT PROGRAM

IV National Water-Quality Assessment Program 

1991–95

1994–98

1997–2001

Not yet scheduled

High Plains Regional

Ground Water Study, 

1999–2004

NAWQA Study Units— 

Assessment schedule

Upper Colorado River Basin

THIS REPORT summarizes major findings about water quality in the Upper Colorado River Basin that emerged 

from an assessment conducted between 1996 and 1998 by the U.S. Geological Survey (USGS) National WaterQuality Assessment (NAWQA) Program. Water quality is discussed in terms of local and regional issues and 

compared to conditions found in all 36 NAWQA study areas, called Study Units, assessed to date. Findings are also 

explained in the context of selected national benchmarks, such as those for drinking water quality and the 

protection of aquatic organisms. The NAWQA Program was not intended to assess the quality of the Nationís 

drinking water, such as by monitoring water from household taps. Rather, the assessments focus on the quality of 

the resource itself, thereby complementing many ongoing Federal, State, and local drinking-water monitoring 

programs. The comparisons made in this report to drinking-water standards and guidelines are only in the context 

of the available untreated resource. Finally, this report includes information about the status of aquatic communities and the condition of instream habitats as elements of a complete water-quality assessment.

Many topics covered in this report reflect the concerns of officials of State and Federal agencies, water-resource 

managers, and members of stakeholder groups who provided advice and input during the Upper Colorado River 

Basin assessment. Basin residents who wish to know more about water quality in the areas where they live will find 

this report informative as well. 

THE NAWQA PROGRAM seeks to improve scientific and public understanding of water quality in the Nationís 

major river basins and ground-water systems. Better understanding facilitates effective resource management, 

accurate identification of water-quality priorities, and successful development of strategies that protect and 

restore water quality. Guided by a nationally consistent study design and shaped by ongoing communication 

with local, State, and Federal agencies, NAWQA assessments support the investigation of local issues and trends 

while providing a firm foundation for understanding water quality at regional and national scales. The ability to 

integrate local and national scales of data collection and analysis is a unique feature of the USGS NAWQA 

Program.

The Upper Colorado River Basin is one of 51 water-quality assessments initiated since 1991, when the U.S. 

Congress appropriated funds for the USGS to begin the NAWQA Program. As indicated on the map, 36 

assessments have been completed, and 15 more assessments will conclude in 2001. Collectively, these assessments 

cover about one-half of the land area of the United States and include water resources that are available to more 

than 60 percent of the U.S. population.
Summary of Major Findings 1

SUMMARY OF MAJOR FINDINGS

UTAH COLORADO

UPPER

COLORADO

RIVER BASIN

Forest

 Rangeland

Barren land 

and tundra

 Agriculture

Urban

Water

PERCENTAGE

OF TOTAL AREA

AREA, IN

SQUARE MILES

0 20 40 60

2,0006,000

10,000

0 20 40 60 MILES

0 20 40 60 KILOMETERS

38o

39o

40o

108o

109o

107o

106o

EXPLANATION

Physiographic

province

boundary

Southern Rocky

Mountains

Physiographic

Province

Colorado Plateau

Physiographic Province

Denver

Colorado

River

Land use from Fegeas and others (1983) and Hitt (1995).

Small Streams Major 

Rivers Agri- Urban Mining culture

Colorado Plateau

Nitrate2

Trace Elements4

Outlet of

Study

Unit

Selected Indicators of Stream-Water Quality

a

Pesticides1

1Insecticides, herbicides, and pesticide metabolites, sampled in water.

4Selenium and metals (such as cadmium, lead, and zinc), sampled in water.

Percentage of samples with concentrations greater than or 

equal to health-related national guidlines for drinking water,

protection of aquatic life, or contact recreation

Percentage of samples with concentrations less than health-related

national guidelines for drinking water, protection of aquatic life, or 

contact recreation

Percentage of samples with no detection (a Percentage is 1 or less

and may not be clearly visible)

Not assessed

Total 

 Phosphorus3

2Nitrate (as nitrogen), sampled in water.

Southern Rocky

Mountains

Major 

Rivers

Small 

Streams

3Total phosphorus, sampled in water.

Stream and River Highlights

Streams and rivers in the Upper Colorado River 

Basin (UCOL) are very different in the two major 

physiographic provinces. In general, streams within 

the Southern Rocky Mountains are characterized by 

lower sediment and dissolved-solids concentrations, 

cooler temperatures, and somewhat higher gradients 

than streams in the Colorado Plateau. Sediment, salinity, and nutrient (nitrogen and phosphorus) concentrations increase along the major rivers as the water flows 

from the upstream areas in the Southern Rocky Mountains down through the Colorado Plateau. 

Coupled with the general differences due to physiography and geology are the effects of different land 

uses. Recreation and urban development are becoming 

major land-use issues throughout the basin, precious 

metal mining was historically prevalent in the Southern Rocky Mountains, and intensive agriculture is 

located in the valleys of the Colorado Plateau. 

Most of the streams and rivers sampled within the 

UCOL met State and Federal water-quality guidelines. 

Major exceptions to this statement were trace-element 

concentrations in some streams in the Southern Rocky 

Mountains and selenium concentrations in some streams in 

the Colorado Plateau.

ï In the Southern Rocky Mountains, concentrations of 

nutrients (nitrogen and phosphorus) were generally low 

but were greater in urban streams than in streams in 

areas with minimal development (p. 6). 

ï Urban streams in the Southern Rocky Mountains had 

greater amounts of algae and a change in the invertebrate 

community from pollution-sensitive insects to pollutiontolerant insects compared to streams in areas with minimal development (p. 6ñ7). Similarly, in some mining 

areas of the Southern Rocky Mountains, the invertebrate 

community was also composed of pollution-tolerant 

insects, indicating more degraded sites (p. 13). 

The Upper Colorado River Basin (UCOL) of the National 

Water-Quality Assessment (NAWQA) Program includes the 

17,800-square-mile drainage basin of the Colorado River 

upstream from the Colorado-Utah State line. The study 

area is almost equally divided between the Southern 

Rocky Mountains and the Colorado Plateau Physiographic 

Provinces. Population in the basin is approximately 

308,000. The major use of water is irrigation, but 

transmountain diversions provide water to more than 

1 million people in the eastern part of Colorado (outside of 

the study area). 
 2 Water Quality in the Upper Colorado River Basin

Urban Urban Rangeland Forest

Shallow

Ground Water

Bacteria

Nitrate

Radon

Trace 

 Elements

Pesticides

Volatile

 Organics

Supply Wells

Percentage of samples with concentrations greater than

or equal to health-related national guidelines for drinking 

water

Percentage of samples with concentrations less than

health-related national guidelines for drinking water

Percentage of samples with no detection

Selected Indicators of Ground-Water Quality

ï Concentrations of trace elements, such as cadmium, 

zinc, copper, and lead, in streambed sediments in 

many historical mining areas were greater than 

guidelines for the protection of aquatic life 

(p. 11ñ12).

ï Pesticides were commonly detected in streams in 

agricultural areas of the Colorado Plateau during the 

growing season; however, the concentrations were 

typically low. Pesticide concentrations that exceeded 

guidelines for the protection of aquatic life were 

detected in only 5 of 90 samples (p. 16). Not all 

detected pesticides have established guidelines.

ï The herbicides atrazine and alachlor were detected 

in more than one-half of the water samples collected 

in agricultural areas of the Colorado Plateau. These 

compounds, commonly used for weed control in 

corn, were also commonly detected in agricultural 

areas nationwide (p. 17). 

ï Nutrient and suspended-sediment concentrations in 

streams in the Colorado Plateau were typically 

greater than concentrations found in streams in other 

areas of the UCOL (p. 18ñ19). These concentrations 

can generally be associated with a more degraded 

status of algae, invertebrates, and fish (p. 19). 

 Major Influences on Streams and Rivers

ïUrban development

ïAbandoned/inactive mines

ïAgricultural return flows

Ground-Water Highlights

Historical ground-water-quality data for the UCOL 

are limited. The studies completed in the UCOL by 

NAWQA provide baseline information that can be 

used for identifying future water-quality changes. With 

the exception of radon, ground-water quality in the 

urban areas of the Southern Rocky Mountains generally met Federal and State standards for drinking 

water. The presence of a few elevated nitrate concentrations, a few pesticides, and generally low concentrations of volatile organic compounds indicate some 

influence on the quality of ground water from human 

activities. Bacteria were detected in ground-water 

samples and can occur naturally or indicate human 

influences. 

ï A concentration of nitrate greater than the U.S. Environmental Protection Agency (USEPA) drinkingwater standard was found in 1 of 57 shallow groundwater samples collected in urban land-use settings 

(p. 8).

ï Ground water in urban areas recharged in the late 

1980s or 1990s tends to have higher concentrations of 

nitrate than ground water recharged before the 1980s 

(p. 10).

ï Pesticides and volatile organic compounds were 

detected infrequently and generally at concentrations 

less than drinking-water standards. In only one sample, 

dichloromethane and tetrachloroethene, which are solvents, were detected at concentrations greater than 

their drinking-water standards (p. 10). Low concentrations of methyl tert-butyl ether (MTBE), a gasoline 

additive, were detected in shallow ground water in four 

of the five urban areas sampled (p. 9).

ï Total coliform bacteria were detected in 21 percent of 

the shallow ground-water samples collected in urban 

areas in the Southern Rocky Mountains; none of the 

samples contained the potentially pathogenic Escherichia coli (E. coli) bacteria (p. 10).

ï Radon, a naturally occurring radioactive gas, was 

detected in all wells sampled in urban areas in the 

Southern Rocky Mountains. Concentrations were 

greater than the proposed USEPA drinking-water standard of 300 picocuries per liter. Currently (2000), 

radon in drinking water is not regulated; however, if a 

new drinking-water regulation is implemented, treatment of drinking water for radon may be required in 

the UCOL (p. 9).

 Major Influences on Ground Water

ïUrban development in the Southern Rocky Mountains

ïNatural background conditions
 Introduction to the Upper Colorado Basin 3

INTRODUCTION TO THE UPPER COLORADO RIVER BASIN

GARFIELD

MESA

MONTROSE

OURAY

HINSDALE

SAGUACHE

GUNNISON

PITKIN

EAGLE

ROUTT

GRAND

RIO BLANCO

SUMMIT

GRAND

DELTA

Delta

Montrose

Ouray

Glenwood Springs

Gunnison

Crested Butte

Vail

Silverthorne

Breckenridge

Fraser Winter Park/

Basin boundary

County boundary

EXPLANATION

Physiographic 

province boundary

Aspen

Colorado River

Grand

Junction

Southern

Rocky

Mountains

Physiographic

Province

Colorado

Plateau

Physiographic

Province

Grand

Lake

106o

109o

108o

40o

107o

38

0 20 40 60 MILES

0 20 40 60 KILOMETERS

o

39o

Uncompahgre River

Gunnison

River

CONT

NI ENTAL

DIVID E

Cool and clear mountain streams are present 

in the forested areas of the Southern Rocky 

Mountains. (Photograph by Scott Mize, 

U.S. Geological Survey.)

high plateaus bordered by steep 

cliffs along valleys in the west. 

Because of differences in altitude 

of about 10,000 feet from east to 

west, the climate ranges from 

alpine conditions to semiarid/arid 

conditions. Precipitation ranges 

from 40 inches or more per year at 

high elevations in the eastern part 

of the basin to less than 10 inches 

per year at low elevations in the 

western part of the basin (fig. 2). 

The Upper Colorado River Basin 

encompasses about 17,800 square 

miles. The primary river, the Colorado River, originates in the mountains of central Colorado and flows 

about 230 miles southwest into 

Utah. The basin is composed of 

two physiographic provinces: the 

Southern Rocky Mountains and the 

Colorado Plateau (fig. 1). The 

topography varies from rugged 

mountainous regions in the east to 

Snowmelt Runoff Dominates 

the Streamflow in Many 

Areas of the UCOL

The amount of water derived 

from the winter snowpack generally determines the magnitude and 

quality of streamflow for the 

UCOL. Streamflows are typically 

highest in the spring and lowest 

Streams have been affected by runoff and discharge from past and present mined areas. 

(Photograph by Jeffrey B. Bails, U.S. Geological Survey.)

Urban development is occurring in areas of the 

Southern Rocky Mountains. (Photograph by 

Scott Mize, U.S. Geological Survey.)

Figure 1. The combinations of physiography and land use produce different environments found in the UCOL.

Physiographic provinces from Fenneman, 1946.

The Colorado Plateau contains warm, saline 

streams that drain sedimentary geologic settings. 

(Photograph by Jeffrey Deacon, U.S. Geological 

Survey.)

Agriculture is a major land use in the 

Colorado Plateau. (Photograph by 

Scott Mize, U.S. Geological Survey.)
4 Water Quality in the Upper Colorado River Basin

0 20 40 60 MILES

0 20 40 60 KILOMETERS

38o

39o

40o

106o

107o

108o

109o

0 to 10

10 to 20

20 to 30

30 to 40

greater than 40

Precipitation, in inches

EXPLANATION

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

CUBIC FEET PER SECOND

 DAILY MEAN STREAMFLOW, IN

Mean of historical daily streamflow 1970-95

Daily mean streamflow

Range (minimum to maximum) of historical data 1970-95

Colorado River at State LIne

Oct Jan Apr July Oct Jan Apr July Oct Oct Jan Apr July

WATER YEAR 1996 WATER YEAR 1997 WATER YEAR 1998

Surface water

Ground water

COMMERCIAL

PRIVATEDOMESTICSUPPLY

INDUSTRIAL

AND MINING

LIVESTOCK

POWER

PUBLIC 

SUPPLY

IRRIGATION

TOTAL

3,800

0

20

40

60

80

100

WATER WITHDRAWALS,

IN MILLIONS OF GALLONS PER DAY

ESTIMATED WATER WITHDRAWALS IN 1995

~

~

~

~

100

PERCENTAGE OF TOTAL

WATER WITHDRAWALS

2

1

(38) Within basin population served,

in thousands

(38)

(239)

0

during the winter (fig. 3). The 

primary data-collection period for 

the UCOL study was water years 

1996ñ98. Streamflow during water 

years 1996ñ97 was above average 

for most of the basin. Streamflow 

during water year 1998 was about 

average. High streamflows will 

dilute many water-quality constituents, resulting in lower concentrations. Suspended sediment and 

constituents associated with sediment may have larger concentrations during periods of high flow 

than during low flow. 

Irrigation is the Principal 

Water Use Within the UCOL 

Irrigation accounts for 97 percent of the water use in the UCOL 

(fig. 4). Ninety-nine percent of the 

water used in the Study Unit is 

derived from surface-water sources 

(U.S. Geological Survey, 1995). 

Ground water accounts for 1 percent of water use and is an important resource in remote and rural 

areas where the water is used primarily for domestic purposes.

Water diverted eastward from 

the UCOL, through transmountain 

diversions, is used by many municipalities in the eastern plains of 

Colorado. This diverted water from 

the UCOL constitutes about 35 percent of the water supply for the city 

of Denver (Denver Water Department, 1999) and about 65 percent 

of the water supply for Colorado 

Springs (Scott Campbell, Colorado Springs Water Utility, oral 

commun., 2000). In addition, the 

Colorado Big Thompson project, 

using water diverted from the 

UCOL, provides complete or 

partial supply for more than 30 cities and towns in northern Colorado 

(Northern Colorado Water Conservancy District, 2000). Transmountain diversions can affect the water 

quality in the basin because the 

diversions can account for a substantial portion of the local streamflow in upstream areas. In addition, 

the diverted water commonly has 

low salinity that is no longer available to dilute more mineralized 

water in the downstream part of the 

Study Unit. Figure 2. Average annual precipitation 

(1951ñ80) in the UCOL (Colorado 

Climate Center, 1984).

Figure 3. Streamflows in the UCOL were above average in water 

years 1996 and 1997. Water year 1998 streamflow was near 

average.

Figure 4. Water use in the basin is primarily derived from surface water; 

however, ground water is used for some domestic and public water 

supplies. Transmountain diversions to eastern Colorado from the UCOL 

accounted for about 451 million gallons per day in 1995 (Upper Colorado 

River Commission, 1999).
Introduction to the Upper Colorado River Basin 5 

0 20 40 60 MILES

0 20 40 60 KILOMETERS

Shale

Sandstone

Carbonate

Volcanic and intrusive

Igneous and metamorphic

Undivided sedimentary

Geology

EXPLANATION

38o

39o

109o 108o

40o

107o

106o

Water Quality is Influenced 

by Geologic Factors

The underlying bedrock in the 

Study Unit is made up of crystalline and sedimentary rocks (fig. 5). 

Alluvium consisting of stream, 

landslide, terrace, and glacial 

deposits is present in valleys 

throughout the basin. Weathering 

of the different geologic units 

affects water-quality conditions in 

the basin. The sedimentary, igneous, and metamorphic rocks contribute material such as salts and 

trace elements to the streams. High 

concentrations of some materials, 

particularly salts, are derived from 

the sedimentary rocks, which are 

more common in the western part 

of the basin. Also, highly mineralized areas in the upper basin contribute trace metals to surface and 

ground water. Selenium occurs naturally in the shale bedrock of the 

middle and lower reaches of the 

basin and is present in surface and 

ground water. In addition, mineral 

hot springs located primarily in 

carbonate rock units in the northcentral part of the basin contribute 

about 13 percent of the total salt 

load at the outlet of the UCOL 

(U.S. Department of the Interior, 

1995; Butler, 1996).

Water Quality is Influenced 

by Land Use

The UCOL study was designed 

to investigate land-use influences 

on water quality (see ìStudy Unit 

Design,î page 21, for details). 

Urban development, mining, and 

agricultural were the three primary 

land uses investigated in the 

UCOL.

Urban development has the 

potential to affect the quality of 

surface and ground water by adding nutrients, bacteria, pesticides, 

hydrocarbons, trace elements, and 

salts from point and nonpoint 

sources and by changes to the natural landscape. Urban land use 

accounts for only 1 percent in the 

UCOL, which has a population of 

about 308,000 people (Bureau of 

the Census, 1999). By the year 

2020, the population is projected to 

increase to more than 500,000 

(Colorado Department of Local 

Affairs, 2000). Resident population 

increases do not reflect development and services for vacation 

properties. There are large seasonal 

fluctuations in nonresident populations within the basin due to recreational activities. During the 1996ñ

97 ski season, more than 9 million 

skiers visited ski areas within the 

UCOL (Colorado Ski Country 

USA, 2000). Effects on water quality from urban development are 

evident in some communities in the 

Southern Rocky Mountains.

Lode and placer mining, a historically significant land use in the 

UCOL, was common throughout 

the Southern Rocky Mountains. 

Streams and ground water have 

been affected by point-source mine 

discharge and nonpoint-source runoff from mined areas. 

Areas of intensive agriculture 

are located primarily in the Colorado Plateau. Salinity, sediment, 

nutrients, pesticides, and selenium 

and other trace elements are common constituents in agricultural 

runoff. These constituents can have 

an adverse effect on the surface 

water, ground water, and aquatic 

life.

Topography representative of the Southern Rocky 

Mountains. (Photograph by Jeffrey Deacon, 

U.S. Geological Survey.)

Figure 5. The bedrock geology within the UCOL 

changes from predominately igneous, metamorphic, 

and volcanic rock types in the eastern and central 

areas to predominantly sedimentary rock types in the 

western areas (Tweto, 1979; Green, 1992).
6 Water Quality in the Upper Colorado River Basin

MAJOR FINDINGS

109o

108o

107o

106o

39o

38o

40o

EXPLANATION

Streambed-sediment 

sampling site and number

in mining area

Streambed-sediment

sampling site and number

in non-mining area

Multiple streambedsediment sampling

sites and numbers

in mining area

Stream monitoring site

Urban land use

Agriculture land use

County boundary

Physiographic province 

boundary 0 20 40 60 MILES

0 20 40 60 KILOMETERS

Blue River

Eagle River

Roaring Fork R.

ColoradoRiver

Uncompahgre R.

Grand

Junction

Delta

Montrose Gunnison

Winter

Park/

Fraser

Vail

Crested

Butte

Colorado Plateau

Physiographic Province

Southern Rocky Mountains

Physiographic Province

Grand Valley

(23 agriculture

synoptic sites)

Uncompahgre Valley

(20 agriculture

synoptic sites)

Colorado River below

Baker Gulch (reference site)

French Gulch

Silverthorne

Gore Creek

Eagle

County Summit

County

Mesa

County

Montrose

County

Delta

County

Reed Wash

Colorado River

near Cameo

Gunnison River

near Grand Junction

Colorado River

near ColoradoUtah State line

Dry Creek

1

3

2

4

6 5

7

8-14

15 16 17

19 18

20 21

23

22

24

25

26 27 28

29

30

31

32

33

34 35 36

37

Gunnison River

East River

Urban Development is a 

Water-Quality Issue Within 

the Southern Rocky 

Mountains 

Recreation in the mountains of 

Colorado is becoming a significant 

land-use activity in many areas. 

Urban development and the infrastructure to support recreation have 

increased substantially in the last 

decade. Between 1990 and 1997, 

the population increase in Summit 

and Eagle Counties exceeded 40 

percent (http://www.colorado.

edu/libraries/govpubs/colonumb/ 

counties.htm). In addition to resident population increases, seasonal population fluxes due to 

recreation are large. These temporary population increases occur in 

winter during periods of extreme 

low flow and minimal dilution in 

rivers and streams. 

Although urban development 

may be only a small percentage of 

total watershed area, development 

and transportation systems tend to 

be adjacent to riparian areas in 

mountainous terrain (fig. 6). This 

land-use pattern has placed human 

populations in locations that have 

the greatest effects on the quality of 

the water resources. Surface- and 

ground-water studies were implemented to investigate the waterquality issues in urban areas of the 

Southern Rocky Mountains.

Surface-water studies investigated the effects of urban land 

use. Two stream-monitoring sites 

were located in areas of urban 

development (fig. 6). The Gore 

Creek site is downstream from 

Vail, and the East River site is 

downstream from Crested Butte. 

Development in Vail is approaching build-out, whereas there is 

potential for large increases of 

development in the Crested Butte 

area. The Colorado River below 

Baker Gulch, a reference site with 

little urban development in the 

Southern Rocky Mountains, was 

also sampled monthly to provide a 

comparison with other sites. 

Nutrient concentrations at 

sites in areas of urban development were greater than concentrations at the reference site.

Concentrations of nitrite plus 

nitrate and total phosphorus were 

slightly elevated at Gore Creek and 

East River compared to reference 

concentrations (fig. 7). Concentrations for nitrate were below the 

10-mg/L Colorado instream standard at all three sites. Un-ionized 

ammonia concentrations, computed 

from dissolved ammonia, pH, and 

temperature, did not exceed State 

instream standards. Dissolved and 

orthophosphate phosphorus concentrations were greater at Gore 

Creek than the other sites. Gore 

Creek and East River are not 

wastewater-effluent-dominated 

streams such as might be found in 

large metropolitan areas; however, 

small amounts of nitrogen and 

phosphorus can increase algal 

growth and eutrophication processes.

The amount of algae and the 

types of aquatic invertebrates 

(insects) are influenced by nutrient enrichment from urban 

sources. The amount of algae 

(algal biovolume) determined from 

algae samples collected in 1996 

and 1997 was largest in Gore Creek 

(fig. 8), where nutrient levels were 

higher. The percentage of the 

invertebrate community represented by pollution sensitive 

Figure 6. Sampling sites and study areas were selected 

to assess effects of urban, mining, and agricultural land uses on water quality.
Major Findings 7 

10

1

0.1

0.01

0.001

NITRITE AMMONIA

PLUS NITRATE

TOTAL

PHOSPHORUS PHOSPHORUS

DISSOLVED ORTHOPHOSPHATE

Colorado River 

below Baker Gulch

(reference site)

Gore Creek

(urban site)

East River

Maximum

Minimum

Median

Median less than

laboratory reporing level

CONCENTRATION, IN 

MILLIGRAMS PER LITER

(urban site)

0

0. 5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

Colorado

River below

Baker Gulch

(reference site)

East

River

(urban

site)

Gore

Creek

(urban 

site)

ALGAL BIOVOLUME, 

IN CUBIC CENTIMETERS PER SQUARE METER

0

1 0

2 0

3 0

4 0

5 0

6 0

7 0

Colorado

River below

Baker Gulch

(reference site)

East

River

(urban

site)

Gore

Creek

(urban

site)

Mayflies, Stoneflies, Caddisflies

Midges

MEDIAN PERCENT COMPOSITION

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

0.22

0.24

0.26

0.28

0

1,000

2,000

3,000

CONCENTRATION, IN 

MILLIGRAMS PER LITER

INSTANTANEOUS DISCHARGE, IN 

CUBIC FEET PER SECOND

WATER YEAR 1996 WATER YEAR 1997 WATER YEAR 1998

Instantaneous discharge

Nitrite plus nitrate East River

OCT JAN APR JULY OCT JAN APR JULY OCT JAN APR JULY OCT

insects 

(mayflies, stoneflies, and caddisflies) was greater at sites with less 

urban influence (Colorado River 

below Baker Gulch, fig. 8). The 

percentage of midges (insects generally tolerant of pollution) 

increased with increasing urban 

influence (East River and Gore 

Creek sites, fig. 8). Even though 

the percentage of midges was 

greater at Gore Creek, the invertebrate status of Gore Creek was less 

degraded than other urban sites in 

the NAWQA Program (p. 8). 

Nutrient concentrations were 

generally largest during winter.

Concentrations of nitrite plus 

nitrate and dissolved and total 

phosphorus were greatest during 

the late winter low-flow period 

prior to snowmelt runoff (fig. 9). 

With the onset of snowmelt runoff, 

nutrient concentrations were 

diluted. Algal uptake of nutrients 

during warm weather (JulyOctober) probably lower concentrations during the summer. With 

reduced dilution and diminished 

algal uptake, nutrient concentrations increase again during the winter low-flow period. 

Ground-water studies investigated the effects of urban land 

use on water in selected alluvial 

aquifers. Although many communities in the UCOL rely on surface 

water as their primary source of 

drinking water, a few mountain 

towns and many thousands of 

individual homes in the Southern 

Rocky Mountains use ground 

water as their primary water 

source. Effects of urban land use 

can be indicated by elevated concentrations of nitrate, detections of 

synthetic organic compounds (pesticides and VOCs), and bacteria.

Figure 8. Algal biovolume (the amount of algae) was greater at Gore Creek, 

which also has greater urban development. The percentage of mayflies, 

stoneflies, and caddisflies decreased, and the percentage of midges (indicative 

of more degraded water quality) increased with urban development. Sites shown 

in order of increasing urban development.

Figure 9. Nutrient concentrations were greatest during the late winter low-flow 

period prior to peak snowmelt runoff. This pattern was similar for total phosphorus 

at East River and for nitrite plus nitrate and total phosphorus at Gore Creek.

Figure 7. Concentrations of nitrite plus nitrate and total phosphorus were 

greater at sites with urban development (Gore Creek and East River) than at 

the reference site (Colorado River below Baker Gulch). Sites shown in order of 

increasing urban development. A log scale is used due to the large range of 

concentrations.
8 Water Quality in the Upper Colorado River Basin

Ground water was sampled from 

shallow monitoring wells in the 

Crested Butte, Gunnison, Silverthorne, Vail, and Winter Park/

Fraser areas (fig. 6). Domestic 

(household and private) and public 

supply drinking-water wells of various depths were also sampled in 

urban areas throughout the Southern Rocky Mountains. 

Some ground-water samples 

collected in urban areas contained elevated levels of nitrate.

Nutrients in ground water can originate from various natural sources 

(such as atmospheric deposition or 

dissolution of geologic materials); 

however, elevated concentrations 

in ground water are often related to 

human activities, such as effluent 

from septic systems or the application of fertilizers. Nitrate concentrations greater than the USEPA 

Maximum Contaminant Level 

(MCL) drinking-water standard of 

10 mg/L (U.S. Environmental Protection Agency, 1996) were 

detected in one sample collected 

from a shallow monitoring well in 

an urban area but in none of the 

drinking-water wells. Nutrient concentrations in undeveloped areas 

(determined from data from the 

20 NAWQA Study Units that 

began in 1991) indicate a national 

background concentration for 

nitrate of 2.0 mg/L (U.S. Geological Survey, 1999). The undeveloped areas are considered to be 

minimally affected by agriculture, 

urban development, or associated 

land uses. Twenty percent of the 

samples collected from monitoring 

wells (and none of the samples collected from drinking-water wells) 

contained nitrate concentrations 

greater than 2.0 mg/L. These findings indicate that portions of the 

Within the UCOL, there are changes in the algal and invertebrate communities in areas of urban development. Algal biovolume (amount of algae) and midges (insects considered more tolerant of degraded conditions) 

were greater at sites with urban development than sites with little urban development. However, with the exception of algal status at the Gore Creek site, biological indices for UCOL urban sites are in the lowest 25 percent 

of urban sites from other NAWQA Study Units. The Gore Creek watershed is more urbanized than the East 

River watershed, and the changes in the algal community reflect increased nutrient concentrations at this site, 

making it more typical of other urban sites nationally. The invertebrate and fish communities are ranked among 

the least degraded nationally at both UCOL urban sites. 

Explanation of Biological Rankings

The three selected biological indicators respond to 

changes in stream degradation. Degradation can 

result from a variety of factors that modify habitat or 

other environmental features such as land use, water 

chemistry, and flow. Algal status focuses on the 

changes in the percentage of certain algae in 

response to increasing siltation and often is positively 

correlated with higher nutrient concentrations in 

many regions of the Nation. Invertebrate status is the 

average of 11 invertebrate metrics that summarize 

changes in richness, tolerance, trophic conditions, 

and dominance associated with water-quality degradation. Fish status focuses on changes in the percentage of tolerant fish species that make up the total 

number of fish. "Tolerant" fish are reported to thrive 

in degraded water quality. For all indicators, higher 

values indicate degraded water quality.

Site name

Colorado River below Baker Gulch

(reference site)

East River 

(area of urban development)

Gore Creek

(area of urban development)

Algal Invertebrate Fish

status status status

Lowest 25 percent nationally, least degraded sites

Middle 50 percent nationally

EXPLANATION

Biological indicators

BIOLOGICAL MEASURES INDICATE THAT URBAN SITES IN

THE UCOL ARE LESS DEGRADED WHEN COMPARED TO

OTHER URBAN SITES NATIONALLY
Major Findings 9 

shallow ground-water system have 

been affected by urban land use, 

but these effects were not found in 

the deeper ground water used for 

drinking water.

Generally, low levels of pesticides and volatile organic compounds were detected in ground 

water from shallow alluvial aquifers in urban areas. Most agriculture (and pesticide use) in the basin 

occurs in the Colorado Plateau 

where ground-water studies were 

not conducted. The pesticides that 

were detected in the ground water 

sampled in the Southern Rocky 

Mountains were primarily herbicides used for controlling grasses 

and weeds in nonagricultural areas. 

Concentrations were very low (less 

than 0.1 μg/L) for most of the pesticides detected. Two herbicides, 

bromacil and prometon, were 

detected in urban areas at concentrations less than the USEPA drinking-water guidelines (U.S. 

Environmental Protection Agency, 

1996). 

Volatile organic compounds 

(VOCs) were detected in groundwater samples at generally low 

concentrations. The six most frequently detected VOCs were 

methyl tert-butyl ether (MTBE), 

tetrachloroethene, chloroform, 

1,1,1-trichloroethane, 1,2,4-trimethylbenzene, and dichloro-methane (fig. 10). MTBE, a 

gasoline additive, was detected in 

at least one well in four of the five 

urban areas where shallow ground 

water was sampled. In addition, 

Figure 10. VOCs were detected at low frequencies in monitoring and 

drinking-water wells sampled in the Southern Rocky Mountain 

Physiographic Province. With a few (3) exceptions, concentrations of 

VOCs were substantially less than water-quality standards.

Radon concentrations in alluvial aquifers of the UCOL are among the highest of all NAWQA ground-water 

samples nationwide (S.J. Ryker, USGS, written commun., 1999). Radon is a naturally occurring, colorless, odorless, radioactive gas derived from the decay of uranium. Radon has been identified as a human carcinogen and 

can enter a building from seepage of air through dirt floors, cracks in concrete floors or walls, floor drains, or 

through the use of water supplied from wells. A greater risk of exposure to radon exists in urban areas due to the 

prevalence of enclosed structures, such as basements, which can trap radon gas.

Though the USEPA does not currently (2000) regulate radon in drinking water, there is a proposed maximum 

contaminant level (MCL) of 300 picocuries per liter (pCi/L) for radon in drinking water (U.S. Environmental 

Protection Agency, 1999). Radon concentrations were greater than the proposed MCL for all wells sampled in 

the Southern Rocky Mountains. Higher radon concentrations were measured in the Winter Park/Fraser and 

Silverthorne areas. Igneous and metamorphic rocks, which can contain uranium-bearing minerals, are common 

rock types in these areas.

r

Ranking of ground-water radon concentrations

relative to all NAWQA ground-water studies

(data from multiple wells in indicated areas)

Greater than the 95th percentile

Between the 90th and 95th percentile

Between the 75th and 90th percentile

1,000 in at least 25 percent of samples

600 in at least 25 percent of samples

300 in at least 25 percent of samples

300 in fewer than 25 percent of samples

Study Units’ radon concentrations 

in ground water, in picocuries 

per liter (pCi/L)

EXPLANATION

RADON CONCENTRATIONS IN UCOL GROUND WATER WERE

GENERALLY HIGHER THAN OTHER AREAS OF THE NATION
10 Water Quality in the Upper Colorado River Basin

MTBE was detected in water from 

one municipal well. MTBE concentrations greater than the drinking-water lifetime health advisory 

of 20ñ40 μg/L (U.S. Environmental Protection Agency, 1997) were 

not detected. However, once 

MTBE enters the ground water, it 

is less vulnerable to decomposition 

and travels farther than other 

gasoline compounds (Squillace and 

others, 1996).

Tetrachloroethene is present in 

solvents for adhesives and is also a 

by-product of dry cleaning. Chloroform can occur naturally or result 

from the chlorination of drinking 

water. 1,1,1-Trichloroethane is 

present in solvents and cleaning 

agents. 1,2,4-Trimethylbenzene is 

present in petroleum by-products. 

Dichloromethane is predominantly 

used as a solvent in paint strippers 

and removers. Concentrations of 

dichloromethane and tetrachloroethene were greater than the 

USEPA drinking-water standard of 

5 μg/L at one site in Silverthorne.

Total coliform bacteria were 

detected in 21 percent of the 

ground-water samples collected 

in urban areas. Total coliform 

bacteria were detected only in samples collected from the shallow 

monitoring wells and in none of the 

water samples from drinking-water 

wells. Bacteria in ground water 

may occur naturally in soils or may 

be related to human or animal 

waste and, therefore, may be an 

indication of the sanitary quality of 

the water (Myers and Sylvester, 

1997). However, the presence of 

total coliform bacteria does not 

necessarily indicate the presence of 

potentially pathogenic bacteria 

such as Escherichia coli (E. coli), 

which was not detected in any of 

the samples. 

Figure 10. Volatile organic compounds were detected at low frequencies in 

monitoring and drinking-water wells sampled in the Southern Rocky Mountains. 

With a few exceptions (2 samples), concentrations of VOCs were substantially 

less than water-quality standards. All concentrations shown are greater than 

0 μg/L. (MCL, maximum contaminant level; HA, health advisory.)

Chlorofluorocarbons (CFCs) were used to determine the age 

of ground water

Shallow ground water, which is used for drinking water in part of the 

Southern Rocky Mountains, is generally young (less than 10 years old) 

and is more susceptible to contamination as a result of land-use practices. 

The age of the ground water refers to the time from when the water 

recharged, or entered, the aquifer to the time it was withdrawn from the 

aquifer. The presence of contaminants, if any, in ground water can reflect 

land-use conditions at the time of recharge. The age of the ground water 

was determined in five urban areas where water-quality samples were 

collected from shallow alluvial aquifers. The age of ground water at most 

of the sites sampled ranged from 0 to 10 years old. Ground-water ages of 

greater than 10 years were found in 7 of 25 wells. 

In the samples where CFC dates were obtained, four of the five nitrate 

concentrations greater than 2.0 mg/L were from recently recharged 

ground water (10 years or younger). This is an indication that current land 

use may be affecting water quality. Increasing urban development may 

add nitrate to the ground water from different sources, such as septic systems, application of fertilizers, and domestic animal wastes. Effects of 

increased urban development on ground-water resources are not extensive 

in the study area at present.

CONCENTRATION, IN MICROGRAMS PER LITER

CHLOROFORM

DICHLOROMETHANE

METHYL TERT-BUTYL ETHER

TETRACHLOROETHENE

1,1,1-TRICHLOROETHANE

1,2,4-TRIMETHYLBENZENE

0 5 10 15 20 25

0 50 100 150 200 250

FREQUENCY OF VOC DETECTION, IN PERCENT

Frequency of detection

MCL or HA

Concentration

Urban land use in the Southern Rocky Mountains, 

near Fraser, Colorado. (Photograph by Jeffrey B. 

Bails, U.S. Geological Survey.)
Major Findings 11 

ments in streambed sediment can 

be used to identify stream reaches 

affected by mining and can be 

used to determine sources of trace 

elements. The occurrence and 

distribution of trace elements were 

characterized by collecting 

streambed-sediment samples at 

29 sites in mining districts (fig. 6 

and table 1) and at 8 background 

(non-mining) sites in the Southern 

Rocky Mountains.

Concentrations of cadmium, 

copper, lead, and zinc in 

streambed sediment were high at 

some sites downstream from 

mining areas (Deacon and Driver, 

1999). Median concentrations of 

cadmium (Cd) and zinc (Zn) in 

samples from most mining districts 

exceeded the Canadian Sediment 

Quality Guidelines Probable Effect 

Level (PEL), which is a sediment 

guideline (fig. 11). The PEL 

defines the concentration level 

above which adverse effects to 

aquatic biota are predicted to occur 

The Quality of Streams and 

Rivers is Affected by 

Historical Mining Activities

Streams affected by mine drainage, from abandoned/inactive 

mines, are present throughout 

much of the Rocky Mountains of 

Colorado. Metal mining in the 

UCOL has been an important part 

of the economy of Colorado since 

the late 1800s. As a result, many 

streams in the upper part of the 

basin contain heavy metals and 

other toxic elements that affect 

stream-water quality. Knowledge 

of mine-drainage effects on a body 

of water is essential for assessing 

water quality with regard to human 

consumption, recreation, and 

aquatic life.

 Because of the potential exposure of aquatic organisms to trace 

elements in streambed sediment, 

trace-element concentrations in 

streambed sediment serve as an 

indicator of potential toxicity to 

aquatic life. Sampling trace elefrequently (Canadian Council of 

Ministers of the Environment, 

1999). National sediment concentration guidelines have not been 

established for the United States. 

Concentrations of copper and lead 

were also elevated and exceeded 

the PEL in several mining districts. 

The mining and mineralized areas 

of the UCOL generally result in 

higher trace-element concentrations in streambed sediment than 

are detected in other areas studied 

within the NAWQA Program 

(p. 12).

Collecting samples from several types of media provides a 

better understanding of trace elements in the environment. In 

addition to streambed sediment, 

which can store trace elements, the 

overlying stream water can also 

be a source of trace-element exposure to aquatic organisms. Because 

invertebrates are continuously 

exposed to water-quality conditions, these organisms integrate 

effects of contaminants over time 

and provide a measurement of 

water quality. Invertebrate indicators of streams contaminated by 

trace elements include reduced 

abundance and a shift in commuMining land use in the Southern Rocky 

Mountains. (Photograph by Jeffrey Deacon, 

U.S. Geological Survey.)

Table 1. Mining districts and sampling sites in the Southern Rocky Mountains 

Mining district1 River/Stream [site number(s) in 

figure 6]2

Aspen Hunter Creek (24)

Breckenridge Blue River, French Gulch, Swan River 

(7, 10, 11, 12, 13, 14, 15, 16, 17)

Climax Tenmile Creek (18)

Crested Butte Oh-Be-Joyful Creek, Coal Creek, 

Slate, East Rivers (25, 26, 27, 28)

Gilman Cross Creek, Eagle River (22, 23)

Lake City (Carson, Burrows, Sherman 

Districts) 

Lake Fork of the Gunnison River, 

Hensen Creek (31, 32)

Montezuma Peru Creek, Snake River (4, 5, 6)

Ouray (Red Mountain, Sneffels, 

Uncompahgre Districts) 

Canyon Creek, Red Mountain Creek, 

Uncompahgre River (33, 34, 35, 36, 

37)

Urad-Henderson South Fork of Williams Fork, 

Williams Fork (2, 3)

1Information from Davis and Streufert (1990).

2

Background (non-mining) sites 1, 8, 9, 19, 20, 21, 29, 30.
12 Water Quality in the Upper Colorado River Basin

nity composition from sensitive 

insects, such as mayflies, to more 

tolerant insects, such as midges. 

Lower mayfly abundance can be 

related to increased trace-element 

concentrations (Clements and 

Kiffney, 1995; Clements, 1994; 

Kiffney and Clements, 1994). 

Concentrations of trace elements in 

transplanted aquatic moss also provide information about the occurrence and bioavailability of trace 

elements (Carter and Porter, 1997). 

In order to assess the source(s) 

and environmental effects of trace 

elements, a more detailed study 

was conducted in the Blue River 

Basin; this study included the collection of water, streambed sediments, reservoir sediments, and 

aquatic moss samples and an 

assessment of the habitat and invertebrate communities. 

The median concentrations for cadmium, copper, lead, and zinc in streambed sediment from sites in the 

UCOL were higher than the median concentrations of the same trace elements sampled in other Study Units 

of the national NAWQA Program. The data available on trace elements include 541 samples from the 

NAWQA Study Units (Rice, 1999) and 37 samples from the UCOL. Mineralized areas and historical mining 

activities in the UCOL have resulted in higher concentrations of some trace elements in streams than those 

concentrations that typically are found in other parts of the United States.

Figure 11. Median concentrations of cadmium and zinc in streambed sediments were greater than the Canadian Probable 

Effect Level in most mining districts of the UCOL.

MEDIAN CONCENTRATION OF ZINC, 

IN MICROGRAMS PER GRAM

0

2,000

4,000

6,000

8,000

10,000

MEDIAN CONCENTRATION OF CADMIUM,

IN MICROGRAMS PER GRAM

10

20

30

40

50

60

Probable Effect Level is

0

Aspen

Breckenridge

Lake City

Montezuma

Gilman

Crested Butte

Climax

Ouray

Urad-Henderson

Background

Probable Effect Level is

315 micrograms per gram

Aspen

Breckenridge

Lake City

Montezuma

Gilman

Crested Butte

Climax

Ouray

Urad-Henderson

Background

3.5 micrograms per gram

CADMIUM ZINC

 

 0 .1

 

 1

 

 10

 

 100

 

 1,0 0 0

 

1 0,0 0 0

 1 0 0,0 0 0

MINIMUM

MEDIAN

MAXIMUM NATIONAL

UCOL

CADMIUM COPPER ZINC LEAD

CONCENTRATION, IN MICROGRAMS  PER GRAM

TRACE ELEMENTS IN STREAMBED SEDIMENTS OF THE UCOL

WERE OFTEN GREATER THAN CONCENTRATIONS DETECTED

AT OTHER SITES NATIONALLY
Major Findings 13 

cantly degraded. Farther downstream, where underground mine 

seepage contributes to surface runoff (site 6), zinc concentrations in 

the water, streambed sediment, and 

aquatic moss were high and the 

invertebrate communities were 

degraded. The most affected site 

along French Gulch was site 7, 

located near the confluence with 

the Blue River. 

Site 1, upstream from French 

Gulch on the Blue River, was characterized by lower zinc concentrations in water, moss, and sediment 

than downstream sites, indicating 

that the French Gulch basin is contributing zinc to the Blue River. 

Downstream from the confluence 

of French Gulch with the Blue 

River (site 8), concentrations of 

zinc in water, moss, and streambed 

sediment were higher than background levels but slightly lower 

than in French Gulch. Also at site 

8, brown trout livers had the highest concentrations of zinc of any 

sites sampled in the Southern 

Rocky Mountains (Deacon and 

Stephens, 1998). The invertebrate 

community in the Blue River 

downstream from French Gulch 

was degraded (site 8). The site conditions remain moderately affected 

downstream to Dillon Reservoir 

(site 10).

Mining activities have affected 

trace-element concentrations in 

the bottom sediment of Dillon 

Reservoir. Dillon Reservoir was 

constructed in 1963 in an area with 

a long history of mining activity. 

Sources of trace elements in Dillon 

Reservoir, a drinking-water supply 

for the city of Denver, are located 

in the Blue River, Snake River, and 

Tenmile Creek Basins. The reservoir is accumulating some trace 

elements. For example, loads 

calculated using streamflow and 

Mining activities have affected 

trace-element concentrations and 

aquatic invertebrates in French 

Gulch and the Blue River. Samples from different media were 

used to investigate the effects of 

mining activities on the water quality and associated biota at 10 sites 

along the Blue River and French 

Gulch, a tributary of the Blue River 

(fig. 12). Sites 2 and 3 (fig. 12) are 

background sites on French Gulch 

and are minimally affected by mining activities. Zinc concentrations 

in water and streambed sediment 

and zinc accumulated by aquatic 

moss at these background sites 

were lower than those from sites 

downstream from the mined areas. 

The invertebrate community structure (as indicated by mayfly abundance and percent midges) was 

minimally affected at the background sites.

 Although habitat conditions at 

site 4 were degraded and zinc concentrations were greater than those 

upstream, the invertebrate community was not found to be signifiwater concentration indicate that 

only 37 percent of the zinc that 

enters Dillon Reservoir leaves the 

reservoir (fig. 12, top left graph). 

Sediment cores were collected at 

several locations in Dillon Reservoir. Concentrations of lead and 

zinc throughout the core collected 

near the dam exceeded the PEL. 

Cadmium, lead, and zinc concentrations in sediment cores from the 

Blue River, Snake River, and Tenmile Creek arms of the reservoir 

also were above the PEL (values 

for zinc are shown in the top of 

fig. 12).

 Although bottom sediment concentrations of some trace elements 

exceeded the PEL, concentrations 

in the water column were not high. 

The concentrations of trace elements in the reservoir water column did not exceed the Colorado 

surface-water-quality standards.

Collecting sediment core samples on Dillon Reservoir. (Photograph by Norman Spahr, U.S. Geological 

Survey.)

Sediment core from Dillon Reservoir. (Photograph 

by Norman Spahr, U.S. Geological Survey.)
14 Water Quality in the Upper Colorado River Basin

0 1 2 KILOMETERS

0 1 2 MILES

Study Area

Upper Colorado River Basin

PEL is 315

micrograms 

per gram

ZINC CONCENTRATION

IN RESERVOIR SEDIMENT,

IN MICROGRAMS PER GRAM

0

1,000

2,000

3,000

BLUE RIVER ARM

TENMILE CREEK ARM

SNAKE RIVER ARM

Wirepatch

Mine

Country Boy

Mine

WellingtonOro Mine

Farncomb

Hill

Blue River

Arm

Snake River

Arm

Tenmile Creek

Arm

2

4 3

5

6 7

8

9

10

1

Sampling site with site number and 9 site condition rankings

Zinc in streambed sediment

Percent midges

Mayfly abundance

Dissolved zinc in water

Zinc in aquatic moss

Habitat score

Minimally affected or lower concentrations

Moderately affected or mid-range concentrations

Significantly affected or higher concentrations 

Mine location

EXPLANATION

30,000

15,000

0

TOTAL ZINC LOAD, IN

KILOGRAMS PER YEAR

INCOMING

LOAD

OUTGOING

LOAD

WATER YEAR 1998 Dillon Reservoir

Dillon Reservoir

Breckenridge

Dillon

Reservoir

Figure 12. Different types of sampling media provide a better understanding of conditions at sites sampled in the Blue 

River Basin. Dillon Reservoir sediments are accumulating some trace elements originating from mining areas.
Major Findings 15 

Water-Quality Characteristics 

of Agricultural Areas 

Agricultural land use constitutes 

about 5 percent of the Study Unit 

area (fig. 6). Within the Southern 

Rocky Mountains, agricultural land 

is almost exclusively hay meadows. The agricultural areas of the 

Colorado Plateau (principally the 

Grand Valley near Grand Junction 

in Mesa County and the 

Uncompahgre Valley near Delta 

and Montrose in Delta and Montrose Counties, fig. 6) produce hay, 

corn, small grains, dry beans, 

onions, melons, fruit, and grapes. 

The Grand Valley has about 70,000 

acres of irrigated land, and the 

Uncompahgre Valley contains 

about 86,000 irrigated acres (Butler 

and others, 1996). The market 

value of agricultural products produced in Delta, Mesa, and Montrose Counties was about 145 

million dollars in 1992 (Bureau of 

the Census, 1994). Pesticides, 

nutrients, and sediment are waterquality issues commonly associated with agricultural land use. 

Pesticides were sampled in different media. Pesticides were 

investigated in surface water by 

periodic monitoring at 2 agricultural sites and a one-time synoptic 

sampling at 43 agricultural sites. 

Fish were collected once at three 

agricultural sites and the tissues 

analyzed for organochlorine pesticides. Organochlorine pesticides in 

streambed sediments were sampled 

once at six agricultural sites. 

Ground-water samples were not 

collected in the agricultural areas 

of the UCOL because ground water 

is generally not used for public 

water supply in these areas. 

Selenium in Western Colorado

Selenium, a naturally occurring trace element, is common throughout 

the Western United States in marine sedimentary rocks. It is an essential 

micronutrient for birds, fish, and animals (Mayland, 1994) but at high 

concentrations can be highly toxic to fish and wildlife. Selenium can be 

very mobile in the environment and the mobility can be accelerated by 

irrigation. As irrigation water is applied to soils containing selenium, 

the selenium is leached out of the soils and into surface and ground 

water. Selenium in wetlands, ponds, and lakes is incorporated into bed 

sediment and can be bioaccumulated by wildlife, including fish and 

birds (Ohlendorf and others, 1986). Areas of the Western United States 

susceptible to selenium contamination from irrigation, which include 

the Grand and 

Uncompahgre Valleys in western Colorado, have been 

identified by Seiler 

and others (1999).

Extensive irrigated agriculture is 

present in the Grand 

and Uncompahgre 

Valleys of the Colorado Plateau in western Colorado (fig. 6). 

Irrigation drainage 

from these areas may 

account for as much 

as 75 percent of the 

selenium load in the 

Colorado River near 

the Colorado-Utah 

State line (Butler and others, 1996). It is estimated that 61 percent of the 

selenium load to Lake Powell in Utah originates from these agricultural 

areas in the UCOL (Engberg, 1999). Primary source areas of selenium 

in western Colorado are the western one-half of the Grand Valley and 

the eastern side of the Uncompahgre River Valley where the residual 

soils and alluvium are derived primarily from the Mancos Shale, a 

marine shale containing selenium.

 A study in 1991ñ93 of irrigation drainage in the Grand and 

Uncompahgre River Valleys detected relatively high concentrations of 

selenium in many surface-water and streambed-sediment samples 

(Butler and others, 1996). Concentrations of selenium greater than the 

aquatic-life guidelines were also detected in the UCOL surface-water 

sampling in agricultural areas during 1995ñ98 and at one streambedsediment sampling site in 1995. Investigations of selenium in western 

Colorado for remediation planning are continuing through the U.S. 

Department of the Interior National Irrigation Water Quality Program 

and the Gunnison Basin Selenium Task Force.

UCOL

Agriculture

65 samples at 

at 2 sites

UCOL

Agriculture

2 sites

Eastern

Uncompahgre

River Valley

32 sites*

Western 

Grand

Valley

30 sites*

Eastern

Uncompahgre

River Valley

5 sites*

Western 

Grand

Valley

7 sites*

DISSOLVED SELENIUM,

IN MICROGRAMS PER LITER

SELENIUM, 

IN MICROGRAMS PER GRAM

0.1

1

10

100

1,000

1

10

100

Maximum

Median

Minimum

Individual

Values

SURFACE WATER

STREAMBED SEDIMENT

USEPA

guideline

for protection 

U.S. Fish

and Wildlife

guideline

for protection 

of aquatic 

life is 5 

 of aquatic life

 is 4 mg/g

* Data from Butler and others, 1996.

mg/L
16 Water Quality in the Upper Colorado River Basin

breakdown products, DDE and 

DDD, were detected in streambed 

sediments at five of the six agricultural sites sampled and in fish tissue at all three of the agricultural 

sites where fish tissue samples 

were collected (Stephens and 

Deacon, 1998). Concentrations of 

DDT and DDE in streambed sediment at two sites exceeded the 

Canadian Sediment Quality Guidelines PEL (Canadian Council of 

Ministers of the Environment, 

1999). The DDD concentration at 

one site exceeded the PEL. Dieldrin (a restricted use insecticide 

since 1974) was detected in streambed sediments at two of the six 

sites and in fish tissue at all three 

sites. Insecticides detected in fish 

tissue and streambed sediments 

were generally not detected in 

agricultural streams showed that 

the total number of pesticides 

detected was greatest during April 

through August (Bauch and Spahr, 

2000). Pesticide detections per 

month for Dry Creek are shown in 

figure 13. Concentrations of atrazine were found to be greater from 

May through August than during 

other periods of the year (fig. 13). 

The seasonal pattern of concentrations was similar for other pesticides and reflects the growing 

season for the Grand and 

Uncompahgre Valleys.

Pesticides were detected in 40 

of 43 agricultural streams.

Thirty-one pesticides (21 herbicides and 10 insecticides) were 

detected at least once during a May 

1998 agricultural stream synoptic 

study in the Grand Valley and 

Uncompahgre Valley areas. Atrazine and alachlor were detected in 

more than 50 percent of the samples. Concentrations of atrazine did 

not exceed aquatic-life guidelines. 

Guidelines are not available for 

alachlor. 

Some insecticides have persisted in streambed sediment and 

fish tissue, although their use has 

been banned or restricted. DDT 

was banned in 1972, but DDT or its 

0

1

2

3

4

5

6

7

8

9

10

O ND J FMAM J JA S

0

0.02

0.04

0.06

0.08

0.10

0.12

MEDIAN NUMBER OF PESTICIDES

DETECTED PER SAMPLE

WATER YEAR 1997

MEDIAN ATRAZINE CONCENTRATION PER 

SAMPLE, IN MICROGRAMS PER LITER

Median number of 

pesticide detections

Median atrazine concentration

DRY CREEK

Pesticides were commonly 

detected in agricultural areas of 

the UCOL, but concentrations 

were generally low. Most pesticide 

detections in surface water were 

not at concentrations of concern. 

Freshwater aquatic-life guidelines 

were exceeded occasionally; however, guidelines have not been 

established for all compounds. 

Only 5 of the 90 samples collected 

in the agricultural areas contained 

pesticides that exceeded established guidelines. The pesticides 

that exceeded guidelines for protection of freshwater aquatic life 

are azinphos-methyl, 1 of 24 samples at Reed Wash; carbaryl, 2 synoptic sites, Indian Wash and 

Orchard Mesa Drain in the Grand 

Valley; diazinon, 1 synoptic site, 

Indian Wash; diuron, 1 synoptic 

site, Indian Wash; and gammaHCH, 1 synoptic site, the drain at 

Blossom Road in the Uncompahgre 

Valley. 

Pesticide detections and concentrations showed seasonal patterns. Periodic sampling at two 

Collecting water samples at an agricultural drain in 

the Grand Valley. (Photograph by Norman Spahr, 

U.S. Geological Survey.)

Figure 13. The number of pesticide detections and median atrazine 

concentrations in surface water are greater during the spring and summer 

months. Atrazine is commonly used for season-long weed control in corn. 

Agriculture and the San Juan Mountains near 

Montrose. (Photograph by Norman Spahr, 

U.S. Geological Survey.)
Major Findings 17 

water samples from the same site, 

probably because these compounds 

are relatively insoluble in water. 

Occurrence of organochlorine pesticides, even at low concentrations, 

is becoming increasingly relevant 

because of recent evidence linking 

these compounds to endocrine disruption (Goodbred and others, 

1997).

Nutrient concentrations in 

streams and rivers reflect point 

and nonpoint sources. National 

background concentrations have 

been determined for some forms of 

nutrients: total nitrogen in streams 

(1.0 mg/L), nitrate in streams 

(0.6 mg/L), and total phosphorus in 

streams (0.1 mg/L) (U.S. Geological Survey, 1999). Relative concentrations of nutrients in surface 

water are linked to the amounts and 

types of substances used and discharged in different land-use settings. These substances can then 

reach the stream through point 

sources (such as wastewater discharge) or nonpoint sources (such 

as precipitation or runoff from agricultural areas). Estimated amounts 

of fertilizer applied during 1997 in 

Delta, Mesa, and Montrose Counties were about 14,100,000 pounds 

of nitrogen and 1,800,000 pounds 

of phosphorus (Jeffrey Stoner, 

U.S. Geological Survey, written 

commun., 2000). Fertilizer use in 

these counties accounted for about 

77 percent of the total estimated 

fertilizer usage for the UCOL.

Nutrient concentrations in 

areas of agricultural land use 

were generally greater than in 

areas of other land uses. Median 

concentrations of ammonia, nitrite 

plus nitrate, total phosphorus, dissolved phosphorus, and orthophosphate were greater at agriculture 

sites than at the Colorado Plateau 

reference and mixed land-use sites 

(fig. 14). The Colorado Plateau 

reference site has some limited 

agriculture upstream (livestock/

hay meadows), so is not represenThe three most commonly detected herbicides at the two agricultural monitoring sites in the UCOL (one site 

each in the Grand and Uncompahgre Valleys) also were among the top 10 herbicides detected in surface-water 

samples at 62 agricultural sites in 35 nationally distributed NAWQA Study Units. The percentages of samples 

with detections for atrazine, alachlor, and metolachlor are shown below and are based on more than 1,550 samples for the national sites and 39 samples at the UCOL sites. Atrazine, alachlor, and metolachlor are commonly 

used for weed control in corn. Alachlor and metolachlor are also used for weed control in dry beans. Other herbicides that were frequently detected 

(present in over one-third of the samples) in the UCOL but not shown in 

the graph include trifluralin, DCPA, 

2,4-D, cyanazine, and deethylatrazine 

(a breakdown product of atrazine). 

These herbicides also were commonly 

detected at other agricultural sites 

across the Nation. Median concentrations of the commonly detected herbicides in the UCOL were less than or 

similar to the median concentrations 

for the national sites. Concentrations 

of atrazine and metolachlor were less 

than the Canadian guidelines for the 

protection of aquatic life [1.8 μg/L for 

atrazine and 7.8 μg/L for metolachlor 

(Environment Canada, 1999)]. Guidelines have not been established for 

alachlor.

0

Atrazine Alachlor Metolachlor

10

20

30

40

50

60

70

80

90

62 Agriculture sites from NAWQA Study Units

2 Agriculture sites from the UCOL

HERBICIDE

PERCENTAGE OF SAMPLES WITH 

DETECTIONS 

EXPLANATION

0

0.005

0.010

0.015

0.020

0.025

0.030

0.035

0.040

0.045

0.050

MEDIAN CONCENTRATION, IN

MICROGRAMS PER LITER

Median concentration

Median less than 0.002 mg/L

HERBICIDES COMMONLY DETECTED IN THE UCOL WERE

ALSO COMMONLY DETECTED IN OTHER AGRICULTURAL

AREAS NATIONALLY
18 Water Quality in the Upper Colorado River Basin

tative of natural conditions but is 

probably representative of small 

streams in the Colorado Plateau. 

Median concentrations of nutrients 

at agricultural sites also were 

greater than median concentrations 

at mixed land-use and urban sites 

within the Southern Rocky Mountains. The urban areas shown in the 

bar chart are downstream from Vail 

and Crested Butte, Colorado (fig. 

6), and are streams that are not 

dominated by wastewater effluent 

such as might be found in large 

metropolitan areas. Concentrations 

of nitrite and nitrate were within 

State standards for agricultural 

water use. Water from the agricultural streams is not commonly used 

for domestic supply.

Geology and agriculture contribute to elevated suspendedsediment concentrations in the 

Colorado Plateau. Suspendedsediment concentrations in the 

streams and rivers of the Colorado 

Plateau were much greater than 

concentrations in the Southern 

Rocky Mountains (fig. 15), due in 

large part to differences between 

the sedimentary geology of the 

Figure 14. Concentrations of nutrients in agricultural areas of the UCOL were 

greater than concentrations in other land-use settings. A log scale is used due to 

the large range of concentrations.

Total nitrogen (the sum of nitrite, nitrate, ammonia, and organic nitrogen) concentrations at the UCOL agricultural monitoring sites (Reed Wash and Dry Creek) were ranked in the group of national agricultural sites with the 

highest concentrations. The map below shows a comparison of average annual total nitrogen concentrations at the 

two UCOL agricultural sites with agricultural sites in other NAWQA Study Units. The average concentrations for 

the UCOL sites were 3.8 milligrams per liter for Reed Wash and 3.2 milligrams per liter for Dry Creek and are 

less than State instream standards. Average annual total phosphorus concentrations at the two agricultural sites in 

the UCOL also ranked among the group of national agricultural sites with the highest total phosphorus concentrations. 

0.01

0.001

0.1

1

10

Ammonia Total Phosphorus Orthophosphate

Agriculture Sites Southern Rocky Mountains 

Colorado Plateau Reference Site Urban Sites

Southern Rocky Mountains 

Mixed Land-Use Sites Colorado Plateau Mixed

 Land-Use Sites

Median below 0.01 mg/L

MEDIAN CONCENTRATION, IN 

Dissolved

Phosphorus

Nitrite Plus

Nitrate

NUTRIENT

MILLIGRAMS PER LITER

Reed Wash

Dry Creek

TOTAL NITROGEN IN STREAMS-AGRICULTURAL AREAS

EXPLANATION

Average annual concentration of total nitrogen,

in milligrams per liter

Average annual total nitrogen input,

NITROGEN CONCENTRATIONS AT THE UCOL AGRICULTURAL

SITES WERE GREATER THAN CONCENTRATIONS FOR MANY

AGRICULTURAL SITES NATIONWIDE
Major Findings 19 

Biological indicator

Colorado Plateau and the igneousmetamorphic geology of the Southern Rocky Mountains. Agricultural return flows also contribute to 

the greater sediment concentrations 

measured at the agricultural sites. 

The reference site in the Colorado Plateau also had elevated sediment concentrations. Any rain or 

snowmelt event in these areas tends 

to substantially increase the sediment concentrations of streams and 

rivers because of the high erodibility of the soils. 

Figure 15. Suspended-sediment 

concentrations were greatest in the 

agricultural areas of the Colorado 

Plateau.

0

20

40

60

80

100

120

140

160

180

200

MEDIAN SUSPENDED-SEDIMENT CONCENTRATION, 

IN MILLIGRAMS PER LITER

Agricultural Sites

Reference Site

Mixed Land-Use Sites

 Urban Sites

Mixed Land-Use Sites

Colorado Plateau

Southern

Rocky 

Mountains

The elevated nutrient and sediment concentrations found in the agricultural and surrounding areas of the Colorado Plateau help to explain the 

prevalence of more tolerant biological species. Algal, invertebrate, and fish 

communities in the Colorado Plateau generally consist of species more tolerant to nutrients and sediments. These result in higher degradation rankings for all three biological measures. The biological measures in the 

Colorado Plateau indicate that agricultural and mixed land-use sites in the 

UCOL are above the national average in terms of degradation. These rankings compare UCOL agricultural sites to other NAWQA agricultural sites 

and UCOL mixed land-use sites to other NAWQA mixed land-use sites 

nationally.

Explanation of Biological Rankings

The three selected biological indicators respond to changes in stream degradation. Degradation can result from a variety of factors that modify habitat or 

other environmental features such as land use, water chemistry, and flow. Algal 

status focuses on the changes in the percentage of certain algae in response to 

increasing siltation and often is positively correlated with higher nutrient 

concentrations in many regions of the Nation. Invertebrate status is the average 

of 11 invertebrate metrics that summarize changes in richness, tolerance, trophic 

conditions, and dominance associated with water-quality degradation. Fish status focuses on changes in the percentage of tolerant fish species that make up 

the total number of fish. "Tolerant" fish are reported to thrive in 

degraded water quality. For all indicators, higher values indicate degraded water 

quality.

Sediment and water-quality sampling at Reed 

Wash. (Photograph by Norman Spahr, U.S. Geological Survey.)

BIOLOGICAL MEASURES INDICATE

THAT UCOL AGRICULTURAL AND

COLORADO PLATEAU MIXED LANDUSE SITES RANK AMONG THE MORE

DEGRADED SITES NATIONALLY

Biological indicator
20 Water Quality in the Upper Colorado River Basin

Salinity in the Colorado River Basin

A serious water-quality issue in the Colorado River Basin is salinity defined 

as the concentration of dissolved mineral salts or total dissolved solids in 

water. Salinity increases in the Colorado River in a downstream direction; the 

dissolved-solids concentration is about 50 mg/L in the upstream mountain 

areas and averages about 850 mg/L at Imperial Dam, Arizona (Kircher, 1984). 

In the UCOL, annual dissolved-solids loads in the Colorado River ranged 

from about 17,700 tons at Hot Sulphur Springs in the Southern Rocky Mountains to more than 3,300,000 tons near the Colorado-Utah State line.

 Major sources of salinity in the Colorado River Basin are mineral springs 

and nonpoint-source runoff. The major human influence is irrigated agriculture. About 11 percent of the salt load in the Colorado River near the U.S.ñ

Mexico border is contributed from the Grand Valley and Uncompahgre Valley 

(lower Gunnison River Basin) agricultural areas (U.S. Department of the 

Interior, 1999). Much of the soil in these areas is derived from and overlies the 

Mancos Shale, a saline marine deposit. Deep percolation of irrigation water 

and seepage losses from irrigation systems leach salt from the soil and shale, 

increasing the salinity of return flows. Salinity-control projects have been 

constructed throughout the Colorado River Basin, including two projects in 

the UCOLóthe Grand Valley Unit and the Lower Gunnison Basin Unit. 

As part of the study of salinity in the Colorado River Basin, trends in dissolved-solids concentrations in the basin have been investigated in numerous 

studies (Vaill and Butler, 1999; Bauch and Spahr, 1998; Butler, 1996; Liebermann and others, 1989; Kircher, 1984). The most recent study (Vaill and 

Butler, 1999) determined that 

since the 1960s there have 

been, in general, downward 

trends in flow-adjusted annual 

and monthly dissolved-solids 

concentrations and loads in the 

Colorado River Basin upstream 

from Lake Powell in Utah, 

except in the Yampa River 

Basin. In the UCOL, there 

were downward trends both 

upstream and downstream 

from the salinity-control 

projects in the Grand Valley 

and the lower Gunnison River 

Basin. With the downward 

trends as evidence, it appears 

that both natural processes and 

human efforts such as salinitycontrol projects may be 

decreasing salinity loading in 

the Colorado River Basin.

0

3,500,000

3,000,000

2,500,000

2,000,000

1,500,000

1,000,000

500,000

Colorado River at 

Hot Sulphur Springs

Colorado River 

near Dotsero

Colorado River

near Cameo

Colorado River 

near ColoradoUtah State line

Mean annual dissolved-solids loads increase greatly 

between sites in the Southern Rocky Mountains and

sites in the Colorado Plateau. Data based on water

years 1970 to 1993. (Butler,1996; Bauch and Spahr,

1998)

ANNUAL DISSOLVED-SOLIDS LOAD, IN TONS

DOWNSTREAM DIRECTION

Colorado 

Plateau

Southern

Rocky

Mountains

0

7,000

6,000

5,000

4,000

3,000

2,000

1,000

MEAN ANNUAL STREAMFLOW, IN CUBIC FEET PER SECOND

LOAD

STREAMFLOW
 Study Unit Design 21

STUDY UNIT DESIGN

Surface-water

chemistry

EXPLANATION

Basic fixed sites

Intensive fixed sites

Agriculture synoptic 

Urban synoptic 

Southern Rocky Mountains

Physiographic Province

Colorado Plateau

Physiographic Province

Ground-water

chemistry

EXPLANATION

Urban land-use study sites

Aquifer survey site

Aquifer survey site in or near mining areas

Prominent alluvial deposits in the 

Southern Rocky Mountains 

Southern Rocky Mountains

Physiographic Province

Colorado Plateau

Physiographic Province

Stream ecology

EXPLANATION

Basic fixed sites

Trace-element synoptic site

Eagle River synoptic site

Southern Rocky Mountains

Physiographic Province

Colorado Plateau

Physiographic Province

GROUND-WATER CHEMISTRY

To evaluate the effects of urban land 

use on shallow ground-water quality, 

five areas within the Southern Rocky 

Mountains that are undergoing urban 

development and use ground water as a 

primary drinking-water source, were 

studied. An overall assessment of 

water quality in predominantly alluvial 

aquifers of the Southern Rocky Mountains was also completed. In addition 

to the overall assessment, wells were 

selected in or near mining areas. Alluvial aquifers were selected for these 

studies because they are generally productive and can be susceptible to landuse practices.

SURFACE-WATER CHEMISTRY

The basic fixed site network was established to investigate the differences in streamwater quality associated with land use and 

environmental settings within the UCOL. 

Basic fixed sites were sampled monthly to 

determine temporal variability of water-quality constituents. The three intensive fixed sites 

(a subset of the basic fixed site network) were 

sampled weekly to monthly to further define 

temporal variability. Synoptic studies were 

designed to investigate agriculture and urban 

development effects on water quality. Synoptic sites were sampled one or two times to 

determine spatial influences of land use on 

water chemistry.

STREAM ECOLOGY

Ecological assessments were done at all 

basic fixed sites plus one additional site on 

the Blue River. A synoptic study in mining 

areas of the Southern Rocky Mountains 

investigated trace elements in streambed 

sediment, aquatic moss, and surface water. 

A characterization of the algal and invertebrate communities and nutrient concentrations in surface water was completed at 

five sites on the Eagle River.
22 Water Quality in the Upper Colorado River Basin

SUMMARY OF DATA COLLECTION IN THE UPPER COLORADO RIVER BASIN, 1996ñ98

Study

component What data were collected and why Types of sites sampled Number of 

sites

Sampling frequency 

and period

Surface-Water Chemistry

Basic fixed 

sitesñgeneral 

water chemistry

Monthly samples collected for major ions, nutrients, organic 

carbon, and suspended sediment to describe concentration variability and loads. Daily streamflow also collected or computed. 

Streams and rivers representing urban 

development, mining, agricultural, and 

mixed land use.

14 Monthly plus additional 

high- or low-flow samples for water years 

1996ñ98

Intensive fixed 

sites

All constituents collected for the fixed sites. Weekly to 

monthly samples collected to describe temporal variability in pesticide and volatile organic compounds concentrations.

A subset of the fixed site network. One site 

representing urban development, one 

site representing agricultural land use, 

and the outlet of the Study Unit.

3 Weekly to monthly plus 

additional high- or lowflow samples for water 

year 1997

Synoptic 

sitesñagriculture

One time sample to describe the spatial variability of pesticides and nutrients in agricultural areas.Agricultural drains, streams and rivers in 

the Grand and Uncompahgre Valleys. 

Outlet of the Study Unit.

43 May 1998

Synoptic 

sitesñurban 

development

Nutrient and algae samples along an upstream to downstream profile in areas of urban development to investigate influences of urban development. Upstream to downstream sites along seven 

tributary rivers.

30 March and September 

1998

Ground-Water Chemistry

Land-use 

effectsñUrban

Samples collected for major ions, nutrients, 18 trace elements, radon, dissolved organic carbon, 87 pesticides, 

86 volatile organic compounds, bacteria (total coliform 

and E. coli), and chlorofluorocarbons to describe the 

effects of urban development on the shallow ground 

water in five urban areas of the Southern Rocky Mountains.

Shallow monitoring wells 25 Spring and Fall 1997

Aquifer 

surveyñ

Southern 

Rocky 

Mountains 

Samples collected for major ions, nutrients, 18 trace elements, radon, dissolved organic carbon, 47 pesticides, 86 

volatile organic compounds, and bacteria (total coliform 

and E. coli) to describe the water-quality conditions in 

selected alluvial aquifers throughout the Southern Rocky 

Mountains Physiographic Province.

Private and municipal drinking-water wells

Monitoring well 

Spring

28

1

1

Once in 1997

Aquifer 

surveyñ

Southern 

Rocky Mountains in or 

near mining 

areas

Samples collected for same as above (except that 13 of these 

sites were not sampled for pesticides or volatile organic 

compounds) to describe the water-quality conditions in 

selected alluvial aquifers throughout the Southern Rocky 

Mountains Physiographic Province for wells located in or 

near mining areas.

Private and municipal drinking-water wells

Spring

14

1

Once in 1997

Stream Ecology

Basic fixed sites Fish, invertebrate, and algae communities, trace elements, 

and organics in streambed sediment and fish tissue, and 

habitat data were collected to assess the occurrence and 

distribution within the UCOL.

Streams and rivers representing urban 

development, mining, agricultural, and 

mixed land use.

15 Fish community, invertebrate community, and 

algae August, 1996ñ98;

Habitat August 1996;

Streambed sediment and 

fish tissue August-October 

1995

Synoptic sitesñ

trace elements

Trace-element concentrations in streambed sediment, 

aquatic moss, and water; and invertebrate community 

structure to assess the spatial extent and magnitude of 

trace-element contamination from mining areas. 

Areas of mining land use and background 

sites in areas of no mining.

32 August 1998

Synoptic sitesñ

Eagle River

Invertebrates, algae, and nutrients in water to characterize 

current conditions in an area of extensive urban development.

Sites within and downstream from developed areas. Additional sites in areas that 

may be developed in the future.

5 February and September 

1997
GLOSSARY 

Glossary 23

AlgaeóChlorophyll-bearing, nonvascular, primarily aquatic 

species that have no true roots, stems, or leaves; most 

algae are microscopic, but some species can be as large 

as vascular plants.

AlluviumóDeposits of clay, silt, sand, gravel or other particulate rock material left by a river in a streambed, on a 

flood plain, delta, or at the base of a mountain.

Alluvial aquiferóA water-bearing deposit of unconsolidated material (sand and gravel) left behind by a river 

or other flowing water.

AmmoniaóA compound of nitrogen and hydrogen (NH3) 

that is a common by-product of animal waste. Ammonia readily converts to nitrate in soils and streams.

Aquatic-life guidelineó Water-quality guidelines for protection of aquatic life. Often refers to U.S. Environmental Protection Agency water-quality criteria for 

protection of aquatic organisms. See also Water-quality 

guidelines.

Basinó See Drainage basin.

Benthic invertebratesó Insects, mollusks, crustaceans, 

worms, and other organisms without a backbone that 

live in, on, or near the bottom of lakes, streams, or 

oceans.

Bioaccumulationó The biological sequestering of a substance at a higher concentration than that at which it 

occurs in the surrounding environment or medium. 

Also, the process whereby a substance enters organisms 

through the gills, epithelial tissues, dietary, or other 

sources.

Breakdown productó A compound derived by chemical, 

biological, or physical action upon a pesticide. The 

breakdown is a natural process which may result in a 

more toxic or a less toxic compound and a more persistent or less persistent compound.

Chlorofluorocarbonsó A class of volatile compounds consisting of carbon, chlorine, and fluorine. Commonly 

called freons, which have been used in refrigeration 

mechanisms, as blowing agents in the fabrication of 

flexible and rigid foams, and, until several years ago, as 

propellants in spray cans.

Communityó In ecology, the species that interact in a common area.

Concentrationó The amount or mass of a substance 

present in a given volume or mass of sample. Usually 

expressed as microgram per liter (water sample) or 

micrograms per kilogram (sediment or tissue sample).

Confluenceó The flowing together of two or more streams; 

the place where a tributary joins the main stream.

Constituentó A chemical or biological substance in water, 

sediment, or biota that can be measured by an analytical 

method.

Cubic foot per second (ft3/s, or cfs)ó Rate of water discharge representing a volume of 1 cubic foot passing a 

given point during 1 second, equivalent to approximately 7.48 gallons per second or 448.8 gallons per 

minute or 0.02832 cubic meter per second.

Detectó To determine the presence of a compound.

DDTó Dichloro-diphenyl-trichloroethane. An organochlorine insecticide no longer registered for use in the 

United States.

Dischargeó Rate of fluid flow passing a given point at a 

given moment in time, expressed as volume per unit of 

time.

Dissolved constituentóOperationally defined as a constituent that passes through a 0.45-micrometer filter.

Drainage basinó The portion of the surface of the Earth 

that contributes water to a stream through overland runoff, including tributaries and impoundments.

Eutrophicationó The process by which water becomes 

enriched with plant nutrients, most commonly phosphorus and nitrogen.

Health advisoryó Nonregulatory levels of contaminants in 

drinking water that may be used as guidance in the 

absence of regulatory limits. Advisories consist of estimates of concentrations that would result in no known 

or anticipated health effects (for carcinogens, a specified cancer risk) determined for a child or for an adult 

for various exposure periods.

Instream standardsó See Water-quality standards.

Invertebrateó An animal having no backbone or spinal 

column. See also Benthic invertebrates.

Loadó General term that refers to a material or constituent 

in solution, in suspension, or in transport; usually 

expressed in terms of mass or volume.

Maximum contaminant level (MCL)ó Maximum permissible level of a contaminant in water that is delivered to 

any user of a public water system. MCLs are enforceable standards established by the U.S. Environmental 

Protection Agency.

Medianó The middle or central value in a distribution of 

data ranked in order of magnitude. The median is also 

known as the 50th percentile.

Micrograms per liter (μg/L)ó A unit expressing the concentration of constituents in solution as weight (micrograms) of solute per unit volume (liter) of water; 

equivalent to one part per billion in most streamwater 

and ground water. One thousand micrograms per liter 

equals 1 mg/L.

Midgeó A small fly in the family Chironomidae. The larval 

(juvenile) life stages are aquatic.
24 Water Quality in the Upper Colorado River Basin

Milligrams per liter (mg/L)ó A unit expressing the concentration of chemical constituents in solution as 

weight (milligrams) of solute per unit volume (liter) of 

water; equivalent to one part per million in most 

streamwater and ground water. One thousand micrograms per liter equals 1 mg/L.

Monitoring welló A well designed for measuring water 

levels and testing ground-water quality.

Mouthó The place where a stream discharges to a larger 

stream, a lake, or the sea.

Nitrateó An ion consisting of nitrogen and oxygen (NO3

-

). 

Nitrate is a plant nutrient and is very mobile in soils.

Nonpoint sourceó A pollution source that cannot be 

defined as originating from discrete points such as pipe 

discharge. Areas of fertilizer and pesticide applications, 

atmospheric deposition, manure, and natural inputs 

from plants and trees are types of nonpoint source pollution.

Nutrientó Element or compound essential for animal and 

plant growth. Common nutrients in fertilizer include 

nitrogen, phosphorus, and potassium.

Organochlorine pesticideó A class of organic insecticides 

containing a high percentage of chlorine. Includes 

dichlorodiphenylethanes (such as DDT), chlorinated 

cyclodienes (such as chlordane), and chlorinated benzenes (such as lindane). Most organochlorine insecticides were banned because of their carcinogenicity, 

tendency to bioaccumulate, and toxicity to wildlife.

Pesticideó A chemical applied to crops, rights of way, 

lawns, or residences to control weeds, insects, fungi, 

nematodes, rodents or other "pests".

Phosphorusó A nutrient essential for growth that can play 

a key role in stimulating aquatic growth in lakes and 

streams.

Picocurie (pCi)ó One trillionth (10-12) of the amount of 

radioactivity represented by a curie (Ci). A curie is the 

amount of radioactivity that yields 3.7 x 1010 radioactive disintegrations per second (dps). A picocurie yields 

2.22 disintegrations per minute (dpm) or 0.037 dps.

Radonó A naturally occurring, colorless, odorless, radioactive gas formed by the disintegration of the element 

radium; damaging to human lungs when inhaled.

Reference siteó A NAWQA sampling site selected for its 

relatively undisturbed conditions.

Sedimentó Particles, derived from rocks or biological 

materials, that have been transported by a fluid or other 

natural process, suspended or settled in water.

Speciesó Populations of organisms that may interbreed and 

produce fertile offspring having similar structure, habits, and functions.

Streambed sedimentó The material that temporarily is stationary in the bottom of a stream or other watercourse.

Study Unitó A major hydrologic system of the United 

States in which NAWQA studies are focused. Study 

Units are geographically defined by a combination of 

ground- and surface-water features and generally 

encompass more than 4,000 square miles of land area.

Surface wateró An open body of water, such as a lake, 

river, or stream.

Suspended sedimentóParticles of rock, sand, soil, and 

organic detritus carried in suspension in the water column, in contrast to sediment that moves on or near the 

streambed.

Synoptic sitesó Sites sampled during a short-term investigation of specific water-quality conditions during 

selected seasonal or hydrologic conditions to provide 

improved spatial resolution for critical water-quality 

conditions.

Trace elementó An element found in only minor amounts 

(concentrations less than 1.0 milligram per liter) in 

water or sediment; includes arsenic, cadmium, chromium, copper, lead, mercury, nickel, zinc and selenium.

Un-ionized ammoniaó The neutral form of ammonianitrogen in water, usually occurring as NH4OH. Unionized ammonia is the principal form of ammonia that 

is toxic to aquatic life. The relative proportion of unionized to ionized ammonia (NH4

+) is controlled by 

water temperature and pH. At temperatures and pH values typical of most natural waters, the ionized form is 

dominant.

Volatile organic compounds (VOCs)ó Organic chemicals 

that have a high vapor pressure relative to their water 

solubility. VOCs include components of gasoline, fuel 

oils, and lubricants, as well as organic solvents, fumigants, some inert ingredients in pesticides, and some 

by-products of chlorine disinfection.

Water-quality guidelinesó Specific levels of water quality 

which, if reached, may adversely affect human health or 

aquatic life. These are nonenforceable guidelines issued 

by a governmental agency or other institution.

Water-quality standardsó State-adopted and U.S. Environmental Protection Agency-approved ambient standards for water bodies. Standards include the use of the 

water body and the water-quality criteria that must be 

met to protect the designated use or uses.

Water yearó The continuous 12-month period, October 1 

through September 30, in U.S. Geological Survey 

reports dealing with the surface-water supply. The 

water year is designated by the calendar year in which 

it ends and which includes 9 of the 12 months. Thus, the 

year ending September 30, 1980, is referred to as water 

year 1980.
REFERENCES 

References 25

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waters of the Upper Colorado River Basin, Colorado: 

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Deacon, J.R., and Driver, N.E., 1999, Distribution of trace 

elements in streambed sediment associated with mining 

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Deacon, J.R., and Stephens, V.C., 1998, Trace elements in 

streambed sediment and fish liver at selected sites in the 

Upper Colorado River Basin, Colorado, 1995ñ1996: 

U.S. Geological Survey Water-Resources Investigations 

Report 98ñ4124, 19 p.

Denver Water Department, 1999, Comprehensive annual 

financial report; Denver Water Department: 96 p.

Engberg, R.A., 1999, Selenium budgets for Lake Powell and 

the Upper Colorado River Basin: Journal of the American Water Resources Association, v. 35, no. 4, p. 771ñ

786.

Environment Canada, 1999, Canadian water-quality guidelines for the protectin of aquatic life, Summary tables: 

Environment Canada, Environmental Quality Division, 

Guidelines and Standards Division, accessed October 

31, 2000, at 

URL http://www.ec.gc.ca/ceqg-rcqe/water.htm.

Fegeas, R.G., Claire, R.W., Guptil, S.C., Anderson, K.E., and 

Hallam, C.A., 1983, U.S. Geological Survey digital cartographic data standardsóLand use and land cover digital data: U.S. Geological Survey Circular 895ñE, 

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special map, scale 1:7,000,000.

Goodbred, S.L., Gilliom, R.J., Gross, T.S., Denslow, N.P., 

Bryant, W. L., and Schoeb, T.R., 1997, Reconnaissance 

of 17β-estradiol, 11-ketotestosterone, vitellogenin, and 

gonad histopathology in common carp of United States 

streamsóPotential for contaminant-induced endocrine 

disruption: U.S. Geological Survey Open-File Report 

96ñ627, 47 p.

Green, G.N., 1992, The digital geological map of Colorado 

in Arc/Info format: Denver, U.S. Geological Survey 

(revised April 12, 1995), Open-File Report 0507, scale 

1:500,000.
26 Water Quality in the Upper Colorado River Basin, 1996-98

Hitt, K.J., 1995, Refining 1970's land-use data with 1990 

population data to indicate new residential development: U.S. Geological Survey Water-Resources Investigations Report 94ñ4250, 15 p.

Kiffney, P.M., and Clements, W.H., 1994, Structural 

responses of benthic macroinvertebrate communities 

from different stream orders to zinc: Environmental 

Toxicology and Chemistry v. 13, p. 389ñ395.

Kircher, J.E., 1984, Dissolved solids in the Colorado River 

Basin, in U.S. Geological Survey, National water summary 1984óHydrologic events, selected water-quality 

trends, and ground-water resources: U.S. Geological 

Survey Water-Supply Paper 2275, p. 74ñ78.

Liebermann, T.D., Mueller, D.K., Kircher, J.E., and 

Choquette, A.F., 1989, Characteristics and trends of 

streamflow and dissolved solids in the Upper Colorado 

River Basin, Arizona, Colorado, New Mexico, Utah, 

and Wyoming: U.S. Geological Survey Water-Supply 

Paper 2358, 64 p.

Mayland, H.F., 1994, Selenium in plant and animal nutrition, 

in Frankenberger, W.T., Jr., and Benson, Salley, eds., 

Selenium in the environment: New York, Marcel 

Dekker, Inc. p. 29ñ45.

Myers, D.N., and Sylvester, M.A., 1997, Fecal indicator bacteria: U.S. Geological Survey Techniques of WaterResources Investigations, book 9, chap. A7, 38 p.

Northern Colorado Water Conservancy District, 2000, Colorado Big Thompson Project: Northern Colorado Water 

Conservancy District, accessed September 11, 2000, at 

http://www.ncwcd.org/cgi-bin/ncwcd?go=CBT

Ohlendorf, H.M., Hoffman, D.J., Saiki, M.K., and Aldrich, 

T.W., 1986, Embryonic mortality and abnormalities of 

aquatic birdsóApparent impacts of selenium from irrigation drainwater: Science of the Total Environment, 

v. 52, p. 49ñ63.

Rice, K.C., 1999, Trace-element concentrations in streambed sediment across the conterminous United States: 

Environmental Science and Technology, v. 33, no. 15, 

p. 2499ñ2504.

Seiler, R. L., Skorupa, J.P., and Peltz, L.A., 1999, Areas susceptible to irrigation-induced selenium contamination 

of water and biota in the Western United States: U.S. 

Geological Survey Circular 1180, 36 p.

Squillace, P.J., Pankow, J.F., Korte, N.E., and Zogorski, J.S., 

1996, Environmental behavior and fate of methyl tertbutyl ether (MTBE): U.S. Geological Survey Fact Sheet 

FSñ203ñ96, 6 p.

Stephens, V.C., and Deacon, J.R., 1998, Distribution and 

concentrations of selected organochlorine pesticides 

and PCBís in streambed sediment and whole-body fish 

in the Upper Colorado River Basin, 1995ñ96: U.S. 

Geological Survey Fact Sheet FSñ167ñ97, 6 p.

Tweto, Ogden, comp., 1979, Geologic map of Colorado: 

U.S. Geological Survey State Geologic Map, scale 

1:500,000 (reprinted).

U.S. Department of the Interior, 1995, Quality of water, Colorado River BasinóProgress report no. 17: U.S. 

Department of the Interior, 96 p.

U.S. Department of the Interior, 1999, Quality of 

wateróColorado River Basin: Denver, Colo., Bureau 

of Reclamation Progress Report 19, 93 p. plus appendix.

U.S. Environmental Protection Agency, 1996, Drinking 

water regulations and health advisories: Washington, 

D.C., U.S. Environmental Protection Agency Report 

822ñBñ96ñ002, Office of Water [pagination unknown].

U.S. Environmental Protection Agency, 1997, Drinking 

water advisory: Consumer acceptability and health 

effects analysis on methyl tert-butyl ether (MTBE): 

Washington D.C., U.S. Environmental Protection 

Agency Report 822ñFñ97ñ008, Office of Water, 4 p.

U.S. Environmental Protection Agency, rev. October 18, 

1999, Proposed radon in drinking water rule: U.S. Environmental Protection Agency Report EPA 815ñFñ99ñ

006: accessed March 6, 2000, at 

http://www.epa.gov/OGWDW/radon/fact.html

U.S. Geological Survey, 1995, Water use in the United 

States: U.S. Geological Survey, accessed March 6, 

2000, at http//water.usgs.gov/wateruse/ 

U.S. Geological Survey, 1999, The quality of our Nationís 

watersóNutrients and pesticides: U.S. Geological Survey Circular 1225, 82 p.

Upper Colorado River Commission, 1999, Fifty-first annual 

report of the Upper Colorado River Commission, September 30, 1999: Salt Lake City, Utah, 92 p.

Vaill, J.E., and Butler, D.L., 1999, Streamflow and dissolved-solids trends, through 1996, in the Colorado 

River Basin upstream from Lake PowellóColorado, 

Utah, and Wyoming: U.S. Geological Survey WaterResources Investigations Report 99ñ4097, 47 p.

Additional Publications of the UCOL Study Unit:

Apodaca, L.E., 1997, Analysis of ground-water-quality data 

of the Upper Colorado River Basin, water years 1972ñ

92: U.S. Geological Survey Water-Resources Investigations Report 97ñ4240, 31 p.

Apodaca, L.E., and Bails, J.B. 1999, Fraser River Watershed, 

ColoradoóAssessment of available water-quantity and 

water-quality data through water year 1997: U.S. Geological Survey Water-Resources Investigations Report 

98ñ4255, 58 p.

Apodaca, L.E., and Bails, J.B., 2000, Water quality in alluvial aquifers of the Southern Rocky Mountains Physiographic Province, Upper Colorado River Basin, 
References 27

Colorado, 1997: U.S. Geological Survey WaterResources Investigations Report 99ñ4222, 68 p.

Apodaca, L.E., and Bails, J.B., 2000, Ground-water-quality 

assessment of selected wells in the Fraser River Watershed, Colorado, August 1998: U.S. Geological Survey 

Water-Resources Investigations Report 99ñ4243, 8 p.

Apodaca, L.E., Driver, N.E., and Bails, J.B., 2000, Occurrence, transport, and fate of trace elements, Blue River 

Basin, Summit County, ColoradoóAn integrated 

approach: Environmental Geology, v. 39, no.8,

p. 901ñ913.

Apodaca, L.E., Driver, N.E., Stephens, V.C., and Spahr, 

N.E., 1996, Environmental setting and implications on 

water quality, Upper Colorado River Basin, Colorado 

and Utah: U.S. Geological Survey Water-Resources 

Investigations Report 95ñ4263, 33 p.

Apodaca, L.E., Stephens, V.C., and Driver, N.E., 1996, What 

affects water quality in the Upper Colorado River 

Basin: U.S. Geological Survey Fact Sheet FSñ109ñ96, 

4 p.

Bauch, N.J. and Apodaca, L.E., 1995, Bibliography, indices, 

and data sources of water-related studies, Upper Colorado River Basin, Colorado and Utah, 1972ñ1995: U.S. 

Geological Survey Open-File Report 95ñ450, 282 p.

Deacon, J.R., 1997, Biological and contaminant investigations, Upper Colorado River BasinóWhatís been done 

and how can the information be used?: U.S. Geological 

Survey Fact Sheet FSñ032ñ97, 2 p.

Deacon, J.R., and Mize, S.V., 1997, Effects of water quality 

and habitat on composition of fish communities in the 

Upper Colorado River Basin: U.S. Geological Survey 

Fact Sheet FSñ122ñ97, 6 p.

Deacon, J.R., Mize, S.V., and Spahr, N.E., 1999, Characterization of selected biological, chemical, and physical 

conditions at fixed sites in the Upper Colorado River 

Basin, Colorado, 1995ñ98: U.S. Geological Survey 

Water-Resources Investigations Report 99ñ4181, 35 p. 

Deacon, J.R., and Spahr, N.E., 1998, Water-quality and biological community characterization at selected sites on 

the Eagle River, Colorado, September 1997 and February 1998: U.S. Geological Survey Water-Resources 

Investigations Report 98ñ4236, 8 p.

Deacon, J.R., and Stephens, V.C., 1996, Summary of biological and contaminant investigations related to stream 

water quality and environmental setting in the Upper 

Colorado River Basin, 1938ñ1995: U.S. Geological 

Survey Water-Resources Investigations Report 96ñ

4172, 37 p.

Driver, N.E., 1994, National Water-Quality Assessment ProgramñUpper Colorado River Basin: U.S. Geological 

Survey Open-File Report 94ñ102, 2 p.

Greve, A.I., Spahr, N.E., Van Metre, P.C., and Wilson, J.T., 

in press, Identification of water-quality trends using 

sediment cores from Dillon Reservoir, Summit County, 

Colorado: U.S. Geological Survey Water-Resources 

Investigations Report 01ñ4022.

Spahr, N.E., and Boulger, R.W., 1997, Interim results of 

quality-control sampling of surface water for the Upper 

Colorado River National Water-Quality Assessment 

Study Unit, water years 1995ñ96: U.S. Geological Survey Water-Resources Investigations Report 97ñ4227, 

34 p.

Spahr, N.E., Boulger, R.W., and Szmajter, R.J., 2000, Water 

quality at basic fixed sites in the Upper Colorado River 

Basin National Water-Quality Assessment Study Unit, 

October 1995ñSeptember 1998: U.S. Geological Survey Water-Resources Investigations Report 99ñ4223, 

63 p.

Spahr, N.E., and Deacon, J.R., 1998, Water-quality characterization of the Slate and East Rivers during the winter 

recreational season, December, 1996: U.S. Geological 

Survey Open-File Report 98ñ279, 9 p.

Spahr, N.E., Driver, N.E., and Stephens, V.C., 1996, The 

Upper Colorado River National Water-Quality Assessment Program Surface-Water Monitoring Network: 

U.S. Geological Survey Fact Sheet FSñ191ñ96, 4 p.

Spahr, N.E., and Wynn, K.H., 1997, Nitrogen and phosphorus in surface waters of the Upper Colorado River 

Basin: Journal of the American Water Resources Association, v. 33, no. 3, p. 547ñ560.
28 Water Quality in the Upper Colorado River Basin

Streams in agricultural areas 

Streams in urban areas

Streams and rivers draining mixed land uses 

Shallow ground water in agricultural areas

Shallow ground water in urban areas 

Major aquifers 

Detected concentration in Study Unit

Frequencies of detection, in percent. Detection frequencies 

were not censored at any common reporting limit. The lefthand column is the study-unit frequency and the right-hand 

column is the national frequency 

Not measured or sample size less than two

Study-unit sample size. For ground water, the number of 

samples is equal to the number of wells sampled

National ranges of detected concentrations, by land use, in 36 

NAWQA Study Units, 1991–98—Ranges include only samples

in which a chemical was detected

Drinking-water quality (applies to ground water and surface water)

Protection of aquatic life (applies to surface water only)

Prevention of eutrophication in streams not flowing directly into 

lakes or impoundments

No benchmark for drinking-water quality

No benchmark for protection of aquatic life

*

**

66 38

Other herbicides detected

Acetochlor (Harness Plus, Surpass) * **

Benfluralin (Balan, Benefin, Bonalan) * **

Bentazon (Basagran, Bentazone) **

Bromacil (Hyvar X, Urox B, Bromax) 

Cyanazine (Bladex, Fortrol) 

2,4-DB (Butyrac, Butoxone, Embutox Plus, Embutone) * **

Dicamba (Banvel, Dianat, Scotts Proturf) 

EPTC (Eptam, Farmarox, Alirox) * **

Ethalfluralin (Sonalan, Curbit) * **

Oryzalin (Surflan, Dirimal) * **

Prometon (Pramitol, Princep) **

Simazine (Princep, Caliber 90) 

Tebuthiuron (Spike, Tebusan) 

Trifluralin (Treflan, Gowan, Tri-4, Trific)

Herbicides not detected

Acifluorfen (Blazer, Tackle 2S) **

Bromoxynil (Buctril, Brominal) * 

Butylate (Sutan +, Genate Plus, Butilate) **

Chloramben (Amiben, Amilon-WP, Vegiben) **

Clopyralid (Stinger, Lontrel, Transline) * **

Dacthal mono-acid (Dacthal breakdown product) * **

Dichlorprop (2,4-DP, Seritox 50, Lentemul) * **

2,6-Diethylaniline (Alachlor breakdown product) * **

Dinoseb (Dinosebe) 

Diuron (Crisuron, Karmex, Diurex) **

CHEMICALS IN WATER

Concentrations and detection frequencies, Upper Colorado River 

Basin, 1996–98—Detection sensitivity varies among chemicals and, 

thus, frequencies are not directly comparable among chemicals

Lowest

25 percent

Middle

50 percent

Highest

25 percent

National water-quality benchmarks

National benchmarks include standards and guidelines related to 

drinking-water quality, criteria for protecting the health of aquatic life, and 

a goal for preventing stream eutrophication due to phosphorus. Sources 

include the U.S. Environmental Protection Agency and the Canadian 

Council of Ministers of the Environment

|

|

|

--

This appendix is a summary of chemical concentrations 

and biological indicators assessed in the Upper Colorado 

River Basin. Selected results for this Basin are graphically 

compared to results from as many as 36 NAWQA Study 

Units investigated from 1991 to 1998 and to national 

water-quality benchmarks for human health, aquatic life, or 

fish-eating wildlife. The chemical and biological indicators 

shown were selected on the basis of frequent detection, 

detection at concentrations above a national benchmark, 

or regulatory or scientific importance. The graphs illustrate 

how conditions associated with each land use sampled in 

the Upper Colorado River Basin compare to results from 

across the Nation, and how conditions compare among 

the several land uses. Graphs for chemicals show only 

detected concentrations and, thus, care must be taken to 

evaluate detection frequencies in addition to concentrations when comparing study-unit and national results. 

For example, simazine concentrations in Upper Colorado 

River Basin agricultural streams were similar to the 

national distribution, but the detection frequency was much 

higher (72 percent compared to 18 percent). 

CONCENTRATION, IN MICROGRAMS PER LITER

 0.0001 0.001 0.01 0.1 1 10 100 1,000 

Study-unit frequency of detection, in percent

National frequency of detection, in percent

Pesticides in water—Herbicides

Study-unit sample size

12

Alachlor (Lasso, Bronco, Lariat, Bullet) **

64 44 | 39 -- 20 | 0 78 45 | 9

-- 3 | 0 0 <1 | 25 0 1 | 32

Atrazine (AAtrex, Atrex, Atred, Gesaprim) 85 88 | | 39 -- 86 | | 0 78 87 | | 9

-- 40 | 0 16 30 | 25 0 18 | 32

2,4-D (Aqua-Kleen, Lawn-Keep, Weed-B-Gone) 38 15 | | 39 -- 18 | | 0 44 11 | | 9

-- <1 | 0 0 1 | 25 -- <1 | 0

DCPA (Dacthal, chlorthal-dimethyl) * **

72 18 39 -- 30 0 78 20 9

-- 1 0 12 1 25 0 <1 32

Deethylatrazine (Atrazine breakdown product) * ** 72 75 39 -- 62 0 33 75 9

-- 39 0 8 28 25 3 19 32

Metolachlor (Dual, Pennant) 54 81 | | 39 -- 64 | | 0 78 83 | | 9

-- 18 | 0 0 9 | 25 0 5 | 32

APPENDIX—WATER-QUALITY DATA FROM THE UPPER COLORADO 

RIVER BASIN IN A NATIONAL CONTEXT

For a complete view of Upper Colorado River Basin data and for additional information about specific benchmarks used, visit our Web site at 

http://water.usgs.gov/nawqa/. Also visit the NAWQA Data Warehouse for access to NAWQA data sets at http://water.usgs.gov/nawqa/data. 
Water-Quality Data in a National Context 29 

CONCENTRATION, IN MICROGRAMS PER LITER

 0.0001 0.001 0.01 0.1 1 10 100 1,000 

Study-unit frequency of detection, in percent

National frequency of detection, in percent

Pesticides in water—Insecticides

Study-unit sample size

Volatile organic compounds (VOCs) in ground water

These graphs represent data from 16 Study Units, sampled from 1996 to 1998

Study-unit frequency of detection, in percent

National frequency of detection in percent Study-unit sample size

CONCENTRATION, IN MICROGRAMS PER LITER

 0.001 0.01 0.1 1 10 100 1,000 10,000 

Other insecticides detected 

Carbaryl (Carbamine, Denapon, Sevin) 

Carbofuran (Furadan, Curaterr, Yaltox) 

Chlorpyrifos (Brodan, Dursban, Lorsban) 

Diazinon (Basudin, Diazatol, Neocidol, Knox Out) 

gamma-HCH (Lindane, gamma-BHC) 

Malathion (Malathion) 

cis-Permethrin (Ambush, Astro, Pounce) * **

Phorate (Thimet, Granutox, Geomet, Rampart) * **

Propargite (Comite, Omite, Ornamite) * **

Terbufos (Contraven, Counter, Pilarfox) **

Insecticides not detected

Aldicarb (Temik, Ambush, Pounce) 

Aldicarb sulfone (Standak, aldoxycarb) 

Aldicarb sulfoxide (Aldicarb breakdown product) 

Dieldrin (Panoram D-31, Octalox, Compound 497) 

Disulfoton (Disyston, Di-Syston) **

Ethoprop (Mocap, Ethoprophos) * **

Fonofos (Dyfonate, Capfos, Cudgel, Tycap) **

alpha-HCH (alpha-BHC, alpha-lindane) **

3-Hydroxycarbofuran (Carbofuran breakdown product) * **

Methiocarb (Slug-Geta, Grandslam, Mesurol) * **

Methomyl (Lanox, Lannate, Acinate) **

Methyl parathion (Penncap-M, Folidol-M) **

Oxamyl (Vydate L, Pratt) **

Parathion (Roethyl-P, Alkron, Panthion, Phoskil) * 

Propoxur (Baygon, Blattanex, Unden, Proprotox) * **

Other VOCs detected

Benzene 

Bromodichloromethane (Dichlorobromomethane) 

2-Butanone (Methyl ethyl ketone (MEK)) * 

n-Butylbenzene (1-Phenylbutane) * 

sec-Butylbenzene * 

Carbon disulfide * 

Chloroethane (Ethyl chloride) * 

Chloromethane (Methyl chloride) 

1,3-Dichlorobenzene (m-Dichlorobenzene) 

Dichlorodifluoromethane (CFC 12, Freon 12) 

Dichloromethane (Methylene chloride) 

Diethyl ether (Ethyl ether) * 

1,2-Dimethylbenzene (o-Xylene) 

1,3 & 1,4-Dimethylbenzene (m-&p-Xylene) 

1-4-Epoxy butane (Tetrahydrofuran, Diethylene oxide) * 

Ethenylbenzene (Styrene) 

1-Ethyl-2-methylbenzene (2-Ethyltoluene) * 

Ethylbenzene (Phenylethane) 

Iodomethane (Methyl iodide) * 

Isopropylbenzene (Cumene) * 

p-Isopropyltoluene (p-Cymene) * 

4-Methyl-2-pentanone (Methyl isobutyl ketone (MIBK)) * 

Methylbenzene (Toluene) 

Naphthalene 

2-Propanone (Acetone) * 

n-Propylbenzene (Isocumene) * 

Tetrachloroethene (Perchloroethene) 

Tetrachloromethane (Carbon tetrachloride) 

1,2,3,5-Tetramethylbenzene (Isodurene) * 

1,1,1-Trichloroethane (Methylchloroform) 

Trichloroethene (TCE) 

Trichloromethane (Chloroform) 

1,2,3-Trimethylbenzene (Hemimellitene) * 

1,3,5-Trimethylbenzene (Mesitylene) * 

VOCs not detected

tert-Amylmethylether (tert-amyl methyl ether (TAME)) * 

Bromobenzene (Phenyl bromide) * 

Bromochloromethane (Methylene chlorobromide) 

Bromoethene (Vinyl bromide) * 

Bromomethane (Methyl bromide) 

tert-Butylbenzene * 

3-Chloro-1-propene (3-Chloropropene) * 

1-Chloro-2-methylbenzene (o-Chlorotoluene) 

1-Chloro-4-methylbenzene (p-Chlorotoluene) 

Chlorobenzene (Monochlorobenzene) 

Chlorodibromomethane (Dibromochloromethane) 

Chloroethene (Vinyl chloride) 

1,2-Dibromo-3-chloropropane (DBCP, Nemagon) 

1,2-Dibromoethane (Ethylene dibromide, EDB) 

Dibromomethane (Methylene dibromide) * 

trans-1,4-Dichloro-2-butene ((Z)-1,4-Dichloro-2-butene) * 

1,2-Dichlorobenzene (o-Dichlorobenzene) 

1,4-Dichlorobenzene (p-Dichlorobenzene) 

Fenuron (Fenulon, Fenidim) * **

Fluometuron (Flo-Met, Cotoran) **

Linuron (Lorox, Linex, Sarclex, Linurex, Afalon) * 

MCPA (Rhomene, Rhonox, Chiptox) 

MCPB (Thistrol) * **

Metribuzin (Lexone, Sencor) 

Molinate (Ordram) * **

Napropamide (Devrinol) * **

Neburon (Neburea, Neburyl, Noruben) * **

Norflurazon (Evital, Predict, Solicam, Zorial) * **

Pebulate (Tillam, PEBC) * **

Pendimethalin (Pre-M, Prowl, Stomp) * **

Picloram (Grazon, Tordon) 

Pronamide (Kerb, Propyzamid) **

Propachlor (Ramrod, Satecid) **

Propanil (Stam, Stampede, Wham) * **

Propham (Tuberite) **

2,4,5-T **

2,4,5-TP (Silvex, Fenoprop) **

Terbacil (Sinbar) **

Thiobencarb (Bolero, Saturn, Benthiocarb) * **

Triallate (Far-Go, Avadex BW, Tri-allate) * 

Triclopyr (Garlon, Grandstand, Redeem, Remedy) * ** 

Azinphos-methyl (Guthion, Gusathion M) * 5 3 | 39 -- 1 | 0 0 2 | 9

-- <1 0

p,p'-DDE 5 8 | | 39 -- 2 | | 0 0 4 | | 9

-- 4 | 0 0 2 | 25 0 2 | 32

Methyl tert-butyl ether (MTBE) 

-- 4 | 0 12 16 | 25 6 6 | 32

1,2,4-Trimethylbenzene (Pseudocumene) * 

-- 19 0 80 18 25 41 19 32
30 Water Quality in the Upper Colorado River Basin

CONCENTRATION, IN MILLIGRAMS PER LITER

 0.001 0.01 0.1 1 10 100 1,000 10,000 100,000 

CONCENTRATION, IN MILLIGRAMS PER LITER

 0.001 0.01 0.1 1 10 100 1,000 10,000 100,000 

Nutrients in water

Study-unit frequency of detection, in percent

National frequency of detection, in percent Study-unit sample size

Dissolved solids in water

Study-unit frequency of detection, in percent

National frequency of detection, in percent Study-unit sample size

1,2-Dichloroethane (Ethylene dichloride) 

1,1-Dichloroethane (Ethylidene dichloride) * 

1,1-Dichloroethene (Vinylidene chloride) 

trans-1,2-Dichloroethene ((E)-1,2-Dichlorothene) 

cis-1,2-Dichloroethene ((Z)-1,2-Dichloroethene) 

1,2-Dichloropropane (Propylene dichloride) 

2,2-Dichloropropane * 

1,3-Dichloropropane (Trimethylene dichloride) * 

trans-1,3-Dichloropropene ((E)-1,3-Dichloropropene) 

cis-1,3-Dichloropropene ((Z)-1,3-Dichloropropene) 

1,1-Dichloropropene * 

Diisopropyl ether (Diisopropylether (DIPE)) * 

Ethyl methacrylate * 

Ethyl tert-butyl ether (Ethyl-t-butyl ether (ETBE)) * 

Hexachlorobutadiene 

1,1,1,2,2,2-Hexachloroethane (Hexachloroethane) 

2-Hexanone (Methyl butyl ketone (MBK)) * 

Methyl acrylonitrile * 

Methyl-2-methacrylate (Methyl methacrylate) * 

Methyl-2-propenoate (Methyl acrylate) * 

2-Propenenitrile (Acrylonitrile) 

1,1,2,2-Tetrachloroethane * 

1,1,1,2-Tetrachloroethane 

1,2,3,4-Tetramethylbenzene (Prehnitene) * 

Tribromomethane (Bromoform) 

1,1,2-Trichloro-1,2,2-trifluoroethane (Freon 113) * 

1,2,4-Trichlorobenzene 

1,2,3-Trichlorobenzene * 

1,1,2-Trichloroethane (Vinyl trichloride) 

Trichlorofluoromethane (CFC 11, Freon 11) 

1,2,3-Trichloropropane (Allyl trichloride)

CONCENTRATION, IN PICOCURIES PER LITER

Trace elements in ground water

Arsenic 

-- 58 | 0 24 36 | 25 22 37 | 45

Chromium 

-- 85 | 0 100 79 | 25 58 73 | 45

Radon-222 

-- 99 | 0 100 100 | 25 100 97 | 45

Uranium 

-- 64 | 0 52 35 | 25 49 33 | 45

Zinc 

-- 28 | 0 4 29 | 25 84 66 | 45

Other trace elements detected

Lead 

Selenium 

Trace elements not detected

Cadmium

Study-unit frequency of detection, in percent

National frequency of detection, in percent Study-unit sample size

CONCENTRATION, IN MICROGRAMS PER LITER

 0.01 0.1 1 10 100 1,000 10,000 100,000 

 0.01 0.1 1 10 100 1,000 10,000 100,000 

Ammonia, as N * **

80 84 87 38 86 85 48 75 284

-- 78 0 36 71 25 23 70 44

Dissolved ammonia plus organic nitrogen, as N * ** 85 78 87 9 74 86 33 62 286

-- 28 0 16 30 25 5 24 44

Dissolved nitrite plus nitrate, as N ** 100 95 | 87 98 97 | 86 87 91 | 285

-- 81 | 0 84 74 | 25 91 71 | 44

Orthophosphate, as P * **

75 79 87 52 72 85 61 74 286

-- 59 0 28 52 25 57 61 44

Total phosphorus, as P * ** 86 92 | 87 67 90 | 86 81 88 | 286

Dissolved solids * ** 100 100 87 100 100 86 100 100 296

-- 100 0 100 100 25 100 100 45
Water-Quality Data in a National Context 31 

Fish tissue from streams in agricultural areas

Fish tissue from streams in urban areas

Fish tissue from streams draining mixed land uses

Sediment from streams in agricultural areas 

Sediment from streams in urban areas 

Sediment from streams draining mixed land uses

Protection of fish-eating wildlife (applies to fish tissue)

Protection of aquatic life (applies to bed sediment)

No benchmark for protection of fish-eating wildlife

No benchmark for protection of aquatic life

|

|

**

CHEMICALS IN FISH TISSUE

AND BED SEDIMENT

Concentrations and detection frequencies, Upper Colorado River 

Basin, 1996–98—Detection sensitivity varies among chemicals and, 

thus, frequencies are not directly comparable among chemicals. 

Study-unit frequencies of detection are based on small sample sizes; 

the applicable sample size is specified in each graph

Lowest

25 percent

Middle

50 percent

Highest

25 percent

National benchmarks for fish tissue and bed sediment

National benchmarks include standards and guidelines related to 

criteria for protection of the health of fish-eating wildlife and aquatic 

organisms. Sources include the U.S. Environmental Protection Agency, 

other Federal and State agencies, and the Canadian Council of 

Ministers of the Environment

*

Other organochlorines detected

DCPA (Dacthal, chlorthal-dimethyl) * **

Heptachlor epoxide (Heptachlor breakdown product) * 

Heptachlor+heptachlor epoxide (sum of heptachlor and heptachlor epoxide) **

Hexachlorobenzene (HCB) **

Toxaphene (Camphechlor, Hercules 3956) * **

Organochlorines not detected

Chloroneb (Chloronebe, Demosan) * **

Endosulfan I (alpha-Endosulfan, Thiodan) * **

Endrin (Endrine) 

gamma-HCH (Lindane, gamma-BHC, Gammexane) * 

Total-HCH (sum of alpha-HCH, beta-HCH, gamma-HCH, and delta-HCH) **

Isodrin (Isodrine, Compound 711) * **

p,p'-Methoxychlor (Marlate, methoxychlore) * **

o,p'-Methoxychlor * **

Mirex (Dechlorane) **

Total PCB 

Pentachloroanisole (PCA) * **

cis-Permethrin (Ambush, Astro, Pounce) * **

trans-Permethrin (Ambush, Astro, Pounce) * **

CONCENTRATION, IN MICROGRAMS PER KILOGRAM

(Fish tissue is wet weight; bed sediment is dry weight)

 0.1 1 10 100 1,000 10,000 100,000 

CONCENTRATION, IN MICROGRAMS PER KILOGRAM

(Fish tissue is wet weight; bed sediment is dry weight)

 0.1 1 10 100 1,000 10,000 100,000 

National ranges of concentrations detected, by land use, in 36 

NAWQA Study Units, 1991–98—Ranges include only samples

in which a chemical was detected

Detected concentration in Study Unit

Frequencies of detection, in percent. Detection frequencies 

were not censored at any common reporting limit. The lefthand column is the study-unit frequency and the right-hand 

column is the national frequency

Not measured or sample size less than two

Study-unit sample size

66 38

--

12

Organochlorines in fish tissue (whole body)

and bed sediment

Study-unit frequency of detection, in percent

National frequency of detection, in percent Study-unit sample size

Study-unit frequency of detection, in percent

National frequency of detection, in percent Study-unit sample size

Total Chlordane (sum of 5 chlordanes) 

80 38 | 5 0 75 | 2 25 56 | 8

0 9 | 6 0 57 | 2 0 11 | 6

o,p'+p,p'-DDD (sum of o,p'-DDD and p,p'-DDD) * 

40 49 5 0 69 2 12 50 8

33 27 | 6 0 50 | 2 0 20 | 6

p,p'-DDE * ** 100 90 5 100 94 2 75 92 8

83 48 6 0 62 2 33 39 6

o,p'+p,p'-DDE (sum of o,p'-DDE and p,p'-DDE) * 

100 90 5 100 94 2 75 92 8

83 48 | 6 0 62 | 2 33 39 | 6

Total DDT (sum of 6 DDTs) **

100 90 | 5 100 94 | 2 75 93 | 8

83 49 6 0 66 2 33 41 6

o,p'+p,p'-DDT (sum of o,p'-DDT and p,p'-DDT) * 

60 31 5 0 53 2 25 29 8

50 19 | 6 0 38 | 2 0 11 | 6

Dieldrin (Panoram D-31, Octalox) * 100 53 5 0 42 2 38 38 8

33 13 | 6 0 30 | 2 0 9 | 6

Dieldrin+aldrin (sum of dieldrin and aldrin) **

100 52 | 5 0 42 | 2 38 38 | 8

33 13 6 0 29 2 0 9 6
32 Water Quality in the Upper Colorado River Basin

CONCENTRATION, IN MICROGRAMS PER KILOGRAM, DRY WEIGHT

 0.1 1 10 100 1,000 10,000 100,000 

Study-unit frequency of detection, in percent

National frequency of detection, in percent

Semivolatile organic compounds (SVOCs)

in bed sediment

Study-unit sample size

Other SVOCs detected

Acridine **

Anthracene 

Benz[a]anthracene 

Benzo[a]pyrene 

Benzo[b]fluoranthene **

Benzo[ghi]perylene **

Benzo[k]fluoranthene **

Butylbenzylphthalate **

Chrysene 

p-Cresol **

Di-n-butylphthalate **

Di-n-octylphthalate **

Dibenz[a,h]anthracene 

Diethylphthalate **

1,2-Dimethylnaphthalene **

1,6-Dimethylnaphthalene **

Dimethylphthalate **

2-Ethylnaphthalene **

9H-Fluorene (Fluorene) 

Indeno[1,2,3-cd]pyrene **

1-Methyl-9H-fluorene **

2-Methylanthracene **

4,5-Methylenephenanthrene **

1-Methylphenanthrene **

1-Methylpyrene **

Naphthalene 

Pentachloronitrobenzene **

Phenanthrene 

Pyrene 

2,3,6-Trimethylnaphthalene **

SVOCs not detected

Acenaphthene 

Acenaphthylene 

C8-Alkylphenol **

Azobenzene **

Benzo[c]cinnoline **

2,2-Biquinoline **

4-Bromophenyl-phenylether **

4-Chloro-3-methylphenol **

bis(2-Chloroethoxy)methane **

2-Chloronaphthalene **

2-Chlorophenol **

4-Chlorophenyl-phenylether **

1,2-Dichlorobenzene (o-Dichlorobenzene) **

1,3-Dichlorobenzene (m-Dichlorobenzene) **

1,4-Dichlorobenzene (p-Dichlorobenzene) **

3,5-Dimethylphenol **

2,4-Dinitrotoluene **

Isophorone **

Isoquinoline **

Nitrobenzene **

N-Nitrosodi-n-propylamine **

N-Nitrosodiphenylamine **

Phenanthridine **

Quinoline **

1,2,4-Trichlorobenzene **

CONCENTRATION, IN MICROGRAMS PER GRAM

(Fish tissue is wet weight, bed sediment is dry weight)

 0.01 0.1 1 10 100 10,000 1,000 

Study-unit frequency of detection, in percent

National frequency of detection, in percent

Trace elements in fish tissue (livers) and 

bed sediment

Study-unit sample size

Anthraquinone **

17 21 6 50 83 2 0 39 6

9H-Carbazole **

17 19 6 50 76 2 0 33 6

Dibenzothiophene **

17 12 6 100 64 2 33 30 6

2,6-Dimethylnaphthalene **

100 65 6 100 74 2 100 77 6

bis(2-Ethylhexyl)phthalate **

100 91 6 100 99 2 100 95 6

Fluoranthene 

100 66 | 6 100 97 | 2 100 78 | 6

Phenol **

100 81 6 100 82 2 100 80 6

Arsenic * 

40 56 5 0 38 2 88 76 8

100 99 | 3 100 98 | 2 100 97 | 6

Cadmium * 

80 77 5 100 72 2 75 95 8

100 98 | 3 100 100 | 2 100 98 | 6

Chromium * 40 62 5 100 72 2 62 54 8

100 100 | 3 100 99 | 2 100 100 | 6

Copper * 100 100 5 100 100 2 100 100 8

100 100 | 3 100 99 | 2 100 100 | 6
Water-Quality Data in a National Context 33 

 0 10 20 30 40 50 60 70 80 90 100

 0 5 10 15 20

 Invertebrate status indicator

Undeveloped

Agricultural

Urban

Mixed

 Fish status indicator

Undeveloped

Agricultural

Urban

Mixed

Biological indicator value, Upper Colorado River Basin, by 

land use, 1996–98

Biological status assessed at a site

National ranges of biological indicators, in 16 NAWQA Study 

Units, 1994–98

Streams in undeveloped areas

Streams in agricultural areas

Streams in urban areas

Streams in mixed-land-use areas

75th percentile

25th percentile

BIOLOGICAL INDICATORS

Higher national scores suggest habitat disturbance, water-quality 

degradation, or naturally harsh conditions. The status of algae, 

invertebrates (insects, worms, and clams), and fish provide a 

record of water-quality and stream conditions that waterchemistry indicators may not reveal. Algal status focuses on the 

changes in the percentage of certain algae in response to 

increasing siltation, and it often correlates with higher nutrient 

concentrations in some regions. Invertebrate status averages 11 

metrics that summarize changes in richness, tolerance, trophic 

conditions, and dominance associated with water-quality 

degradation. Fish status sums the scores of four fish metrics 

(percent tolerant, omnivorous, non-native individuals, and percent 

individuals with external anomalies) that increase in association 

with water-quality degradation

 Algal status indicator

Undeveloped

Agricultural

Urban

Mixed

CONCENTRATION, IN MICROGRAMS PER GRAM

(Fish tissue is wet weight, bed sediment is dry weight)

 0.01 0.1 1 10 100 10,000 1,000 

Study-unit frequency of detection, in percent

National frequency of detection, in percent Study-unit sample size

Lead * 

20 11 5 0 41 2 25 41 8

100 100 | 3 100 100 | 2 100 99 | 6

Mercury * 

20 71 5 50 59 2 62 80 8

100 82 | 3 100 97 | 2 100 93 | 6

Nickel * **

40 42 5 0 44 2 38 50 8

100 100 3 100 100 2 100 100 6

Selenium * 100 99 5 100 100 2 100 99 8

100 100 | 3 100 100 | 2 100 100 | 6

Zinc * 

100 100 5 100 100 2 100 100 8

100 100 | 3 100 99 | 2 100 100 | 6
A COORDINATED EFFORT

Coordination with agencies and organizations in the Upper Colorado River Basin Study Unit was integral to the 

success of this water-quality assessment. We thank those who served as members of our liaison committee. 

Federal Agencies

Bureau of Land Management

Bureau of Reclamation

National Park Service-Curecanti National Recreation Area

National Park Service

Natural Resources Conservation Service

U.S. Bureau of Mines

U.S. Environmental Protection Agency

U.S. Fish and Wildlife Service

U.S. Forest Service

State Agencies

Colorado Department of Public Health and Environment

Colorado Division of Minerals and Geology 

Colorado Division of Wildlife

Colorado Geological Survey

Colorado River Basin Salinity Control Forum

Colorado River Water Conservation District

Colorado Water Conservation Board

Eagle County

Eagle River Water and Sanitation District

East Grand Water Quality Board

Grand County Water & Sanitation District

Grand Junction Drainage District

Grand County Commissioners

Denver Water 

Local Agencies

City of Aurora

City of Gunnison

City of Grand Junction

Clifton Water District

Crested Butte South Metropolitan District

Gunnison County

Mesa County Water Association

Mt. Crested Butte Water and Sanitation District

Northern Colorado Water Conservancy District

Northwest Colorado Council of Governments

Silvercreek Water and Sanitation District 

Summit County Water Quality Committee

Town of Crested Butte

Town of Fraser

Town of Granby 

Town of Silverthorne

Town of Winter Park

Town of Vail 

Uncompahgre Valley Water Users Association

Upper Gunnison River Water Conservancy District

Universities

Colorado State University Cooperative Extension

Other public and private organizations

Colorado Water Resources Research Institute

Gunnison Basin POWER

Sierra Club 

Vail Associates

We thank the following individuals for contributing to this effort. 

Bob Boulger, lead technician.

Jeff Foster, Dave Hartle, and Dennis Smits for data collection.

Adrienne Greve, Jason Gurdak, Scott Mize, Cory Stephens, and Rick Szmajter for 

 data collection and compilation.

Earl and Frances Partch, Virgil and Lee Spann Ranches Inc., Dos Rios Golf Course, and Maryvale Associates 

 for allowing us to drill monitoring wells on their property. 

Gail Cordy, Tyler Martineau, Sarah Ryker, and Edward Wang for review of manuscript.

Mary Kidd and Betty Palcsak for editorial review.

Alene Brogan for manuscript layout.

John Evans and Loretta Ulibarri for illustrations.
Spahr and others— Water Quality in the Upper Colorado River Basin

U.S. Geological Survey Circular 1214

National Water-Quality Assessment (NAWQA) Program

Upper Colorado River Basin

NAWQA

Colorado

River

Gun nison

River

Grand

Junction

Glenwood

Springs

WinterPark/ Fraser

V

Aspen

Crested

Butte

Gunnison

Ouray

Delta

Montrose

Breckenridge

ail