U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2011–3041

April 2011

Prepared in cooperation with the Wyoming Department of Environmental Quality

Wyoming Groundwater-Quality Monitoring Network

Printed on recycled paper

Introduction

A wide variety of human activities have the potential to 

contaminate groundwater. In addition, naturally occurring constituents can limit the suitability of groundwater for some uses. 

The State of Wyoming has established rules and programs to 

evaluate and protect groundwater quality based on existing and 

potential uses. The Wyoming Groundwater-Quality Monitoring 

Network (WGQMN) is a cooperative program between the 

U.S. Geological Survey (USGS) and the Wyoming Department 

of Environmental Quality (WDEQ) and was implemented in 

2009 to evaluate the water-quality characteristics of the State’s 

groundwater. Representatives from USGS, WDEQ, U.S. 

Environmental Protection Agency (USEPA), Wyoming Water 

Development Office, Wyoming State Geological Survey, and 

Wyoming State Engineer’s Office formed a steering committee, 

which meets periodically to evaluate progress and consider 

modifications to strengthen program objectives. The purpose 

of this fact sheet is to describe the WGQMN design and 

objectives, field procedures, and water-quality analyses. USGS 

groundwater activities in the Greater Green River Basin also are 

described.

Network Design and Objectives

The WGQMN is designed to include wells that are in 

priority areas where groundwater has been identified as an 

important source of drinking water to public and private water 

supplies, is susceptible to contamination, and is overlain by 

one or multiple land-use activities that could negatively affect 

groundwater resources (Bedessem and others, 2003) (fig. 1, 

table 1). The State identified 33 priority areas and grouped 

them together by major basin for implementation purposes 

(table 1). Groundwater-quality samples will be collected from 

20 to 30 wells within each priority area. Wells to be selected for 

sampling will be completed in Quaternary-age unconsolidated 

aquifers and shallow (less than 500 feet deep) bedrock aquifers. 

Data collection and reporting activities by the USGS as part of 

the WGQMN will include the following:

• Measurement of the water level in each well;

• Collection of groundwater samples from each well to be 

analyzed for a wide variety of natural and human-made 

constituents; 

• Analysis of select samples for constituents such as stable 

isotopes to help determine recharge characteristics of the 

groundwater; 

• Reporting of analytical results through a publicly available 

USGS water-quality Web site (http://waterdata.usgs.gov/

wy/nwis/qw/); and

• Periodic summaries of groundwater data in published 

USGS Fact Sheets and Scientific Investigations Reports. 

Field Procedures

Site selection, field measurements, and water-quality sampling procedures are performed in accordance with approved 

methods in the USGS National Field Manual for the Collection of Water-Quality Data (U.S. Geological Survey, variously 

dated). Prior to sampling, the depth to water in the well is 

measured to the nearest 0.01 foot, if possible. If a pump is not 

permanently installed in the well, a submersible pump is used 

for purging and sampling. Field properties (temperature, pH, 

oxidation-reduction potential, specific conductance, dissolved 

oxygen, and turbidity) are measured and recorded regularly 

during purging. Each well is purged by removing a minimum of 

three casing volumes of standing water. After purging, samples 

are collected when field properties have stabilized. Sample-collection connections are made at the wellhead or other sampling 

point to allow the use of a mobile water-quality laboratory to 

process the samples (figs. 2 and 3). Samples are preserved and 

containerized on site, according to individual analytical method 

requirements. 

Details about the site and well are useful for interpreting 

analytical results. Field documentation includes groundwaterquality notes, which are used to record information about 

sampling conditions, analytical laboratories, calibration, well 

condition, water-level measurements, well purging and associated stability measurements, and quality-control samples. 

Analytical services request forms are used to record the USGS 

site identification number, sample date and time, requested 

laboratory schedules and codes, and types of bottles and their 

treatments. Photographs are used to document the well condition and surrounding land uses. 
Figure 1. Groundwater with the highest priority for sampling is shown as red and yellow (modified from Bedessem 

and others, 2003).

1

2

3

4

7

9

14

15

16

17

18

13

33

32

30

31

28

24

23

22 21

20

19

29

25

10

11

12

26

6

27 5

8

WIND/BIGHORN

RIVER BASIN

POWDER/TONGUE

RIVER BASIN

NORTHEAST

RIVER BASIN

PLATTE

RIVER BASIN GREATER GREEN

RIVER BASIN

BEAR

RIVER

BASIN

SNAKE/SALT

RIVER BASIN

0

0 60 KILOMETERS

30 60 MILES Lambert projection, standard parallels 33 and 45

degrees north, central meridian 107.5 degrees west

110°

44°

42°

108° 106°

Aquifer Prioritization for Ambient

Groundwater Monitoring

Aquifer prioritization

Low

Low–moderate

Moderate–high

High

No data

Map number (see table 1) for

 moderate–high and high

 priority areas

15

EXPLANATION
Table 1. Priority areas identified for inclusion in the Wyoming Groundwater-Quality Monitoring Network.

Site 

number 

(fig. 1)

Priority 

area

Basin

Site 

number 

(fig. 1)

Priority 

area

Basin

1 Cody/Wapiti Wind/Bighorn 18 LaGrange/Hawk Springs Platte

2 Emblem Wind/Bighorn 19 Wheatland Platte

3 Thermopolis/Big Horn River/Worland Wind/Bighorn 20 Slater/Chugwater Platte

4 Dubois/Crowheart Wind/Bighorn 21 Cheyenne Platte

5 Riverton/Wind River Wind/Bighorn 22 Laramie/Tie Siding Platte

6 Lander/Hudson Wind/Bighorn 23 Laramie River Platte

7 Sheridan/Dayton Powder/Tongue 24 Little Laramie River Platte

8 Buffalo Powder/Tongue 25 Baggs Greater Green

9 Gillette/Rozet Powder/Tongue 26 Big Piney/Marbleton Greater Green

10 Rawlins Platte 27 Pinedale/Boulder/Daniel Greater Green

11 Saratoga Platte 28 Mountain View Greater Green

12 Elk Mountain Platte 29 Rock Springs Greater Green

13 Casper/Evansville/Alcova Platte 30 Cokeville Bear

14 Glenrock/Douglas/Orin Platte 31 Evanston Bear

15 Torrington Platte 32 Star Valley Snake/Salt

16 Yoder/Veteran Platte 33 Jackson/Teton Village Snake/Salt

17 Huntley and by border Platte

Figure 2. Mobile water-quality laboratory used for the collection of samples 

from groundwater wells.
Water-Quality Analyses

Groundwater samples are analyzed for major ions, trace 

elements, nutrients, and volatile organic compounds at the 

USEPA Region 8 Laboratory in Denver, Colo., and for total 

dissolved solids, dissolved organic carbon, and stable isotopes 

at various USGS laboratories. Coliform bacteria (total coliform 

and E. coli) colony counts and alkalinity values are determined 

in the field. Select samples also may be analyzed for wastewater 

compounds, radionuclides (tritium, gross-alpha and gross-beta 

radioactivity, and radon-222), total petroleum hydrocarbons 

(diesel-range and gasoline-range organics), dissolved hydrocarbon gases, and biological activity reaction tests. 

USGS Groundwater Activities in the Greater Green 

River Basin

Although the WGQMN scope is Statewide, water-quality 

sampling will be implemented by basin. Sampling by the 

USGS began in December 2009 in five priority areas within the 

Greater Green River Basin. The WGQMN in the Greater Green 

River Basin builds on existing USGS projects in the basin such 

as the Wyoming Landscape Conservation Initiative, not only 

to leverage limited resources, but also to improve the understanding of groundwater. A recently completed summary of 

physical and chemical characteristics of groundwater resources 

(Clarey and others, 2010) and an ongoing project by Bowen 

and others (2010) were used to select wells to be sampled in 

unconsolidated and bedrock aquifers within the priority areas 

for the Greater Green River Basin. Selection of basins for future 

sampling will be conducted in consultation with the WDEQ and 

will be based on groundwater management needs of the State.

Figure 3. Wellhead connections for groundwater sampling 

that lead to the mobile water-quality laboratory and discharge 

line.

References Cited

Bedessem, M.E., Casey, Brenda, Frederick, Kevin, and 

Nibbelink, Nathan, 2003, Phase I: Aquifer prioritization, 

Final report: Prepared for the Wyoming Department of 

Environmental Quality by the University of Wyoming 

Department of Civil and Architectural Engineering, Laramie, 

Wyo., variously paged.

Bowen, Z.H., Aldridge, C.L., Anderson, P.J., Assal, T.J., 

Biewick, L.R.H., Blecker, S.W., Bristol, S., Carr, N.B., 

Chalfoun, A.D., Chong, G.W., Diffendorfer, J.E., Fedy, B.C., 

Garman, S.L., Germaine, S., Grauch, R.I., Holloway, J., 

Homer, C., Kauffman, M.J., Keinath, D., Latysh, N., Manier, 

D., McDougal, R.R., Melcher, C.P., Miller, K.A., Montag, J., 

Nutt, C.J., Potter, C.J., Sawyer, H., Schell, S., Shafer, S.L., 

Smith, D.B., Stillings, L.L., Tuttle, M., and Wilson, A.B., 

2010, U.S. Geological Survey Science for the Wyoming 

Landscape Conservation Initiative—2009 Annual Report: 

U.S. Geological Survey Open-File Report 2010–1231, 

106 p., accessed March 7, 2011, at http://pubs.usgs.gov/

of/2010/1231/.

Clarey, K.E., Bartos, Timothy, Copeland, David, Hallberg, 

L.L., Clark, M.L., and Thompson, M.L., 2010, Available 

groundwater determination, Technical memorandum, Green 

River Basin Water Plan II—Groundwater study Level I 

(2007–2009): Prepared for the Wyoming Water Development Commission by the Wyoming State Geological Survey, 

Laramie, Wyo., variously paged, accessed March 7, 2011, 

at http://waterplan.state.wy.us/plan/green/2010/finalrept/

gw-tpage_preface.pdf.

U.S. Geological Survey, variously dated, National field manual 

for the collection of water-quality data: U.S. Geological 

Survey Techniques of Water-Resources Investigations, book 

9, chaps. A1–A9, available online at http://pubs.water.usgs.

gov/twri9A. 

For More Information

Visit the USGS Wyoming Water Science Center Web site 

at: http://wy.water.usgs.gov/projects/gw_monitoring/index.htm, 

or contact:

Gregory K. Boughton

USGS Wyoming Water Science Center

2617 E. Lincolnway, Suite B

Cheyenne, WY 82001

(307) 775-9161

gkbought@usgs.gov

Jane Francis

Wyoming Department of Environmental Quality

122 West 25th Street, Herschler Building

Cheyenne, WY 82002

(307) 777-7092

jfranc@wyo.gov

This fact sheet is available at http://pubs.usgs.gov/

fs/2011/3041 or from U.S. Geological Survey, Information 

Services, Box 25286, Denver Federal Center, Denver, CO 

80225.