U.S. GEOLOGICAL SURVEY

Water-Resources Investigations Report 01–4034

Review and Analysis of Available 

Streamflow and Water-Quality Data 

for Park County, Colorado, 1962–98

By Robert A. Kimbrough

Denver, Colorado

2001

Prepared in cooperation with

PARK COUNTY and the

CENTER OF COLORADO WATER CONSERVANCY DISTRICT
U.S. DEPARTMENT OF THE INTERIOR

GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director

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. Geological Survey.

For additional information write to: Copies of this report can be purchased

U.S. Geological Survey

Information Services

Box 25286

Federal Center

Denver, CO 80225

from:

District Chief

U.S. Geological Survey

Box 25046, Mail Stop 415

Denver Federal Center

Denver, CO 80225–0046
CONTENTS III

CONTENTS

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

Introduction............................................................................................................................................................................ 2

Purpose and Scope....................................................................................................................................................... 2

Acknowledgments ....................................................................................................................................................... 4

Description of the Study Area ............................................................................................................................................... 4

Data Sources and Compilation .............................................................................................................................................. 9

Methods of Water-Quality Data Review and Analysis.......................................................................................................... 10

Streamflow............................................................................................................................................................................. 12

Surface-Water Quality ........................................................................................................................................................... 17

Physical Properties....................................................................................................................................................... 17

Major Ions and Dissolved Solids ................................................................................................................................. 30

Nutrients ...................................................................................................................................................................... 32

Temporal Trends in Nutrient Concentrations .................................................................................................... 33

Phosphorus Loads at Selected Surface-Water Sites in the South Platte River Basin ........................................ 37

Trace Elements............................................................................................................................................................. 37

Suspended Sediment.................................................................................................................................................... 42

Ground-Water Quality ........................................................................................................................................................... 42

Physical Properties....................................................................................................................................................... 50

Major Ions and Dissolved Solids ................................................................................................................................. 50

Nutrients ...................................................................................................................................................................... 52

Trace Elements and Radon .......................................................................................................................................... 52

Springwater Quality............................................................................................................................................................... 53

Physical Properties....................................................................................................................................................... 61

Major Ions and Dissolved Solids ................................................................................................................................. 61

Nutrients ...................................................................................................................................................................... 61

Trace Elements............................................................................................................................................................. 61

Summary................................................................................................................................................................................ 63

References.............................................................................................................................................................................. 65

FIGURES

1–5. Maps showing:

1. Location of Park County, Colorado.................................................................................................................. 3

2. Average annual precipitation in Park County, 1961–90 ................................................................................... 5

3. Land cover for Park County ............................................................................................................................. 6

4. Locations of wells in Park County, 1996.......................................................................................................... 7

5. Generalized surficial geology of Park County ................................................................................................. 8

6. Explanation of a concentration plot ......................................................................................................................... 11

7. Map showing selected streamflow-gaging stations in Park County......................................................................... 13

8. Graph showing mean monthly streamflow at selected surface-water sites in Park County..................................... 16

9–11. Maps showing:

9. Surface-water-quality sites in Park County, 1962–98 ...................................................................................... 18

10. Surface-water-quality sites in the (A) Mosquito Creek Basin and (B) upper North Fork South 

Platte River Basin, Park County, 1962–98 ....................................................................................................... 19

11. Water types and median specific conductance at selected surface-water sites in Park County ....................... 31

12. Graph showing distribution of surface-water sampling dates for (A) ammonia, (B) nitrate, and 

(C) total phosphorus................................................................................................................................................. 34
IV CONTENTS

13–16. Boxplots showing:

13. Distribution of (A) nitrate concentrations by land use/land cover, (B) nitrate concentrations 

at sites with 10 or more samples, and (C) map showing median nitrate concentrations at all 

surface-water sites sampled.............................................................................................................................. 35

14. Distribution of (A) total phosphorus concentrations by land use/land cover, (B) total phosphorus 

concentrations at sites with 10 or more samples, and (C) map showing median total phosphorus 

concentrations at all surface-water sites sampled ............................................................................................ 36

15. Distribution of (A) phosphorus concentrations, (B) streamflow, and (C) phosphorus loads 

for selected sites in Park County ...................................................................................................................... 38

16. Distribution of trace-element concentrations for areas of Park County, 1962–98 ........................................... 40

17. Graph of (A) relation between streamflow and suspended-sediment concentrations for sites 103 

and 119, and (B) map showing the number of suspended-sediment samples per site, Park County, 

1962–98.................................................................................................................................................................... 43

18. Map showing aquifer type determined from screened interval for wells sampled by the 

U.S. Geological Survey in Park County................................................................................................................... 51

19. Boxplot showing distribution of pH by aquifer type for wells in Park County, 1974–75, 1998 ............................. 52

20. Map showing fluoride concentrations in ground water, Park County, 1974–75, 1998 ............................................ 54

21. Boxplot and map showing distribution of dissolved solids (A) by aquifer type, and (B) in Park County .............. 55

22. Graph showing relation between dissolved-sulfate and dissolved-solids concentrations in ground water, 

1974–75, 1998.......................................................................................................................................................... 56

23. Boxplots showing nitrate concentrations (A) by aquifer types in Park County in the 1970’s, and 

(B) in domestic wells in subdivisions northeast of Bailey, Colorado ...................................................................... 56

24. Boxplots showing concentrations of dissolved (A) iron, (B) manganese, and (C) zinc in aquifer types

in Park County, 1974–75, 1998................................................................................................................................ 57

25. Map showing specific conductance in springwater, Park County, 1974–75, 1998.................................................. 58

26. Boxplots showing concentrations of dissolved (A) aluminum, (B), iron, and (C) manganese in springs 

emanating from aquifer types, Park County, 1974–75, 1998................................................................................... 62

TABLES

1. Sources of water-related data for Park County, 1962–98........................................................................................ 9

2. Hydrologic characteristics for selected streamflow-gaging stations in Park County.............................................. 14

3. Characteristics of surface-water-quality sites in Park County, 1962–98................................................................. 20

4. Summary of surface-water-quality data for Park County, 1962–98........................................................................ 28

5. Surface-water sites in Park County having chloride or sulfate concentrations larger than 250 milligrams 

per liter in at least one sample................................................................................................................................. 32

6. Results of seasonal Kendall test for trends of selected nutrient species in Park County ........................................ 37

7. Characteristics of ground-water-quality sites in Park County, 1962–98................................................................. 44

8. Summary of ground-water-quality data for Park County, 1962–98........................................................................ 49

9. General description of selected aquifers sampled in Park County.......................................................................... 53

10. Characteristics of springwater-quality sites in Park County, 1962–98 ................................................................... 59

11. Summary of springwater-quality data for Park County, 1962–98........................................................................... 60
CONTENTS V

CONVERSION FACTORS, DEFINITIONS, AND ABBREVIATIONS

Temperature in degrees Celsius (° C) may be converted to degrees Fahrenheit (° F) as follows:

°F = 1.8 (°C) + 32

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (μS/cm at 25°C).

Concentrations of chemical constituents in water are given either in milligrams per liter (mg/L) or micrograms per liter (μg/L).

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

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

Altitude, as used in this report, refers to distance above or below sea level

Additional Abbreviations

cols/100 mL colonies per 100 milliters

μm micrometer

pCi/L picocuries per liter

Multiply By To obtain

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)

foot (ft) 0.3048 meter (m)

inch 2.54 centimeter (cm)

mile (mi) 1.609 kilometer (km)

pound (lb) 0.4536 kilogram (kg)

square mile (mi2) 2.590 square kilometer (km2)
Abstract 1

Review and Analysis of Available Streamflow and 

Water-Quality Data for Park County, Colorado, 

1962–98

By Robert A. Kimbrough

Abstract

Information on streamflow and surfacewater and ground-water quality in Park County, 

Colorado, was compiled from several Federal, 

State, and local agencies. The data were reviewed 

and analyzed to provide a perspective of recent 

(1962–98) water-resource conditions and to help 

identify current and future water-quantity and 

water-quality concerns.

Streamflow has been monitored at more 

than 40 sites in the county, and data for some sites 

date back to the early 1900’s. Existing data indicate a need for increased archival of streamflow 

data for future use and analysis. In 1998, streamflow was continuously monitored at about 

30 sites, but data were stored in a data base for 

only 10 sites.

Water-quality data were compiled for 

125 surface-water sites, 398 wells, and 30 springs. 

The amount of data varied considerably among 

sites; however, the available information provided 

a general indication of where water-quality 

constituent concentrations met or exceeded waterquality standards. 

 Park County is primarily drained by 

streams in the South Platte River Basin and to a 

lesser extent by streams in the Arkansas River 

Basin. In the South Platte River Basin in Park 

County, more than one-half the annual streamflow 

occurs in May, June, and July in response to 

snowmelt in the mountainous headwaters. The 

annual snowpack is comparatively less in the 

Arkansas River Basin in Park County, and 

mean monthly streamflow is more consistent 

throughout the year. In some streams, the timing 

and magnitude of streamflow have been altered 

by main-stem reservoirs or by interbasin water 

transfers. 

Most values of surface-water temperature, 

dissolved oxygen, and pH were within recommended limits set by the Colorado Department of 

Public Health and Environment. Specific conductance (an indirect measure of the dissolved-solids 

concentration) generally was lowest in streams 

of the upper South Platte River Basin and higher 

in the southern one-half of the county in the 

Arkansas River Basin and in the South Platte 

River downstream from Antero Reservoir. 

Historical nitrogen concentrations in 

surface water were small. Nitrite was not 

detected, most un-ionized ammonia concentrations were less than 0.02 milligram per liter, and 

all nitrate concentrations were less than 1.2 milligrams per liter. Nitrate concentrations were higher 

in urban and built-up areas than in rangeland and 

forest areas. Most median concentrations of total 

phosphorus at individual sites were less than 

0.05 milligram per liter, and concentrations were 

not significantly different among urban and builtup, rangeland, and forest areas. An upward trend 

in total phosphorus concentration was determined 

for flow from the East Portal of the Harold D. 

Roberts Tunnel, but the slope of the trend line 

was small and the concentrations were equal or 

nearly equal to the detection limit of 0.01 milligram per liter. Using median phosphorus loads 

for two South Platte River sites, the annual phosphorus load transported out of Park County in 

the South Platte River was calculated to be about 

10,000 pounds. 
2 Review and Analysis of Available Streamflow and Water-Quality Data for Park County, Colorado, 1962–98

Median iron and manganese concentrations 

for most areas of Park County were less than 

in-stream water-quality standards, even though 

several individual concentrations were one 

to two orders of magnitude larger than the standards. The largest concentrations of aluminum, 

cadmium, chromium, copper, iron, manganese, 

nickel, and zinc were from the upper North Fork 

South Platte River Basin or the Mosquito Creek 

Basin. 

All ground-water concentrations of chloride 

and most ground-water concentrations of sulfate 

were less than the U.S. Environmental Protection 

Agency (USEPA) drinking-water standard of 

250 milligrams per liter. Median dissolved-solids 

concentrations in ground water ranged from 

160 milligrams per liter in the crystalline-rock 

aquifers to 257 milligrams per liter in the 

sedimentary-rock aquifers. Dissolved-solids 

concentrations greater than the USEPA drinkingwater standard of 500 milligrams per liter were 

detected in about 10 percent of the wells and in all 

aquifer types sampled but were most common in 

samples from the sedimentary-rock aquifers 

between the towns of Jefferson and Hartsel.

 Nitrate concentrations in ground water 

greater than the USEPA drinking-water standard 

of 10 milligrams per liter were measured primarily in samples collected during the 1990’s in 

wells located in subdivisions northeast of Bailey. 

Nitrate concentrations in these subdivision wells 

were significantly larger than concentrations 

measured in wells in the same area in the 1970’s, 

indicating a possible increase in ground-water 

contamination.

Most trace-element concentrations 

measured in Park County ground water were less 

than USEPA drinking-water standards; however, 

standards for iron, manganese, and zinc were 

exceeded in a small number of samples. Traceelement concentrations exceeding the standards 

occurred in each aquifer type, and median 

concentrations of iron, manganese, and zinc 

were similar among aquifer types. 

The physical and chemical characteristics 

of springwater in Park County varied greatly and 

were dependent on the type of rock in which the 

water originated. Specific conductance was 

lowest in springs originating in the crystallinerock aquifers of Precambrian age and highest 

in a spring that may originate in evaporite beds 

in a sedimentary-rock aquifer that is composed 

of the Maroon Formation of Paleozoic age. 

INTRODUCTION

Located about 50 miles west of the Front Range 

urban centers of Denver and Colorado Springs (fig. 1), 

Park County was one of the fastest growing counties in 

Colorado in 1998, based on percentage of change in 

population. With increasing population and development comes an increased demand for water resources 

and the potential to affect the quality of the resource. 

Local entities in Park County are interested in 

obtaining current and objective information regarding 

water quantity and water quality in Park County. This 

information can be used to determine better land-use 

and water-management practices to protect existing 

resources and help identify current and future waterquantity and water-quality concerns.

Prior to an assessment of current hydrologic 

conditions, a review and analysis of available waterresources data are useful. A review of historical data 

helps to identify gaps in available data and allows 

for prioritizing and focusing future studies. In 1999, 

the U.S. Geological Survey (USGS), in cooperation 

with Park County and the Center of Colorado 

Water Conservancy District, compiled and analyzed 

available information on streamflow and surfacewater and ground-water quality in Park County for 

1962–98.

Purpose and Scope

This report presents available data for 

surface- and ground-water resources in Park County 

for 1962–98. Specific objectives of this report are 

(1) to summarize historical data on streamflow and 

on the quality of surface-water and ground-water 

resources, (2) to analyze historical data and assess the 

broad-scale spatial and temporal variability in streamflow and water quality, and (3) where possible, to 

identify, describe, and explain the primary natural 

and human factors that affect observed streamflow 

and water quality in Park County.
INTRODUCTION 3

Continental

Divide

LOCATION MAP

Arkansas River 

Basin

Harold D. Roberts Tunnel

South Platte River Basin

EXPLANATION

Division between South Platte

and Arkansas River Basins

Continental Divide

Highway

Antero

Reservoir

Spinney

Mountain

Reservoir

Elevenmile

Canyon

Reservoir

Currant Creek

Lake

George

West Fourmile Creek

Platte

River

South

Rock Creek

South

Fork

Middle

Fork

Tarryall Creek

North Fork

South Platte River

Michigan Creek

Tarryall Creek

S alt

Creek

Trout Creek

Fourmile Creek

Craig Creek

Deer Creek

Elk Creek

Lost Creek

Badger Creek

Buffalo Gulch

Base from U.S. Geological Survey digital data, 1:100,000

Universal Transverse Mercator projection,

Zone 13

0 5 10 15

0 5 10 15 20 MILES

20 KILOMETERS

39°

106°

105°30'

Figure 1. Location of Park County, Colorado.
4 Review and Analysis of Available Streamflow and Water-Quality Data for Park County, Colorado, 1962–98

Streamflow data were compiled for 

43 streamflow-gaging stations, and water-quality 

data were summarized for 125 surface-water sites, 

398 wells, and 30 springs. Water-quality analyses 

exist for various properties and constituents including 

water temperature, dissolved oxygen, pH, specific 

conductance, nutrients (nitrogen and phosphorus), 

major ions, trace elements, radon, radionuclides, and 

suspended sediment. In this report, the term “surface 

water” refers to rivers and streams and does not 

include lakes, reservoirs, wetlands, or ponds.

Acknowledgments

The author thanks the many individuals 

and agencies that provided water-quantity and 

water-quality data for Park County. Special thanks 

are extended to Lynda James, Bob Barford, and 

Tom Eisenman of Park County; Steve Bohman, 

Denver Water; Doug Darling, City of Aurora; 

Joni Nuttle, Colorado Department of Public Health 

and Environment; Anne Seiler, Rivers of Colorado 

Water Watch Network; and Robert Cooper, Office 

of the State Engineer, Colorado Division of Water 

Resources. The author also thanks USGS employees 

Sharon Qi and Jennifer Flynn for their assistance 

with data aggregation and management.

DESCRIPTION OF THE STUDY AREA

Located adjacent to the eastern side of the 

Continental Divide, Park County encompasses about 

2,210 mi2

 in central Colorado (fig. 1). Park County is 

located in the Front Range Section of the Southern 

Rocky Mountains Physiographic Province (Dennehy 

and others, 1993). Most of Park County is situated in 

the headwaters area of the South Platte River Basin. 

The major tributaries to the South Platte River in the 

county are Tarryall Creek and the South, Middle, and 

North Forks of the South Platte River (hereinafter 

referred to as the South Fork, Middle Fork, and North 

Fork) (fig. 1). About 13 percent of the county lies 

within the Arkansas River Basin. Major tributaries 

in the Arkansas River Basin include Badger, Currant, 

and West Fourmile Creeks (located in southern Park 

County, fig. 1).

The terrain in Park County is varied. A large, 

grass-covered plateau referred to as South Park is situated in central Park County, and high mountain peaks 

border the county to the north and west. Land-surface 

altitude ranges from 14,000-ft mountain peaks along 

the Continental Divide in the northwestern part of the 

county to about 7,200 ft where the South Platte River 

exits the eastern side of the county. Average annual 

precipitation (1961–90) ranges from about 10 to 

40 inches (Daly and Taylor, 1998) and varies with 

altitude (fig. 2). Precipitation amounts greater than 

18 inches per year occur in the Mosquito Range and 

mountains along the Continental Divide in the western 

part of the county, in the unnamed mountain range in 

the northern part of the county, and in the Platte River, 

Kenosha, and Tarryall Mountains in the eastern part of 

the county. Much of the mountain precipitation is in 

the form of snow, which on average accumulates to 

more than 300 inches per year in the mountains north 

and west of Alma (fig. 2). Annual average precipitation is least in an area surrounding the town of Hartsel 

(fig. 2). 

Land cover in Park County is 53 percent natural 

herbaceous plants, grasses, and sedges (herbaceous 

rangeland at lower altitudes, tundra at higher altitudes); 39 percent forest (deciduous and evergreen); 

5 percent alpine (mixture of tundra, snow, ice, and 

barren rock); 2 percent pasture or hay; and 1 percent 

open water (fig. 3). Trees and shrubs also exist with 

the herbaceous land cover but generally account for 

less than 25 percent of the cover.

The population of Park County in 1998 was 

13,330. Some of the major urban areas in Park County 

include the towns of Alma, Bailey, Fairplay, and Lake 

George (fig. 3). Built-up land use is a subcategory of 

urban land use. Built-up areas consist of low-density 

housing and other development and are located along 

stream valleys or in land parcels referred to as subdivisions. The extent of built-up areas in Park County 

may be inferred from a figure showing existing wells 

in the county in 1996 (fig. 4). Although the towns of 

Alma, Bailey, and Fairplay have public water-supply 

systems, most county residences receive their 

domestic water supply from individual wells. The 

largest clusters of wells are located in the northwestern 

part of the county near Alma and Fairplay, in areas to 

the west and south of Jefferson, and in the North Fork 

of the South Platte River Basin northeast of Bailey. 

Wells in the Arkansas River Basin are located primarily in the southeastern corner of the county from 

Guffey east to the county line.

The surficial geology of Park County (fig. 5) 

ranges from unconsolidated alluvial deposits of 

Quaternary age to crystalline rocks of Precambrian 

age (Tweto, 1979; Klein and others, 1978). The 
DESCRIPTION OF THE STUDY AREA 5

youngest rocks in Park County are the unconsolidated 

alluvial deposits of Quaternary age. Glacial material 

consisting of gravel, cobbles, and boulders in or near 

the mountains are the most extensive alluvial deposits, 

and valley-fill material consisting predominantly of 

sand and gravel occurs along all major and most minor 

streams throughout the county. Located in middle Park 

County in north-south-trending bands are outcrops of 

the South Park Formation, a sedimentary rock of 

Tertiary age. Other sedimentary rocks of Tertiary age 

include the Wagontongue and Antero Formations, 

which occur in the vicinity of Hartsel and in the southwest part of the county. The Wagontongue Formation 

contains reworked volcanic material; the Antero 

Formation is composed of conglomerate, sandstone, 

lacustrine limestone, and interbedded volcanic flows. 

Continental

Divide

Platte River Mountains

Kenosha Mountains

Tarryall Mountains

Mosquito Range

10 to 12

12 to 14

14 to 18

18 to 24

24 to 32

32 to 40

EXPLANATION

Average annual precipitation,

in inches per year

Antero

Reservoir

Spinney

Mountain

Reservoir

Elevenmile

Canyon

Reservoir

Currant Creek

West Fourmile Creek

Platte

River

South

Rock Creek

South

Fork

Middle

Fork

Tarryall Creek

North Fork

South Platte River

Michigan Creek

Tarryall Creek

Lake

George

Base from U.S. Geological Survey digital data, 1:100,000

Universal Transverse Mercator projection,

Zone 13

0 5 10 15 20 MILES

0 5 10 15 20 KILOMETERS

39°

106°

105°30'

Figure 2. Average annual precipitation in Park County, 1961–90.
6 Review and Analysis of Available Streamflow and Water-Quality Data for Park County, Colorado, 1962–98

An extensive series of intrusive and volcanic rocks 

of Tertiary and Cretaceous age cover a large part of 

southern Park County extending from near Hartsel, 

south to the county line. These rocks primarily 

consist of pre-ash and intra-ash-flow andesitic lava, 

breccia, tuff, and conglomerate. Sedimentary rocks of 

Cretaceous and Jurassic age form north-south-trending 

bands in middle Park County and are predominantly 

composed of Pierre Shale and, to a lesser extent, the 

Niobrara Shale and Dakota Sandstone of Cretaceous 

age, and the Morrison and Entrada Formations of 

Jurassic age. The sedimentary rocks of Paleozoic 

Herbaceous plants,

grasses, and sedges

Evergreen forest

Deciduous forest

Alpine

Pasture or hay

Open water

EXPLANATION

Badger Creek

Buffalo Gulch

Salt Creek

Currant Creek

West Fourmile Creek

South

Platte River

South

Fork

Fourmile Creek

Middle

Fork

Trout Creek Tarryall Cr

Michigan Cr

Jefferson Cr

North Fork

Craig Creek

South Platte River

Deer Creek

Elk Creek

Tarryall Creek

Lake

George

Hartsel

Alma

Fairplay

Jefferson Bailey

Alpine land cover determined from GIRAS (Geographic Information

Retrieval and Analysis System) land-use data (Fegeas and others, 1983),

remaining covers determined from Landsat Thematic Mapper images

obtained between July 1991 and June 1994 (U.S. Geological Survey Earth

Resources Observation Systems Data Center, written commun., 1999).

Base from U.S. Geological Survey digital data, 1:100,000

Universal Transverse Mercator projection,

Zone 13

0 5 10 15

0 5 10 15 20 MILES

20 KILOMETERS

105 30' o

106o

39o

Figure 3. Land cover for Park County.
DESCRIPTION OF THE STUDY AREA 7

age on the eastern flanks of the Mosquito Range 

in western Park County consist of the Leadville 

Limestone and Sawatch Sandstone Formations 

of pre-Pennsylvanian age and arkosic sandstone, 

conglomerate, shale, and limestone of Pennsylvanian 

age. The crystalline rocks of Precambrian age occupy 

about 45 percent of the land surface in the county, 

primarily on the eastern side, and include igneous 

granites belonging to three distinct age groups of 1, 

1.4, and 1.7 billion years and metamorphic rocks 

composed of gneiss, schist, and migmatite that are 

1.7 to 1.8 billion years old.

The four primary aquifer types in Park County 

are alluvial aquifers of Quaternary age; sedimentaryrock aquifers of Tertiary, Cretaceous, Jurassic, and 

Paleozoic age; volcanic-rock aquifers of Tertiary 

age; and crystalline-rock aquifers of Precambrian 

age (Klein and others, 1978). Alluvial aquifers are 

0 5 10 15 20 MILES

0 5 10 15 20 KILOMETERS

Alma

Fairplay

Guffey

Jefferson

Bailey

Hartsel

Platte

River

South

South

Fork

Middle

Fork

North Fork

South Platte River

Tarryall Creek

Deer Creek

Badger Creek

EXPLANATION

Basin boundary

Wells

Lake

George

Base from U.S. Geological Survey digital data, 1:100,000

Universal Transverse Mercator projection,

Zone 13

39°

106°

105°30'

Figure 4. Locations of wells in Park County, 1996 (Office of the State Engineer, Colorado 

Division of Water Resources, written commun., 1999).
8 Review and Analysis of Available Streamflow and Water-Quality Data for Park County, Colorado, 1962–98

EXPLANATION

Unconsolidated alluvial deposits

 of Quaternary age

Sedimentary rocks of Tertiary age

Intrusive and volcanic rocks of

 Tertiary and Cretaceous age

Sedimentary rocks of Cretaceous and

 Jurassic age

Sedimentary rocks of Paleozoic age

Crystalline rocks of Precambrian age

Lake George

Base from U.S. Geological Survey digital data, 1:100,000

Universal Transverse Mercator projection,

Zone 13

0 5 10 15

0 5 10 15 20 MILES

20 KILOMETERS

39°

106°

105°30'

Figure 5. Generalized surficial geology of Park County (Green, 1992; Tweto, 1979).
DATA SOURCES AND COMPILATION 9

composed of unconsolidated alluvial deposits 

of Quaternary age. The principal geologic units 

of the sedimentary-rock aquifers include the Antero, 

Florissant Lake Beds, South Park, and Wagontongue 

Formations of Tertiary age; the Pierre Shale and 

Dakota Sandstone of Cretaceous age; the Entrada 

Formation of Jurassic age, and the Leadville and 

Maroon Formations of Paleozoic age. A principal 

geologic unit of the volcanic-rock aquifers is the 

Thirtynine Mile Andesite of Tertiary age. The principal geologic units of the crystalline-rock aquifers 

are the Boulder Creek, Silver Plume, and Pikes 

Peak Granite of Precambrian age.

DATA SOURCES AND COMPILATION

Data collected by a variety of Federal, State, 

and local agencies during1962–98 are used in this 

report. Sources for surface-water-, ground-water-, 

and springwater-quality data are listed in table 1. 

Streamflow data were retrieved in electronic format 

from the USGS National Water Information System 

(NWIS) data base and from the Office of the State 

Engineer, Colorado Division of Water Resources 

(SEO). Most water-quality data were obtained from 

the U.S. Environmental Protection Agency’s (USEPA) 

Storage and Retrieval (STORET) system, the USGS 

NWIS data base, or data bases maintained on personal 

Table 1. Sources of water-related data for Park County, 1962–98

[E, electronic; P, paper; WEB, World Wide Web; NWIS, U.S. Geological Survey National Water Information System; STORET, U.S. Environmental 

Protection Agency Storage and Retrieval System; PC, personal computer]

Agency Number of

sites/samples

Data

format

Data source

(data-base name, data-base type,

or publication)

Streamflow

Office of the State Engineer, Colorado Division of 

Water Resources

24 sites E WEB-accessed data base.

U.S. Geological Survey 19 sites E NWIS data base.

Surface-water quality

City of Aurora 2/97 E PC-based data base.

Colorado Department of Public Health and Environment 58/95 E, P STORET data base, and

Simsiman, 1998.

Colorado Division of Wildlife, Rivers of Colorado 

Water Watch Network

7/311 E WEB-accessed data base.

Colorado Geological Survey 2/50 E STORET data base.

Denver Water 15/1,145 E STORET and

PC-based data bases.

National Park Service 11/11 E STORET data base.

Park County Department of Environmental Health 24/159 P McBride and Cooper, 1991,

Johnson and Cooper, 1993,

Johnson, 1993, 1994.

U.S. Forest Service 12/63 E STORET data base.

U.S. Geological Survey 72/3, 970 E, P NWIS data base.

Ground-water quality

Park County Department of Environmental Health 194/194 P Nitrate in domestic wells, 1994–95,

unpublished data.

U.S. Forest Service 24/75 P Nitrate in campground wells, Pike

National Forest, unpublished data.

U.S. Geological Survey 180/180 E NWIS data base.

Springwater quality

National Park Service 7/7 E STORET data base.

U.S. Geological Survey 23/30 E NWIS data base.
10 Review and Analysis of Available Streamflow and Water-Quality Data for Park County, Colorado, 1962–98

computers (PC) by individual agencies. Some of the 

information was accessed using the internet through 

the World Wide Web. A small amount of data was 

obtained from written documents or reports. Detailed 

information on sample-collection procedures and analysis was not available for all of the water-quality data; 

however, the water-quality data summarized in this 

report were assumed to be reliable for the general 

assessment of water-quality conditions in Park County. 

Acquired water-quality data were entered into a 

PC-based relational data base to facilitate the analysis 

of historical and current (1998) water-quality conditions in Park County.

METHODS OF WATER-QUALITY DATA 

REVIEW AND ANALYSIS

This report includes statistical summaries of 

constituent concentrations and physical properties 

in surface water, ground water, and springs. Because 

laboratory analytical methods differed among agencies, the laboratory analytical reporting (or detection) 

limits for given constituents were not consistent. Data 

that are less than reporting limits are censored data. In 

order to statistically summarize constituent concentrations and not exclude all of the censored data, a 

common reporting limit is desirable. For the data used 

in this report, the most common reporting limit was 

kept, values that were censored above the most 

common reporting limit were deleted, and censored 

values below the most common reporting limit were 

converted to the most common limit. Statistical 

summaries also may be influenced by the occurrence 

of more frequent sampling at a particular site. To 

reduce this bias, the number of analyses used for the 

statistical summaries was limited to two samples per 

month per site.

Water-quality results are graphically displayed 

in this report. Boxplots are used primarily for 

displaying the variability in a concentration data set 

(fig. 6). These plots show five percentiles of the data 

distribution: the 10th, 25th, 50th (median), 75th, and 

90th percentiles. Boxplots are only displayed for data 

sets with at least nine samples. Data sets with fewer 

than nine samples are plotted as individual data points 

(fig. 6). A constituent reporting limit typically is the 

lower limit on a concentration plot (fig. 6); thus, individual data points less than the reporting limit are not 

shown. Similarly, a part of a concentration boxplot 

may be missing from the graph if a particular constituent has several concentrations less than the reporting 

limit. A second graphical technique used in this report 

shows the spatial distribution of median constituent 

concentrations at sampling sites throughout Park 

County in map form. The concentration intervals used 

in figures 11, 13, 14, 21, and 25 are (1) less than the 

25th percentile (white dots), (2) between the 25th and 

50th percentiles (yellow dots), (3) between the 50th 

and 75th percentiles (orange dots), (4) between the 

75th and 90th percentiles (red dots), and (5) greater 

than the 90th percentile (red triangles). The values of 

the percentiles in these figures were obtained from the 

statistical summary tables (tables 4, 8, and 11). In 

order to use all data compiled for Park County, the 

median concentration at some sites may be the constituent concentration determined from a single sample. 

Larger data sets are desired to determine more accurately the actual variability of a constituent concentration at a particular site.

Water-quality data were analyzed using 

nonparametric statistical methods. Nonparametric 

methods are not strongly influenced by outliers, 

require few assumptions about the statistical properties 

of a data set, and are suitable for use with small data 

sets. The Mann-Whitney U test (Helsel and Hirsch, 

1992) was used to determine if significant statistical 

differences exist between two data sets. Attained 

significance levels, or p-values, were reported to determine the strength of each test at a 95-percent confidence level. A statistical difference in median values 

for three or more data sets was evaluated with the 

Kruskal-Wallis test (Helsel and Hirsch, 1992). If a 

significant difference between medians was indicated, 

individual differences between medians were evaluated by applying Tukey’s multiple comparison test 

(Helsel and Hirsch, 1992) to the rank-transformed 

data. Letters were placed next to the median of each 

boxplot (fig. 6) to show the results of the multiple 

comparison tests. Boxplots identified by the same 

letter indicate that the medians were not significantly 

different, whereas differing letters indicate significantly different medians. For the Mann-Whitney, 

Kruskal-Wallis, and Tukey’s tests, an alpha value 

of 0.05 was used to evaluate the significance of test 

results, and censored values in the tested data sets 

were treated as equal to the reporting limit.
METHODS OF WATER-QUALITY DATA REVIEW AND ANALYSIS 11

Nutrient concentrations at selected sites were 

tested for time trends by using the seasonal Kendall 

test (Hirsch and others, 1991). In order to provide 

current information on nutrient trends in surface water, 

only sites having nutrient data from samples collected 

in the 1990’s were considered for testing. The Kendall 

test accounts for seasonal effects on nutrient concentrations by comparing data within the same season; 

therefore, sites used for calculating trends needed a 

data set with a minimum of quarterly sampling. Additionally, at least one-half of the data must have been 

uncensored and present in the first and last one-third of 

the record (Lanfear and Alexander, 1990). Concentrations used for trend analysis were not adjusted for variability due to streamflow because correlations were 

not observed between discharge and concentrations.

The nutrient data obtained from various sources 

for this report were reported using several different 

conventions. For example, nitrate nitrogen data were 

reported as dissolved nitrate as nitrogen, total nitrate 

as nitrogen, and dissolved nitrate as nitrate. In order 

to reduce the number of nutrient species discussed, 

nutrient data in this report have been grouped into 

equivalent nitrogen and phosphorus species using 

methods described by Mueller and others (1995). 

The nutrient species summarized in this report are 

ammonia and un-ionized ammonia as nitrogen (hereinafter referred to as ammonia), nitrite as nitrogen 

(hereinafter referred to as nitrite), nitrate as nitrogen 

(hereinafter referred to as nitrate), dissolved orthophosphorus as phosphorus (hereinafter referred 

to as orthophosphorus), and total phosphorus. 

(21) (6)

10,000

0.1

0.2

0.5

1

2

5

10

20

50

100

200

500

1,000

2,000

5,000

90th percentile

75th percentile

50th percentile (median)

25th percentile

Values less than

the 10th percentile

Values greater than the

90th percentile

10th percentile

CONCENTRATION

Number of samples

Data sets with fewer than 9

samples are plotted as

individual data points

Data set A Data set B

A

Multiple-comparison

group

The smallest value on a concentration plot typically is the 

constituent reporting limit

Figure 6. Explanation of a concentration plot.
12 Review and Analysis of Available Streamflow and Water-Quality Data for Park County, Colorado, 1962–98

The distribution of nitrate and total phosphorus 

in surface water is classified by land use/land cover 

in this report. The land-use/land-cover classifications 

were determined by the land use/land cover upstream 

from or in the vicinity of the surface-water sampling 

sites. Land-use/land-cover classifications used in 

the analysis of the data were urban and built-up 

land use, rangeland (herbaceous rangeland at lower 

altitude and pasture), and forest (deciduous and evergreen). Land-use/land-cover classifications were 

determined only for sites with nitrate and total phosphorus data.

The water-quality data have been compared to 

standards or guidelines where applicable. Standards 

for several constituents have been set for most stream 

segments in Park County (Colorado Department of 

Public Health and Environment, 1998a, 1999a). Standards are based on a stream’s designated classification 

with regard to aquatic life, recreation, drinking-water 

supply, and agriculture. Standards for several trace 

elements are site specific because a mean stream hardness value is needed to calculate the numerical standard by using a formula. These types of standards, 

referred to as Table Value Standards by the Colorado 

Department of Public Health and Environment 

(CDPHE), are not calculated in this report. Traceelement standards also are designated as acute or 

chronic. Acute standards, which apply to 24-hour 

periods, usually are higher than chronic standards, 

which apply to 30-day periods. When both standards 

apply, the lower numerical standards are used for 

comparison with water-quality data in this report. All 

standards are levels not to be exceeded more than once 

every 3 years on average; therefore, constituent 

concentrations in individual samples that exceed these 

criteria may not necessarily indicate a violation of a 

standard. 

Most ground-water-quality data for Park County 

were obtained from domestic wells that are a source of 

drinking water in individual homes; therefore, the 

ground-water data have been compared to USEPA 

maximum contaminant levels (MCL’s) and secondary 

maximum contaminant levels (SMCL’s) for drinking 

water (U.S. Environmental Protection Agency, 1996). 

Water-quality data for springs also are compared to 

USEPA drinking-water standards. The USEPA MCL’s 

are enforceable standards that apply to finished 

drinking water in all public water-supply systems and 

are not legally applicable to individual domestic wells. 

Comparisons between the USEPA criteria and Park 

County ground-water and springs data are offered only 

as a point of reference for the constituents and physical properties measured in Park County. 

STREAMFLOW

Streamflow has been monitored at more than 

40 streamflow-gaging stations in Park County with 

data for some sites dating back to the early 1900’s 

(fig. 7, table 2). Streamflow is currently (1998) 

monitored at 30 sites (table 2), although flow data 

are currently archived or stored in USGS or SEO data 

bases for only 10 of the 30 sites (table 2). Aside from 

the three sites where interbasin water transfers are 

monitored (sites SG1, SG20, SG37, table 2), active 

sites with currently archived data are located on the 

South Fork, North Fork, and Tarryall Creek (one site 

per stream); on the main-stem South Platte River 

(three sites), and on Badger Creek in the Arkansas 

River Basin (fig. 7). Active sites without archived 

data are concentrated in the Middle Fork and Tarryall 

Creek Basins (fig. 7) and are primarily operated for 

the purpose of administering water rights on a daily 

or real-time basis from April through September. 

Streamflow data are not currently collected or archived 

on the North Fork South Platte near the county line, 

anywhere along the Middle Fork South Platte, nor on 

the main-stem South Platte at the county line (fig. 7). 

 In the South Platte River Basin in Park County, 

most streamflow is derived from snowmelt in the 

mountainous areas of the watersheds and more than 

one-half the annual streamflow occurs in May, June, 

and July (fig. 8A and B). During the remainder of the 

year, streamflow is typically less than one-third the 

mean annual flow. With the absence of high mountain 

peaks and a large winter snowpack, the annual distribution and magnitude of streamflow in the Arkansas 

River Basin in Park County differs from that in the 

South Platte. Aside from a small snowmelt peak in 

April and May, average monthly streamflow in Badger 

Creek remains fairly consistent throughout the year 

(fig. 8C). 

The influence of physiography on streamflow 

also is indicated by measures of runoff (table 2). 

Runoff is largest at stations located near the mountains 

where precipitation amounts are highest. Runoff 

decreases with increasing drainage area, indicating 

that areas at lower altitude contribute less runoff than 

the mountain areas.
STREAMFLOW 13

0 5 10 15 20 MILES

0 5 10 15 20 KILOMETERS

SG1

SG2

SG3

SG4

SG5

SG6

SG7

SG8

SG9

SG16

SG10

SG11

SG12

SG

SG14

SG

SG

SG

SG19

SG20

SG21 SG22

SG23

SG24

SG25

SG26

SG29

SG28 SG27

SG30

SG32

SG33

SG

SG

SG

SG37 SG40

SG36

SG38

SG39

SG

SG41

SG43

Bailey

Harold D. Roberts Tunnel

Antero

Reservoir

Spinney

Mountain

Reservoir

Elevenmile

Canyon

Reservoir

Platte

River

South

South

Fork

Middle

Fork

Tarryall

North Fork

South Platte River

Tarryall Creek

Trout Creek

Fourmile Creek

Deer Creek

Buffalo Gulch

Creek

Lake George

Base from U.S. Geological Survey digital data, 1:100,000

Universal Transverse Mercator projection,

Zone 13

EXPLANATION

Active streamflow gage with data

stored in a USGS or SEO data base,

and site number

Active streamflow gage, data currently not

stored in a data base, and site number

Discontinued streamflow gage,

and site number

(site numbers from table 2)

SG12

SG11

SG10

39°

106°

105°30'

Figure 7. Selected streamflow-gaging stations in Park County (USGS, U.S. Geological Survey; SEO, Office of the State 

Engineer, Colorado Division of Water Resources).
14 Review and Analysis of Available Streamflow and Water-Quality Data for Park County, Colorado, 1962–98

Table 2. Hydrologic characteristics for selected streamflow-gaging stations in Park County

[--, no data or not computed] 

Site

no.

(fig. 7)

Site

name

Site

identifier

Period of

record stored

in a data base,

in water years1

Drainage

area,

in square

miles

Mean

annual

streamflow,

in cubic feet

per second

Mean

annual

runoff,

in inches

Gage status,

 as of

December

1998

SG1 Hoosier Pass Tunnel at Montgomery

Reservoir

09042000 1953–98 28 11.8 -- Active

SG2 Middle Fork South Platte River

above Montgomery Reservoir

MFKABMCO None -- -- -- Active

SG3 Middle Fork South Platte River

below Montgomery Reservoir

MFKBLMCO None -- -- -- Active

SG4 Middle Fork South Platte River

above Fairplay

06693980 1979–80 62.2 50.5 11.0 Discontinued

SG5 Spring Branch above Middle Fork

South Platte River, near Fairplay

SPRBRNCO None -- -- -- Active

SG6 Middle Fork South Platte River 

near Prince Ditch at Garo

MFKPRICO None -- -- -- Active

SG7 Trout Creek near Garo TROGARO None -- -- -- Active

SG8 Middle Fork South Platte River 

at Santa Maria Ranch

MFSTMCO None -- -- -- Active

SG9 Middle Fork South Platte River 

near Hartsel

06694100 1979–80 250 60.5 3.3 Discontinued

SG10 South Fork South Platte River 

above Fairplay

06694400 1979–80 50.3 28.4 7.7 Discontinued

SG11 South Fork South Platte River 

above Antero Reservoir

SFKANTCO None -- -- -- Active

SG12 South Fork South Platte River 

below Antero Reservoir

06694650 1976–98 -- 28.3 -- Active

SG13 Fourmile Creek near Fairplay 06694700 1979–80 12.0 13.4 15.2 Discontinued

SG14 Fourmile Creek at High Creek

Ranch

FOUHIGCO None -- -- -- Active

SG15 Fourmile Creek near Hartsel FOUHARCO None -- -- -- Active

SG16 South Platte River above Spinney

Mountain Reservoir

06694920 1986–98 -- 102 -- Active

SG17 South Platte River above Elevenmile

Canyon Reservoir

06695000 1940–98 880 88.5 1.4 Active

SG18 South Platte River near Lake George 06696000 1930–98 963 83.1 1.2 Active

SG19 South Platte River at Lake George 06696200 1912–29 1,084 114 1.4 Discontinued

SG20 Boreas Pass Ditch at Boreas Pass 09046000 1933–40,

1949–98

-- 0.14 -- Active

SG21 Tarryall Creek at Upper Station near

Como

06696980 1979–86 -- 20.7 11.9 Discontinued

SG22 Tarryall Creek at U.S. Highway 285

near Como

TARCOMCO None 23.7 -- -- Active

SG23 Tarryall Creek below Park Gulch

near Como

06697100 1998 72.9 12.4 2.3 Active

SG24 French Creek near Jefferson 06697200 1986–90 4.6 -- -- Active

SG25 Schattinger Flume above Michigan

Creek

SCHFLMCO None -- -- -- Active

SG26 Michigan Creek near Jefferson 06697450 1979–86 23.1 15.0 8.8 Active

SG27 Jefferson Creek near Jefferson 06698000 1979–86 11.8 8.9 10.2 Active

SG28 Ohler Gulch near Jefferson OHGJEFCO None -- -- -- Active
STREAMFLOW 15

The natural hydrology of the South Platte 

River in Park County has been affected by water 

management. The timing and magnitude of streamflow have been altered by a network of irrigation 

ditches, reservoirs, and interbasin water transfers from 

the Arkansas and Colorado River Basins. The effects 

of reservoir management on a 15-mile reach of the 

main-stem South Platte River are illustrated in 

figure 8D. Streamflow in this reach of the river is 

routed through two main-stem reservoirs: Spinney 

Mountain and Elevenmile Canyon Reservoirs. The 

hydrograph for the South Platte River upstream from 

Spinney Mountain Reservoir (site SG16) shows characteristics of flow in a natural mountain stream. After 

peaking in June from snowmelt runoff, streamflow 

progressively decreases through February until snowmelt begins again in March. Ground-water return 

flows are the predominant source of water in the river 

from October through February. The hydrograph for 

the South Platte River downstream from Elevenmile 

Canyon Reservoir (site SG18) shows how reservoir 

operations affect both the timing and magnitude of 

streamflow. Downstream from Elevenmile Canyon 

Reservoir, the annual streamflow peak has shifted to 

later in the year (July). In addition, the magnitude of 

the annual peak is reduced so that water stored in the 

reservoir may be released at a higher rate throughout 

the remainder of the year. 

SG29 Deadman Gulch near Jefferson DEDJEFCO None -- -- -- Active

SG30 Jefferson Creek below Snyder 

Creek

JEFSYNCO None -- -- -- Active

SG31 Tarryall Creek near Jefferson 06698500 1913–17,

1978–81

183 42.2 3.1 Discontinued

SG32 Rock Creek above Tarryall Creek 06699000 1987–90 45.5 -- -- Active

SG33 Tarryall Creek below Rock Creek

near Jefferson

06699005 1984–97 230 50.8 3.0 Active

SG34 Tarryall Creek below Tarryall

Reservoir

TARCRECO 1975–80 -- -- -- Discontinued

SG35 Tarryall Creek near Lake George 06699500 1944,

1950–55

434 29.0 1.7 Discontinued

SG36 North Fork South Platte River at

Grant

06722500 1911–17 49.0 31.2 8.6 Discontinued

SG37 East Portal Harold D. Roberts 

Tunnel near Grant

09050590 1964–98 -- 67.2 -- Active

SG38 Duck Creek near Grant 06704500 1995–97 7.8 6.3 11.0 Discontinued

SG39 Geneva Creek at Grant 06705500 1914–17,

1995–97

74.6 74.2 13.5 Discontinued

SG40 North Fork South Platte River 

below Geneva Creek at Grant

06706000 1909–98 127 2

72.0 7.7 Active

SG41 North Fork South Platte River 

at Bailey

PLABAICO None -- -- -- Active

SG42 Deer Creek near Bailey 393040105340400 1997 13.4 16.6 16.8 Discontinued

SG43 Badger Creek, upper station, 

near Howard3

07093740 1982–98 106 45.9 0.8 Active

1

Data bases maintained by the U.S. Geological Survey or Colorado State Engineers Office.

2Adjusted for inflow from Harold D. Roberts Tunnel since 1964.

3

Located about 3 miles downstream from the Park County boundary.

4Computed with 1982–86 data (gage operation has been seasonal since 1987).

Table 2. Hydrologic characteristics for selected streamflow-gaging stations in Park County—Continued

[--, no data or not computed] 

Site

no.

(fig. 7)

Site

name

Site

identifier

Period of

record stored

in a data base,

in water years1

Drainage

area,

in square

miles

Mean

annual

streamflow,

in cubic feet

per second

Mean

annual

runoff,

in inches

Gage status,

 as of

December

1998
16 Review and Analysis of Available Streamflow and Water-Quality Data for Park County, Colorado, 1962–98

Oct Nov Dec Jan Feb March April May June July Aug Sept

0

200

100

Oct Nov Dec Jan Feb March April May June July Aug Sept

0

150

50

100

Oct Nov Dec Jan Feb March April May June July Aug Sept

0

15

5

10

MEAN MONTHLY STREAMFLOW, IN CUBIC FEET PER SECOND

Oct Nov Dec Jan Feb March April May June July Aug Sept

0

400

100

200

300

Upstream from Spinney Mountain Reservoir (site SG16)

Downstream from Elevenmile Canyon Reservoir (site SG18)

Oct Nov Dec Jan Feb March April May June July Aug Sept

MONTH

0

400

100

200

300 1942-63

1964-98

Site SG33, Tarryall Creek below Rock Creek near Jefferson, 1984-97

Site SG36, North Fork South Platte River at Grant, 1911-17

Site SG43, Badger Creek, upper station, near Howard, 1982-86

Site SG40, North Fork South Platte River below Geneva Creek at Grant

South Platte River, 1986-98

A

B

C

D

E

Mean annual flow

Mean annual flow

Mean annual flow

Figure 8. Mean monthly streamflow at selected surface-water sites in Park County (site 

numbers from table 2).
SURFACE-WATER QUALITY 17

The magnitude of increases in streamflow 

from an interbasin water transfer is shown for the 

North Fork South Platte River in figure 8E. Diversions 

beginning in 1964 from Lake Dillon in the Colorado 

River Basin have increased the mean annual flow 

in the North Fork by about 90 percent, and mean 

streamflow has increased during every month. Additions to streamflow as a percentage of pretransfer 

mean monthly flow are largest from July through 

March, when the percentage of increase ranges from 

100 percent in July to almost 300 percent in January 

and February.

SURFACE-WATER QUALITY

Surface-water-quality data were obtained for 

125 sites in Park County (figs. 9 and 10, table 3). 

Sites sampled in close proximity to each other by 

various agencies have been combined under one site 

number in table 3, but information pertaining to data 

gathered by each sampling agency is provided. The 

period of record, total number of samples collected, 

and types of acquired data varied considerably among 

the 125 sites. More than one-half (79) of the sites have 

had fewer than 10 samples collected, whereas 15 sites 

have had more than 100 samples collected. A few sites 

were sampled several times in each decade since the 

1960’s including site 36 on the South Fork, site 46 on 

the main-stem South Platte River, sites 89 and 110 on 

the North Fork, and site 92, the East Portal of the 

Harold D. Roberts Tunnel.

Water-quality data for surface water in Park 

County are summarized in table 4. The physical properties usually measured in the field (water temperature, 

dissolved oxygen, pH, and specific conductance) have 

been measured at most surface-water sites. Constituents commonly sampled for include major ions, nutrients (nitrogen and phosphorus), and trace elements. 

Physical properties and constituents sampled for less 

frequently are alkalinity, hardness, turbidity, bacteria, 

organic carbon, radionuclides, and suspended 

sediment.

Physical Properties

Water temperatures ranged from 0° to 26.0°C in 

surface water, and only 1 percent of the temperatures 

were higher than 20°C, the CDPHE in-stream standard 

for streams in Park County. Most dissolved-oxygen 

concentrations were larger than the CDPHE minimum 

in-stream standard of 6.0 mg/L. Four of five dissolvedoxygen concentrations less than the standard were 

from the South Fork downstream from Antero 

Reservoir (sites 36 and 39, fig. 9) and may be indicative of dissolved-oxygen concentrations in water 

released from the bottom of the reservoir. Most pH 

values were within the 6.5 to 9.0 standard for surface 

water set by the CDPHE. About 9 percent of the pH 

values were less than 6.5, and almost all of these were 

from the North Fork upstream from Geneva Creek and 

in the tributaries Handcart Gulch and Geneva Creek 

(fig. 10B). About 1 percent of the pH values were 

larger than 9.0, and most of these were from the South 

Fork downstream from Antero Reservoir (site 36, 

fig. 9).

Specific conductance is an indirect measure 

of the dissolved-solids concentration (the dissolvedsolids component of surface water is discussed in 

more detail in the next section). The conversion 

factor between specific conductance and dissolved 

solids is usually between 0.55 and 0.75 (Hem, 

1989). Because it is easily obtained with a field meter, 

measurement of specific conductance has been done 

at many surface-water sites in Park County, and the 

number of measurements is greater than the number 

of dissolved-solids analyses. 

Specific conductance in surface water ranged 

from 8 to 24,000 μS/cm. Specific conductance was 

lowest at sites in the mountains near the headwaters of 

the Middle and North Forks and Tarryall Creek watersheds in the northern one-half of the county (fig. 11) 

(primarily Elk Creek, Deer Creek, and tributaries in 

upper Geneva, Tarryall, and Mosquito Creeks) (figs. 9 

and 10). Specific-conductance values in the interquartile range of all values (indicated by yellow and orange 

dots in fig. 11) were primarily in the North Fork, 

Tarryall, and Middle Fork Basins. The highest values 

of specific conductance generally were detected in 

the southern one-half of the county in the main-stem 

South Platte River or Arkansas River Basin but also 

were found in Handcart Gulch in the North Fork 

Basin (sites 82 and 83); along Park Gulch in the 

Tarryall Creek Basin (sites 57–60); and Trout Creek 

in the Middle Fork Basin (site 31). With a value of 

20,600 μS/cm, the median specific conductance in 

Salt Creek (site 35) was at least one order of magnitude larger than the median of any other stream in the 

county.
18 Review and Analysis of Available Streamflow and Water-Quality Data for Park County, Colorado, 1962–98

0 5 10 15 20 MILES

Area shown in figure 10A

Area shown in figure 10B

124

75

Harold D. Roberts Tunnel

88

EXPLANATION

Number of samples (with

site number from table 3)

Less than 10

10 to 50

51 to 100

More than 100

Platte

River

South

South

Salt

Fork

Creek

Middle

Fourmile Creek

Trout Creek

Fork

North Fork

South Platte River

Tarryall Creek

Tarryall Creek

Michigan Creek

Deer Creek

Craig Creek

Lost Creek

Elk Creek

Badger Creek

Buffalo Creek

Currant Creek

West Fourmile Creek

Lake

George

Antero

Reservoir

Spinney

Mountain

Reservoir Elevenmile

Canyon

Reservoir

Base from U.S. Geological Survey digital data, 1:100,000

Universal Transverse Mercator projection,

Zone 13

39°

106°

105°30'

Figure 9. Surface-water-quality sites in Park County, 1962–98.
SURFACE-WATER QUALITY 19

A

B

EXPLANATION

Number of samples

(with site number from table 3)

Less than 10

10 to 50

51 to 100

More than 100

River

(from fig. 9)

(from fig. 9)

0 1 MILE

0 1 KILOMETER

0 1 MILE

0 1 KILOMETER

South Platte

Middle Fork

Alma

Buckskin

Creek

Mosquito

Creek

South Mosquito Creek

North

Fork

South Platte R

Geneva

Creek

Harold D. Roberts Tunnel

Handcart Gulch

Figure 10. Surface-water-quality sites in the (A) Mosquito Creek Basin and (B) upper North Fork South Platte 

River Basin, Park County, 1962–98.
20 Review and Analysis of Available Streamflow and Water-Quality Data for Park County, Colorado, 1962–98 Table 3. Characteristics of surface-water-quality sites in Park County, 1962–98 [no., number; latitude and longitude in degrees, minutes, and seconds; USGS, U.S. Geological Survey; CDPHE, Colorado Department of Public Health and Environment; P

of Environmental Health; ROCWWN, Rivers of Colorado Water Watch Network; CGS, Colorado Geological Survey; DW, Denver Water; USFS, U.S. Forest Service; NPphysical properties; MI, major ions; TE, trace elements; N, nutrients; B, bacteria; R, radionuclides; O, other constituents (carbon, turbidity, or suspended sediment); Urbadetermined] Site no. (figs. 9–10) Site Name Site identifier Latitude Longitude Data source Period of record No. of samples Ty

1 Middle Fork South Platte River above

Alma, CO

391740106035400 391740 1060354 USGS 1971 and 1974 3 PP, MI

2 Middle Fork South Platte River above

Mosquito Creek

LM–SW20 391613 1060304 CDPHE 1996 1 PP, TE MCBRIDE8 391613 1060302 PCDEH 1990 3 PP, MIMF1 391617 1060302 CDPHE 1988–99 2 PP, TE

3 Upper Mosquito Creek LM–SW01 391801 1060916 CDPHE 1996 1 PP, TE 

M9 391800 1060912 CDPHE 1990 2 PP, MI

4 Mosquito Creek above the North

London Mill

M8 391748 1060909 CDPHE 1990 1 PP 

5 Mosquito Creek below Tributary

from Oliver Twist Mine

LM–SW03 391741 1060908 CDPHE 1996 1 PP, TE M6 391736 1060858 CDPHE 1990 1 PP, TE

6 Mosquito Creek below North 

London Mine

LM–SW07 391729 1060856 CDPHE 1996 1 PP, TE 

7 Mosquito Creek above road to 

Alma-American Mine

M3 391704 1060811 CDPHE 1990 2 PP, MI

8 Mosquito Creek below AlmaAmerican tailings M2 391654 1060811 CDPHE 1988–90 4 PP, MI

MC1 391654 1060811 CDPHE 1988–89 2 PP, TE

9 Mosquito Creek above road to

London Mine

LM–SW08 391654 1060736 CDPHE 1996 1 PP, TE M1 391647 1060745 CDPHE 1988–90 4 PP, MIMC2 391647 1060745 CDPHE 1988–89 2 PP, TE

10 South Mosquito Creek headwaters

area

LM–SW09 391551 1060942 CDPHE 1996 1 PP, TE 

11 South Mosquito Creek above Butte

tailings

SMC1 391612 1060903 CDPHE 1988–89 2 PP, TE 

12 South Mosquito Creek above 

No Name Creek

LM–SW10 391619 1060857 CDPHE 1996 1 PP, TE SMC2 391616 1060855 CDPHE 1988 1 PP, TE

13 No Name Creek above London 

Extension Mine Discharge

LM–SW12 391618 1060910 CDPHE 1996 1 PP, TE NN1 391621 1060911 CDPHE 1988 1 PP

14 No Name Creek above South 

Mosquito Creek

LM–SW13 391619 1060858 CDPHE 1996 1 PP, TE NN2 391618 1060903 CDPHE 1988–89 2 PP, TE

15 South Mosquito Creek below 

No Name Creek

LM–SW14 391621 1060846 CDPHE 1996 1 PP, TE 
SURFACE-WATER QUALITY 21

16 South Mosquito Creek below London

Mine Discharge

SMC3 391625 1060834 CDPHE 1988–89 2 PP, TE 

17 South Mosquito Creek next to London

Mine tailings

SMC4 391631 1060822 CDPHE 1988–89 2 PP, TE 

18 South Mosquito Creek below London

Mine tailings

LM–SW15 391637 1060757 CDPHE 1996 1 PP, TE SMC5 391637 1060753 CDPHE 1988–89 2 PP, TE

19 Mosquito Creek below South Mosquito

Creek

MC3 391628 1060645 CDPHE 1988–89 2 PP, TE 

20 Mosquito Creek below MontgomeryAlma/Betts Mill tailings LM–SW17 391614 1060559 CDPHE 1996 1 PP, TE 

21 Mosquito Creek at Park City MC4 391634 1060537 CDPHE 1988–89 2 PP, TE 22 Mosquito Creek at Kootchie Kootchie

Road

LM–SW18 391626 1060450 CDPHE 1996 1 PP, TE 

23 Mosquito Creek at mouth 5988 391613 1060314 CDPHE 1997–98 4 PP, M

BELOW PC 391608 1060307 ROCWWN 1993–95 46 PP, TELM–SW19 391614 1060322 CDPHE 1996 1 PP, TEMC5 391612 1060304 CDPHE 1988–89 2 PP, TEMCBRIDE9 391609 1060305 PCDEH 1990 3 PP, MI

24 Middle Fork South Platte River below

Mosquito Creek

LM–SW21 391606 1060259 CDPHE 1996 1 PP, TE MF2 391603 1060257 CDPHE 1988–89 2 PP, TE

25 Middle Fork South Platte River below

Pennsylvania Creek

LM–SW22 391444 1060236 CDPHE 1996 1 PP, TE MF3 391438 1060235 CDPHE 1988 1 PP, TE

26 Middle Fork South Platte River above

Fairplay, CO

06693980 391412 1060143 USGS 1977–80 37 PP 391412106014200 391412 1060142 CGS 1973–76 30 PP. MICOUNTY RD 14 391410 1060143 ROCWWN 1992–95 46 PP, TELM–SW23 391408 1060143 CDPHE 1996 1 PP, TE

27 Sacramento Creek near mouth near

Fairplay, CO

391338106023300 391338 1060233 USGS 1971 1 PP, MI

28 Middle Fork South Platte River below

Sacramento Creek

LM–SW24 391641 1060124 CDPHE 1996 1 PP, TE MF4 391346 1060052 CDPHE 1988–89 2 PP, TE

29 Middle Fork South Platte River below

Fairplay, CO

391002105563800 391002 1055638 USGS 1972 and 1974 3 PP, MI391309105593500 391309 1055935 CGS 1972–76 20 RMF5 391000 1055608 CDPHE 1989 1 TE

Table 3. Characteristics of surface-water-quality sites in Park County, 1962–98—Continued[no., number; latitude and longitude in degrees, minutes, and seconds; USGS, U.S. Geological Survey; CDPHE, Colorado Department of Public Health and Environment; Pof Environmental Health; ROCWWN, Rivers of Colorado Water Watch Network; CGS, Colorado Geological Survey; DW, Denver Water; USFS, U.S. Forest Service; NPphysical properties; MI, major ions; TE, trace elements; N, nutrients; B, bacteria; R, radionuclides; O, other constituents (carbon, turbidity, or suspended sediment); Urbadetermined] 

Site no.

(figs. 9–10) Site Name Site identifier Latitude Longitude Data source Period of record No. of samples Ty
22 Review and Analysis of Available Streamflow and Water-Quality Data for Park County, Colorado, 1962–98 30 Middle Fork South Platte River at Highway 9 near Garo 001103 390631 1055326 DW 1973–81, 1983–91, 1994 80 PP, MI

MCBRIDE11 390653 1055434 PCDEH 1990 3 PP, MI

31 Trout Creek near mouth near Garo 390802105534200 390802 1055342 USGS 1974 2 PP, MI32 Middle Fork South Platte River near Hartsel, CO 06694100 390120 1054529 USGS 1977–79 36 PP 

390105105451800 390105 1054518 USGS 1974 2 PP, MI

33 South Fork South Platte River below Rough and Tumbling Creek 06694400 390457 1060252 USGS 1977–80 34 PP 

390458105024900 390458 1050249 USGS 1974 2 PP, MI

34 South Fork South Platte River above Antero Reservoir 001101 390422 1055827 DW 1971, 1973–92, 1994, 1997–98 65 PP, MI

390419105582600 390419 1055826 USGS 1972 1 PP, MIMCBRIDE10 390415 1055825 PCDEH 1990 3 PP, MI

35 Salt Creek above Antero Reservoir 385750105552500 385750 1055525 USGS 1974 2 PP, MI36 South Fork South Platte River below Antero Reservoir 001102 385940 1055345 DW 1962–63, 1965, 1967–82, 1984–98 134 PP, MI

37 Fourmile Creek near Fairplay, CO 06694700 391104 1060347 USGS 1977–80 36 PP 

089801 391031 1060306 USFS 1968–72 10 PP, MI

38 Four Mile Creek at mouth 390126105490500 390126 1054905 USGS 1974 2 PP, MI39 South Fork South Platte River at Hartsel, CO 001104 390115 1054815 DW 1973–81, 1984–88, 1994, 1997–98 54 PP, MI

390112105474600 390112 1054746 USGS 1974 2 PP, MI

40 South Platte River above Spinney Mountain Reservoir 001125 385910 1054052 DW 1997–98 5 PP, TE

41 Buffalo Gulch at mouth 385831105384000 385831 1053840 USGS 1974 2 PP, MI42 South Platte River below Spinney Mountain Reservoir BLWSPINNEYAUR 385822 1053702 AURORA 1992–98 34 PP, MI

43 South Platte River above Elevenmile 

Canyon Reservoir

001105 385804 1053454 DW 1967, 1971,

1973–80, 1984–92,

1997–98

73 PP, MI

06695000 385803 1053451 USGS 1972, 1978–86,

1992

191 PP, MI

385804105345500 385804 1053455 USGS 1974 2 PP, MI

Table 3. Characteristics of surface-water-quality sites in Park County, 1962–98—Continued[no., number; latitude and longitude in degrees, minutes, and seconds; USGS, U.S. Geological Survey; CDPHE, Colorado Department of Public Health and Environment; Pof Environmental Health; ROCWWN, Rivers of Colorado Water Watch Network; CGS, Colorado Geological Survey; DW, Denver Water; USFS, U.S. Forest Service; NPphysical properties; MI, major ions; TE, trace elements; N, nutrients; B, bacteria; R, radionuclides; O, other constituents (carbon, turbidity, or suspended sediment); Urbadetermined] 

Site no.

(figs. 9–10) Site Name Site identifier Latitude Longitude Data source Period of record No. of samples Ty
SURFACE-WATER QUALITY 23

44 Simms Creek above Elevenmile

Canyon Reservoir

FLFO_NURE_21 385342 1052921 NPS 1976 1 PP, MI

45 Ranger Station Gulch above 

Elevenmile Canyon Reservoir

FLFO_NURE_04 385335 1052841 NPS 1976 1 PP, MI

46 South Platte River below Elevenmile

Canyon Reservoir

001106 385418 1052821 DW 1962–98 142 PP, MI06696000 385419 1052822 USGS 1975, 1978–87 204 PP, M

47 South Platte River above Messenger

Gulch

FLFO_NURE_22 385557 1052442 NPS 1976 1 PP, MI

48 Messenger Gulch at Mouth FLFO_NURE_20 385604 1052438 NPS 1976 1 PP, MI49 Fish Creek above County Line FLFO_NURE_62 385516 1052127 NPS 1976 1 PP, MI50 Twin Creek at mouth 385821105213300 385821 1052133 USGS 1974–75 3 PP, M

FLFO_NURE_19 385822 1052124 NPS 1976 1 PP, MI

51 South Platte River below Lake George

at Lake George, CO

001113 385911 1052146 DW 1975–81, 1984–90,

1998

49 PP, MI

SCHOOL BRIDGE 385822 1053702 ROCWWN 1993–94, 1996–97 36 PP, TE

52 Adamans Creek above Link Creek FLFO_NURE_23 385910 1052554 NPS 1976 1 PP, M53 South Platte River below Lake 

George, CO

390135105205900 390135 1052059 USGS 1974–75 3 PP, MI

54 South Platte River above Cheesman 080401 390423 1051813 USFS 1968–71 7 PP, MI55 Tarryall Creek above Como, CO 06696980 392022 1055437 USGS 1977–86 97 PP 

392022105543900 392022 1055439 USGS 1974 2 PP, MI

56 Tarryall Creek at U.S. Highway 285

near Como, CO

391958105520200 391958 1055202 USGS 1998 1 PP, MIMCBRIDE7 391956 1055201 PCDEH 1990 3 PP, MI

57 Park Gulch above Como, CO 391922105535400 391922 1055354 USGS 1997 1 PP, MI58 Park Gulch below Como, CO 391847105530400 391847 1055304 USGS 1997 1 PP, MI59 Park Gulch above King Mine near

Como, CO

391755105515600 391755 1055156 USGS 1997 1 PP, MI

60 Park Gulch above Slater Ditch near

Como, CO

391628105502100 391628 1055021 USGS 1997 1 PP, MI

61 Tarryall Creek below Park Gulch near

Como, CO

06697100 391654 1054711 USGS 1997–98 29 PP, MI391653105471200 391653 1054712 USGS 1974 2 PP, MI

62 French Creek near Jefferson, CO 06697200 392321 1053807 USGS 1986–90 39 PP 63 Michigan Creek above Jefferson, CO 06697450 392132 1055027 USGS 1977–86, 1998 95 PP, MI

MCBRIDE6 392103 1054955 PCDEH 1990 3 PP, MI

Table 3. Characteristics of surface-water-quality sites in Park County, 1962–98—Continued[no., number; latitude and longitude in degrees, minutes, and seconds; USGS, U.S. Geological Survey; CDPHE, Colorado Department of Public Health and Environment; Pof Environmental Health; ROCWWN, Rivers of Colorado Water Watch Network; CGS, Colorado Geological Survey; DW, Denver Water; USFS, U.S. Forest Service; NPphysical properties; MI, major ions; TE, trace elements; N, nutrients; B, bacteria; R, radionuclides; O, other constituents (carbon, turbidity, or suspended sediment); Urbadetermined] 

Site no.

(figs. 9–10) Site Name Site identifier Latitude Longitude Data source Period of record No. of samples Ty
24 Review and Analysis of Available Streamflow and Water-Quality Data for Park County, Colorado, 1962–98 64 Jefferson Creek below Jefferson Lake near Jefferson, CO 392453105501100 392453 1055011 USGS 1998 1 PP, MI

FS0212001000001 392500 1055000 USFS 1976–80 11 PP, MI

65 Jefferson Creek near Jefferson, CO 06698000 392324 1054838 USGS 1977–86 92 PP 

MCBRIDE5 392334 1054838 PCDEH 1990 3 PP, MI

66 Deadman Creek near Jefferson Creek FS0212001000002 392600 1053000 USFS 1976–80 9 PP, MI67 Michigan Creek below Jefferson, CO 391918105454500 391918 1054545 USGS 1974 2 PP, MI68 Tarryall Creek near Jefferson, CO 06698500 391742 1054305 USGS 1977–81 109 PP, MI69 Rock Creek near Jefferson, CO 06699000 391729 1054143 USGS 1986–90, 1995 45 PP 70 Tarryall Creek below Rock Creek near Jefferson, CO 06699005 391713 1054143 USGS 1983–97 137 PP, N 

71 Tarryall Creek near mouth 001107 390448 1052526 DW 1967–68, 1970–71, 1973–74, 1981, 1984–90 38 PP, MI

080201 390455 1052442 USFS 1968–72 7 PP, MI390425105240600 390425 1052406 USGS 1972 1 PP, MI390426105240500 390426 1052405 USGS 1974–75 3 PP, MI

72 Monkey Creek FS0212004000007 391730 1053330 USFS 1980 1 PP, MI73 No Name Creek FS0212004000006 391715 1053245 USFS 1980 1 PP, MI74 Indian Creek FS0212004000005 391645 1053100 USFS 1980 1 PP, M75 South Fork Lost Creek FS0212004000003 391700 1053030 USFS 1980 2 PP, MI76 North Fork Lost Creek FS0212004000004 391715 1053020 USFS 1980 2 PP, MI77 Tributary northwest of Missouri Mine NFSP15 393112 1055132 CDPHE 1990 1 PP 78 North Fork South Platte River NFSP9 393059 1055056 CDPHE 1990 1 TE 79 North Fork South Platte River above Gibson Lake Trail NFSP6 392929 1054927 CDPHE 1990 1 PP, TE 

NFSP7 393018 1055006 CDPHE 1990 1 PP, TE 80 North Fork South Platte River above Hall Creek Campground BJOHNSON5 392903 1054839 PCDEH 1992–94 13 PP, MI

MCBRIDE3 392904 1054840 PCDEH 1990 3 PP, MINFSP17 392910 1054859 CDPHE 1990 1 PP, TENFSP5 392908 1054848 CDPHE 1990 1 PP, TE

81 Handcart Gulch near headwaters 113 393117 1054954 USGS 1979 1 PP, MI

BJOHNSON1 393115 1055006 PCDEH 1992 6 PP, MIBJOHNSON2 393117 1054955 PCDEH 1992–94 10 PP, MI

Table 3. Characteristics of surface-water-quality sites in Park County, 1962–98—Continued[no., number; latitude and longitude in degrees, minutes, and seconds; USGS, U.S. Geological Survey; CDPHE, Colorado Department of Public Health and Environment; Pof Environmental Health; ROCWWN, Rivers of Colorado Water Watch Network; CGS, Colorado Geological Survey; DW, Denver Water; USFS, U.S. Forest Service; NPphysical properties; MI, major ions; TE, trace elements; N, nutrients; B, bacteria; R, radionuclides; O, other constituents (carbon, turbidity, or suspended sediment); Urbadetermined] 

Site no.

(figs. 9–10) Site Name Site identifier Latitude Longitude Data source Period of record No. of samples Ty
SURFACE-WATER QUALITY 25

82 Handcart Gulch below headwaters BJOHNSON3 393046 1054923 PCDEH 1992 6 PP, MI83 Handcart Gulch at mouth 147 392904 1054827 USGS 1979 1 PP, M

BJOHNSON4 392905 1054829 PCDEH 1992–94 13 PP, MIHANDCART 392905 1054827 CDPHE 1990 1 PP, TEMCBRIDE2 392906 1054830 PCDEH 1990 3 PP, MI

84 North Fork South Platte River below

Handcart Gulch

BJOHNSON6 392858 1054824 PCDEH 1992–94 13 PP, MI

85 North Fork South Platte River above

Beaver Creek

392832105461700 392832 1054617 USGS 1971 1 PP, MINFSP4 392833 1054620 CDPHE 1990 1 PP, TE

86 Beaver Creek BEAVER 392830 1054616 CDPHE 1990 1 PP, TE 87 North Fork South Platte River 1 mile

above Webster

MCBRIDE4 392738 1054411 PCDEH 1990 3 PP, MI

88 Hoosier Creek FS0212007000002 392600 1054630 USFS 1980 4 PP, O 89 North Fork South Platte River at

Webster, CO

001201 392724 1054312 DW 1967–81, 1983–90,

1994

134 PP, MI

392725105432400 392725 1054324 USGS 1972 1 PP, MI5915 392709 1054323 CDPHE 1997–98 5 PP, MINFSP2 392724 1054314 CDPHE 1990 1 PP, TENFSP3 392726 1054321 CDPHE 1990 1 PP, TE

90 North Fork South Platte River 

1.5 miles above Roberts Tunnel

BJOHNSON7 392731 1054223 PCDEH 1992–94 13 PP, MI

91 North Fork South Platte River above

Roberts Tunnel

392740105404400 392740 1054044 USGS 1974 1 PP, MI5913 392739 1054045 CDPHE 1997–98 5 PP, MI

92 East Portal Harold D. Roberts Tunnel 002402 392741 1054043 DW 1966–71, 1974–83,

1985, 1987–98

144 PP, MI

392742105403500 392742 1054035 USGS 1974 1 PP, MI

93 North Fork South Platte River below

Roberts Tunnel

BJOHNSON8 392739 1054037 PCDEH 1992 6 PP, MI

94 North Fork South Platte River at 

Grant, CO

06702500 392733 1053949 USGS 1968 1 PP 392737105394700 392737 1053947 USGS 1974 1 PP, MI

95 Geneva Creek above Smelter Gulch 102 393348 1054607 USGS 1979 1 PP, M

393348105460415 393348 1054604 USGS 1995 3 PP, MIBJOHNSON11 393351 1054620 PCDEH 1992–94 13 PP, MI

Table 3. Characteristics of surface-water-quality sites in Park County, 1962–98—Continued[no., number; latitude and longitude in degrees, minutes, and seconds; USGS, U.S. Geological Survey; CDPHE, Colorado Department of Public Health and Environment; Pof Environmental Health; ROCWWN, Rivers of Colorado Water Watch Network; CGS, Colorado Geological Survey; DW, Denver Water; USFS, U.S. Forest Service; NPphysical properties; MI, major ions; TE, trace elements; N, nutrients; B, bacteria; R, radionuclides; O, other constituents (carbon, turbidity, or suspended sediment); Urbadetermined] 

Site no.

(figs. 9–10) Site Name Site identifier Latitude Longitude Data source Period of record No. of samples Ty
26 Review and Analysis of Available Streamflow and Water-Quality Data for Park County, Colorado, 1962–98 96 Geneva Creek above Duck Creek near Grant, CO 393148105435600 393148 1054356 USGS 1971–72 2 PP, MI

393153105440109 393153 1054401 USGS 1994–97 26 PP, MIBJOHNSON10 393152 1054403 PCDEH 1992–94 13 PP, MI

97 Duck Creek above Mill Gulch near Grant, CO 393243105430814 393243 1054308 USGS 1995 3 PP, MI

98 Duck Creek near Grant, CO 06704500 393149 1054350 USGS 1994–97 702 PP, MI99 Bruno Gulch above Geneva Park near Grant, CO 393141105445808 393141 1054458 USGS 1995–97 18 PP, MI

100 Geneva Creek above Scott Gomer Creek 393018105421707 393018 1054217 USGS 1994–95 5 PP, MI

101 Scott Gomer Creek at mouth near Grant, CO 393028105421706 393028 1054217 USGS 1994–97 22 PP, MI

102 Geneva Creek above Callahan Gulch near Grant, CO 392856105413700 392856 1054137 USGS 1972 1 PP, MI

103 Geneva Creek near Grant, CO 06705500 392820 1054054 USGS 1994–97 797 PP, MI

080701 392836 1054100 USFS 1968–71 8 PP, MI5980 392829 1054107 CDPHE 1997 2 PP, MIBJOHNSON9 392802 1054029 PCDEH 1992 6 PP, MIMCBRIDE1 392803 1054030 PCDEH 1990 3 PP, MI

104 Geneva Creek at mouth at Grant, CO 146 392737 1053948 USGS 1979 1 PP, MI

392735105394705 392735 1053947 USGS 1995 4 PP, MI392738105394600 392738 1053946 USGS 1974 2 PP, MI

105 North Fork South Platte River below Geneva Creek 001205 392733 1053947 DW 1975–80, 1984–92, 1994 62 PP, MI

06706000 392726 1053929 USGS 1972, 1978–87 181 PP, MI5910 392734 1053949 CDPHE 1997–98 5 PP, MINFSP1 392733 1053945 CDPHE 1990 1 PP, TE

106 North Fork South Platte River at

Bridge G14E

BJOHNSON12 392717 1053826 PCDEH 1992–94 12 PP, MI

107 North Fork South Platte River below

Long Meadows Farm

BJOHNSON13 392555 1053414 PCDEH 1994 2 PP, MI

108 North Fork South Platte River near

Fitzsimmons Middle School

FITZ 392512 1053206 ROCWWN 1993–97 68 PP, TE RANCH 392512 1053237 ROCWWN 1992–97 71 PP, TE

Table 3. Characteristics of surface-water-quality sites in Park County, 1962–98—Continued[no., number; latitude and longitude in degrees, minutes, and seconds; USGS, U.S. Geological Survey; CDPHE, Colorado Department of Public Health and Environment; Pof Environmental Health; ROCWWN, Rivers of Colorado Water Watch Network; CGS, Colorado Geological Survey; DW, Denver Water; USFS, U.S. Forest Service; NPphysical properties; MI, major ions; TE, trace elements; N, nutrients; B, bacteria; R, radionuclides; O, other constituents (carbon, turbidity, or suspended sediment); Urbadetermined] 

Site no.

(figs. 9–10) Site Name Site identifier Latitude Longitude Data source Period of record No. of samples Ty
SURFACE-WATER QUALITY 27

109 North Fork South Platte River near

Glenn Isle Rock

GI ROCK 392443 1053032 ROCWWN 1992–94 22 PP, TE 

110 North Fork South Platte River at

Bailey, CO

001202 392408 1052754 DW 1967–74, 1981,

1983–90, 1994

96 PP, MI

FU BRIDGE 392411 1052758 ROCWWN 1992–94 22 PP, TENFORKAURORA 392413 1052800 AURORA 1993–98 63 PP, MI

111 North Fork South Platte River above

Craig Creek

392258105254400 392258 1052544 USGS 1974 2 PP, MI

112 Craig Creek at mouth 392258105254500 392258 1052545 USGS 1974 2 PP, M113 North Fork South Platte River below

Craig Creek

001206 392300 1052545 DW 1975–80, 1983–88 41 PP, MI

114 Deer Creek near Bailey, CO 393040105340400 393040 1053404 USGS 1996–97 617 PP, MI115 Deer Creek above County Line 392532105244900 392532 1052449 USGS 1974 2 PP, MI116 Roland Gulch 392617105242700 392617 1052427 USGS 1974 1 PP, MI117 Elk Creek near Harris Park, CO 393013105293500 393013 1052935 USGS 1972–73 4 PP, M118 Elk Creek above County Line 392958105242400 392958 1052424 USGS 1974 2 PP, MI119 Badger Creek above County Line 384148105494000 384148 1054940 USGS 1974 2 PP, MI

107093740 383932 1054848 USGS 1981–84, 1987–98 333 PP, MI

120 Currant Creek above County Line 384318105305900 384318 1053059 USGS 1974 2 PP, M121 West Fourmile Creek below

Bumgarner Creek

FLFO_NURE_39 384654 1052546 NPS 1976 1 PP, MI

122 West Fourmile Creek above 

Cottonwood Creek

FLFO_NURE_41 384623 1052138 NPS 1976 1 PP, MI

123 Cottonwood Creek at mouth FLFO_NURE_67 384649 1052131 NPS 1976 1 PP, MI124 Cobb Creek at mouth FLFO_NURE_40 384627 1052058 NPS 1976 1 PP, MI125 South Platte River above 

Cheesman Lake2

001116 390946 1051835 DW 1984–92, 1997–98 28 PP, TE

1Located in Fremont County 3 miles downstream from county line.2Located in Jefferson County 3 miles downstream from county line.

Table 3. Characteristics of surface-water-quality sites in Park County, 1962–98—Continued[no., number; latitude and longitude in degrees, minutes, and seconds; USGS, U.S. Geological Survey; CDPHE, Colorado Department of Public Health and Environment; Pof Environmental Health; ROCWWN, Rivers of Colorado Water Watch Network; CGS, Colorado Geological Survey; DW, Denver Water; USFS, U.S. Forest Service; NPphysical properties; MI, major ions; TE, trace elements; N, nutrients; B, bacteria; R, radionuclides; O, other constituents (carbon, turbidity, or suspended sediment); Urbadetermined] 

Site no.

(figs. 9–10) Site Name Site identifier Latitude Longitude Data source Period of record No. of samples Ty
28 Review and Analysis of Available Streamflow and Water-Quality Data for Park County, Colorado, 1962–98

Table 4. Summary of surface-water-quality data for Park County, 1962–98

[--, no data; <, less than; no., number; mg/L, milligrams per liter; μg/L, micrograms per liter; TVS, table value standard; pCi/L, picocuries per liter; 

cols/100 mL, colonies per 100 milliliters; μS/cm, microsiemens per centimeter at 25 degrees Celsius; ° C, degrees Celsius; CaCO3, calcium carbonate]

Constituent or property Number of

analyses

Minimum

Concentration or value at indicated percentile Maximum

Standard or

 guideline1

10 25 50 75 90

Physical properties

Water temperature (° C) 2,614 0.0 0.0 2.0 6.0 10.5 15.0 26.0 20.0

Oxygen, dissolved (mg/L) 517 0.1 7.5 8.1 9.0 10.0 10.9 20.0 6.0

pH (standard units) 1,516 2.9 6.6 7.4 7.8 8.2 8.5 10.5 6.5–9.0

Specific conductance (μS/cm) 1,750 8 60 90 170 320 720 24,000 --

Major ions and dissolved solids, in mg/L

Bicarbonate, dissolved 119 3 21 71 120 180 243 520 --

Calcium, dissolved 382 <0.1 4.5 6.7 12.3 31.5 53.0 770 --

Chloride, dissolved 734 <0.1 0.4 2.0 5.0 80.0 221 7,600 2

250

Fluoride, dissolved 198 <0.1 <0.1 0.1 0.2 0.4 0.7 3.0 --

Magnesium, dissolved 769 <0.1 1.6 2.9 5.6 21.8 34.0 318 --

Potassium, dissolved 241 <0.5 0.6 0.8 1.0 1.6 2.7 80 --

Silica, dissolved 311 0.5 2.2 4.5 8.0 10.7 17.0 42.0 --

Sodium, dissolved 311 <0.1 1.0 1.6 2.9 5.3 13.0 4,900 --

Sulfate, dissolved 748 <0.3 6.7 23.0 45.0 99.0 196 2,100 2

250

Dissolved solids 504 16 48 86 142 242 394 15,700 --

Nutrients, in mg/L

Ammonia 478 <0.05 <0.05 <0.05 <0.05 0.05 0.11 1.0 --

Un-ionized ammonia 301 <0.01 <0.01 <0.01 <0.01 <0.01 0.01 0.05 0.02

Nitrate 804 <0.05 <0.05 <0.05 0.06 0.12 0.23 1.1 2

10

Nitrite 240 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 0.05

Orthophosphorus 230 <0.01 <0.01 <0.01 <0.01 0.02 0.03 0.1 30.05

Phosphorus, total 861 <0.01 <0.01 <0.01 0.02 0.04 0.08 2.6 4

0.1

Trace elements, in μg/L

Aluminum, dissolved 252 <50 <50 <50 100 1,600 6,460 18,600 --

Aluminum, total 331 <1 10 30 70 218 696 16,000 --

Arsenic, dissolved 163 <1 <1 <1 <1 <1 1 9 --

Arsenic, total 101 <1 <1 <1 <1 <1 <1 <1 5

50

Barium, dissolved 59 11 20 30 58 71 79 200 --

Barium, total 346 <10 10 29 50 76 100 371 --

Boron, total 48 <12 <12 <12 <12 55 105 142 6

750

Cadmium, dissolved 193 <1 <1 <1 <1 2 10 60 7

TVS

Cadmium, total 797 <1 <1 <1 <1 <1 1 60 --
SURFACE-WATER QUALITY 29

Trace elements, in μg/L—Continued

Chromium, dissolved 170 <1 <1 <1 <1 10 50 80 811

Chromium, total 451 <1 <1 <1 <1 1 3 82 --

Copper, dissolved 313 <1 <1 <1 5 30 72 220 9

TVS

Copper, total 821 <1 <1 2 5 10 20 590 --

Iron, dissolved 449 <10 <10 40 110 280 1,020 24,800 2

300

Iron, total 1,056 <10 30 70 170 396 920 47,000 101,000

Lead, dissolved 226 <2 <2 <2 <2 9 210 370 11TVS

Lead, total 723 <1 <1 <1 <1 3 11 480 --

Manganese, dissolved 428 <5 <5 10 40 127 317 2,715 2,1250

Manganese, total 979 <5 8 19 40 77 131 970 131,000

Mercury, dissolved 58 <0.2 <0.2 <0.2 <0.2 <0.2 <0.2 0.8 --

Mercury, total 309 <0.2 <0.2 <0.2 <0.2 <0.2 0.2 1 140.01

Molybdenum, dissolved 224 <10 <10 <10 <10 10 40 150 --

Molybdenum, total 329 <2 <2 <2 2 52 164 509 --

Nickel, dissolved 153 <1 <1 <1 10 30 60 110 15TVS

Nickel, total 261 <5 <5 <5 <5 5 10 300 --

Selenium, dissolved 70 <1 <1 <1 <1 <1 2 15 165

Selenium, total 186 <5 <5 <5 <5 <5 <5 <5 1710

Silver, dissolved 104 <1 <1 <1 <1 <1 <1 2 18TVS

Silver, total 476 <1 <1 <1 <1 <1 1 26 --

Uranium, dissolved 194 <1 <1 1 2 3 4 85 --

Zinc, dissolved 390 <3 <3 5 30 80 190 5,300 19TVS

Zinc, total 833 <4 4 11 26 45 126 7,000 --

Other constituents or properties

Alkalinity, total (as CaCO3) 1,145 1 18 38 84 127 160 350 --

Alpha, dissolved gross (μg/L) 38 <1 1 3 6 9 10 12 --

Alpha, total (pCi/L) 26 <1 <1 <1 2 7 14 28 --

Beta, dissolved gross (μg/L) 40 <1 2 2 3 3 4 6 --

Beta, total (pCi/L) 26 <1 <1 <1 7 60 186 314 --

Carbon, organic, dissolved 

(mg/L)

82 <0.1 1.1 1.9 3.8 8.3 13 110 --

Carbon, organic, total (mg/L) 250 <0.1 0.8 1.4 2.3 3.6 4.4 33 --

Fecal coliform (cols/100 mL) 630 <1 <1 <1 <1 6 32 4,000 202,000

Table 4. Summary of surface-water-quality data for Park County, 1962–98—Continued

[--, no data; <, less than; no., number; mg/L, milligrams per liter; μg/L, micrograms per liter; TVS, table value standard; pCi/L, picocuries per liter; 

cols/100 mL, colonies per 100 milliliters; μS/cm, microsiemens per centimeter at 25 degrees Celsius; °C, degrees Celsius; CaCO3, calcium carbonate]

Constituent or property Number of

analyses

Minimum

Concentration or value at indicated percentile Maximum

Standard or

 guideline1

10 25 50 75 90
30 Review and Analysis of Available Streamflow and Water-Quality Data for Park County, Colorado, 1962–98

Major Ions and Dissolved Solids

The major ions summarized in this report 

(bicarbonate, calcium, chloride, fluoride, magnesium, 

potassium, silica, sodium, and sulfate) are constituents 

commonly dissolved in most natural waters. For 

watersheds without substantial development, the presence of major ions dissolved in water is the result of 

interactions between surface and ground water, soils, 

and the aquifer material.

In many Park County streams, the dominant 

ions in solution are the cations calcium and magnesium and the anion bicarbonate. Calcium-magnesiumbicarbonate type waters are found in the mountain 

tributaries in the South and North Fork Basins 

(sites 33, 115, 118), throughout the Middle Fork and 

Tarryall Creek Basins, and in Badger and Currant 

Creeks in the Arkansas River Basin (fig. 11). In some 

streams of the upper North Fork Basin (site 89 on the 

North Fork, site 96 on Geneva Creek), sulfate replaces 

bicarbonate as the dominant anion. Sulfate in surface 

water of the upper North Fork Basin has been attributed to the weathering of pyrite-bearing rocks in that 

part of the county (Bassett and others, 1992). The 

presence of several ions at nearly equivalent concentrations in the main-stem South Platte River downstream from Hartsel to the county line (for example, 

Other constituents or properties—Continued

Fecal streptococcus

(cols/100 mL)

572 <1 <1 <1 1 14 48 1,140 --

Hardness, total

(mg/L as CaCO3)

1,390 2.4 30 56 105 182 262 2,600 --

Sediment, suspended (mg/L) 341 <1 2 6 21 86 182 2,990 --

1Acute or chronic water-quality standards for most streams in Park County (Colorado Department of Public Health and Environment, 1998a, 1999a). 2Not applicable to Geneva Creek and tributaries of Geneva Creek downstream from Scott Gomer Creek (Colorado Department of Public Health and 

Environment, 1999a). 3Recommended limit for orthophosphate where rivers enter lakes and reservoirs (U.S. Environmental Protection Agency, 1986).

4Recommended limit for controlling eutrophication in rivers (U.S. Environmental Protection Agency, 1986).

5

Geneva Creek and tributaries of Geneva Creek downstream from Scott Gomer Creek, 100 μg/L (Colorado Department of Public Health and Environment, 1999a). 6Not applicable to Geneva Creek upstream from Scott Gomer Creek (Colorado Department of Public Health and Environment, 1999a).

7

South Mosquito Creek, 1.9 μg/L; Geneva Creek upstream from Scott Gomer Creek, 2 μg/L (Colorado Department of Public Health and Environment, 

1999a).8Geneva Creek upstream from Scott Gomer Creek, 25 μg/L (Colorado Department of Public Health and Environment, 1999a). 9

Geneva Creek upstream from Scott Gomer Creek, 70 μg/L (Colorado Department of Public Health and Environment, 1999a). 10Geneva Creek upstream from Scott Gomer Creek, 1,200 μg/L (Colorado Department of Public Health and Environment, 1999a). 11Geneva Creek upstream from Scott Gomer Creek, 4 μg/L (Colorado Department of Public Health and Environment, 1999a). 12West Fourmile Creek, 99 μg/L; South Mosquito Creek, 118 μg/L (Colorado Department of Public Health and Environment, 1998a, 1999a). 13Geneva Creek upstream from Scott Gomer Creek, 1,700 μg/L; not applicable in Arkansas River Basin (Colorado Department of Public Health and 

Environment, 1998a, 1999a). 14Geneva Creek upstream from Scott Gomer Creek, 0.05 μg/L (Colorado Department of Public Health and Environment, 1999a). 15Geneva Creek upstream from Scott Gomer Creek, 50 μg/L (Colorado Department of Public Health and Environment, 1999a). 16Dissolved selenium standard only applicable in Arkansas River Basin (Colorado Department of Public Health and Environment, 1998a, 1999a). 17Geneva Creek upstream from Scott Gomer Creek, 50 μg/L; not applicable in Arkansas River Basin (Colorado Department of Public Health and 

Environment, 1998a, 1999a). 18Geneva Creek upstream from Scott Gomer Creek, 1 μg/L (Colorado Department of Public Health and Environment, 1999a). 19Mosquito Creek downstream from South Mosquito Creek, 220 μg/L; South Mosquito Creek, 580 μg/L; Geneva Creek upstream from Scott Gomer 

Creek, 540 μg/L (Colorado Department of Public Health and Environment, 1999a). 20Tributaries to South and Middle Fork South Platte River, Mosquito Creek downstream from South Mosquito Creek, South Mosquito Creek, 

Arkansas River Basin, 200 colonies per 100 mL (Colorado Department of Public Health and Environment, 1998a, 1999a).

Table 4. Summary of surface-water-quality data for Park County, 1962–98—Continued

[--, no data; <, less than; no., number; mg/L, milligrams per liter; μg/L, micrograms per liter; TVS, table value standard; pCi/L, picocuries per liter; 

cols/100 mL, colonies per 100 milliliters; μS/cm, microsiemens per centimeter at 25 degrees Celsius; °C, degrees Celsius; CaCO3, calcium carbonate]

Constituent or property Number of

analyses

Minimum

Concentration or value at indicated percentile Maximum

Standard or

 guideline1

10 25 50 75 90
SURFACE-WATER QUALITY 31

Site 96

Site 119 Site 120

Cl

SO4

HCO3

Na

K Mg

Ca

Cl

Na

Site 35

Site 39

Site 53

HCO3

Ca

Mg

EXPLANATION

Cl SO4

HCO3

Na

K

Mg

Ca

Percent major ions, in

milliequivalents per liter

ANIONS

Ca - calcium

Mg - magnesium

K - potassium

Na - sodium

CATIONS

HCO3 - bicarbonate

SO4 - sulfate

Cl - chloride

Median specific conductance, in

microsiemens per centimeter

(with site number from table 3)

Less than 96

96 to 180

181 to 390

391 to 725

Greater than 725

SO4

Ca

Mg

SO4

Ca

Mg

Site 89

HCO3

Ca

Site 118

HCO3

Ca

Mg

Site 29

HCO3

Ca

Mg

Site 1

HCO3

Ca

Site 64

Mg

HCO3

Ca

Mg

HCO3 Mg

Na

Ca

Site 71

(only predominant

ions are labeled)

HCO3 Na

Mg

Ca Cl

SO4

40

41

43

Site 115

Ca

HCO3

65

66

64

Ca

HCO3

Mg

Site 33

35 48

Salt Creek

South

Fork Middle

Fork South Platte

Currant Creek

West Fourmile Creek

Badger Creek

River

Tarryall Creek

Tarryall Creek

North

Fork

Deer Creek

Elk Creek

Base from U.S. Geological Survey 

digital data, 1:100,000

Universal Transverse Mercator projection,

Zone 13

39°

106°

105°30'

Figure 11. Water types and median specific conductance at selected surface-water sites in Park County.
32 Review and Analysis of Available Streamflow and Water-Quality Data for Park County, Colorado, 1962–98

site 53 in fig. 11) probably results from the mixing of 

sodium-chloride type water in the lower South Fork 

with calcium-magnesium-bicarbonate water in the 

Middle Fork. The source of sodium and chloride in 

the lower South Fork is Salt Creek (site 35, fig. 11), 

a saline tributary that flows into the South Fork at 

Antero Reservoir. Springs discharging from evaporite 

beds in the Maroon Formation of Pennsylvanian and 

Permian age are the likely source of sodium and chloride in Salt Creek (Klein and others, 1978). 

 The CDPHE has set in-stream standards of 

250 mg/L for two of the major ions—chloride and 

sulfate—that are applicable to most surface waters 

in Park County. The sites where chloride and sulfate 

concentrations have exceeded the standards in at least 

one sample are listed in table 5. Several of the sites 

with higher chloride and sulfate concentrations are 

located on the South Fork and main-stem South Platte 

River downstream from Antero Reservoir. The source 

of chloride and sulfate in this reach may be Salt Creek 

(site 35, fig. 9), where chloride and sulfate concentrations as high as 7,600 and 2,100 mg/L, respectively, 

have been measured.

Dissolved solids is a computed or direct 

measurement of the total dissolved-constituent 

concentration. Major ions make up the bulk of 

dissolved-solids concentration; other constituents 

such as nitrogen, phosphorus, organic carbon, and 

the trace elements listed in table 4 account for the 

remainder. The CDPHE has not set standards for 

dissolved solids in State waters; however, there is 

a recommended limit for treated drinking water of 

500 mg/L (U.S. Environmental Protection Agency, 

1996). Additionally, crop losses might occur 

when dissolved-solids concentrations reach about 

700–850 mg/L in irrigation water (U.S. Department 

of the Interior, 1994). At least 90 percent of the 

dissolved-solids concentrations in surface-water 

samples collected in Park County were less than 

500 mg/L. Dissolved solids were highest in Salt Creek 

(site 35, fig. 9) where concentrations were at least one 

order of magnitude larger than at any other site.

Nutrients

 Nitrogen and phosphorus are essential nutrients 

for plant growth; however, excessive nutrient concentrations accelerate the growth of algae and other 

aquatic plants, which may lead to degraded aquatic 

habitat. Additionally, high nitrogen concentrations, in 

the form of un-ionized ammonia, can be toxic to fish. 

Natural sources of nutrients include atmospheric 

inputs, phosphate minerals in rocks and soils, and 

breakdown products from the decomposition of 

organic matter. Elevated nutrient levels in water may 

Table 5. Surface-water sites in Park County having chloride or sulfate concentrations larger than 250 milligrams per liter in at 

least one sample

[--, not computed or concentration less than 250 milligrams per liter]

Site no.

(fig. 9) Site name Period of

sampling

Number of

samples

Concentration,

in milligrams per liter

Chloride Sulfate

MinimumMaximum Median Minimum

Maximum Median

31 Trout Creek near mouth near Garo 1974 2 -- -- -- 170 380 275

35 Salt Creek above Antero Reservoir 1974 2 5,100 7,600 6,350 1,800 2,100 1,950

36 South Fork South Platte River below 

Antero Reservoir

1962–82 52 125 1,020 348 65 780 256

39 South Fork South Platte River at 

Hartsel, CO

1973–81 29 70 532 209 50 450 186

41 Buffalo Gulch at mouth 1974 2 -- -- -- 380 410 395

43 South Platte River above Elevenmile 

Canyon Reservoir

1967–80 31 12 460 140 46 300 150

46 South Platte River below Elevenmile 

Canyon Reservoir

1962–82 51 -- -- -- 48 325 140

58 Park Gulch below Como, CO 1997 1 -- -- -- -- 1,990 --

59 Park Gulch above King Mine near 

Como, CO

1997 1 -- -- -- -- 1,580 --
SURFACE-WATER QUALITY 33

originate from anthropogenic sources such as phosphate detergents, wastewater discharges, seepage from 

septic systems, and fertilizers.

The surface-water sites at which selected 

nutrient species have been collected and the dates of 

sample collection are presented in figure 12. Nutrient 

data have been collected in most of the subbasins in 

the county; however, data for ammonia or total phosphorus for the Arkansas River Basin were not found 

during the data search. Most ammonia data were 

collected after 1983, and most nitrate and total phosphorus data were collected after the early 1970’s. 

Several sites have data for ammonia from the mid1980’s to present (1998), and total phosphorus from 

the early 1970’s to present, but at some of these same 

sites, sampling for nitrate was discontinued in the 

early 1990’s. Several sites in the upper Tarryall Creek 

Basin (sites 56–61, 63, 64) and the Geneva Creek 

Basin in the upper North Fork Basin (sites 95–101, 

103, 104) were sampled for all three constituents 

in the latter 1990’s. 

Historical nitrogen concentrations in surface 

water in Park County were small (table 4). Nitrite was 

not detected and most un-ionized ammonia concentrations were less than the CDPHE chronic standard of 

0.02 mg/L, and all nitrate concentrations were less 

than the CDPHE in-stream standard of 10 mg/L. Even 

though nitrate concentrations were small, there was 

some variability in concentration among the major 

land-use/land-cover classifications and among sites 

throughout the county (fig. 13A–C). Nitrate concentrations in surface water were significantly higher in 

urban and built-up areas than in rangeland and forest 

areas (fig. 13A). In the North Fork Basin, median 

nitrate concentrations primarily were between 0.05 

and 0.12 mg/L and were highest (0.19 mg/L) at the 

East Portal of the Harold D. Roberts Tunnel (site 92) 

(fig. 13B, C). With the exception of sites 64 and 66, 

all median nitrate concentrations in the Tarryall Creek 

Basin were below the detection limit of 0.05 mg/L 

(fig. 13B, C). Some of the highest median nitrate 

concentrations were in the Middle Fork upstream and 

downstream from Fairplay (sites 26 and 29); however, 

the median concentrations at these sites were determined from only two samples collected at each site 

in the early 1970’s. Median nitrate concentrations 

at other sites on the Middle Fork, South Fork, and 

main-stem South Platte River ranged from less than 

0.05 mg/L to 0.13 mg/L.

There are no CDPHE standards for phosphorus 

in surface water; however, for controlling eutrophication, the USEPA has recommended that concentrations 

of total phosphorus be less than 0.1 mg/L in rivers 

and orthophosphorus be less than 0.05 mg/L where 

rivers enter lakes and reservoirs (U.S. Environmental 

Protection Agency, 1986). Most phosphorus concentrations in Park County surface water were less than 

the USEPA recommendations (table 4).

Among the nutrients listed in table 4, analyses 

were most numerous for total phosphorus. Total phosphorus concentrations were not significantly different 

among urban and built-up, rangeland, and forest landuse/land-cover classifications, and for each classification median concentrations were less than 0.05 mg/L 

(fig. 14A). Median total phosphorus concentrations 

were less than 0.1 mg/L at all surface-water sites and 

less than 0.05 mg/L at most sites (fig. 14B, C). Median 

total phosphorus concentrations were lowest at sites in 

the upstream areas of the South Platte watershed—for 

example, sites 96, 97, 99, and 114 in the North Fork 

Basin, sites 56, 57, 63 and 64 in the Tarryall Creek 

Basin, and site 23 in the Middle Fork Basin. Median 

total phosphorus concentrations were highest in the 

South Platte River above Spinney Mountain Reservoir 

(site 40), Park Gulch above Slater Ditch (site 60), 

Tarryall Creek near mouth (site 71), and the mainstem South Platte River near the county line (site 125) 

(median concentrations at sites 40 and 60 were determined from fewer than 10 samples).

Temporal Trends in Nutrient Concentrations

Concentrations of nitrate or total phosphorus 

were tested for time trends at four sites having data 

that met the statistical requirements discussed in 

the “Methods of Water-Quality Data Review and 

Analysis” section of this report. Data for other nutrient 

species such as ammonia, nitrite, and orthophosphorus 

did not meet the requirements for trend testing either 

because most of the results were less than the detection limit or because continuous seasonal data were 

not available for the 1990’s. 

At three of four sites, the period of record for 

analyzing trends in total phosphorus extended from 

the 1970’s to the 1990’s, whereas data for analyzing 

nitrate trend at one site were limited to the 1990’s 

(table 6). As indicated by p-values greater than 0.05 in 

table 6, no trend was observed for nitrate, and with the 

exception of site 92, no trends were observed for total 

phosphorus. Total phosphorus showed a statistically 

significant (p-value less than 0.05) upward trend at 

site 92, the East Portal of the Harold D. Roberts 

Tunnel; however, the trend may not be of great 

environmental importance because the rate of change 
34 Review and Analysis of Available Streamflow and Water-Quality Data for Park County, Colorado, 1962–98

1960

1970

1980

1990

2000

1960

1970

1980

1990

2000

1960

1970

1980

1990

2000

SITE NUMBER

TIME, IN YEARS

Nitrate

Ammonia

Total Phosphorus

Middle

Fork

South

Fork

Main

stem Tarryall North Fork

Middle

Fork

South

Fork Main stem Tarryall North Fork

B

C

South

Middle Fork

Fork Main stem Tarryall North Fork

A

Arkansas

303436394042434651

125

565758596061636468707189929596979899

100101103104105110114

1

262930313233343536383941424346505153

125

5556575859606163646667687071899192949596979899

100101103104105110112113114115116117118119120

23303436394042434651

125

565758596061636468718991929596979899

100101103104105110113114117

Figure 12. Distribution of surface-water sampling dates for (A) ammonia, (B) nitrate, and (C) total phosphorus (site numbers 

from table 3).
SURFACE-WATER QUALITY 35

0 5 10 15 20 MILES

0 5 10 15 20 KILOMETERS

(350) (304) (150)

Urban or

built-up

Rangeland Forest

0.05

10

0.1

0.2

0.5

1

2

NITRATE CONCENTRATION,IN MILLIGRAMS PER LITER

LAND USE/LAND COVER

A B

C

(45) (49) (33) (23) (31) (15) (36) (34) (44) (49) (30) (22) (78) (21) (41) (46) (21) (86) (24) 3034363942434651616871899298 103 105 110 113 114

0.05

10

0.1

0.2

0.5

1

2

5

NITRATE CONCENTRATION,IN MILLIGRAMS PER LITER

98

All values less than 0.05

SURFACE-WATER SITE NUMBER

EXPLANATION

Median nitrate concentration,

in milligrams per liter,

with site number from table 3

1

30

50

119

Less than 0.05

0.05 to 0.06

0.07 to 0.12

0.13 to 0.23

South

Fork

South

South

Platte

Platte

Currant Creek

West Fourmile Creek

Badger Creek

River

River

Tarryall Creek

North Fork

Lake

George

Middle Fork

Boxplot explanation on pages 10-11

A

B B

Base from U.S. Geological Survey digital data, 1:100,000

Universal Transverse Mercator projection,

Zone 13

39°

106°

105°30'

Figure 13. Distribution of (A) nitrate concentrations by land use/land cover, (B) nitrate concentrations at sites with 

10 or more samples, and (C) median nitrate concentrations at all surface-water sites sampled.
36 Review and Analysis of Available Streamflow and Water-Quality Data for Park County, Colorado, 1962–98

(363) (337) (161)

Urban or

built-up

Rangeland Forest

0.01

10

0.1

TOTAL PHOSPHORUS 

CONCENTRATION, IN 

MILLIGRAMS PER LITER

SURFACE-WATER SITE NUMBER

A B

C

1

40

(56) (68) (43) (20) (31) (14) (41) (30)(49)(66)(30) (25) (74)(19) (47) (51) (22) (96) (22)(12) 3034363942434651616871899298 103 105 110 113 114 125

0.01

10

0.1

1

TOTAL PHOSPHORUS 

CONCENTRATION, IN 

MILLIGRAMS PER LITER

EXPLANATION

Median total phosphorus 

concentration, in milligrams

per liter, with site number

from table 3

23

59

34

60

Less than 0.01

0.01 to 0.02

0.03 to 0.04

0.05 to 0.08

LAND USE/LAND COVER

0 5 10 15 20 MILES

0 5 10 15 20 KILOMETERS

39°

106°

105°30'

South

Fork

South

South

Platte

Platte

Currant Creek

West Fourmile Creek

Badger Creek

River

River

Tarryall Creek

North Fork

Lake

George

Middle Fork

Boxplot explanation on pages 10-11

Bailey

A

A

A

Base from U.S. Geological Survey digital data, 1:100,000

Universal Transverse Mercator projection,

Zone 13

Figure 14. Distribution of (A) total phosphorus concentrations by land use/land cover, (B) total phosphorus concentrations 

at sites with 10 or more samples, and (C) median total phosphorus concentrations at all surface-water sites sampled.
SURFACE-WATER QUALITY 37

(slope) of the trend line is small and the trend is 

evident in very low concentrations that are equal 

or nearly equal to the detection limit of 0.01 mg/L. 

Continued phosphorus sampling would help to better 

define this apparently upward trend at site 92.

Phosphorus Loads at Selected Surface-Water 

Sites in the South Platte River Basin

Loads are the amount of a constituent transported in streamflow and are calculated by multiplying 

stream discharge and concentration. Phosphorus loads 

in the upper South Platte River Basin are of particular 

concern because limits on phosphorus loading into 

Chatfield Reservoir from the upper South Platte River 

watershed have been proposed (Colorado Department 

of Public Health and Environment, 1999c). Load 

calculations for two sites with substantial total phosphorus data—the South Platte River below Elevenmile 

Canyon Reservoir (site 46) and the North Fork South 

Platte River at Bailey (site 110)—give an indication of 

the amount of phosphorus that may be transported out 

of Park County in the South Platte River. Load calculations for the East Portal Harold D. Roberts Tunnel 

(site 92) provide an estimate of the amount of phosphorus in surface water diverted from Summit County 

to the North Fork Basin in Park County. 

The phosphorus concentrations and streamflow 

measured at each of the three sites during 1971–98 

and the resultant phosphorus loads are presented in 

figure 15. Streamflow data were not available for 

the North Fork South Platte River at Bailey, so daily 

mean discharges for a site on the North Fork 10 miles 

upstream from Bailey (site SG40, table 2) were used 

instead. To examine seasonal variability, the values 

for each parameter are grouped into two time periods: 

April through September and October through March. 

At all three sites, significantly higher (p<0.05) phosphorus loads during April through September coinciding with significantly higher (p<0.05) streamflow 

for the same time period indicates that streamflow 

influences the variability in load more than phosphorus concentration. Even though larger phosphorus 

concentrations were more frequent during low flow 

(October through March) than high flow, concentrations were not significantly (p>0.05) different between 

the two time periods.

During April through September, median 

total phosphorus loads ranged from about 15 pounds 

per day at the East Portal Harold D. Roberts Tunnel 

and North Fork South Platte River at Bailey to about 

25 pounds per day at the South Platte River below 

Elevenmile Canyon Reservoir. Median total phosphorus loads during the low-flow time of year 

(October–March) ranged from 6 to 12 pounds per day. 

Using the seasonal median phosphorus loads for the 

two South Platte River sites, the annual phosphorus 

load transported out of Park County in the South Platte 

River was calculated to be about 10,000 pounds.

Trace Elements

The term “trace elements” commonly refers to 

substances that almost always occur in concentrations 

less than 1.0 mg/L in natural water. As a result, traceelement concentrations are usually reported in “micrograms per liter” (equivalent to “parts per billion”). 

Table 6. Results of seasonal Kendall test for trends of selected nutrient species in Park County

[mg/L, milligrams per liter]

Site no.

(figs. 9, 10) Site name Period of

analysis

Trend

direction

p-value of

tau test

Magnitude of

trend slope,

in percent

per year

Median

concentration

(mg/L)

Nitrate

110 North Fork South Platte River at Bailey 1993–98 None 0.737 -- 0.10

Total phosphorus

36 South Fork South Platte River below 

Antero Reservoir

1971–98 None 0.212 -- 0.03

46 South Platte River below

Elevenmile Canyon Reservoir

1971-98 None 0.838 -- 0.04

92 East Portal Harold D. Roberts Tunnel 1975–95 Upward 0.006 0.1 0.02

110 North Fork South Platte River at Bailey, CO 1993–98 None 0.145 -- 0.01
38 Review and Analysis of Available Streamflow and Water-Quality Data for Park County, Colorado, 1962–98

1

10

100

1,000

April-Sept Oct-March

1

10

100

1,000

April-Sept Oct-March

1

10

100

1,000

April-Sept Oct-March

1

10

100

1,000

April-Sept Oct-March 1

10

100

1,000

April-Sept Oct-March

0.01

0.1

1

April-Sept Oct-March

0.01

0.1

1

April-Sept Oct-March

0.01

1

April-Sept Oct-March

PHOSPHORUS LOAD,IN POUNDS PER DAY

STREAMFLOW,

IN CUBIC FEET PER SECOND

1

10

100

1,000

April-Sept Oct-March

PHOSPHORUS CONCENTRATION,

IN MILLIGRAMS PER LITER

A

B

C

p =.78 p = .34 p = .90

p < .001 p < .001 p < .001

p = .002 p < .001 p = .004

Site 46, South Platte

River below Elevenmile

Canyon Reservoir

Site 46, South Platte

River below Elevenmile

Canyon Reservoir

Site 46,

South Platte River below

Elevenmile Canyon Res.

Site 110, North Fork

South Platte River at

Bailey

Site SG40, North Fork

South Platte River below

Geneva Creek at Grant

Site 110, North Fork

South Platte River at

Bailey

Site 92, East Portal 

Harold D, Roberts

Tunnel

Site 92, East Portal 

Harold D, Roberts

Tunnel

Site 92, East Portal 

Harold D, Roberts

Tunnel

0.1

(39) (27) (39) (33) (42) (51)

(39) (27) (39) (33) (42) (51)

(39) (27) (39) (33) (42) (51)

Boxplot explanation on pages 10-11

Figure 15. Distribution of (A) phosphorus concentrations, (B) streamflow, and (C) phosphorus loads for selected sites 

in Park County (site numbers from table 3).
SURFACE-WATER QUALITY 39

Trace-element concentrations in Park County have 

been reported as “total” or “dissolved.” Total concentrations are determined from aliquots of unfiltered 

sample water, whereas dissolved concentrations are 

determined from water that has been passed through 

a filter prior to analysis (usually a 0.45-μm pore-size 

filter). Total concentrations also are reported as “total 

recoverable,” meaning the sample has gone through a 

more rigorous digestion procedure prior to analysis. 

Most unfiltered trace-element data for Park County 

have been reported as “total” concentrations. Some 

total recoverable concentrations were acquired during 

the historical data compilation, and these values are 

grouped with the “total” concentrations in table 4. 

 Surface-water-quality data were compiled for 

17 trace elements (table 4). Most of the trace elements 

have dissolved and total analyses but not always at the 

same sites; thus, the maximum dissolved concentration for an element may be larger than the maximum 

total concentration (for example, aluminum in table 4). 

Many trace elements were detected in less than onehalf the analyses, as indicated by the “less than” values 

at the 50th percentile (table 4). Trace elements such 

as aluminum, barium, iron, and manganese may have 

been more commonly detected because they are abundant in the types of igneous and sedimentary rocks in 

Park County.

 Several of the trace-element water-quality 

standards listed in table 4 have not been exceeded, 

including standards for total and dissolved selenium 

and for total arsenic, boron, and manganese. Standards 

have been exceeded for dissolved chromium, iron, and 

manganese and for total iron and mercury. Evidence 

for total mercury concentrations exceeding the standard is weak because most total mercury detections 

(29 of 47 detections) were equal to the analytical 

reporting limit of 0.2 μg/L. In the future, use of a 

mercury analysis with a lower reporting limit is 

probably warranted because of the relatively low 

standard for mercury (0.01 μg/L).

Concentrations of selected trace elements have 

been plotted in boxplots and are grouped by areas of 

the county (fig. 16). The areas primarily are the major 

subwatersheds in the county or specific areas where 

numerous trace-element data have been collected. The 

North Fork Basin has been divided into two areas for 

trace-element analysis, and the most upstream site in 

the lower part is the North Fork South Platte River 

below Geneva Creek (site 105). The Mosquito Creek 

Basin (in the Middle Fork Basin, fig. 10A) and the 

upper North Fork Basin are two areas where extensive 

trace-element sampling has occurred, primarily 

because acidic, trace-element-enriched waters are 

present in these areas (McHugh and others, 1988; 

McBride and Cooper, 1991; Bassett and others, 

1992; Johnson and Cooper, 1993; Johnson, 1993, 

1994; Colorado Department of Public Health and 

Environment, 1998b; Simsiman, 1998; and Stevens, 

1999). Drainage from abandoned mines is the source 

of acidic water in the Mosquito Creek Basin and parts 

of the North Fork Basin. Acidic waters also occur 

naturally in parts of the North Fork Basin, primarily 

in the upper parts of the Geneva Creek Basin.

 Historical trace-element analyses were most 

numerous for iron and manganese. Median iron 

concentrations in each area of Park County were less 

than the CDPHE in-stream standards (300 μg/L for 

dissolved iron, 1,000 μg/L for total recoverable iron), 

even though several individual concentrations were 

one to two orders of magnitude larger than the standards (fig. 16). Some of the largest iron concentrations 

occurred in South Mosquito Creek in the Mosquito 

Creek Basin (fig. 10A); and at several sites in the 

upper North Fork Basin, including Handcart Gulch, 

the North Fork South Platte River downstream from 

Handcart Gulch, and upper Geneva Creek (fig. 10B). 

The small amount of data for these stream segments 

(most sites were sampled fewer than five times) indicates that iron standards probably are exceeded in 

these waters. Large iron concentrations also occurred 

in the lower North Fork Basin, primarily in the North 

Fork South Platte River near Bailey (fig. 9). Large 

total iron concentrations in the North Fork South Platte 

River near Bailey were infrequent and were probably 

caused by the transport of total iron in streamflow 

from the upper part of the basin to the lower part. 

All concentrations of total manganese in 

each area of Park County were less than the CDPHE 

in-stream standard of 1,000 μg/L, and with the exception of the upper North Fork, all median concentrations of dissolved manganese in each area were 

less than the CDPHE in-stream standard of 50 μg/L 

(fig. 16). In the upper North Fork, dissolved manganese concentrations ranging between 200 and 

1,500 μg/L primarily occurred in Handcart Gulch and 

upper Geneva Creek (fig. 10B), indicating that manganese standards may be exceeded in these areas. The 

largest concentrations of dissolved manganese were 

not measured in the upper North Fork Basin but in 

Park Gulch in the Tarryall Creek Basin. The streamflow associated with the Park Gulch manganese 

concentrations was very small (0.01 ft3

/s).
40 Review and Analysis of Available Streamflow and Water-Quality Data for Park County, Colorado, 1962–98

Mosquito

Creek

Basin

Fork Fork

South

stem

Main Tarryall

Creek

Basin Fork

North

Upper

Fork

North

Lower Arkansas

River

Basin

1

300

2

5

10

20

50

100

200

Copper, dissolved

(191) (31)

1

2

5

10

20

(56) (85)

Mosquito

Creek

Basin

Fork

Middle

Fork

South

stem

Main Tarryall

Creek

Basin Fork

North

Upper

Fork

North

Lower Arkansas

River

Basin

1

300

2

5

10

20

50

100

200

(0)

Copper, total

(111) (197) (210) (153) (9) (0)

1

2

5

10

20

(34) (96) (100)

100

50 Chromium, total

(23) (0) (135) (63)

(59) (80) (100) (148) (218) (171) (21)

100

50 Cadmium, total

(0)

(144) (20) (3) (25) (80) (96) (46) (78) (6)

1

20,000

10

100

1,000

10,000

(0) (0)

Aluminum, total

(18) (11) (4) (4) (48)

50

20,000

100

200

500

1,000

2,000

5,000

10,000 Aluminum, dissolved

(31) (8) (12) (79) (8) (13) (42)

1

100

2

5

10

20

50

(14) (5) (12) (79) (5) (12) (43)

1

100

2

5

10

20

50

CONCENTRATION, IN MICROGRAMS PER LITER

Cadmium, dissolved

Chromium, dissolved

(0)

(0)

(24) (13) (8) (6) (40)

Middle

Figure 16. Distribution of trace-element concentrations for areas of Park County, 1962–98. (Dashed lines for iron and 

manganese are in-stream water-quality standards set by the Colorado Department of Public Health and Environment 

[1998a, 1999a].) Boxplot explanation on pages 10–11.
SURFACE-WATER QUALITY 41

(43) (5) (22) (10) (200) (46) (16) (48)

Mosquito

Creek

Basin

Fork

Middle

Fork

South

stem

Main Tarryall

Creek

Basin Fork

North

Upper

Fork

North

Lower Arkansas

River

Basin

3

8,000

5

10

20

50

100

200

500

1,000

2,000

5,000

Mosquito

Creek

Basin

Fork

Middle

4

8,000

10

20

50

100

200

500

1,000

2,000

5,000

Zinc, dissolved

(64) (93) (113) (168) (221) (155) (19)

Fork

South

stem

Main Tarryall

Creek

Basin Fork

North

Upper

Fork

North

Lower Arkansas

River

Basin

Zinc, total

(0)

5

400

7

10

20

30

40

50

70

100

200

300

(13) (39) (66) (71) (62) (10)

Nickel, total

(1) (3) (102) (2) (45) (0)

1

200

2

5

10

20

50

100 Nickel, dissolved

(0) (0) (0)

CONCENTRATION, IN MICROGRAMS PER LITER

(29) (6) (17) (27) (210) (51) (37) (51)

5

5,000

10

20

50

100

200

500

1,000

2,000

Manganese, dissolved

10

50,000

20

50

100

200

500

1,000

2,000

5,000

10,000

20,000 Iron, dissolved

10

50,000

20

50

100

200

500

1,000

2,000

5,000

10,000

20,000

(7) (8) (95) (151) (228) (264) (19) (29) (204) (49) (39) (94) (66) (235) (17) (0)

Iron, total

(54) (90) (145) (199) (240) (228) (23)

5

5,000

10

20

50

100

200

500

1,000

2,000

(0)

Manganese, total

Figure 16. Distribution of trace-element concentrations for areas of Park County, 1962–98. (Dashed lines for iron and 

manganese are in-stream water-quality standards set by the Colorado Department of Public Health and Environment 

[1998a, 1999a]). Boxplot explanation on pages 10–11—Continued.
42 Review and Analysis of Available Streamflow and Water-Quality Data for Park County, Colorado, 1962–98

Other trace elements in addition to iron or 

manganese also were measured in large concentrations 

in either the Mosquito Creek or upper North Fork 

Basins (fig. 16). Large zinc concentrations primarily 

occurred in South Mosquito Creek and in Mosquito 

Creek downstream from South Mosquito Creek 

(fig. 10A) but also occurred in Geneva Creek 

(fig. 10B). Large concentrations of aluminum, 

cadmium, chromium, copper, and nickel were most 

common in Handcart Gulch, the North Fork South 

Platte River downstream from Handcart Gulch, and 

upper Geneva Creek (fig. 10B).

 Mosquito Creek, South Mosquito Creek, 

sections of the North Fork South Platte River downstream from Handcart Gulch, and Geneva Creek have 

been identified as being impaired with respect to 

elevated trace-element concentrations and are listed on 

the 1998 303(d) list (Colorado Department of Public 

Health and Environment, 1998b). The 303(d) list identifies water-quality-limited segments within Colorado 

and is prepared by the CDPHE, Water Quality Control 

Division (WQCD), to fulfill section 303(d) of the 

Federal Clean Water Act.

Suspended Sediment

Suspended sediment is fragments of rock and 

soil transported in suspension by streams. Overland 

flow and channel scour are natural erosional sources 

of suspended sediment in streams and are influenced 

by soils, land cover, slope, aspect, climate, and streamflow. In Park County, activities that may disturb 

land surfaces and increase erosion and subsequent 

suspended-sediment concentrations are urban and 

suburban development, mining, logging, agriculture 

(primarily grazing), and pedestrian (recreation) traffic 

along streambanks. 

The CDPHE has not set numeric standards 

for suspended-sediment concentrations in streams; 

however, a narrative standard pertaining more to 

sediment deposition states that surface waters shall be 

free from substances attributable to human activities 

which can settle to form bottom deposits that are detrimental to beneficial uses (Colorado Department of 

Public Health and Environment, 1999b). Based 

primarily on evaluations by the U.S. Forest Service, 

the WQCD has listed the South Platte River downstream from Elevenmile Canyon Reservoir to the 

county line on the 1998 303(d) list for impairment 

by sediment (Colorado Department of Public Health 

and Environment, 1998b). Additionally, several 

tributaries to the South Platte River between Hartsel 

and Lake George (fig. 17B) may be considered for 

future listing because of sediment issues (Colorado 

Department of Public Health and Environment, 

1998b).

Suspended-sediment data for streams in 

Park County are scarce, and at most sites where 

data are available, fewer than 10 samples have 

been collected (fig. 17B). Most sampling was 

done in the Geneva Creek Basin (sites 98, 103, 

table 3) as part of a water-quality study in the 

Guanella Pass area (Stevens, 1998) or at a site on 

Badger Creek in the Arkansas River Basin (site 119). 

Infrequent sampling for suspended sediment has 

occurred in the upper Tarryall Creek Basin and 

in the Lost Creek Basin (sites 73–76). Only one 

sample was collected from the main-stem South 

Platte River (site 46).

Sampling conducted over an entire flow 

regime is needed to define the variability of 

suspended-sediment concentration in streams. Data 

for Geneva and Badger Creeks (sites 103 and 119) 

show that suspended-sediment concentration generally 

increases with discharge as overland flow from snowmelt or precipitation transports sediment to streams 

(fig. 17A).

GROUND-WATER QUALITY

Data collected by the USGS from 180 wells 

in Park County primarily were used in the statistical 

summaries of ground-water quality in this report 

(tables 7, 8). Additionally, nitrate data collected by 

the Park County Department of Environmental Health 

(PCDEH) and the U.S. Forest Service were included 

with the USGS data for the statistical summaries of 

nitrate in ground water (table 8). Most of the wells 

(162 of 180) were sampled once in the 1970’s as part 

of two USGS studies assessing ground-water quality 

throughout the county or in the vicinity of Lake 

George (Goddard, 1978; Klein and others, 1978). The 

remaining wells were sampled once in the 1990’s, 

primarily in 1998 as part of a ground-water quality 

study in north-central Park County (Bruce and 

Kimbrough, 1999).
GROUND-WATER QUALITY 43

0 5 10 15 20 MILES

0 5 10 15 20 KILOMETERS

1

2,000

2

5

10

20

50

100

200

500

1,000

1 5,000 10 100 1,000 0.1 100 1 10 1

10,000

2

5

10

20

50

100

200

500

1,000

2,000

SUSPENDED-SEDIMENT

CONCENTRATION,

IN MILLIGRAMS PER LITER

Site 103, Geneva Creek

near Grant

Site 119, Badger Creek

above County Line

5,000

A

B

STREAMFLOW, IN CUBIC FEET PER SECOND

EXPLANATION

Number of suspended-sediment

samples, with site numbers from

table 3

Less than 10

10 to 50

Greater than 50

56

68

98

South

Fork

South

South

Platte

Platte

Currant Creek

West Fourmile Creek

Badger Creek

River

River

Tarryall Creek

North Fork

Lake

George

Middle Fork

Base from U.S. Geological Survey digital data, 1:100,000

Universal Transverse Mercator projection,

Zone 13

39°

106°

105°30'

Figure 17. (A) Relation between streamflow and suspended-sediment concentrations for sites 103 and 

119, and (B) the number of suspended-sediment samples per site, Park County, 1962–98.
44 Review and Analysis of Available Streamflow and Water-Quality Data for Park County, Colorado, 1962–98

Table 7. Characteristics of ground-water-quality sites in Park County, 1962–98

[USGS, U.S. Geological Survey; --, no data; PP, physical properties; MI, major ions; TE, trace elements; N, nutrients; B, bacteria; C, carbon]

Site

no.

Site

identification

number

Data

Source

Sampling

date

(month, day,

year)

Water

level1

(feet)

Apparent aquifer 

near well screen

Type of

data

1 393057105301200 USGS 06/26/74 85 Precambrian crystalline rocks PP, MI, TE, N, B

2 393053105312600 USGS 06/26/74 150 Precambrian crystalline rocks PP, MI, TE, N, B

3 393053105303200 USGS 06/27/74 148 Precambrian crystalline rocks PP, MI, TE, N, B

4 393052105423300 USGS 09/07/95 -- -- PP, MI, TE, N, C

5 393041105305700 USGS 06/27/74 283 Precambrian crystalline rocks PP, MI, TE, N, B

6 393041105302500 USGS 06/19/74 -- Precambrian crystalline rocks PP, MI, TE, N, B

7 393040105295400 USGS 06/24/74 110 Precambrian crystalline rocks PP, MI, TE, N, B

8 393030105334300 USGS 06/26/74 167 Precambrian crystalline rocks PP, MI, TE, N, B

9 393029105320800 USGS 06/26/74 -- Precambrian crystalline rocks PP, MI, TE, N, B

10 393028105301700 USGS 06/27/74 50 Precambrian crystalline rocks PP, MI, TE, N, B

11 393023105302000 USGS 06/27/74 388 Precambrian crystalline rocks PP, MI, TE, N, B

12 393015105324700 USGS 06/26/74 90 Precambrian crystalline rocks PP, MI, TE, N, B

13 393011105315600 USGS 06/27/74 140 Precambrian crystalline rocks PP, MI, TE, N, B

14 393006105314600 USGS 06/25/74 -- Precambrian crystalline rocks PP, MI, TE, N

15 393004105313700 USGS 06/27/74 50 Precambrian crystalline rocks PP, MI, TE, N, B

16 393001105240300 USGS 06/18/74 -- Precambrian crystalline rocks PP, MI, TE, N, B

17 392957105322500 USGS 06/26/74 90 Precambrian crystalline rocks PP, MI, TE, N, B

18 392940105313800 USGS 06/25/74 -- Precambrian crystalline rocks PP, MI, TE, N, B

19 392935105301600 USGS 06/24/74 -- Precambrian crystalline rocks PP, MI, TE, N, B

20 392935105290400 USGS 06/24/74 -- Precambrian crystalline rocks PP, MI, TE, N, B

21 392933105414700 USGS 07/18/74 -- Quaternary unconsolidated deposits PP, MI, TE, N, B

22 392925105284900 USGS 06/20/74 225 Precambrian crystalline rocks PP, MI, TE, N, B

23 392923105244700 USGS 06/19/74 -- Precambrian crystalline rocks PP, MI, TE, N, B

24 392920105303000 USGS 06/25/74 275 Precambrian crystalline rocks PP, MI, TE, N, B

25 392920105285400 USGS 06/21/74 145 Precambrian crystalline rocks PP, MI, TE, N, B

26 392918105294800 USGS 06/25/74 -- Precambrian crystalline rocks PP, MI, TE, N, B

27 392911105241600 USGS 06/18/74 -- Precambrian crystalline rocks PP, MI, TE, N, B

28 392908105311500 USGS 06/25/74 85 Quaternary unconsolidated deposits PP, MI, TE, N, B

29 392907105320000 USGS 06/24/74 250 Precambrian crystalline rocks PP, MI, TE, N, B

30 392853105405800 USGS 09/07/95 -- -- PP, MI, TE, N, C

31 392814105293700 USGS 06/20/74 -- Quaternary unconsolidated deposits PP, MI, TE, N, B

32 392813105240800 USGS 06/18/74 -- Precambrian crystalline rocks PP, MI, TE, N, B

33 392751105395900 USGS 07/18/74 -- Precambrian crystalline rocks PP, MI, N, B

34 392744105230900 USGS 06/19/74 -- Precambrian crystalline rocks PP, MI, TE, N, B

35 392734105434800 USGS 07/19/74 -- Precambrian crystalline rocks PP, MI, N, B

36 392734105235500 USGS 06/19/74 -- Precambrian crystalline rocks PP, MI, TE, N, B

37 392732105235300 USGS 06/18/74 -- Precambrian crystalline rocks PP, MI, TE, N, B
GROUND-WATER QUALITY 45

38 392727105292000 USGS 06/20/74 80 Quaternary unconsolidated deposits PP, MI, TE, N, B

39 392720105383600 USGS 07/18/74 -- Precambrian crystalline rocks PP, MI, N, B

40 392701105464500 USGS 07/18/74 -- Precambrian crystalline rocks PP, MI, N, B

41 392659105280300 USGS 06/20/74 26 Quaternary unconsolidated deposits PP, MI, TE, N, B

42 392646105280300 USGS 06/20/74 175 Precambrian crystalline rocks PP, MI, TE, N, B

43 392645105364300 USGS 07/16/74 -- Quaternary unconsolidated deposits PP, MI, N, B

44 392641105470200 USGS 07/18/74 -- Precambrian crystalline rocks PP, MI, TE, N

45 392637105261700 USGS 06/19/74 -- Quaternary unconsolidated deposits PP, MI, TE, N

46 392634105251200 USGS 07/12/74 -- Precambrian crystalline rocks PP, MI, N, B

47 392632105275000 USGS 06/20/74 180 Precambrian crystalline rocks PP, MI, TE, N, B

48 392632105274100 USGS 06/19/74 -- Precambrian crystalline rocks PP, MI, TE, N, B

49 392623105354900 USGS 07/16/74 -- Precambrian crystalline rocks PP, MI, N, B

50 392612105251000 USGS 07/12/74 -- Precambrian crystalline rocks PP, MI, TE, N, B

51 392612105242500 USGS 07/12/74 -- Precambrian crystalline rocks PP, MI, N, B

52 392610105280500 USGS 07/09/74 -- Quaternary unconsolidated deposits PP, MI, N, B

53 392607105245200 USGS 07/12/74 -- Precambrian crystalline rocks PP, MI, N, B

54 392557105262100 USGS 07/11/74 -- Quaternary unconsolidated deposits PP, MI, N

55 392546105270300 USGS 07/10/74 -- Precambrian crystalline rocks PP, MI, N, B

56 392545105342200 USGS 07/16/74 -- Precambrian crystalline rocks PP, MI, TE, N, B

57 392539105281200 USGS 07/09/74 -- Precambrian crystalline rocks PP, MI, TE, N, B

58 392538105254900 USGS 07/11/74 -- Precambrian crystalline rocks PP, MI, N, B

59 392533105274500 USGS 07/10/74 -- Precambrian crystalline rocks PP, MI, N, B

60 392528105331800 USGS 07/17/74 -- Quaternary unconsolidated deposits PP, MI, N, B

61 392527105244200 USGS 07/12/74 -- Precambrian crystalline rocks PP, MI, N, B

62 392525105282800 USGS 07/09/74 -- Quaternary unconsolidated deposits PP, MI, N, B

63 392523105270500 USGS 07/10/74 -- -- PP, MI, N, B

64 392520105270700 USGS 06/27/74 260 Precambrian crystalline rocks PP, MI, TE, N, B

65 392518105254000 USGS 07/11/74 -- Precambrian crystalline rocks PP, MI, N, B

66 392518105242700 USGS 07/12/74 -- Precambrian crystalline rocks PP, MI, N, B

67 392516105331900 USGS 07/17/74 -- Precambrian crystalline rocks PP, MI, TE, N, B

68 392516105272900 USGS 07/10/74 -- Precambrian crystalline rocks PP, MI, TE, N, B

69 392516105260800 USGS 07/10/74 -- Precambrian crystalline rocks PP, MI, N, B

70 392515105315800 USGS 07/17/74 -- Precambrian crystalline rocks PP, MI, N, B

71 392515105244800 USGS 07/11/74 -- Precambrian crystalline rocks PP, MI, N, B

72 392512105252400 USGS 07/11/74 -- Precambrian crystalline rocks PP, MI, TE, N, B

73 392503105263700 USGS 07/10/74 -- Precambrian crystalline rocks PP, MI, N, B

74 392503105244800 USGS 07/11/74 -- Precambrian crystalline rocks PP, MI, N, B

Table 7. Characteristics of ground-water-quality sites in Park County, 1962–98—Continued

[USGS, U.S. Geological Survey; --, no data; PP, physical properties; MI, major ions; TE, trace elements; N, nutrients; B, bacteria; C, carbon]

Site

no.

Site

identification

number

Data

Source

Sampling

date

(month, day,

year)

Water

level1

(feet)

Apparent aquifer 

near well screen

Type of

data
46 Review and Analysis of Available Streamflow and Water-Quality Data for Park County, Colorado, 1962–98

75 392501105322900 USGS 07/19/74 -- Precambrian crystalline rocks PP, MI, N, B

76 392501105250800 USGS 07/11/74 -- Precambrian crystalline rocks PP, MI, N, B

77 392454105334400 USGS 07/17/74 -- Precambrian crystalline rocks PP, MI, N, B

78 392440105264600 USGS 07/09/74 -- Precambrian crystalline rocks PP, MI, N, B

79 392437105305800 USGS 07/19/74 -- Quaternary unconsolidated deposits PP, MI, N, B

80 392434105295900 USGS 07/17/74 -- Quaternary unconsolidated deposits PP, MI, N, B

81 392427105252300 USGS 07/11/74 -- Precambrian crystalline rocks PP, MI, TE, N, B

82 392425105441600 USGS 07/23/74 10 Quaternary unconsolidated deposits PP, MI, N

83 392421105283000 USGS 07/17/74 -- Quaternary unconsolidated deposits PP, MI, TE, N, B

84 392415105512500 USGS 07/23/74 -- Quaternary unconsolidated deposits PP, MI, TE, N

85 392402105293100 USGS 07/19/74 106 Precambrian crystalline rocks PP, MI, TE, N, B

86 392402105274400 USGS 07/10/74 -- Quaternary unconsolidated deposits PP, MI, N, B

87 392336105265200 USGS 07/09/74 -- Quaternary unconsolidated deposits PP, MI, N, B

88 392332105244300 USGS 06/18/74 -- Precambrian crystalline rocks PP, MI, TE, N, B

89 392329105472300 USGS 07/23/74 100 Quaternary unconsolidated deposits PP, MI, TE, N

90 392300105255900 USGS 07/09/74 -- Quaternary unconsolidated deposits PP, MI, N, B

91 392238105475800 USGS 07/23/74 -- Quaternary unconsolidated deposits PP, MI, TE, N

92 392236105475900 USGS 07/23/74 12 Quaternary unconsolidated deposits PP, MI, N

93 392202105493501 USGS 05/07/98 -- Tertiary sedimentary rocks PP, MI, TE, N, C

94 392111106034200 USGS 07/24/74 100 Paleozoic sedimentary rocks PP, MI, TE, N

95 391958106034500 USGS 07/24/74 185 Paleozoic sedimentary rocks PP, MI, TE, N

96 391830105500801 USGS 05/05/98 -- Tertiary sedimentary rocks PP, MI, TE, N, C

97 391717106040000 USGS 07/24/74 67 Quaternary unconsolidated deposits PP, MI, TE, N

98 391716105494401 USGS 05/05/98 -- Tertiary sedimentary rocks PP, MI, TE, N, C

99 391631105480404 USGS 05/06/98 -- Tertiary sedimentary rocks PP, MI, TE, N, C

100 391631105480402 USGS 05/06/98 -- Tertiary sedimentary rocks PP, MI, TE, N, C

101 391631105480401 USGS 05/06/98 -- Tertiary sedimentary rocks PP, MI, TE, N, C

102 391631105461301 USGS 05/12/98 -- Precambrian crystalline rocks PP, MI, TE, N, C

103 391625105501001 USGS 05/04/98 -- Tertiary sedimentary rocks PP, MI, TE, N, C

104 391619106031400 USGS 07/25/74 45 Quaternary unconsolidated deposits PP, MI, TE, N

105 391602105473801 USGS 05/14/98 -- Precambrian crystalline rocks PP, MI, TE, N, C

106 391556106034600 USGS 07/25/74 -- Quaternary unconsolidated deposits PP, MI, TE, N

107 391511105500301 USGS 05/04/98 -- Tertiary sedimentary rocks PP, MI, TE, N, C

108 391452105483503 USGS 06/16/98 -- Precambrian crystalline rocks PP, MI, TE, N, C

109 391452105483502 USGS 06/17/98 -- Tertiary sedimentary rocks PP, MI, TE, N, C

110 391452105483501 USGS 06/17/98 -- Precambrian crystalline rocks PP, MI, TE, N, C

111 391441105474501 USGS 05/12/98 -- Precambrian crystalline rocks PP, MI, TE, N, C

Table 7. Characteristics of ground-water-quality sites in Park County, 1962–98—Continued

[USGS, U.S. Geological Survey; --, no data; PP, physical properties; MI, major ions; TE, trace elements; N, nutrients; B, bacteria; C, carbon]

Site

no.

Site

identification

number

Data

Source

Sampling

date

(month, day,

year)

Water

level1

(feet)

Apparent aquifer 

near well screen

Type of

data
GROUND-WATER QUALITY 47

112 391416106004800 USGS 07/25/74 240 Paleozoic sedimentary rocks PP, MI, TE, N

113 391337105484301 USGS 05/28/98 -- Tertiary sedimentary rocks PP, MI, TE, N, C

114 391314105465501 USGS 06/15/98 -- Precambrian crystalline rocks PP, MI, TE, N, C

115 391112105435600 USGS 09/18/74 -- Quaternary unconsolidated deposits PP, MI, TE, N

116 391103105453500 USGS 09/18/74 -- Precambrian crystalline rocks PP, MI, TE, N

117 390921105453100 USGS 09/17/74 46 Quaternary unconsolidated deposits PP, MI, TE, N

118 390903105422300 USGS 09/17/74 40 Quaternary unconsolidated deposits PP, MI, TE, N

119 390853105434600 USGS 09/17/74 -- Tertiary sedimentary rocks PP, MI, TE, N

120 390831105554200 USGS 09/09/74 10 Quaternary unconsolidated deposits PP, MI, TE, N

121 390807105535500 USGS 09/13/74 36 Quaternary unconsolidated deposits PP, MI, TE, N

122 390719105282900 USGS 11/06/75 -- Precambrian crystalline rocks PP, MI, TE, N

123 390653105591900 USGS 09/11/74 -- Quaternary unconsolidated deposits PP, MI, TE, N

124 390638105532200 USGS 09/09/74 20 Quaternary unconsolidated deposits PP, MI, TE, N

125 390638105260700 USGS 08/14/75 50 Precambrian crystalline rocks PP, MI, TE, N

126 390613105494900 USGS 09/12/74 -- Cretaceous and Jurassic sedimentary 

rocks

PP, MI, TE, N

127 390605106011600 USGS 07/24/74 4 Quaternary unconsolidated deposits PP, MI, TE, N

128 390602105255500 USGS 08/14/75 100 Precambrian crystalline rocks PP, MI, TE, N

129 390552105254500 USGS 08/14/75 120 Precambrian crystalline rocks PP, MI, TE, N

130 390523105440800 USGS 09/17/74 -- Quaternary unconsolidated deposits PP, MI, TE, N

131 390514105252800 USGS 11/05/75 -- Precambrian crystalline rocks PP, MI, TE, N

132 390424105513800 USGS 09/13/74 20 Cretaceous and Jurassic sedimentary 

rocks

PP, MI, TE, N

133 390344105434700 USGS 07/26/74 -- Tertiary sedimentary rocks PP, MI, TE, N

134 390323105582600 USGS 09/11/74 -- Paleozoic sedimentary rocks PP, MI, TE, N

135 390244105432200 USGS 09/18/74 -- Cretaceous and Jurassic sedimentary 

rocks

PP, MI, TE, N

136 390205105203400 USGS 08/15/75 -- Precambrian crystalline rocks PP, MI, TE, N

137 390201105415200 USGS 09/16/74 -- Cretaceous and Jurassic sedimentary 

rocks

PP, MI, TE, N

138 390143105210300 USGS 08/15/75 140 Precambrian crystalline rocks PP, MI, TE, N

139 390142105205700 USGS 08/15/75 65 Quaternary unconsolidated deposits PP, MI, TE, N

140 390140105204700 USGS 08/15/75 170 Precambrian crystalline rocks PP, MI, TE, N

141 390125105475300 USGS 09/12/74 58 Quaternary unconsolidated deposits PP, MI, TE, N

142 390121105294700 USGS 08/14/75 200 Precambrian crystalline rocks PP, MI, TE, N

143 390117105302500 USGS 08/13/75 75 Precambrian crystalline rocks PP, MI, TE, N

144 390117105223700 USGS 11/05/75 80 Precambrian crystalline rocks PP, MI, TE, N

145 390100105452200 USGS 09/12/74 -- Quaternary unconsolidated deposits PP, MI, TE, N

Table 7. Characteristics of ground-water-quality sites in Park County, 1962–98—Continued

[USGS, U.S. Geological Survey; --, no data; PP, physical properties; MI, major ions; TE, trace elements; N, nutrients; B, bacteria; C, carbon]

Site

no.

Site

identification

number

Data

Source

Sampling

date

(month, day,

year)

Water

level1

(feet)

Apparent aquifer 

near well screen

Type of

data
48 Review and Analysis of Available Streamflow and Water-Quality Data for Park County, Colorado, 1962–98

146 390038105282000 USGS 11/05/75 -- Precambrian crystalline rocks PP, MI, TE, N

147 385936105342500 USGS 09/10/74 -- Quaternary unconsolidated deposits PP, MI, TE, N

148 385932105452100 USGS 09/10/74 -- Tertiary sedimentary rocks PP, MI, TE, N

149 385902105214000 USGS 11/06/75 -- Precambrian crystalline rocks PP, MI, TE, N

150 385900105434000 USGS 09/10/74 -- Tertiary volcanic rock PP, MI, TE, N

151 385850105221200 USGS 08/13/75 65 Quaternary unconsolidated deposits PP, MI, TE, N

152 385848105212700 USGS 11/04/75 35 Precambrian crystalline rocks PP, MI, TE, N

153 385834105205600 USGS 11/04/75 85 Tertiary sedimentary rocks PP, MI, TE, N

154 385815105200500 USGS 11/04/75 -- Precambrian crystalline rocks PP, MI, TE, N

155 385813105301500 USGS 08/13/75 75 Precambrian crystalline rocks PP, MI, TE, N

156 385804105202200 USGS 11/04/75 -- Tertiary sedimentary rocks PP, MI, TE, N

157 385737105273600 USGS 08/13/75 122 Precambrian crystalline rocks PP, MI, TE, N

158 385733105503200 USGS 09/11/74 -- Tertiary sedimentary rocks PP, MI, TE, N

159 385730105284000 USGS 08/13/75 300 Precambrian crystalline rocks PP, MI, TE, N

160 385715105522600 USGS 09/11/74 -- Tertiary sedimentary rocks PP, MI, TE, N

161 385633105295200 USGS 08/13/75 -- Precambrian crystalline rocks PP, MI, TE, N

162 385630105290500 USGS 08/14/75 90 Precambrian crystalline rocks PP, MI, TE, N

163 385625105483900 USGS 09/11/74 -- Tertiary sedimentary rocks PP, MI, TE, N

164 385620105304700 USGS 11/05/75 -- Precambrian crystalline rocks PP, MI, TE, N

165 385605105293500 USGS 08/14/75 96 Precambrian crystalline rocks PP, MI, TE, N

166 385512105222200 USGS 11/04/75 165 Precambrian crystalline rocks PP, MI, TE, N

167 385456105235300 USGS 11/04/75 -- Precambrian crystalline rocks PP, MI, TE, N

168 385426105235100 USGS 11/04/75 -- Precambrian crystalline rocks PP, MI, TE, N

169 385349105393800 USGS 09/10/74 50 -- PP, MI, TE, N

170 385208105465500 USGS 09/11/74 -- Tertiary sedimentary rocks PP, MI, TE, N

171 385100105205200 USGS 08/12/75 285 Precambrian crystalline rocks PP, MI, TE, N

172 385050105455600 USGS 09/19/74 -- Quaternary unconsolidated deposits PP, MI, TE, N

173 385050105213800 USGS 08/12/75 225 Tertiary volcanic rock PP, MI, TE, N

174 385046105215000 USGS 08/12/75 -- Quaternary unconsolidated deposits PP, MI, TE, N

175 384857105230800 USGS 08/12/75 113 Tertiary volcanic rock PP, MI, TE, N

176 384754105480400 USGS 09/19/74 -- Tertiary sedimentary rocks PP, MI, TE, N

177 384630105474000 USGS 09/19/74 -- Tertiary sedimentary rocks PP, MI, TE, N

178 384508105312100 USGS 09/19/74 110 -- PP, MI, TE, N

179 384500105311200 USGS 09/19/74 18 Quaternary unconsolidated deposits PP, MI, TE, N

180 384440105532200 USGS 09/19/74 -- Quaternary unconsolidated deposits PP, MI, TE, N

1Water level in feet below land surface measured on sampling date.

Table 7. Characteristics of ground-water-quality sites in Park County, 1962–98—Continued

[USGS, U.S. Geological Survey; --, no data; PP, physical properties; MI, major ions; TE, trace elements; N, nutrients; B, bacteria; C, carbon]

Site

no.

Site

identification

number

Data

Source

Sampling

date

(month, day,

year)

Water

level1

(feet)

Apparent aquifer 

near well screen

Type of

data
GROUND-WATER QUALITY 49

Table 8. Summary of ground-water-quality data for Park County, 1962–98

[No., number; °C, degrees Celsius; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius; --, no data; <, less than; μg/L, 

micrograms per liter; pCi/L, picocuries per liter; cols/100 mL, colonies per 100 milliliters; SMCL, secondary maximum contaminant level; MCL, maximum 

contaminant level; PMCL, proposed maximum contaminant level; CaCO3, calcium carbonate; diss., dissolved; strep., streptococcus]

Constituent

or property

No. of

analyses

Minimum

Concentration or value at indicated percentile

Maximum

Standard

 or guideline

for drinking

water1

1

U.S. Environmental Protection Agency, 1996.

10 25 50 75 90

Physical properties

Water temperature (° C) 170 5.0 7.0 8.5 9.5 11.0 13.0 19.0 --

Oxygen, dissolved (mg/L) 16 0.1 0.1 0.3 0.7 1.6 4.9 6.5 --

pH (standard units) 133 5.4 6.1 6.3 6.8 7.2 7.9 9.7 6.5–8.5 (SMCL)

Specific conductance 180 42 114 210 328 450 742 3,920 --

Major ions and dissolved solids, in mg/L

Calcium, dissolved 144 1.0 13 23 37 56 85 420 --

Chloride, dissolved 180 <0.1 1.0 1.9 4.1 9.7 22 220 250 (SMCL)

Fluoride, dissolved 180 0.1 0.2 0.3 0.5 1.3 2.2 5.6 2 (SMCL)

Magnesium, dissolved 144 0.005 1.8 4.0 8.4 15 28 260 --

Potassium, dissolved 180 <0.1 0.8 1.2 1.9 2.7 4.6 16 --

Sodium, dissolved 144 0.3 3.7 5.9 12 20 54 290 --

Silica, dissolved 144 5.6 9.9 13 17 22 27 73 --

Sulfate, dissolved 144 4.3 7.5 9.9 20 39 136 1,800 250 (SMCL)

Dissolved solids 144 46 77 130 202 284 520 3,310 500 (SMCL)

Nutrients, dissolved, in mg/L

Ammonia 18 <0.02 <0.02 0.02 0.04 0.08 0.11 0.12 --

Nitrate 440 <0.05 <0.05 0.12 0.84 2.7 6.1 24 10 (MCL)

Nitrite 18 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 0.02 1 (MCL)

Orthophosphorus 180 <0.01 <0.01 0.01 0.01 0.02 0.06 0.6 --

Trace elements, dissolved, in μg/L; and radon, in pCi/L

Aluminum 36 3 4 5 10 12 20 80 50–200 (SMCL)

Arsenic 16 <1 <1 <1 <1 <1 <1 <1 50 (MCL)

Barium 18 2 4 8 19 35 63 78 2,000 (MCL)

Cadmium 18 <1 <1 <1 <1 <1 <1 <1 5.0 (MCL)

Chromium 18 <1 <1 <1 1 2 6 7 100 (MCL)

Copper 54 <2 <2 <2 2 7 24 50 1,000 (SMCL)

Iron 144 <10 <10 20 30 60 787 18,000 300 (SMCL)

Lead 54 <2 <2 <2 <2 3 8 12 --

Manganese 143 <10 <10 <10 <10 40 156 3,900 50 (SMCL)

Molybdenum 18 <1 <1 <1 2 7 18 28 --

Nickel 18 <1 <1 <1 <1 1 1 1 100 (MCL)

Selenium 16 <1 <1 <1 <1 <1 1 2.2 50 (MCL)

Silver 18 <1 <1 <1 <1 <1 <1 <1 100 (SMCL)

Uranium 18 <1 <1 1 3 11 17 19 20 (PMCL)

Zinc 63 <1 <1 20 110 622 3,680 11,000 5,000 (SMCL)

Radon 16 1,900 2,000 2,500 4,200 6,300 12,600 27,800 300 (PMCL)

Other constituents or properties

Alkalinity (as CaCO3) 127 5.0 35 68 129 179 216 818 --

Carbon, organic, diss. (mg/L) 18 0.2 0.4 0.6 1.1 2.1 2.9 9.2 --

Fecal coliform (cols/100 mL) 81 <1 <1 <1 <1 <1 <1 80 --

Fecal strep. (cols/100 mL) 81 <1 <1 <1 <1 <1 1 9 --

Hardness (mg/L as CaCO3) 144 3.0 40 74 135 215 302 2,100 --
50 Review and Analysis of Available Streamflow and Water-Quality Data for Park County, Colorado, 1962–98

Almost all of the wells in table 7 were sampled 

for physical properties (water temperature, dissolved 

oxygen, pH, specific conductance), major ions, nutrients, and trace elements, and about one-half of the 

wells were sampled for bacteria (table 7). In 1994–95, 

the PCDEH sampled for nitrate in 194 domestic wells 

in subdivisions northeast of Bailey (Tom Eisenman, 

Park County Department of Environmental Health, 

written commun., 1999). Since 1993, the U.S. Forest 

Service has periodically sampled for nitrate in 21 wells 

located in Forest Service campgrounds in Park County 

(U.S. Forest Service, Pike National Forest, South Park 

Ranger District, written commun., 1999).

Well-completion data were available for 175 

of the wells sampled by the USGS (table 7). Fortythree wells were completed in alluvial aquifers 

composed of unconsolidated valley-fill or glacial 

deposits of Quaternary age. Alluvial wells were 

located throughout the county, primarily near streams 

(fig. 18). More than one-half the wells were completed 

in crystalline-rock aquifers of Precambrian age, and 

most of these were in the northeastern corner of the 

county, north of Bailey, and in the vicinity of Lake 

George (fig. 18). Twenty-nine wells were completed in 

sedimentary-rock aquifers of varying age and composition. Most of the wells completed in sedimentaryrock aquifers were located in a north-south-trending 

band extending from near Jefferson in the north to the 

Hartsel area in the south. Three wells were completed 

in volcanic-rock aquifers of Tertiary age and were 

located near Hartsel and in the West Fourmile Creek 

drainage in the Arkansas River Basin (fig. 18). 

Physical Properties

Water temperature was measured in most of 

the wells sampled by the USGS and ranged from 5°

to 19°C with a median of 9.5°C (table 8). Dissolved 

oxygen—measured in 16 wells sampled in 1998 by the 

USGS (Bruce and Kimbrough, 1999)—ranged from 

0.1 to 6.5 mg/L and was less than 1.0 mg/L in at least 

one-half of the wells (table 8). Values for pH in ground 

water (obtained in 133 of 180 wells) ranged from 5.4 

to 9.7. A small number of pH measurements were 

outside the 6.5–8.5 range that is the SMCL for 

drinking water (U.S. Environmental Protection 

Agency, 1996). Values of pH less than 6.5 primarily 

were in samples from the alluvial and crystalline-rock 

aquifers, whereas the few values larger than 8.5 were 

from the sedimentary and volcanic-rock aquifers 

(fig. 19).

Major Ions and Dissolved Solids

 Water from similar aquifers tends to have a 

similar ionic chemical composition based on the 

percentage of milliequivalents per liter of the major 

ions present. Calcium-bicarbonate-type water was 

found in each aquifer type and predominated in the 

alluvial and crystalline-rock aquifers (table 9). Water 

types found in sedimentary-rock aquifers included 

calcium-sulfate and sodium-sulfate water in aquifers 

composed of the South Park Formation; sodiumsulfate and sodium-bicarbonate water in aquifers 

composed of the Pierre Shale; and magnesiumbicarbonate water in sedimentary-rock aquifers 

of Paleozoic age. In the volcanic-rock aquifer, 

the predominant water type was different in each 

of the three wells sampled (table 9). 

Among the major ions, Federal drinkingwater standards have been set for chloride, sulfate, 

and fluoride (table 8). About 90 percent of all chloride 

concentrations in ground water were at least one 

order of magnitude lower than the USEPA drinkingwater standard of 250 mg/L (table 8) and no concentrations exceeded the standard. A few sulfate concentrations (8 of 144) were larger than the drinkingwater standard of 250 mg/L and occurred primarily 

in wells completed in sedimentary and volcanic-rock 

aquifers. The USEPA guideline for sulfate is based on 

esthetic effects such as taste and odor. Health concerns 

regarding sulfate in drinking water have been raised 

because of its potential laxative effects in infants or 

in people who experience an abrupt change from 

low-sulfate drinking water to high-sulfate drinking 

water (U.S. Environmental Protection Agency, 1999a). 

Fluoride was detected in every groundwater sample at concentrations ranging from 0.1 

to 5.6 mg/L, although only about 10 percent of the 

concentrations exceeded the USEPA drinking-water 

standard of 2 mg/L (table 8). Concentrations larger 

than 2 mg/L almost exclusively were limited to wells 

completed in crystalline-rock aquifers composed of 

the Pikes Peak Granite (fig. 20), an igneous rock of 

Precambrian age. The Pikes Peak Granite crops out 

only on the eastern edge of central Park County and 

in the northeast corner of the county north of Bailey. 

Fluoride concentrations in drinking water greater 

than 2 mg/L may cause dental fluorosis in children, 

and long-term exposure to drinking-water levels 

greater than 4 mg/L may result in serious bone 

disorders (U.S. Environmental Protection Agency, 

1999b).
GROUND-WATER QUALITY 51

0 5 10 15 20 MILES

0 5 10 15 20 KILOMETERS

Lake

George

Sedimentary rocks of Tertiary age

Intrusive and volcanic rocks of 

Tertiary and Cretaceous age

Sedimentary rocks of Cretaceous 

and Jurassic age

Sedimentary rocks of Paleozoic age

Crystalline rocks of Precambrian age

EXPLANATION

Unconsolidated alluvial deposits

of Quaternary age

Geology

Aquifer type 

Alluvial

Crystalline rock

Sedimentary rock

Volcanic rock

Undetermined

Base from U.S. Geological Survey digital data, 1:100,000

Universal Transverse Mercator projection,

Zone 13

39°

106°

105°30'

Geology from Green, 1992; Tweto, 1979

Figure 18. Aquifer type determined from screened interval for wells sampled by the U.S. Geological Survey in Park 

County.
52 Review and Analysis of Available Streamflow and Water-Quality Data for Park County, Colorado, 1962–98

Dissolved-solids concentrations were measured 

in 80 percent of the wells, and median concentrations 

were higher in the alluvial aquifers (252 mg/L) and the 

sedimentary-rock aquifers (257 mg/L) and lower in the 

crystalline-rock aquifers (160 mg/L) (fig. 21A). Data 

for the volcanic-rock aquifers were not included in the 

multiple comparison test because of the small number 

of samples. Dissolved-solids concentrations less than 

130 mg/L (value at the 25th percentile, table 8) primarily occurred in wells completed in the alluvial or 

crystalline-rock aquifers near Jefferson and north of 

Bailey (fig. 21B). Dissolved-solids concentrations 

greater than the USEPA SMCL of 500 mg/L were 

measured in about 10 percent of the wells (table 8) 

sampled and in all aquifer types (fig. 21A) but were 

most common in wells completed in sedimentary-rock 

aquifers between Jefferson and Hartsel (fig. 21B). 

Most wells that exceeded the SMCL for dissolved 

solids also exceeded the SMCL for sulfate (fig. 22).

Nutrients

Ground-water data for the nutrients nitrogen and 

phosphorus are summarized in table 8. The relatively 

small number of ammonia and nitrite analyses were 

collected by the USGS in the 1990’s, whereas most of 

the orthophosphorus analyses (162 analyses) were 

collected in the 1970’s. Some of the nitrate data were 

collected in the 1970’s by the USGS (176 analyses) 

but most (264 analyses) were collected in the 1990’s 

by the PCDEH, USGS, and U.S. Forest Service.

The USEPA (1996) has established MCL’s for 

two species of nitrogen—nitrite and nitrate (table 8). 

All nitrite concentrations in ground water were at least 

one order of magnitude lower than the 1 mg/L MCL 

for nitrite. Most nitrate concentrations in ground water 

were less than the 10 mg/L MCL for nitrate (table 8). 

The few nitrate concentrations larger than 10 mg/L 

primarily were in samples from domestic wells in 

subdivisions northeast of Bailey in the 1990’s.

Elevated nitrate concentrations in ground water 

may result from the seepage of animal waste or septic 

tank effluent. In the crystalline-rock aquifers of Park 

County and nearby Jefferson County, nitrate concentrations above 0.2 mg/L may result from waste 

contamination (Hofstra and Hall, 1975; Goddard, 

1978); thus, many of the wells in the crystalline-rock 

aquifers in Park County may have had some level 

of contamination as early as the 1970’s (fig. 23A). 

Figure 23A also indicates that nitrate concentrations 

were not significantly different between aquifer types 

in the 1970’s, even though some of the highest concentrations occurred in the alluvial and crystalline-rock 

aquifers (the small data set for the volcanic-rock aquifers was not included in the multiple comparison test).

In figure 23B, the PCDEH nitrate data for 

domestic wells located in subdivisions northeast of 

Bailey are plotted with USGS nitrate data for domestic 

wells located in the same subdivisions. The nitrate 

concentrations in samples collected in the 1990’s by 

the PCDEH were significantly higher (p<0.001) than 

the nitrate concentrations in samples collected in 

the 1970’s by the USGS. Although different wells 

were sampled by each agency, higher nitrate concentrations for the 1990’s data set may indicate that 

ground-water contamination is increasing in this part 

of the county. Resampling some of the wells that were 

sampled in the 1970’s could verify these results.

Trace Elements and Radon

Federal drinking-water standards exist for 

most of the trace elements that have been analyzed 

in Park County ground water (table 8). Most traceelement concentrations were less than the standards; 

however, the standards for iron, manganese, and zinc 

were exceeded in a small number of samples. Traceelement concentrations greater than the standards 

occurred in samples from each aquifer type, and 

median concentrations of iron, manganese, and zinc 

were similar among aquifer types (fig. 24). Some 

concentrations of dissolved iron and manganese 

(27) (2) (85) (16)

Alluvial Crystalline 

rock

Sedimentary

rock

Volcanic

rock

5

10

6

7

8

9

AQUIFER TYPE

pH, IN STANDARD UNITS

A

B

B

Figure 19. Distribution of pH by aquifer type for wells 

in Park County, 1974–75, 1998. Boxplot explanation on 

pages 10–11.
SPRINGWATER QUALITY 53

were two orders of magnitude larger than the USEPA 

drinking-water standards of 300 and 50 μg/L for iron 

and manganese, respectively. Elevated manganese and 

iron concentrations do not constitute a health hazard 

but may form red precipitates that stain laundry and 

plumbing fixtures (iron) or black-oxide precipitates 

that affect the taste and esthetics of drinking water 

(manganese) (Hem, 1989). High iron and manganese 

concentrations in the crystalline-rock aquifers may 

be related to localized mineralized zones found along 

fractured areas in the aquifer (Goddard, 1978). The 

distribution of trace-element concentrations greater 

than the standards is not localized and occurs 

throughout Park County.

Naturally occurring radon gas is formed by the 

radioactive decay of uranium. A drinking-water standard of 300 pCi/L was proposed for radon by the 

USEPA (1996); however, the standard has not yet been 

adopted. The national average concentration of radon 

in ground water is 350 pCi/L (Paulsen, 1991). In 1998, 

the USGS sampled for radon in 16 wells east of 

Fairplay that were completed in either crystalline-rock 

aquifers of Precambrian age or the sedimentary-rock 

aquifer of Tertiary age composed of the South Park 

Formation. Radon concentrations in the 16 wells were 

larger than the national average and ranged from 1,900 

to 27,800 pCi/L with a median of 4,200 pCi/L. Radon 

concentrations in ground water in other areas of the 

South Platte River Basin also are higher than the 

national average. Bruce and McMahon (1998) reported 

median radon concentrations of 4,400 pCi/L for a part 

of the crystalline-rock aquifer in the Front Range and 

1,100 pCi/L for the alluvial aquifer adjacent to the 

South Platte River and its tributaries in Denver.

SPRINGWATER QUALITY

Water-quality data are summarized for 30 

springs in Park County (fig. 25; tables 10, 11). Nineteen of the springs were sampled by the USGS in the 

1970’s, 4 springs east of Fairplay were sampled by 

the USGS in 1998 (Bruce and Kimbrough, 1999), 

and 7 springs were sampled in the 1970’s by the 

National Park Service as part of a reconnaissance 

sampling completed near the Florissant Fossil Beds 

National Monument. Almost all of the springs were 

sampled for physical properties, major ions, and trace 

elements, and some of the springs were sampled for 

nutrients and organic carbon. Source aquifers for the 

springs include alluvial aquifers of Quaternary age, 

sedimentary-rock aquifers of Tertiary, Cretaceous, 

Jurassic, and Paleozoic age, and crystalline-rock 

aquifers of Precambrian age.

Table 9. General description of selected aquifers sampled in Park County

[No., number, Ca, calcium; HCO3, bicarbonate; Na, sodium; SO4, sulfate; Mg, magnesium]

Aquifer age Principal geologic unit(s) General lithology No. of

 wells

Predominant water types

(and number of wells)

Alluvial aquifers

Quaternary Alluvium Valley-fill and glacial material

consisting of sand, gravel, cobbles,

and boulders

43 CaHCO3 (27), NaHCO3 (2), NaSO4 (2)

Crystalline-rock aquifers

Precambrian Boulder Creek, Silver Plume, 

and Pikes Peak Granites

Granite, gneiss, and schist 100 CaHCO3 (69)

Sedimentary-rock aquifers

Tertiary South Park Formation Arkosic sandstone and shale, 

volcaniclastic conglomerate

13 CaSO4 (10), NaSO4 (2)

Tertiary Antero Formation Limestone, tuff, tuffaceous sandstone,

conglomerate

4 CaHCO3

Tertiary Florissant Lake Beds Tuffaceous shale and tuff 2 CaHCO3, CaSO4

Tertiary Wagontongue Formation Volcaniclastic conglomerate 2 CaHCO3

Cretaceous Pierre Shale Shale with sandstone interbeds 3 NaSO4 (2), NaHCO3 (1)

Jurassic Entrada Formation Sandstone 1 CaHCO3

Paleozoic not determined Sandstone, shale, and limestone 4 MgHCO3 (3), CaHCO3 (1)

Volcanic-rock aquifers

Tertiary Thirtynine Mile Andesite Andesitic lavas, breccias, tuffs, and

conglomerates

3 MgSO4, NaHCO3, CaHCO3
54 Review and Analysis of Available Streamflow and Water-Quality Data for Park County, Colorado, 1962–98

Geology from Green, 1992; Tweto, 1979

Base from U.S. Geological Survey digital data, 1:100,000

Universal Transverse Mercator projection,

Zone 13

0 5 10 15 20 MILES

0 5 10 15 20 KILOMETERS

39°

106°

105°30'

Platte

River

South

South

Fork Middle

Fork

North Fork

South Platte River

Tarryall Creek

Deer Creek

Badger Creek

Currant Creek

West Fourmile Creek

EXPLANATION

Surficial Geology

Pikes Peak Granite of Precambrian age

Other rocks of Precambrian age

Rocks not of Precambrian age

Fluoride, in milligrams per liter

Less than 2.0

Greater than or equal to 2.0

Elk Creek

Lake

George

Figure 20. Fluoride concentrations in ground water, Park County, 1974–75, 1998.
SPRINGWATER QUALITY 55

0 5 10 15 20 MILES

0 5 10 15 20 KILOMETERS

EXPLANATION

 Alluvial deposits of Quaternary age

Sedimentary rocks of Tertiary age

Intrusive and volcanic rock of

Tertiary and Cretaceous age

Sedimentary rocks of Cretaceous and Jurassic age

Sedimentary rocks of Paleozoic age

Crystalline rocks of Precambrian age

Surficial Geology

Dissolved-solids concentration,

in milligrams per liter

Less than 130

130 to 202

203 to 283

284 to 500

Greater than 500

Alluvial Crystalline

rock

Sedimentary

rock

Volcanic

rock

AQUIFER TYPE

(31) (3) (77) (29)

10

5,000

20

50

100

200

500

1,000

2,000

DISSOLVED-SOLIDS CONCENTRATION,

IN MILLIGRAMS PER LITER

A

B

SMCL

A

B B

Lake

George

Boxplot explanation on pages 10-11

Base from U.S. Geological Survey digital data, 1:100,000

Universal Transverse Mercator projection,

Zone 13

39°

106°

105°30'

Figure 21. Distribution of dissolved solids (A) by aquifer type, and (B) in Park County (dashed line in figure A is the 

Secondary Maximum Contaminant Level for dissolved solids [U.S. Environmental Protection Agency, 1996]; geology 

from Green, 1992, and Tweto, 1979).
56 Review and Analysis of Available Streamflow and Water-Quality Data for Park County, Colorado, 1962–98

10 5,000 100 1,000

1

5,000

2

5

10

20

50

100

200

500

1,000

2,000

Sulfate SMCL

Dissolved solidsSMCL

DISSOLVED SOLIDS, IN MILLIGRAMS PER LITER

SULFATE, IN MILLIGRAMS

PER LITER

(41) (3) (93) (18) (3)

Alluvial Crystalline

rock

Sedimentary

rock

Volcanic

rock

Undetermined

AQUIFER TYPE

0.05

100

0.1

1

10

NITRATE, IN MILLIGRAMS PER LITER

(62) (194)

USGS PCDEH

0.05

100

0.1

1

10

A

B

(1970’s data) (1990’s data)

p < .001

1970's data

A

A

A

Boxplot explanation on pages 10-11

Figure 23. Nitrate concentrations (A) by aquifer types in Park 

County in the 1970’s, and (B) in domestic wells in subdivisions 

northeast of Bailey, Colorado (USGS, U.S. Geological Survey; 

PCDEH, Park County Department of Environmental Health).

Figure 22. Relation between dissolved-sulfate and dissolvedsolids concentrations in ground water, 1974–75, 1998 (SMCL, 

secondary maximum contaminant level for drinking water 

[U.S. Environmental Protection Agency, 1996]).
SPRINGWATER QUALITY 57

(31) (3) (77) (28)

Alluvium Crystalline

rock

Sedimentary

rock

Volcanic

rock

Crystalline

rock

Sedimentary

rock

Volcanic

rock

Crystalline

rock

Sedimentary

rock

Volcanic

rock

10

100,000

100

1,000

10,000

(30) (3) (77) (28)

Alluvium

10

100,000

100

1,000

10,000

CONCENTRATION, IN MICROGRAMS PER LITER

(19) (23) (16)

Alluvium

1

100,000

10

100

1,000

10,000

AQUIFER TYPE

Iron

Manganese

Zinc

A

B

C

(0)

Boxplot explanation on pages 10-11

SMCL

SMCL

SMCL

Figure 24. Concentrations of dissolved (A) iron, (B) manganese, 

and (C) zinc in aquifer types in Park County, 1974–75, 1998 

(dashed lines are secondary maximum contaminant levels for 

drinking water [U.S. Environmental Protection Agency, 1996]).
58 Review and Analysis of Available Streamflow and Water-Quality Data for Park County, Colorado, 1962–98

17 and 18

0 5 10 15 20 MILES

0 5 10 15 20 KILOMETERS

EXPLANATION

Specific conductance, in

microsiemens per centimeter

(with spring number from table 10)

Less than 159

159 to 362

363 to 1,050

1,051 to 4,295

Greater than 4,295

Platte

River

South

South

Fork Middle

Fork

North Fork

South Platte River

Tarryall Creek

Deer Creek

Elk Creek

Badger Creek

Currant Creek

West Fourmile Creek

Lake

George

Base from U.S. Geological Survey digital data, 1:100,000

Universal Transverse Mercator projection,

Zone 13

39°

106°

105°30'

Figure 25. Specific conductance in springwater, Park County, 1974–75, 1998.
S

PRINGWATERQUALITY59

Table 10. Characteristics of springwater-quality sites in Park County, 1962–98[USGS, U.S. Geological Survey; --, no data; Ca, calcium; HCO3, bicarbonate; Na, sodium, SO4, sulfate; Cl, chloride; PP, physical properties; MI, major ions; TE, trace eNPS, National Park Service]

Spring

number

(fig. 25)

Site identifier Data Source Sampling dates (month, year) Aquifer source Principal geologic unit Predo

che

const

1 392942105260500 USGS 6/74 Crystalline-rock aquifer of Precambrian age Pikes Peak Granite Ca-HCO2 392718105252800 USGS 6/74 Crystalline-rock aquifer of Precambrian age -- Ca-HCO3 392440105464900 USGS 7/74 Alluvial aquifer of Quaternary age Alluvium Ca-Na-H4 392312105273700 USGS 774 Alluvial aquifer of Quaternary age -- 5 391449105482801 USGS 5/98 Crystalline-rock aquifer of Precambrian age Silver Plume Granite 6 391438105483600 USGS 5/98 Sedimentary-rock aquifer of Tertiary age South Park Formation 7 391320105464000 USGS 5/98 Crystalline-rock aquifer of Precambrian age -- 8 391220105510800 USGS 9/74 Sedimentary-rock aquifer of Cretaceous age Pierre Shale Ca-Na-S9 391216105484801 USGS 5/98 Sedimentary-rock aquifer of Tertiary age South Park Formation 

10 391112105473800 USGS 9/74 Crystalline-rock aquifer of Precambrian age Silver Plume Granite Ca-HCO11 390949106035300 USGS 7/74, 6/75,

10/75, 7/76

Sedimentary-rock aquifer of Paleozoic age Leadville Limestone Ca-HCO

12 390946106035300 USGS 7/76 -- -- 13 390417105271100 USGS 8/75 Alluvial aquifer of Quaternary age -- Ca-HCO14 390256105502300 USGS 9/74 Sedimentary-rock aquifer of Jurassic age Entrada Formation Ca-HCO15 390129105480800 USGS 4/76 -- -- Na-Cl-H16 390125105375100 USGS 7/74 -- -- 17 390105105474000 USGS 6/75 Sedimentary-rock aquifer of Cretaceous age Dakota Sandstone Na-Cl 18 390105105473900 USGS 7/74, 6/75,

10/75, 1/76, 4/76

Sedimentary-rock aquifer of Cretaceous age Dakota Sandstone Na-Cl 

19 390014105464300 USGS 9/74 -- -- Na-Cl 20 385947105573000 USGS 7/74 Sedimentary-rock aquifer of Paleozoic age -- Na-Cl 21 385725105565700 USGS 7/74 Alluvial aquifer of Quaternary age -- Ca-HCO22 385712105563700 USGS 7/74 Sedimentary-rock aquifer of Paleozoic age Maroon Formation Na-Cl 23 385514105433400 USGS 9/74 Alluvial aquifer of Quaternary age -- 24 FLFO_NURE_01 NPS 8/76 Crystalline-rock aquifer of Precambrian age Silver Plume Granite 25 FLFO_NURE_05 NPS 8/76 -- -- 26 FLFO_NURE_02 NPS 8/76 Crystalline-rock aquifer of Precambrian age Silver Plume Granite 27 FLFO_NURE_15 NPS 8/76 Crystalline-rock aquifer of Precambrian age Silver Plume Granite 28 FLFO_NURE_03 NPS 8/76 -- -- 29 FLFO_NURE_18 NPS 8/76 -- -- 30 FLFO_NURE_16 NPS 8/76 -- -- 
60 Review and Analysis of Available Streamflow and Water-Quality Data for Park County, Colorado, 1962–98

Table 11. Summary of springwater-quality data for Park County, 1962–98

[No., number; °C, degrees Celsius; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius; --, no data or not computed; <, less 

than; μg/L, micrograms per liter; SMCL, secondary maximum contaminant level; MCL, maximum contaminant level; PMCL, proposed maximum contaminant 

level; CaCO3, calcium carbonate]

Constituent

or property

Number of

analyses

Minimum

Concentration or value at indicated percentile

Maximum

Standard

 or guideline

for drinking

water1

1U.S. Environmental Protection Agency, 1996.

10 25 50 75 90

Physical properties

Water temperature (°C) 37 2.5 6.5 9.0 11.0 24.0 45.0 57.0 --

Oxygen, dissolved, 4 0.6 -- -- 3.4 -- -- 6.6 --

pH (standard units) 30 6.0 6.6 6.8 7.2 8.0 8.2 8.7 --

Specific conductance

(μS/cm)

37 120 130 231 375 2,860 4,580 41,400 --

Major ions and dissolved solids, in mg/L

Bicarbonate, dissolved 23 51 71 197 317 483 501 2,030 --

Calcium, dissolved 34 14 18 29 41 110 120 920 --

Chloride, dissolved 28 1.1 1.5 2.4 6.8 820 1,107 15,000 250 (SMCL)

Fluoride, dissolved 28 0.1 0.2 0.2 0.4 2.0 2.9 8.9 2.0 (SMCL)

Magnesium, dissolved 34 1.8 3.0 4.9 18 21 34 180 --

Potassium, dissolved 28 <0.1 1.0 1.1 2.9 32 36 170 --

Sodium, dissolved 27 4.9 5.6 7.9 25 670 902 9,400 --

Silica, dissolved 29 9.0 11 13 19 32 38 44 --

Sulfate, dissolved 27 7.5 10 14 57 307 375 2,300 250 (SMCL)

Dissolved solids 27 87 100 186 379 2,280 2,670 28,200 500 (SMCL)

Nutrients, dissolved, in mg/L

Ammonia 4 0.02 -- -- 0.07 -- -- 1.1 --

Nitrate 27 <0.05 <0.05 <0.05 0.08 0.24 0.43 0.48 10 (MCL)

Nitrite 4 <0.01 -- -- <0.01 -- -- 0.01 1 (MCL)

Orthophosphorus 27 <0.01 <0.01 <0.01 0.01 0.04 0.10 0.14 --

Trace elements, dissolved, in μg/L

Aluminum 7 4 -- -- 10 -- -- 680 50–200 

Arsenic 12 <1 <1 <1 1 2 3 6 50 (MCL)

Barium 6 3 -- -- 23 -- -- 500 2,000 (MCL)

Cadmium 9 <2 -- -- <2 -- -- <2 5.0 (MCL)

Chromium 4 <1 -- -- 1 -- -- 1 100 (MCL)

Copper 19 <4 <4 <4 <4 <4 <4 4 1,000 (SMCL)

Iron 33 <10 20 31 210 428 872 31,890 300 (SMCL)

Lead 8 <1 -- -- <1 -- -- 4 --

Manganese 33 <10 <10 <10 <10 172 217 3,000 50 (SMCL)

Mercury 4 <0.5 -- -- <0.5 -- -- <0.5 --

Molybdenum 5 <6 -- -- <6 -- -- 14

Nickel 5 <1 -- -- 1 -- -- 71 100 (MCL)

Selenium 10 <1 <1 <1 <1 <1 1 1 50 (MCL)

Silver 5 <2 -- -- <2 -- -- <2 100 (SMCL)

Uranium 11 <1 1 1 2 3 8 8 20 (PMCL)

Zinc 27 <20 <20 <20 <20 60 187 695 5,000 (SMCL)

Other constituents

Alkalinity,

(mg/L as CaCO3)

23 42 58 162 260 396 411 1,670 --

Hardness,

(mg/L as CaCO3)

27 42 54 120 210 380 468 3,100 --
SPRINGWATER QUALITY 61

Physical Properties

The temperature of springwater ranged from 

2.5° to 57°C with a median of 11°C. Water temperatures greater than 20°C (68° F) were measured at three 

springs. Water temperature in spring 11 (fig. 25), also 

known as the Rhodes Warm Spring, ranged from 24°

to 27°C. Water temperatures ranging from 45° to 57°C 

(113–135° F) were measured in springs 17 and 18 

(fig. 25), also known as the Hartsel Hot Springs. 

McCarthy and others (1982) indicate that granites of 

Precambrian age are most likely the heat source for the 

Hartsel Hot Springs, and the Dakota Sandstone of 

Cretaceous age is the water source. Dissolved oxygen 

was measured in four springs east of Fairplay 

(springs 5, 6, 7, and 9, fig. 25) and values ranged 

from 0.6 to 6.6 mg/L (table 11). Values for pH ranged 

from 6.0 to 8.7 with a median of 7.2. Measurements of 

specific conductance were obtained for each spring 

listed in this report, and the number of measurements 

was larger than the number of dissolved-solidsconcentration analyses. Specific conductance, an 

indirect measure of the dissolved-solids concentration, 

was low in springs originating in crystalline-rock 

aquifers (springs 1, 2, 5, 7, 10, 24, 26, 27) (fig. 25, 

table 10). Specific conductance was highest in spring 

number 22, which is believed to originate in evaporite 

beds in the Maroon Formation of Paleozoic age (Klein 

and others, 1978). Spring 22 is located upstream from 

Antero Reservoir and is thought to be the source of 

high specific conductance and dissolved-solids 

concentrations in Salt Creek (surface-water site 35, 

fig. 9).

Major Ions and Dissolved Solids

 Major-ion concentrations in springwater 

varied greatly and were influenced by the type of 

rock in which the water originated. Concentrations of 

chloride and sulfate larger than the 250-mg/L USEPA 

SMCL primarily occurred in springs originating from 

sedimentary-rock aquifers (springs 8, 9, 17, 18, 20, 22) 

(table 10). Similar to fluoride concentrations in ground 

water, fluoride concentrations larger than the USEPA 

SMCL of 2 mg/L occurred in springs originating from 

crystalline-rock aquifers (springs 1 and 2) but also 

occurred in a spring originating from a sedimentaryrock aquifer composed of the Dakota Sandstone 

(spring 17) and from two springs with undocumented 

sources (springs 16 and 19). With the exception of 

bicarbonate, fluoride, and silica, the maximum 

concentrations of all major ions (table 11) were 

from spring 22. Dissolved-solids concentrations 

were determined for samples from 20 of the 30 springs 

listed in this report. Several springs had dissolvedsolids concentrations larger than the 500-mg/L 

USEPA SMCL, including springs 8, 9, and 16–22. 

Nutrients

Analyses of ammonia and nitrite for springwater 

were available only for the four springs sampled by the 

USGS in 1998. Ammonia concentrations in the four 

springs ranged from 0.02 to 1.1 mg/L, and nitrite 

concentrations were less than or equal to 0.01 mg/L. 

Nitrate and orthophosphorus were analyzed in samples 

from 20 of the 30 springs. Nitrate concentrations, 

ranging from less than 0.05 to 0.48 mg/L, were less 

than the 10-mg/L USEPA MCL. Dissolved orthophosphorus concentrations in springwater ranged from less 

than 0.01 to 0.14 mg/L.

Trace Elements

With few exceptions, most trace-element 

concentrations in springwater were less than USEPA 

drinking-water standards (table 11). The concentration of dissolved aluminum in spring 16, a spring 

emanating from an undetermined aquifer type, was 

larger than the USEPA SMCL of 200 μg/L (fig. 26). 

Concentrations of dissolved iron larger than the 

USEPA SMCL of 300 μg/L occurred in springs originating in alluvial and sedimentary-rock aquifers and 

in an undetermined aquifer but not in the four springs 

originating in crystalline-rock aquifers (fig. 26). 

Dissolved manganese concentrations larger than the 

USEPA SMCL of 50 μg/L occurred in springs originating from all aquifer types (fig. 26).
62 Review and Analysis of Available Streamflow and Water-Quality Data for Park County, Colorado, 1962–98

(3) (3) (1)

Alluvial Crystalline

rock

Sedimentary

rock

Undetermined

Crystalline

rock

Sedimentary

rock

Undetermined

Crystalline

rock

Sedimentary

rock

Undetermined

1

100,000

10

100

1,000

10,000

(4) (16) (9) (4)

Alluvial

10

100,000

100

1,000

10,000

CONCENTRATION, IN MICROGRAMS PER LITER

(4) (16) (9) (4)

Alluvial

10

100,000

100

1,000

10,000

AQUIFER TYPE

Iron

Manganese

A Aluminum

B

C

(0)

Boxplot explanation on pages 10-11

SMCL

SMCL

SMCL

Figure 26. Concentrations of dissolved (A) aluminum, (B), iron, 

and (C) manganese in springs emanating from aquifer types, Park 

County, 1974–75, 1998 (dashed lines are secondary maximum 

levels for drinking water [U.S. Environmental Protection Agency, 

1996]).
SUMMARY 63

SUMMARY

 In 1999, the USGS, in cooperation with 

Park County and the Center of Colorado Water 

Conservancy District, compiled and analyzed available 

information on streamflow and surface-water and 

ground-water quality in Park County for 1962–98. A 

review of historical data helps to identify gaps in available data and allows for prioritizing and focusing 

future studies.

Park County is primarily drained by headwater streams in the South Platte River Basin and to a 

lesser extent by streams in the Arkansas River Basin. 

Land-surface altitude ranges from about 7,200 to 

14,000 feet, and average annual precipitation ranges 

from 10 to 40 inches. Igneous and metamorphic 

rocks of Precambrian age occupy about 45 percent 

of the land surface, primarily in eastern Park County. 

Sedimentary rocks of Paleozoic age occur on the 

eastern flanks of the Mosquito Range in western Park 

County and sedimentary rocks of Cretaceous, Jurassic, 

and Tertiary age occur in central Park County. 

Volcanic rocks of Cretaceous and Tertiary age cover 

a large portion of southern Park County. Major landcover classifications in Park County are natural herbaceous vegetation, primarily rangeland and tundra 

(53 percent) and forest (39 percent). Built-up areas, a 

subcategory of urban land use, occur throughout Park 

County as evidenced by the large number of domestic 

wells. 

Streamflow has been monitored at more than 

40 sites in the county and is currently (1998) monitored at 30 sites. Streamflow data currently (1998) are 

archived in a data base for only 10 sites because most 

sites are operated for the purpose of administering 

water rights on a daily basis. In the South Platte River 

Basin in Park County, most streamflow is derived from 

snowmelt, and more than one-half the annual streamflow occurs in May, June, and July. In some streams, 

both the timing and magnitude of streamflow have 

been altered by reservoirs operations or by interbasin 

water transfers. 

Surface-water-quality data collected between 

1962 and 1998 were obtained for 125 sites. Constituents typically sampled for at most sites include 

physical properties (water temperature, specific 

conductance, pH, and dissolved oxygen), nutrients 

(nitrogen and phosphorus), major ions, and trace 

elements. Constituents sampled for less frequently 

included turbidity, bacteria, organic carbon, radionuclides, and suspended sediment.

Most values of water temperature, dissolved 

oxygen, and pH in surface water were within recommended limits set by the CDPHE. Specific conductance (an indirect measure of the dissolved-solids 

concentration) generally was lowest in mountain 

streams of the South Platte River Basin. Higher values 

for specific conductance occurred in the main-stem 

South Platte River downstream from Hartsel, the 

Arkansas River Basin, Handcart Gulch in the North 

Fork Basin, Park Gulch in the Tarryall Creek Basin, 

and Trout Creek in the Middle Fork Basin. The median 

specific conductance in Salt Creek, which flows into 

Antero Reservoir, was at least one order of magnitude 

larger than the median in any other stream in the 

county. 

Concentrations of chloride and sulfate in a small 

number of samples from the South Fork and mainstem South Platte River downstream from Antero 

Reservoir have exceeded the CDPHE in-stream standard of 250 mg/L and may result from inflow from 

Salt Creek, where chloride and sulfate concentrations 

as high as 7,600 and 2,100 mg/L, respectively, have 

been measured.

Historical nitrogen concentrations in surface 

water in Park County were small. Nitrite was not 

detected, and most un-ionized ammonia concentrations were less than the CDPHE chronic standard of 

0.02 mg/L. All nitrate concentrations were less than 

1.2 mg/L, well below the CDPHE in-stream standard 

of 10 mg/L. Nitrate concentrations were significantly 

larger in urban and built-up areas than rangeland 

and forest areas. Most median concentrations of total 

phosphorus in surface water were less than 0.05 mg/L. 

Median total phosphorus concentrations were not 

significantly different among sites in urban and 

built-up, rangeland, and forest land-use/land-cover 

settings.

With one exception, no temporal trends were 

detected in nitrate or total phosphorus concentrations 

at four surface-water sites. An upward trend in total 

phosphorus concentration was determined for the East 

Portal of the Harold D. Roberts Tunnel, but the slope 

of the trend line was small and the concentrations were 

near the detection limit of 0.01 mg/L.

 Using data collected from 1971–98, phosphorus 

loads were computed for the South Platte River below 

Elevenmile Canyon Reservoir, the North Fork South 

Platte River at Bailey, and the East Portal of the 

Harold D. Roberts Tunnel. At all three sites, significantly higher phosphorus loads during April through 
64 Review and Analysis of Available Streamflow and Water-Quality Data for Park County, Colorado, 1962–98

September than during October through March 

coincided with significantly higher streamflows; 

streamflow influences the variability in load more 

than phosphorus concentration. Using the median 

phosphorus loads for the two South Platte River 

sites, the annual phosphorus load transported out 

of Park County in the South Platte River was about 

10,000 pounds.

Iron and manganese concentrations in surface 

water larger than CDPHE instream standards primarily 

occurred in upper North Fork South Platte Basin. 

Large zinc concentrations have been measured in the 

Mosquito Creek Basin. Concentrations of aluminum, 

cadmium, chromium, copper, and nickel were largest 

in the North Fork Basin, primarily in Handcart Gulch, 

the North Fork South Platte River downstream from 

Handcart Gulch, and upper Geneva Creek. Mosquito 

Creek, South Mosquito Creek, and sections of the 

North Fork and Geneva Creek have been identified 

by the CDPHE as being impaired by elevated traceelement concentrations.

Suspended-sediment data for streams in Park 

County are scarce, and most sampling has occurred 

at a few sites in Geneva and Badger Creeks. Data 

for Geneva and Badger Creeks show that suspendedsediment concentration generally increases with 

discharge.

Ground-water-quality data exist for alluvial 

aquifers of Quaternary age, crystalline-rock aquifers 

of Precambrian age, sedimentary-rock aquifers of 

varying age and lithology, and volcanic-rock aquifers 

of Tertiary age. Calcium-bicarbonate type water was 

found in each aquifer type and predominated in the 

alluvial and crystalline-rock aquifers. Water types 

were more variable in the sedimentary-rock aquifers 

and included calcium-sulfate and sodium-sulfate water 

in aquifers composed of the South Park Formation of 

Tertiary age, sodium-sulfate and sodium-bicarbonate 

water in aquifers composed of the Pierre Shale of 

Cretaceous age, and magnesium bicarbonate water 

in the aquifers of Paleozoic age.

All chloride concentrations in ground water 

were less than the USEPA drinking-water standard 

of 250 mg/L. Sulfate concentrations larger than the 

250 mg/L USEPA drinking-water standard occurred 

in a small number of samples and primarily in wells 

completed in sedimentary and volcanic-rock aquifers. 

Fluoride was detected in every ground-water sample, 

although only about 10 percent of the concentrations 

exceeded the USEPA drinking-water standard of 

2 mg/L. Concentrations larger than 2 mg/L were 

almost exclusively limited to samples from wells 

completed in the crystalline-rock aquifer composed 

of the Pikes Peak Granite.

Median dissolved-solids concentrations 

were similar among aquifer types and ranged from 

160 mg/L in the crystalline-rock aquifers to 257 mg/L 

in the sedimentary-rock aquifers. Dissolved-solids 

concentrations less than 130 mg/L primarily occurred 

in the alluvial or crystalline-rock aquifers near 

Jefferson or north of Bailey. Dissolved-solids concentrations greater than the USEPA drinking-water standard of 500 mg/L occurred in about 10 percent of the 

wells and were most common in the sedimentary-rock 

aquifers between Jefferson and Hartsel.

Most nitrate concentrations in ground water 

were less than the USEPA drinking-water standard of 

10 mg/L. The few concentrations larger than 10 mg/L 

primarily occurred in samples collected during the 

1990’s from domestic wells located in subdivisions 

northeast of Bailey. The nitrate concentrations in 

samples collected from domestic wells northeast of 

Bailey in the 1990’s were significantly higher than 

nitrate concentrations measured in wells in the same 

subdivisions in the 1970’s. Although different wells 

were sampled during each decade, higher nitrate 

values for the 1990’s sampling may indicate that 

contamination is increasing in this part of the county. 

Resampling some of the wells that were sampled in 

the 1970’s may verify these results.

Most trace-element concentrations measured 

in Park County ground water were less than USEPA 

drinking-water standards; however; standards for 

iron, manganese, and zinc were exceeded in a small 

number of samples. A median radon concentration of 

4,200 pCi/L for samples from 16 wells located east of 

Fairplay was higher than the national average concentration of 350 pCi/L.

Water-quality data were summarized for 

30 springs in Park County. Sources for the springs 

included alluvial aquifers of Quaternary age, 

sedimentary-rock aquifers of Tertiary, Cretaceous, 

Jurassic, and Paleozoic age; and crystalline-rock 

aquifers of Precambrian age. 

Water temperatures were higher than 20°C 

in three springs: the Rhodes Warm Spring and in 

two springs collectively referred to as the Hartsel 

Hot Springs. Specific conductance was lowest in 

springs originating from crystalline-rock aquifers 

of Precambrian age and highest in a spring that 

is believed to originate from a sedimentary-rock 
REFERENCES 65

aquifer that contains evaporite beds of the Maroon 

Formation of Paleozoic age. Several springs had 

dissolved-solids concentrations larger than the 

USEPA drinking-water standard of 500 mg/L.

Analyses of ammonia and nitrite were available 

for only 4 springs, but nitrate and orthophosphorus 

were analyzed in samples from 20 springs. Nitrate 

concentrations, ranging from less than 0.05 to 

0.48 mg/L, were less than the USEPA drinking-water 

standard of 10 mg/L. Dissolved orthophosphorus 

concentrations in springwater ranged from less than 

0.01 to 0.14 mg/L.

With few exceptions, trace-element concentrations in springwater were less than Federal drinkingwater standards. Concentrations of dissolved iron 

larger than the USEPA drinking-water standard of 

300 μg/L occurred in springs originating in alluvial 

and sedimentary-rock aquifers and from an undetermined aquifer type but not in the four springs originating in crystalline-rock aquifers. Dissolved 

manganese concentrations larger than the drinkingwater standard of 50 μg/L occurred in springs originating from all aquifer types sampled.

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April 1997–November 1998: U.S. Geological Survey 

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Johnson, J.B., 1993, Water quality characteristics of streams 

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