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Bitter Root Project History (56 KB) (pdf)
General Description| Plan| Development| Benefits

General Description

Facilities to serve the land in the Bitter Root Project were constructed originally by private interests. The Bureau of Reclamation was authorized in 1930 to rehabilitate the irrigation system and to liquidate its indebtedness.

The project provides irrigation water for 16,700 acres of bench lands surrounding the town of Stevensville on the east side of the Bitterroot River in west-central Montana. Project facilities include a storage dam and reservoir, a diversion dam, and a distribution system.

The official name of the river is Bitterroot; the official name of the project and irrigation district is Bitter Root.

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Water is stored in Lake Como on Rock Creek, one of the west side tributaries of Bitterroot River. Rock Creek Diversion Dam, 1 mile below Lake Como, diverts water into the Bitter Root Irrigation District Canal. A feeder canal from Lost Horse Creek enters the main canal about a mile below the diversion dam, from which point the water flows northerly along the upper edge of the bench lands, generally parallel to and east of the Bitterroot River. The rehabilitated distribution system serves the project lands which lie between the canal and the river.

Facility Descriptions

Como Dam

Completed in 1910 by local irrigators and rehabilitated on its crest and upstream face by the Bureau of Reclamation in 1954, this semihydraulic earthfill dam at the end of a natural lake is 70 feet high with a crest length of 2,550 feet and contains 1,114,000 cubic yards of earth and rock. In 1976, the district built concrete protection walls on each side of the spillway section up to elevation 4,249.0 feet, the same elevation as the crest of the dam. Under the Safety of Dams Program, designs for the walls were furnished to the district to correct low points in the dam fill adjacent to the spillway.

Between 1992 and 1994 major modifications to Como Dam were performed to mitigate concerns associated with seepage and piping, liquidfication during a large seismic event, and overtopping during large floods. During these modifications, the spillway crest was raised to elevation 4246.0 feet increasing the active reservoir capacity from 35,100 acre-feet to 38,500 acre feet. The state of Montana paid for this work and obtained 3,000 acre-feet of capacity for storing water to use in enhancing minimum streamflows in the Bitterroot River.

Rock Creek Diversion Dam and Canal System

Rock Creek Diversion Dam, located 1 mile downstream of Como Dam, is a rockfill structure with timber sheet piling diaphragm and is 10.5 feet high. The canal has an initial capacity of 325 cubic feet per second and is 60 miles long. There is also a 7-mile-long feeder canal that diverts water from Lost Horse Creek and delivers it into the district canal about a mile below Rock Creek Diversion Dam. Extensive rehabilitation to the main canal, flumes, siphons, and distribution system was completed during 1963-1967. On June 15, 1974, floods damaged Siphon No. 1 on the main canal and the supporting steel trestle crossing the Bitterroot River. The damage was repaired and water deliveries were resumed. An extensive lateral system completes the distribution system.

Operating Agencies

The Bitter Root Irrigation District maintains and operates the project.

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In 1805, when Lewis and Clark passed through the Bitterroot Valley, they found the Flathead Indians living there. In 1841, Catholic missionaries came to the valley and established St. Mary`s Mission near the town of Stevensville. The missionaries were responsible for creating interest in the production of crops and livestock. Later, the development of mining, construction of the main line of the Northern Pacific Railway, and establishment of logging camps throughout nearby timber areas created a demand for agricultural products. A thriving community was well established by 1883.

By treaty dated July 16, 1855, and ratified on March 8, 1859, the Flathead Indians agreed to move from the Bitterroot Valley to the Jocko Valley. By passage of the Act of June 5, 1872, Congress provided for the relocation of the Indians to the Jocko Reservation and for the survey and settlement of 15 townships in the Bitterroot Valley.


Following the agreements with the Indians, the Bitterroot Valley experienced many stages of irrigation development which made use of Lake Como and involved rather large-scale construction on the east side of the valley.

In 1920, following a period of generally unsatisfactory irrigation promotion, financial maneuvering, and reorganization, the Bitter Root Irrigation District was formed in accordance with Montana law. In 1923, the district issued bonds to purchase water rights and storage and distribution works.

The district experienced difficulty in retiring its debts, and, in 1930, Congress authorized measures to be undertaken by the Bureau of Reclamation to liquidate the indebtedness, to rehabilitate the project structures, and to loan funds to the district for construction, betterment, or repair work necessary to place the project in good operating condition.


Rehabilitation of the irrigation system of the Bitter Root Irrigation District and the liquidation of its private indebtedness were originally authorized by the Act of July 3, 1930 (46 Stat. 852, Public Law 71-506). The Act of August 26, 1935 (49 Stat. 799, Public Law 74-327) authorized the Secretary of the Interior to amend specific articles of the August 24, 1931, contract between the United States and the irrigation district regarding its obligation. Both of these acts were repealed by the Act of May 6, 1949 (63 Stat. 62, Public Law 81-561) approving a September 16, 1948, contract with the Bitter Root Irrigation District. Further rehabilitation of project facilities was accomplished pursuant to the Rehabilitation and Betterment Act of October 7, 1949 (63 Stat. 724, Public Law 81-335). Flood damage in 1974 was repaired under the Emergency Fund Act of June 26, 1948 (62 Stat. 1052, Public Law 80-790). The authorized purpose of the Bitter Root Project is irrigation.


The project was originally constructed by the Bitter Root Valley Irrigation Company between 1908 and 1910; the Bureau of Reclamation rehabilitated the project beginning in 1930. Additional funds for rehabilitation work were provided in 1936, 1948, and 1956.

Extensive rehabilitation to the canal and distribution system was initiated in 1963 and completed in 1967. Using emergency funds provided by Reclamation, the flood damage of June 15, 1974, was repaired within a few weeks. This work was performed by a contractor hired by the irrigation district. In 1976, the district constructed protective walls on each side of the spillway section with its own funds.

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Principal crops produced are grain, hay, and pasture.


Lake Como is in a beautiful setting in the Bitterroot National Forest. Cabin sites are available through the Forest Service. The reservoir and immediate area are used for camping, picnicking, swimming, and boating, and there is fishing for native and rainbow trout.

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Last updated: Dec 09, 2009