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Little Wood River Project
Little Wood River Dam
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Little Wood River Project History (38 KB) (pdf)
General Description| Plan| Development| Benefits

General Description

Little Wood River Project serves lands within an area 2 miles wide and 12 miles long upstream and downstream from Carey, Idaho, in the south-central section of Idaho. The project provides a supplemental irrigation water supply for approximately 9,550 acres of land. The principal construction feature is the enlarged Little Wood River Dam and Reservoir that serves previously constructed diversion and distribution works. Flood control is provided by operation of the reservoir on a forecast basis.

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An increased water supply to meet the need of water users in the project area was provided by increasing the height of Little Wood River Dam by approximately 35 feet in 1960. This increased the reservoir capacity from 12,100 to 30,000 acre-feet (active 30,000 acre-feet). The diversion and carriage facilities on the project remained unchanged.

Facility Descriptions

Little Wood River Dam

Rehabilitation work included raising the dam crest 39 feet, extending the outlet tunnel downstream 150 feet, and relocating the spillway from right to left abutment. The completed structure has a structural height of 129 feet high, with a zoned earthfill embankment containing about 959,000 cubic yards of material. Outlet works reconstruction included enlargement of the entrance channel to the existing intake structure, construction of a gate chamber with a connecting 6-foot-diameter access shaft and shaft house in the existing tunnel approximately 250 feet downstream from the intake structure, extension of the existing tunnel with a 150-foot-long, 6- by 8-foot conduit and a 60-foot-long, 6- by 10-foot chute, and excavation of a stilling basin in the outlet channel. The spillway consists of an inlet channel, a concrete spillway structure with uncontrolled crest, an outlet channel, and a training wall on the right side of the outlet channel beginning approximately 1,000 feet downstream from the spillway crest.

A one unit, 3,000 kilowatt powerplant was placed in operation in 1985 at the Little Wood River Dam by the Little Wood River Irrigation District pursuant to its license from the Federal Energy Regulatory Commission.

Operating Agencies

The project is owned, maintained and operated by the Little Wood River Irrigation District.

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Settlement of the project area took place in the late 1800`s, principally by people interested in raising livestock. Surrounding foothills and mountains to the north furnished summer grazing.

Earliest water rights have a priority date of 1880 and were granted to meet the individual needs of the early farmers. In 1893, the settlers formed a mutual association and constructed canals on both sides of the river to meet water requirements for new irrigable lands. Carey Lake Reservoir Company was formed in 1912 and obtained a license to divert Little Wood River water and store it in Carey Lake for 2,051 acres east of Carey, Idaho. By 1923 or 1924, no water was available for storage, and, since that time, there has been no irrigation storage in Carey Lake. The lake was purchased by the Idaho Fish and Game Department in 1949.


Investigation of means for regulating the flow of Little Wood River by storage was begun in the spring of 1904 by the Reclamation Service. A reconnaissance survey for reservoir sites on the Little Wood River and tributaries led to the conclusion that costs of storing water would be excessive. The requirement for storage of late-season supplemental water was continuously evident to Little Wood River Valley irrigators after 1940. Several proposals and sites were investigated, but financial difficulties prevented further development until 1936 when construction of the Little Wood River Dam was started by the Works Projects Administration. In 1947, the board of directors of the Little Wood River Irrigation District employed a private engineering firm to investigate the feasibility of raising the dam an additional 35 feet. Although plans and estimates were made, the enlargement proposal was defeated because some individuals were unwilling to obligate their holdings as required by the proposed financial arrangements. However, interest in the project continued and a complete investigation was made by the Bureau of Reclamation beginning in April 1954. A report dated June 1955 was the basis for project authorization.


The project was authorized on August 6, 1956 (70 Stat. 1059, Public Law 84-993). The purposes of the Little Wood Project are irrigation and flood control. Minimum basic recreation facilities and measures to preserve fish and wildlife were also authorized.


The contract for the enlargement of Little Wood River Dam was awarded August 22, 1958, and work was completed in July 1960.

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Principal crops are grain, hay, pasture, and potatoes.

Recreation, Fish & Wildlife

Impoundment of the Little Wood River has increased opportunities for boating and lake fishing. Located far from large population centers, the reservoir has proved to be popular for camping and fishing. The Bureau of Reclamation operates a small campground, picnic area, and boat ramp near the dam. Trout and kokanee salmon are the anglers` primary catch.

Flood Control

Historically, the area had never been free from the threat of flood damage from periodic flooding. Flood control benefits are achieved by operating the reservoir on a forecast basis. Flooding, except for an extremely high flood discharge, has been eliminated in the community of Carey and immediate surrounding area.

The Little Wood River Reservoir has 30,000 acre feet of capacity assigned to flood control. The Little Wood River Project has provided an accumulated $3,152,000 in flood control benefits from 1950 to 1998.

Endangered Species Act

The Pacific Northwest Region consults with the NOAA Fisheries and the US Fish and Wildlife Service to ensure that project operations and other activities do not jeopardize ESA-listed Species or their critical habitats. 

Fish and Wildlife Service (FWS) and National Marine Fisheries Service (NMFS) provided Biological Opinions on Reclamation's Operations and Maintenance of 12 projects and associated facilities in the Snake River Basin above Lower Brownlee Reservoir. The Baker Project is one of the 12 projects covered in the Opinions.

If conditions don't change these Opinions should be valid through 2035.

For more information on ESA related activies please go to:

For more information on the fish and wildlife program, please go to:  http://www.usbr.gov/pn/programs/fish_wild/index.html

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Last updated: Jul 26, 2012