Geohydrology of the Idaho

National Engineering and

Environmental Laboratory,

Eastern Snake River Plain, 

U.S. Department of the Interior Idaho

U.S. Geological Survey

BACKGROUND

In 1949, the U.S. Atomic Energy Commission,

which later became the U.S. Department of Energy,

requested that the U.S. Geological Survey (USGS)

describe the water resources of the area now known as

the Idaho National Engineering and Environmental

Laboratory (INEEL) (fig. 1). The purpose of the resulting study was to characterize these resources before the

development of nuclear-reactor testing facilities. The

USGS since has maintained a monitoring network at the

INEEL to determine hydrologic trends and to delineate

the movement of facility-related radiochemical and

chemical wastes in the Snake River Plain aquifer. This

fact sheet, summarized from two published reports

(Anderson and others, 1996; Bartholomay and others,

1997), describes the geohydrology of the eastern Snake

River Plain (fig. 1) at the INEEL.

Figure 1. Location of the Idaho National Engineering and

Environmental Laboratory (INEEL), Idaho

RECHARGE

The Snake River Plain aquifer is one of the most

productive aquifers in the United States (U.S.

Geological Survey, 1985, p. 193). Recharge to the

Snake River Plain aquifer is principally from

infiltration of applied irrigation water, infiltration of

streamflow, and ground-water inflow from adjoining

mountain drainage basins. Some recharge may be

from direct infiltration of precipitation, although the

small amount of annual precipitation on the plain

(8 inches at the INEEL), evapotranspiration, and the

great depth to water (in places exceeding 900 feet)

probably minimize this source of recharge.

Big Lost Riv er

Little Lost River

Birch Creek

Figure 2. Location of selected geographical features and 

facilities in proximity to the Idaho National Engineering 

and Environmental Laboratory, Idaho

Mackay 

Reservoir

Camas

Creek

Mud 

Lake
The Big Lost River (fig. 2) drains more than 1,400

square miles of mountainous area that includes parts of

the Lost River Range and Pioneer Range west of the

INEEL. Flow in the Big Lost River infiltrates to the

Snake River Plain aquifer along its channel and at

sinks and playas at the river’s terminus. To avoid

flooding at the INEEL facilities, excess runoff has been

diverted since 1958 to spreading areas in the southwestern part of the INEEL, where much of the water

rapidly infiltrates to the aquifer. Other surface drainages that provide recharge to the Snake River Plain

aquifer at the INEEL include Birch Creek, Little Lost

River, and Camas Creek.

The average streamflow in the Big Lost River

below Mackay Reservoir (fig. 2) for the 79-year period

of record (water years 1905, 1913–14, and 1920–95)

was 222,900 acre-feet per year (Brennan and others,

1996, p. 217). During 1992–95, streamflow in the Big

Lost River below Mackay Reservoir ranged from

125,900 acre-feet (56 percent of average flow) during

the 1992 water year (Harenberg and others, 1993,

p. 178) to 310,000 acre-feet (139 percent of average

flow) during the 1995 water year (Brennan and others,

1996, p. 217). Streamflow recorded for the Big Lost

River near Arco during 1993 and 1995 was 10,610 and

84,880 acre-feet per year, respectively.

Before 1989, recharge to the Snake River Plain

aquifer downstream from Arco was substantial because

of infiltration of streamflow from the Big Lost River

channel, diversion areas, sinks, and playas. For

example, measured infiltration losses at various

discharges ranged from 1 to 28 cubic feet per second

per mile (Bennett, 1990, p. 1). Combined discharge in

the Big Lost River below the INEEL diversion near

Arco and the INEEL diversion at its head near Arco

was 7,777 acre-feet per year in 1993 (Harenberg and

others, 1994, p. 210, 212) and 80,080 acre-feet per year

in 1995 (Brennan and others, 1996, p. 221, 223). No

streamflow occurred in the Big Lost River downstream

from Arco during 1992 and 1994.

GEOLOGIC FRAMEWORK OF THE SNAKE 

RIVER PLAIN AQUIFER

The Snake River Plain aquifer consists of a thick

sequence of basalts and sedimentary interbeds filling a

large, arcuate, structural basin about 200 miles long

and 50 to 70 miles wide in southeastern Idaho. The

INEEL is on the west-central part of the eastern Snake

River Plain. The INEEL is underlain by hundreds of

basalt flows, basalt-flow groups, and sedimentary

interbeds; basalt makes up about 90 percent of the

volume of deposits in the unsaturated zone and the

aquifer in most areas. A basalt flow is a solidified body

of rock that was formed by a lateral, surficial

outpouring of molten lava from a vent or fissure (Bates

and Jackson, 1980). A basalt-flow group consists of

one or more distinct basalt flows deposited during a

single eruptive event (Kuntz and others, 1980). All

basalt flows of each group erupted from the same vent

or vents and have similar ages, paleomagnetic

properties, potassium contents, and natural-gamma

emissions (Anderson and Bartholomay, 1995). The

basalt flows, which locally are altered (Fromm and

others, 1994), consist mainly of medium- to dark-gray

vesicular to dense olivine basalt. Individual flows are

as much as 100 feet thick and in places are interbedded

with cinders and thin layers of sediment. Sedimentary

interbeds, which are most abundant between flow

groups, accumulated on the ancestral land surface for

hundreds to hundreds of thousands of years during

periods of volcanic quiescence. Sedimentary interbeds

are as much as 50 feet thick and consist of well to

poorly sorted deposits of clay, silt, sand, and gravel. In

places the interbeds contain cinders and basalt rubble.

GROUND-WATER FLOW

The basalt and sediment underlying the INEEL are

saturated at depth and together form the Snake River

Plain aquifer. Depth to water at the INEEL ranges from

about 200 feet below land surface in the northern part

to about 900 feet in the southern part (Ott and others,

1992); the general direction of ground-water flow is

northeast to southwest at an average hydraulic gradient

of about 4 feet per mile. The effective base of the

aquifer at the INEEL generally coincides with the top

of a thick and widespread layer of clay, silt, sand, and

altered basalt that is older than about 1.6 million years

(Anderson and Bowers, 1995). The top of this layer

ranges in depth from 815 to 1,710 feet below land

surface in the western half of the INEEL. The effective

saturated thickness of the aquifer ranges from about

600 feet near Test Area North to about 1,200 feet near

the Idaho Chemical Processing Plant and the Radioactive Waste Management Complex (fig. 2). Saturated

thickness in the eastern half of the INEEL may be

greater than 1,200 feet. Hydraulic properties of the

aquifer differ considerably from place to place

depending on saturated thickness and the characteristics of the basalt and sediment. In places, the basalt

and sediment in the uppermost part of the aquifer yield

thousands of gallons per minute of water to wells, with

negligible drawdown (Ackerman, 1991). Hydraulic

data for the basalt, sediment, ash, and tuff underlying

the aquifer are sparse, but data from a deep test well

indicate that these deposits are relatively impermeable
compared with the aquifer (Mann, 1986). Localized

zones of perched ground water, which are attributed

mainly to infiltration of water from unlined percolation

ponds and recharge from the Big Lost River, are

present in basalt and sediment overlying the Snake

River Plain aquifer (Cecil and others, 1991).

Water in the Snake River Plain aquifer moves principally through fractures and interflow zones in the

basalt. A significant proportion of the ground water

moves through the upper 200 to 800 feet of basaltic

rocks (Mann, 1986, p. 21). Ackerman (1991, p. 30)

reported a range of transmissivity of basalt in the upper

part of the aquifer from 1.1 to 760,000 feet2 per day.

The hydraulic conductivity of underlying rocks is

0.002 to 0.03 feet per day, several orders of magnitude

smaller (Mann, 1986, p. 21). 

Ground water moves southwestward from the

INEEL and eventually is discharged to springs along

the Snake River downstream from Twin Falls,

100 miles southwest of the INEEL. About 3.7 million

acre-feet of ground water was discharged to these

springs in 1995.

REFERENCES CITED

Ackerman, D.J., 1991, Transmissivity of the Snake River

Plain aquifer at the Idaho National Engineering

Laboratory, Idaho: U.S. Geological Survey WaterResources Investigations Report 91-4058 (DOE/ID22097), 35 p.

Anderson, S.R., Ackerman, Daniel J., Liszewski, M.J., and

Freiburger, R.M., 1996, Stratigraphic data for wells at

and near the Idaho National Engineering Laboratory,

Idaho: U.S. Geological Survey Open-File Report 96-

248 (DOE/ID-22127), 27 p. and 1 diskette.

Anderson, S.R., and Bartholomay, R.C., 1995, Use of

natural-gamma logs and cores for determining

stratigraphic relations of basalt and sediment at the

Radioactive Waste Management Complex, Idaho

National Engineering Laboratory, Idaho: Journal of

the Idaho Academy of Science, v. 31, no. 1, p. 1-10.

Anderson, S.R., and Bowers, Beverly, 1995, Stratigraphy

of the unsaturated zone and uppermost part of the

Snake River Plain aquifer at Test Area North, Idaho

National Engineering Laboratory, Idaho: U.S.

Geological Survey Water-Resources Investigations

Report 95-4130 (DOE/ID-22122), 47 p.

Bartholomay, R.C., Tucker, B.J., Ackerman, D.J., and

Liszewski, M.J., 1997, Hydrologic conditions and

distribution of selected radiochemical and chemical

constituents in water, Snake River Plain aquifer,

Idaho National Engineering Laboratory, Idaho, 1992

through 1995: U.S. Geological Survey WaterResources Investigations Report 97-4086 (DOE/ID22137), 57 p.

Bates, R.L., and Jackson, J.A., eds., 1980, Glossary of

geology (2d ed.): Falls Church Va., American

Geological Institute, 749 p.

Bennett, C.M., 1990, Streamflow losses and ground-water

level changes along the Big Lost River at the Idaho

National Engineering Laboratory, Idaho: U.S.

Geological Survey Water-Resources Investigations

Report 90-4067 (DOE/ID-22091), 49 p.

Brennan, T.S., O’Dell, I., Lehmann, A.K., and Tungate,

A.M., 1996, Water resources data, Idaho, water year

1995—volume 1. Great Basin and Snake River Basin

above King Hill: U.S. Geological Survey Water-Data

Report ID-95-1, 452 p.

Cecil, L.D., Orr, B.R., Norton, T., and Anderson, S.R.,

1991, Formation of perched ground-water zones and

concentrations of selected chemical constituents in

water, Idaho National Engineering Laboratory, Idaho,

1986–88: U.S. Geological Survey Water-Resources

Investigations Report 91-4166 (DOE/ID-22100),

53 p.

Fromm, J.M., Hackett, W.R., and Stephens, J.D., 1994,

Primary mineralogy and alteration of basalts and

sediments in drillcores from the Idaho National

Engineering Laboratory, eastern Snake River Plain

[Abs.]: International Symposium on the Observation

of the Continental Crust Through Drilling, VIIth,

Santa Fe, N. Mex., April 25-30, 1994 [Abstracts],

unpaginated.

Harenberg, W.A., Jones, M.L., O’Dell, I., Brennan, T.S.,

Lehmann, A.K., and Tungate, A.M., 1993, Water

resources data, Idaho, water year 1992—volume 1.

Great Basin and Snake River Basin above King Hill:

U.S. Geological Survey Water-Data Report ID-92-1,

377 p.

-----1994, Water resources data, Idaho, water year 1993—

volume 1. Great Basin and Snake River Basin above

King Hill: U.S. Geological Survey Water-Data

Report ID-93-1, 401 p.

Kuntz, M.A., Dalrymple, G.B., Champion, D.E., and

Doherty, D.J., 1980, Petrography, age, and

paleomagnetism of volcanic rocks at the Radioactive

Waste Management Complex, Idaho National

Engineering Laboratory, Idaho, with an evaluation of

potential volcanic hazards: U.S. Geological Survey

Open-File Report 80-388, 63 p.
Mann, L.J., 1986, Hydraulic properties of rock units and

chemical quality of water for INEL-1—a 10,365-foot

deep test hole drilled at the Idaho National

Engineering Laboratory, Idaho: U.S. Geological

Survey Water-Resources Investigations Report

86-4020 (IDO-22070), 23 p.

Ott, D.S., Edwards, D.D., and Bartholomay, R.C., 1992,

Water-level data for selected wells on or near the

Idaho National Engineering Laboratory, Idaho, 1983

through 1990: U.S. Geological Survey Open-File

Report 92-643 (DOE/ID-22105), 307 p.

U.S. Geological Survey, 1985, National water summary,

1984—Hydrologic events, selected water-quality

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

Survey Water-Supply Paper 2275, 467 p.

For More

Information

USGS State representative

230 Collins Road

Boise, ID 83702

(208) 387-1300

Fax: (208) 387-1372

Email: dc_id@usgs.gov

INEEL Project Office

INEEL, MS 4148

P.O. Box 2230

Idaho Falls, ID 83403

(208) 526-2438

Fax: (208) 526-6002

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U.S. Geological Survey

Fact Sheet FS-130-97

Prepared by: Brennon R. Orr