Nitrate Concentrations in Ground Water in the Henrys Fo

Basin, Eastern Idaho

U.S. Department of the Interior USGS Fact She

U.S. Geological Survey 

In 1998 and 1999, the U.S.

Geological Survey (USGS) completed comprehensive studies of

nitrate concentrations in ground

water in the Henrys Fork Basin in

eastern Idaho (fig. 1A). These

studies were done in cooperation

with the following agencies or

groups: Idaho Division of Environmental Quality (DEQ), District 7 Health Department, Idaho

Department of Water Resources

(IDWR), Idaho Department of

Agriculture (IDAG), Bureau of

Reclamation, Henrys Fork Foundation, Fremont County, and Madison County. This Fact Sheet presents selected results of these

investigations.

Description of the Area

The Henrys Fork Basin in parts of

Teton, Madison, and Fremont Counties in Idaho comprises lower Henrys

Fork (Menan Buttes to about Ashton,

including the Fall River drainage),

Teton River, and upper Henrys Fork

drainages. Detailed descriptions of

climate, geographic setting, land and

water uses, geology, hydrology, and

generalized water quality of the area

are provided in reports listed in the

“Selected References” section, back

of this report.

 Geology and hydrology of the

basin are diverse and complex. Unconsolidated sediment varies in thickness from a few feet to hundreds of

feet; thicknesses are greatest in areas

from Menan Buttes to St. Anthony.

Sediment overlies variable thicknesses of volcanic rocks, and groundwater yielding zones exist in sediment

and volcanic rock units. Regionally,

ground water moves generally southward to southwestward but, in localized areas, ground-water movement

can be northwestward or southeastward (Crosthwaite and others, 1970;

Whitehead, 1978; Spinazola, 1994).

Total well depths vary from tens of

feet to hundreds of feet below land

surface. Some well casings may be

perforated or screened at one or more

intervals or wells may be constructed

with uncased boreholes to increase

well yields.

 Most ground water in the Henrys

Fork Basin is nonthermal (temperature less than 29 degrees Celsius, °C;

84 degrees Fahrenheit, °F), but geothermal water (temperature greater

than 29°C) is present in many parts of

the basin. On the basis of U.S. Environmental Protection Agency (EPA,

1996) standards for public water supplies, ground water in the Henrys

Fork Basin is suitable for most public

and private drinking-water uses.

Ground water in this area is highly or

very highly vulnerable to contamination (Rupert and others, 1991), and

water in a few areas contains contaminants—components that can limit the

water’s suitability for use or can represent degradation of water quality.

Potential pathways of contaminant

movement to ground-water zones

include downward flushing of contaminants by infiltration of precipitation, floodwater, or applied irrigation

water; flushing from soil and unsaturated rocks by seasonal var

ground-water levels; leaka

or into well casings or bor

(especially important in ar

thin layers of soil and sedi

lying volcanic rock); dum

wells; backflushing to wel

water-supply systems; and 

from upgradient ground-w

Contamination from land 

uses can be localized (poin

or widespread (nonpoint s

One of the most widesp

contaminants in the Henry

Basin is nitrate (NO3). In t

nitrate is reported as nitrog

or nitrate-N) in milligrams 

(mg/L, equivalent to parts 

million).

Nitrate-N Concentrat

Ground Water

 Concentrations of nitr

Idaho prior to land and wa

ment probably were less th

From 1995 through 1999, 

concentration (50th percen

nitrate-N in Idaho ground 

about 1.4 mg/L, and the ra

centrations was <0.05 to 1

During the same period, th

nitrate-N concentration in 

Fork Basin was 3.2 mg/L, 

range of concentrations w

38 mg/L.

Large nitrate-N concen

primarily are of concern a

ing-water health risk, and 

mum EPA (1996) limit for 

concentration in public wa

plies is 10 mg/L. Recomm
22

111o 15'

FREMONT

MADISON TETON

Tetonia

Driggs

Victor

Warm

River

Drummond

Ashton

Teton

Hibbard Newdale

St Anthony

Rexburg

Island Park

Reservoir

Ashton

Reservoir

Henrys

Teton

Fork

River

River

Teton

Henrys

Fork

Fall

River

Warm

Moody

Creek

Canyon

Creek

Teton

Creek

Badger

Creek

Conant Creek

Robinson

Creek

T

7

N

T.

8

N.

R. 40 E. R. 41 E. R. 42 E. R. 43 E. R. 44 E. R. 45 E.

T.

9

N.

T.

10

N.

T.

11

N.

T.

12

N.

T

6

N

R. 39 E.

R. 38 E.

MENAN

BUTTES

111o 30' 111o

 45'

111o 45'

111o 30' 111o

 15'

44o 15'

44o 00'

43o 45' 

4

44

Study

area

Boise

0

0 5 10

5 10

15 KILOMETERS

15 MILES

Base from U.S. Geological Survey

digital data, 1:500,000, 1980

Albers Equal-Area projection

Standard parallels 43o

 30', 47o 30',

and -114o

 00', 41o 45'

No false easting or false northing

EXPLANATION

Upper Henrys Fork drainage

Teton River drainage

Lower Henrys Fork drainage

Generalized direction of ground-

 water movement (dashed where

 inferred)—Data from Crosthwaite

 and others (1970); Whitehead (1978);

 Spinazola (1994)

Sampling site where nitrate (as

 nitrogen) concentration was

 less than 5 milligrams per liter

111o 15'

FREMONT

MADISON TETON

Tetonia

Driggs

Victor

Warm

River

Drummond

Ashton

Teton

Hibbard Newdale

St Anthony

Rexburg

Island Park

Reservoir

Ashton

Reservoir

Henrys

Teton

Fork

River

River

Teton

Henrys

Fork

River

Fall

River

Warm

Moody

Creek

Canyon

Creek

Teton

Creek

Badger

Creek

Conant Creek

Robinson

Creek

T.

7

N.

T.

8

N.

R. 40 E. R. 41 E. R. 42 E. R. 43 E. R. 44 E. R. 45 E.

T.

9

N.

T.

10

N.

T.

11

N.

T.

12

N.

T.

6

N.

T.

5

N.

T.

4

N.

T.

3

N.

R. 39 E.

R. 38 E.

MENAN

BUTTES

111o 30' 111o

 45'

111o 45'

111o 30' 111o

 15'

44o 15'

44o 00'

43o 45' 43o

 45'

44o 00'

44o 15'

Figure 1A. Locations of ground-water sampling sites 

where nitrate (as nitrogen) concentrations are less

than 5 milligrams per liter, and generalized directions

of ground-water movement, Henrys Fork Basin, Idaho.

Figure 1B. Locations of ground-water samp

sites where nitrate (as nitrogen) concentratio

are 5 milligrams per liter or greater, Henrys 

Basin, Idaho.

EXPLANATION

Sampling site where nitrate (as

 nitrogen) concentration was 5

 milligrams per liter or greater

5 to 9.9

10 to 19.9

20 or greater
33

for various ranges of nitrate-N in

drinking water are shown in table 1.

Chronic, long-term health risks

from consumption of water containing large nitrate concentrations are

not fully understood. Short-term

effects include the risk of methemoglobinemia (blue-baby syndrome,

characterized by the reduced ability

of blood to carry oxygen) to human

infants, a small percentage of adults,

and young livestock (Mahler and others, 1990, p. 1). Large concentrations

of nitrate-N may be implicated with

an increased incidence of nonHodgkin’s lymphoma (Weisenburger, 1991, p. 309). Anomalous

nitrate-N concentrations also imply

active exchange of water from land

surface to ground-water zones and the

potential for water contamination by

microorganisms or other chemical

compounds (Parliman, 1998, p. 4).

Ground-Water Analyses and

Site Descriptions

From 1995 through 1999, water

samples were collected by the USGS

or DEQ from 319 wells or springs in

the Henrys Fork Basin and analyzed

for nitrate-N concentrations1. For

sites with multiple analyses, only the

most recent analysis per site was used

in this report. Complete site descriptions and water-quality data are available from the USGS District office in

Boise, Idaho. Well locations, total

well depth, and selected water-quality

data are available in MS-EXCEL

spreadsheet format at the Idaho District Web site http://idaho.usgs.gov/

until approximately February 2001.

Locations of ground-water sites

are displayed in figures 1A and 1B

according to ranges of nitrate-N concentrations. Concentrations in most

water samples are relatively small

(less than 5 mg/L). In some parts of

the study area, water contains moderately large nitrate-N concentrations

(5 to 9.9 mg/L) or concentrations

exceeding the EPA (1996) 

contaminant level of 10 mg

tial health risk for some dr

water purposes.

Historical Nitrate-N

Concentrations

Nitrate-N data prior to 

are sparsely distributed or 

the Henrys Fork Basin. M

cal nitrate-N concentration

than 5 mg/L, but concentr

ceeding 20 mg/L were ana

water samples from wells 

Ashton and near Menan B

1970’s. Nitrates could hav

creasing since about the 19

NITRATE (AS NITROGEN), IN

MILLIGRAMS PER LITER

YEARS 

Figure 2. Changes in nitrate (as nitrogen) concentrations, 1964–99, in wa

from wells at Ashton and Drummond, Henrys Fork Basin, Idaho.

1964

1966

27

24

21

18

15

12

9

6

3

0

1980

1984

1990

1992

1994

Ashton well (dashed where data are sparse)

Drummond well (dashed where data are sparse)

1978

1982

1986

1988

1USGS laboratory analyses are reported in units of nitrite plus nitrate as nitrogen (NO2+NO3 as N). DEQ laboratory analyses are re

of nitrate as nitrogen (NO3 as N). Concentrations of nitrite in ground water generally are negligible. For purposes of this report, USGS 

yses are comparable.

Table 1. Drinking-water recommendations for ranges of nitrate

[Modified from Mahler and others, 1990, p. 1; mg/L, milligrams per liter]

Nitrate as nitrogen Nitrate as nitrate

(NO3-N, in mg/L)1 (NO3-NO3, in mg/L)2 Comments

00 to 10 000 to 44 Safe for human and livestock consumption.

11 to 20 045 to 88 Generally safe for human adult and livestock consumption. Do not use 

infants.

21 to 40 089 to 176 Short-term use acceptable for human adult and all livestock consumpt

food or feed sources are very high in nitrate. Long-term use could 

Do not use for human infants.

41 to 100 177 to 440 Moderate to high risk for human adult and young livestock consumpti

bly acceptable for mature livestock if feed is low in nitrate. Do not 

human infants.

Over 100 Over 440 Do not use.

1 Laboratory nitrate analysis reported as nitrogen (N), in mg/L.

2 Laboratory nitrate analysis reported as nitrate (NO3), in mg/L.
44

40

30

20

10

0

LOWER

HENRYS FORK

DRAINAGE

TETON

RIVER

DRAINAGE

UPPER

HENRYS FORK

DRAINAGE

NITRATE (AS NITROGEN),

IN MILLIGRAMS

PER LITER

Figure 3. Nitrate (as nitrogen) data for wells in Henrys Fork Basin, Idaho.

MENAN BUTTES

TO

ST. ANTHONY

ST. ANTHONY

TO

ABOUT ASHTON

FORESTED NON

54

99th percentile

75th percentile

Median

25th percentile

1st percentile

Number of wells

Concentrations in

 upper 1 percent

 of data

137

82

54

83

15

67

LOWER

HENRYS FORK

DRAINAGE

UPPER

HENRYS FOR

DRAINAGE

HENRYS

FORK

BASIN

100

areas where overall nitrate-N concentrations are currently large.

Changes in nitrate-N concentrations over time for water samples

from wells at Drummond and Ashton

are shown in figure 2. Total depth of

both wells is about 300 feet, and hydrogeologic environments and nearby

land-use histories are similar. Few

nitrate-N data are available for either

well from 1950 to about 1980, but the

patterns of increasing nitrate-N concentrations are similar—relatively

low nitrate-N concentrations until

about 1980, then increasing concentrations to 1999 accompanied by seasonal fluctuations in concentrations

each year. Causes for increasing concentrations currently are not fully

understood.

Statistical Summary of

Nitrate-N Data

Statistical summaries (boxplots)

of nitrate-N concentrations for lower

Henrys Fork, Teton River, and upper

Henrys Fork drainages are compared

in figure 3. Median (50th percentile)

concentrations for lower Henrys

Fork and Teton River drainages

are similar (1.6 mg/L and 1.9 mg/L,

respectively), but the median concentration for the upper Henrys Fork area

is 5.7 mg/L. Substantial differences

are also evident in the distribution of

nitrate-N concentrations within each

drainage, as shown in the comparison of summaries for segments of

the lower Henrys Fork drainage—

Menan Buttes to St. Anthony and St.

Anthony to about Ashton. From

Menan Buttes to St. Anthony, the

median concentration is 1.1 mg/L, and

from St. Anthony to about Ashton,

the median is 3.1 mg/L. In the upper

Henrys Fork drainage, large differences in concentrations are evident

between areas with little or no landand water-use development (forested) and areas with extensive and

varied land- and water-use development (nonforested). The median concentration for forested areas is

0.3 mg/L, and the median concentration for nonforested areas is 6.6 mg/L.

Sources of Nitrogen

Rupert (1996) estimated the

amount of total nitrogen input by

cattle manure, fertilizer, legume crops

(such as alfalfa and beans), precipitation, and domestic septic systems for

counties in the upper Snake River

Basin, eastern Idaho and western

Wyoming. The estimates were used

to rank the input of nitrogen by

source and determine the amount of

total nitrogen potentially available to

ground and surface water 

leaching and runoff. Resul

that about 45 percent of th

from fertilizers, 29 percen

tle manure, 19 percent fro

crops, 6 percent from prec

and less than 1 percent fro

tic septic systems. Input fr

manure, fertilizers, and leg

varied widely among coun

flecting differences in land

tices such as cropping patt

numbers of dairies and fee

the Henrys Fork Basin, Ru

cated that fertilizers were 

source of nitrogen input. M

crops were secondary sour

precipitation and domestic 

tems were minor sources o

input.

Nitrogen Isotope Da

One method for estima

sources of nitrogen to grou

is analysis for stable isotop

gen. Stable isotopes are no

tive forms of an element. N

isotopes 15N and 14N cons

isotope pair, and lab analy

mine the ratio of the abund

heavier isotope (15N) to th

lighter isotope (14N) in wa

major potential sources of 

contamination commonly 

acteristic 15N/14N ratios (e
55

permil units, or parts per thousand).

Typical 15N/14N ratio values for nitrogen sources are presented in table 2

(Seiler, 1996, p. 12). Total well

depth, nitrate-N, and nitrogen isotope

ratio data for recent ground-water

samples in the Henrys Fork Basin are

shown in table 3.

Additional nitrogen isotope analyses are available through DEQ for

areas near Ashton where intermediate nitrogen isotope ratio values in

water could indicate a mixture of

nitrogen sources (D. Yashan, DEQ,

written commun., 1999).

Other Sources of Nitrate-N

Data

The comprehensive study of

nitrate-N in ground water in the Henrys Fork Basin has been completed,

but there are ongoing ground-water

quality programs through several

agencies and organizations, including USGS, DEQ, District 7 Health

Department, IDAG, and consultants.

For private wellowners, nitrate-N

analyses are available through local

analytical laboratories. Information

on water quality, health risks, laboratory analyses for private wellowners,

and water-treatment options is available through DEQ and District 7

Health Department agencies.

Additional Information

Needed

Effects of several hydrogeologic

and environmental factors on groundwater quality are not well understood

at this time. Additional information

is needed in the following areas:

(1) causes of increasing nitrate-N

concentrations since about 1980;

(2) effects of well construction on

contamination of multiple wateryielding zones; (3) seasonal change in

nitrate-N concentrations; (4) seasonal change in water levels and

directions of ground-water movement in major water-yielding zones,

particularly in the Fall River drainage; (5) comparative age dates of

water in major water-yielding zones

to help determine rates of contaminant movement; and (6) groundwater/surface-water relations in areas

where nitrate-N concentrations are

large. Large nitrate-N concentrations

in ground water could contribute to

increased nitrate-N concentrations in

surface water, potentially resulting in

deterioration of surface-water quality.

Acknowledgments

Special thanks are extended to

wellowners in the study area for

access to property and permission to

collect water samples from their

wells. Additional thanks are extended

to personnel from the City of Ashton, Lockheed Martin Idaho Technologies Company, Brown an

well, URS Greiner Woodw

and Ricks College for info

and unpublished data for t

—by D.J. Parliman

Selected References

Brown and Caldwell, 1994, J.R. 

pany Soilbuilders Facility, D

Idaho: Boise, Brown and Ca

lished report on file in the B

the U.S. Geological Survey, 

ments.

Bureau of Reclamation, 1977, G

studies—Henrys Fork, Teto

Fremont and Madison Coun

Boise, Bureau of Reclamati

Clark, G.M., Maret, T.R., Ruper

Maupin, M.A., Low, W.H., 

1998, Water quality in the u

River Basin, Idaho and Wyo

1995: U.S. Geological Surv

1160, 35 p.

Crosthwaite, E.G., (1960), Geol

hydrology of the Rexburg ar

U.S. Geological Survey unp

on file in the Boise office of 

logical Survey, 17 p.

——— 1979, Chemical analyse

water related to geothermal 

in the Teton River area, east

U.S. Geological Survey Ope

Report 79–687, 14 p.

Crosthwaite, E.G., Mundorff, M

Walker, E.H., 1970, Ground

of the lower Henrys Fork re

Idaho: U.S. Geological Surv

ply Paper 1879–C, 22 p., 1 

Embree, G.F., Lovell, M.D., and 

1978, Drilling data from Su

ploration well, Madison Cou

U.S. Geological Survey Ope

Report 78–1095, 1 pl.

Gellenbeck, D.J., 1994, Isotopic 

and sources of nitrate in gro

from western Salt River Val

Table 2. Nitrogen isotope ratios of

common sources of nitrate in water

Potential contaminant 15N/14N

ratio source (permil)

Precipitation -3

Commercial fertilizer -4 to +4

Organic nitrogen in soil +4 to +9

Animal waste Greater than +10

Table 3. Total well depth, dissolved nitrate (as nitrogen), and nitrogen isotope ratio data1 for selected wells, Henrys For

Idaho

[mg/L, milligrams per liter]

Nitrate, 15N

Depth of well, dissolved stable iso

Water sample source Sample date total (feet) (mg/L as N) (per

Well near Hibbard..................................... 06-15-99 240 25.9 2

Well near St. Anthony............................... 06-29-99 113 27.2 

Well at Drummond ................................... 06-30-99 310 21.1 8

Well near Ashton ...................................... 10-06-98 60 18.5 9

06-25-99 60 30.4 10

Well at Ashton .......................................... 10-06-98 289 8.33 5

1

Analyses from the U.S. Geological Survey National Water-Quality Laboratory, Denver, Colorado. Nitrogen isotopes, 15N/14N as nitrate and amm
66

U.S. Geological Survey Water-Resources

Investigations Report 94–4063, 53 p.

Ham, H.H., 1968, Replacement ground water

supply—first phase, Lower Teton Division, Teton Basin Project, Idaho: Boise,

Bureau of Reclamation, 28 p.

Haskett, G.I., 1972, Groundwater investigations of the Rexburg Bench—second

phase, Lower Teton Division, Teton Basin

Project, Idaho: Boise, Bureau of Reclamation, 21 p.

Howarth, R.B., 1999, Assessment of sources

of elevated nitrate in ground water in

northwest Ada County, Idaho, using environmental isotopes: Boise, Idaho Division

of Environmental Quality, Boise Regional

Office, Ground Water Quality Technical

Report no. 11, 50 p., 2 apps.

Idaho Department of Water Resources, 1998,

Henrys Fork and Mud Lake areas (hydrologic data): Boise, unpublished map report

on file in Boise office of the U.S. Geological Survey, 1 pl.

Jorgensen Engineering and Land Surveying,

P.C., 1999, City of Ashton—water supply

system nitrate mitigation study (draft):

Jackson, Wyo., unpublished, 42 p.

Kilburn, Chabot, 1964, Ground water in the

upper part of the Teton Valley, Teton

Counties, Idaho and Wyoming: U.S. Geological Survey Water-Supply Paper 1789,

60 p., 4 pl.

Kirkham, V.R.D., 1925, Press bulletin concerning geologic conditions, oil possibilities, and drilling progress in Teton County,

Idaho: Idaho Bureau of Mines and Geology Press Bulletin no. 15, 4 p.

Mahler, R.L., Porter, Ernestine, and Taylor,

Roy, 1990, Quality water for Idaho—

nitrate and groundwater: Moscow, University of Idaho, College of Agriculture, Current Information Series no. 872, 2 p.

Maupin, M.A., 1995, Water-quality assessment of the upper Snake River Basin,

Idaho and western Wyoming—environmental setting, 1980–92: U.S. Geological

Survey Water-Resources Investigations

Report 94–4221, 35 p.

Meachum, Teresa, 1999, Nitrates in groundwater—a study of levels in southeast

Idaho: Idaho Falls, University of Idaho,

unpublished M.S. thesis, 48 p., 2 apps.

Parliman, D.J., 1983, Reconnaissance of

ground-water quality, eastern Snake

River Basin, Idaho: U.S. Geological Survey Water-Resources Investigations

Report 82–4004, 100 p., 4 pls.

——— 1998, Ground-water quality in northern Ada County, lower Boise River Basin,

Idaho, 1985–96: U.S. Geological Survey

Fact Sheet FS–054–98, 6 p.

Ray, H.A., Kjelstrom, L.C., Crosthwaite, E.G.,

and Low, W.H., 1978, The flood in southeastern Idaho from the Teton Dam failure

of June 5, 1976, with a section on ground

water fluctuations and on quality of surface and ground water: U.S. Geological

Survey Open-File Report 77–765, 48 p.,

3 pls.

Rupert, M.G., 1994, Analysis of data on nutrients and organic compounds in ground

water in the upper Snake River Basin,

Idaho and western Wyoming, 1980–91:

U.S. Geological Survey Water-Resources

Investigations Report 94–4135, 40 p.

——— 1996, Major sources of nitrogen input

and loss in the upper Snake River Basin,

Idaho and western Wyoming, 1990: U.S.

Geological Survey Water-Resources

Investigations Report 96–4008, 15 p.

——— 1997, Nitrate (NO2+NO3-N) in

ground water of the upper Snake River

Basin, Idaho and western Wyoming,

1991–95: U.S. Geological Survey WaterResources Investigations Report 97–4174,

47 p.

——— 1998, Probability of detecting atrazine/desethyl-atrazine and elevated concentrations of nitrate (NO2+NO3-N) in

ground water in the Idaho part of the upper

Snake River Basin: U.S. Geological Survey Water-Resources Investigations

Report 98–4203, 32 p., 1 pl.

Rupert, Michael, Dace, Tana, Maupin, Molly,

and Wicherski, Bruce, 1991, Ground water

vulnerability assessment—Snake River

Plain, southern Idaho: Boise

Department of Health and W

sion of Environmental Qual

Seiler, R.L., 1996, Methods for 

sources of nitrogen contami

ground water in valleys in W

Nevada: U.S. Geological Su

File Report 96–461, 29 p.

Spinazola, J.M., 1994, Geohydr

ulation of flow and water lev

aquifer system in the Mud L

eastern Snake River Plain, e

U.S. Geological Survey Wat

Investigations Report 93–42

Spinazola, J.M., Tungate, A.M., 

T.L., 1992, Geohydrologic a

data from wells in the Mud 

eastern Idaho, 1988–91: U.

Survey Open-File Report 92

Tungate, A.M., 1995, Hydrogra

levels in observation wells in 

93: U.S. Geological Survey 

Report 95–458, 422 p.

U.S. Environmental Protection 

Drinking water regulations a

advisories: U.S. Environmen

Agency, Office of Water, 822

18 p.

URS Greiner Woodward Clyde, 

Farm Service facility, Parke

tle, URS Greiner Woodward 

published report on file in B

the U.S. Geological Survey.

Weisenburger, D.D., 1991, Pote

consequences of ground-wa

tion by nitrates in Nebraska, 

Kuzelka, R.D., and Ennenga

Nitrate contamination—exp

quence, and control: Berlin, 

lag, p. 309–315.

Whitehead, R.L., 1978, Water re

upper Henrys Fork Basin in 

Boise, Idaho Department of 

Resources Water Informatio

no. 46, 48 p., 6 pls.

Banner photo: Upper Henrys Fork Basin,

Idaho.

Photo at left: Warm River Springs on

Henrys Fork northeast of Ashton, Idaho

(Photo by D.J. Parliman, 1998).

Printed on recycled paper Printed on recycled paper

For more information about

U.S. Geological Survey program

publications, and resources in

Idaho, visit our Web site at

http://idaho.usgs.gov

or contact:

District Chief

U.S. Geological Survey, WRD

230 Collins Road

Boise, ID 83702-4520