Western Snake River Plain- Treasure Valley Water Use
Approximately half of the land in the Treasure Valley is irrigated agriculture, and of this, approximately 74% is irrigated with surface water. Surface irrigation water is distributed through an extensive series of canals. The largest of these, the New York Canal, diverts approximately 2,500 cfs in a typical irrigation season. The canals are operated by a variety of irrigation districts, canal companies, and other entities.

An acre-foot is an expression of water quantity. One acre-foot will cover one acre of ground one foot deep. An acre-foot contains 43,560 cubic feet, 1,233 cubic meters, or 325,829 gallons (U.S.).About 1,380,000 acre feet per year are diverted for agricultural irrigation from the Boise River. In addition, approximately 360,000 acre feet are diverted from the Payette River to the Treasure Valley.

Ground water is used to irrigate approximately 42,300 acres of farmland, primarily in the southern portion of the valley. In addition, many of the irrigators dependent on surface water supplies use supplemental irrigation wells during periods of drought. It is estimated that approximately 72,000 acre feet of ground water are withdrawn annually for agricultural irrigation. The image above shows a typical pivot irrigation system in the Treasure Valley.

Most municipal water in the Treasure Valley comes from ground water. Municipal water is supplied by a variety of entities, including public companies, cities, and water districts. The Idaho Department of Environmental Quality has compiled a map. The largest water purveyor in the Treasure Valley is United Water Idaho (UWI). UWI provides water services to about 190,000 people in Boise and surrounding communities. The company is a subsidiary of United Water Resources, one of the nation's largest water services companies

United Water Idaho customers receive their water from both groundwater and surface water sources. Groundwater is drawn from wells drilled into deep aquifers that produce about 14 billion gallons of water per year. The groundwater quality is excellent and free from harmful bacterial contamination. As a result, treatment is limited to disinfection with chlorine. Unfortunately, the advantages of excellent bacteria-free groundwater are often accompanied by disadvantages like high iron and manganese content. This is associated with discoloration problems -- some of United Water's groundwater sources have a high iron and manganese content. We are improving these sources with geoscience techniques to screen out water high in these minerals or by adding a phosphate compound to hold these minerals in solution.

Eight percent of United Water Idaho (UWI) water is drawn from the Boise River at the Marden Street Treatment Plant; 89 wells supply , and 92% is pumped from a total of 89 wells scattered throughout the Boise area. The Marden Lane Water Treatment Plant is a conventional filtration plant that produces about 1.8 billion gallons of water per year. Treatment involves filtering to remove particulate matter, followed by disinfection with chlorine to destroy any harmful bacteria. We also adjust the pH to reduce the water's corrosiveness and decrease the possibility of dissolving metals from household plumbing. Some facts from United Water Idaho's website:

Source of Supply
Total capacity
92 million gallons per day
Water treatment plant
1 with a capacity of 16 million gallons/day
Operating wells
89 with a capacity of 76 million gallons/day
Average well pumpage
650 gallons per minute
Average well depth
550 feet
Deepest well
1,120 feet
Water Usage in 1999
Water delivered 15.8 billion gallons
Average daily usage 43.2 million gallons
Peak usage 85.5 million gallons
Distribution System
System coverage 160 square miles
Pressure Zones 6
Mains 845.6 miles
Main size 2 inches to 24 inches
Reservoirs 27
Reservoir Capacity 31.05 million gallons
Booster stations 38

Commercial & Industrial
Industrial ground water use is difficult to quantify because many industries rely on different water sources, such as a combination of municipal supply and self-supplied water.Also, municipal suppliers usually do not distinguish between commercial and industrial use, i.e., the commercial category includes small businesses, multi-family housing, and industrial facilities.That said, the estimated self-supplied industrial ground water withdrawals in 1996 are shown in the table below (Urban and Petrich, 1998).

Industry (1)
Total Self-Supplied
Industrial Withdrawal
Agriculture (3)
Food Processing
Manufacturing (4)
Micron Technology (5)
Wood Products (6)

1. Industry categories and 1995 employee census data from Idaho Dept. of Employment, Research and Analysis, except for Micron Technology, Inc, which supplied its own population and water use data for 1995.
3. Agriculture category refers to amount of water personally consumed by the employee; does not include irrigation water, livestock water, or other agricultural uses. Rate of 15 gpd/person obtained from Idaho Water Law Handbook, 1988, Appendix IV; value for "day camps, no lunch served."
4. Manufacturing category includes electronics industries (except Micron Technology, Inc. of Boise, which is considered separately).
5. This rate reflects the amount of water pumped from Micron wells only; an additional 123 gpd/employee was purchased from United Water Idaho.
6. Wood products category includes lumber and wood industries, such as lumber, plywood, and cabinet making. It does not include pulp and paper industries.

Original content compiled by Christian Petrich, Margie Wilkins, Tondee Clark, and Tony Morse.
Photo provided by Idaho Department of Water Resources.
Adaptation for the Digital Atlas of Idaho by Ean Harker- design/html, Kyle Raverty- content, 11-2002.
Information supplied by the Idaho Department of Water Resources; 1301 North Orchard Street Boise, Idaho 83706 (208) 327-7900.