U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2018–3036

July 2018

Idaho Water Use, 2015

The ability to quantify water resources hinges on the 

understanding of water use by the population. The demand humans 

place on the water cycle varies across the United States, driven by 

both need and availability. The U.S. Geological Survey quantifies 

water use nationally, at the county scale, with estimates of water 

withdrawals and deliveries, by category of use (for example, 

irrigation, thermoelectric power, industrial, public supply, 

including domestic deliveries and self-supply domestic, livestock, 

mining, and aquaculture) and source (fresh and saline groundwater 

or surface water) every 5 years (Dieter and others, 2018). 

Estimates of water use are an important component of the water 

budget to help manage water supplies and plan for the future. 

Understanding water use in Idaho is important not only at the local 

(county) and State scales, but also at the National level because 

Idaho ranked third in the Nation for total water use in 2015 (C.A. 

Dieter, U.S. Geological Survey, written commun., 2018).

This fact sheet describes calendar year 2015 freshwater 

withdrawals by source and by each Idaho county. An associated 

data release (Murray, 2018) provides the data discussed herein. 

Freshwater withdrawals totaled 17,737 million gallons per 

day (Mgal/d) during 2015. Surface water accounted for 70 

percent of total withdrawals for all categories of use, mostly 

for irrigation of crops and aquaculture production (fig. 1). 

Withdrawals for mining activities were mostly from surface 

water, whereas the remaining categories of use—public supply, 

domestic, industrial, livestock, irrigation of golf courses, 

and thermoelectric power—relied largely on groundwater 

withdrawals (fig. 1). Most withdrawals occurred in southern 

Idaho counties to support irrigated agriculture (fig. 2).

Top Three Water Uses

Irrigation, aquaculture, and public supply/domestic water 

withdrawals totaled 17,534 Mgal/d in 2015, accounting for 

more than 99 percent of total withdrawals for all categories 

(fig. 3). Other categories of use—industrial, livestock, mining, 

irrigation of golf courses, and thermoelectric power—accounted 

for less than 1 percent of Idaho’s total withdrawals in 2015.

Idaho withdrew 17,737 million gallons of freshwater per day (Mgal/d) in 2015, about 70 percent withdrawn from surface water sources 

(above). Withdrawals by source for each category of water use in 2015 are shown (right), along with the total volume and the relative 

percentage of Idaho’s total water withdrawals. Most withdrawals were for irrigated crops (86 percent), sustained aquaculture (11 percent), 

or water for public supply and (or) domestic uses (2 percent). The remaining categories of use composed less than 1 percent of Idaho’s 

total withdrawals. In 2015, 1.79 Mgal/d of groundwater was withdrawn for thermoelectric power generation (less than 0.01 percent of total 

withdrawals; not shown). 

Total 2015 withdrawals

Groundwater Surface water

Irrigation: Crops

15,273 Mgal/d (86%)

Public supply

276 Mgal/d (1.6%)

Industrial

58 Mgal/d (0.32%)

Mining 

23 Mgal/d (0.13%)

Aquaculture

1,965 Mgal/d (11%)

Self-supplied domestic

70 Mgal/d (0.40%)

Livestock

51 Mgal/d (0.29%)

Irrigation: Golf courses

19 Mgal/d (0.11%)

5,353 Mgal/d

12,384 Mgal/d

Figure 1. Withdrawals by source and category in Idaho, 2015.
Irrigation—15,273 million gallons per day

Estimated withdrawals to irrigate nearly 3.78 million acres of 

crops in Idaho was 15,273 Mgal/d (17,108,000 acre-feet per year) 

in 2015, accounting for 86 percent of total water withdrawn for 

all uses (fig. 1). Although most of Idaho’s crops were irrigated 

from surface water sources (primarily the Snake River), irrigation 

was also the largest use of Idaho groundwater withdrawals 

(4,882 Mgal/d; 91 percent of 2015 Idaho groundwater 

withdrawals). In 2015, crops consumptively used an estimated 58 

percent of these total withdrawals—the remaining 42 percent was 

returned to the water cycle by conveyance losses, surface runoff, 

and infiltration. In 2015, irrigation withdrawals were the second 

largest in the United States, behind only California (C.A. Dieter, 

U.S. Geological Survey, written commun., 2018). The Western 

United States relies heavily on applied irrigation water, especially 

where seasonal rainfall is not sufficient to support healthy 

crops. Estimated withdrawals include all water diverted for 

irrigation, and includes conveyance losses and consumptive use 

(evapotranspiration [ET] from crops and soil). Consumptive use 

by county is shown relative to the total irrigation withdrawal in 

figure 3.

Aquaculture—1,965 million gallons per day

The second largest category of water use, aquaculture, was 

1,965 Mgal/d, accounting for 11 percent of total withdrawals in 

Idaho during 2015, 98 percent was from surface-water sources. 

Idaho has consistently ranked first in the Nation for aquaculture 

water use, as it was in 2015 (C.A. Dieter, U.S. Geological 

Survey, written commun., 2018) due to the use of flow-through 

raceways, the predominate type of facility used for aquaculture. 

Reported withdrawals represent the initial diversion to 

aquaculture operations, and these diverted flows return to the 

river after passing through the facility with relatively little water 

lost to evaporation.

Public Supply and Domestic Water—276 million gallons per day

Public supply includes all water withdrawn by a publicly 

owned community water system, and accounted for 1.6 percent 

of total withdrawals in Idaho during 2015, almost entirely 

(89 percent) from groundwater. In 2015, 276 Mgal/d were 

withdrawn for public supply and domestic uses with 84 percent 

of the public supply water withdrawals delivered to domestic—or 

household—users. The remaining withdrawals for public supply 

were for industrial or commercial uses; public parks, pools, 

and buildings; maintenance of water systems; or lost by leaky 

infrastructure.

Domestic water includes indoor and outdoor water used at 

a residence, and includes self-supplied and publicly supplied 

volumes. Seventy-six percent of Idaho residents have water 

supplied by a community water system (a public supply 

delivery) and the remaining 24 percent are self-supplied. Selfsupplied residents either own a well or connect to a well that 

supplies water to less than 20 residences. In 2015, domestic 

deliveries from public supply were 234 Mgal/d and self-supplied 

domestic water withdrawals were 70 Mgal/d. 

IDAHO 

OWYHEE 

CUSTER 

LEMHI 

VALLEY 

ELMORE 

BLAINE 

BUTTE 

CASSIA 

BOISE 

CLARK 

SHOSHONE 

BONNER 

BINGHAM 

CLEARWATER 

ADA 

FREMONT 

CARIBOU 

POWER 

LATAH 

ONEIDA 

LINCOLN 

TWIN

FALLS

ADAMS 

BONNEVILLE 

CAMAS 

KOOTENAI 

BOUNDARY 

BANNOCK 

WASHINGTON 

GEM JEFFERSON 

BEAR

LAKE 

NEZ PERCE 

BENEWAH 

GOODING 

MINIDOKA 

FRANKLIN 

JEROME 

CANYON 

LEWIS 

TETON 

MADISON 

PAYETTE 

EXPLANATION

Total county withdrawals

in million gallons per day

1

10

100

1,000

Figure 2. Withdrawals by county in Idaho, 2015. 

Water use is highest in southern Idaho counties 

where irrigated agriculture is prevalent.
In 2015, Idaho households had the highest per capita 

domestic water use in the Nation. The 2015 statewide average 

was 184 gallons per person per day, and was 102 gallons per 

person per day higher than the National average (Dieter and 

Maupin, 2017). The high domestic per capita use in Idaho is 

common across the Western United States because the dry 

climate leads to more household water that is used for lawn and 

garden irrigation. In 2015, domestic per capita water use was at 

or below the National average of 82 gallons per person per day 

in only five counties in Idaho: Bear Lake, Bingham, Bonner, 

tac18-1210_fig03 Withdrawals, in million gallons per day

0

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

Ada

Adams

Bannock

Bear LakeBenewah Bingham

Blaine

Boise

Bonner

Bonneville

Boundary Butte

Camas

Canyon

Caribou

Cassia

Clark

Clearwater Custer

Elmore

Franklin

Fremont

Gem

Gooding

Idaho

Jefferson

Jerome

Kootenai

Latah

Lemhi Lewis

Lincoln

Madison

Minidoka

Nez Perce

Oneida

Owyhee

Payette

Power

Shoshone

Teton

Twin Falls

Valley Washington

County

Irrigation-Crops Aquaculture Public supply Consumptive irrigation (ET)

EXPLANATION

Figure 3. Withdrawals by major category within each county in Idaho.

EXPLANATION

38 to 81

82 to 147

148 to 213

214 to 304

305 to 450

451 to 908

Domestic per capita use, 

 in gallons per person per day

Figure 4.—Gross per capita domestic water use in Idaho, 2015. 

EXPLANATION

Total population, in thousands

1 to 3

14 to 27

28 to 45

46 to 110

111 to 207

208 to 434

NampaBoise

Caldwell

Pocatello

Idaho Falls

Couer

d'Alene

Meridian

Lewiston

Post Falls

Twin Falls

Figure 5. Total population of Idaho in 2015.
Boundary, and Gem Counties (fig. 4). Idaho is largely a rural 

state, with an approximate population of 1.7 million in 2015. 

Some counties have low populations with small total amounts 

of water withdrawals despite their high per capita domestic 

use (fig. 5).

Trends, 1985–2015

Idaho withdrew the third largest quantity of water in the 

Nation in 2015 (C.A. Dieter, written commun., 2018), and 

changes in withdrawals over time are important in discussions 

of water resources at a National level. Idaho has seen 

steady population growth since 1990 (fig. 6), but total water 

withdrawals have remained steady or have slightly decreased in 

that time. The public supply population (those supplied water 

by a community water system) increased from 2010 to 2015, 

whereas the self-supplied population decreased. About 40 

percent of this population growth occurred in Ada and Canyon 

Counties. Because irrigation dominates water withdrawals in 

Idaho, fluctuations in total withdrawals year-to-year largely 

depend on changes in irrigation withdrawals, and therefore will 

vary with weather patterns and irrigation practices. 

Future Needs

A better understanding and quantification of the top three 

water uses—irrigation of crops, aquaculture, and public and 

(or) domestic supply—would provide improved estimates of 

water use at the State level. Because most withdrawals in Idaho

are used to irrigate crops, it is especially crucial to understand 

water use in agricultural counties. Local climate conditions affect 

water demand during the growing season, and more research 

is needed to quantify these seasonal variations in water use for 

irrigation. Aquaculture accounts for the second largest amount 

of water withdrawals in Idaho. However, much of the water 

withdrawn for aquaculture is returned to the local source (river 

or stream). Quantifying the consumptive use of water withdrawn 

for aquaculture would help to understand its importance relative 

to the water that returns to the water cycle. As the population of 

Idaho continues to grow, water managers would benefit from more 

detailed water use information in rapidly growing urban centers. It 

may be important to understand why Idaho has the highest rate of 

domestic per capita use in the Nation and it may be of particular 

importance to investigate what amount of domestic withdrawals 

are being used to irrigate lawns and gardens. In Ada and Canyon 

Counties, which include a population center with high irrigation 

withdrawals, increased urban development may dramatically 

increase or decrease water use over time as land use changes.

Estimating water use more often than every 5 years, and at 

sub-county levels would provide a better spatial and temporal 

resolution of the human demand on water resources in Idaho. 

The diversity across the State in climate, population, and land 

use contributes to the varied water use by category in Idaho 

counties. Continued monitoring of the human effects on the 

hydrologic cycle will help ensure that demands can be balanced 

with water availability from a local to global scale.

tac18-1210_fig06

0

200

400

600

800

1,000

1,200

1,400

1,600

1,800

Population, in thousands

0

5,000

10,000

15,000

20,000

25,000

Withdrawals, in million gallons per day

1985 1990 1995 2000 2005 2010 2015

Years

EXPLANATION

Groundwater Surface water Population (thousands)

Acknowledgments

Valuable data and (or) support for this study were provided 

by the Idaho Department of Water Resources; Idaho Department 

of Environmental Quality; U.S. Department of Agriculture 

(NASS, NRCS, and Idaho extension offices); Idaho Golf Course 

Superintendents Association; Idaho Department of Fish and 

Game; U.S. Fish and Wildlife Service; Bureau of Reclamation; 

U.S. Census Bureau; Idaho Department of Commerce; 

University of Idaho; U.S. Energy Information Administration; 

U.S. Geological Survey Water-Use Availability and Use Science 

Program; and many city and county offices in Idaho.

References Cited

Dieter, C.A., and Maupin, M.A., 2017, Public supply and 

domestic water use in the United States, 2015: U.S. 

Geological Survey Open-File Report 2017–1131, 6 p., https://

doi.org/10.3133/ofr20171131.

Dieter, C.A., Maupin, M.A., Caldwell, R.R., Harris, M.A., 

Ivahnenko, T.I., Lovelace, J.K., Barber, N.L., and 

Linsey, K.S., 2018, Estimated use of water in the United 

States in 2015: U.S. Geological Survey Circular 1441, 65 p., 

https://doi.org/10.3133/cir1441. [Supersedes USGS Open-File 

Report 2017-1131.]

Murray, E.M., 2018, Water use by source and category in Idaho 

counties, 2015: U.S. Geological Survey data release, 

https://doi.org/10.5066/P92AXN0O.

Figure 6. Withdrawals by source in Idaho, 1985–2015.

Author: 

Erin M. Murray

For more information:

U.S. Geological Survey, 230 Collins Road, Boise, Idaho 83702

https://www.usgs.gov/centers/id-water

Publishing support provided by the U.S. Geological Survey, 

Tacoma Publishing Service Center

ISSN 2327-6932 (online)

https://doi.org/10.3133/fs20183036

https://.doi.org/10.3133/fsxxxxxxxx