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Chief Joseph Dam Project
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General Description| Plan| Development| Benefits

General Description

Chief Joseph Dam, constructed by the Corps of Engineers, is on the Columbia River in north-central Washington and is a key structure in the comprehensive development of the Columbia River Basin. Storage water from the reservoir, and power revenues to assist in paying for irrigation features, are necessary for present and future irrigation development of the area.

Four divisions of the Chief Joseph Dam Project have been authorized: Foster Creek, Greater Wenatchee, Okanogan-Similkameen, and Chelan.

Lands of the Foster Creek Division are along the Columbia River near its confluence with the Okanogan River. The division includes the Bridgeport Bar and Brewster Flat Units, which have been constructed and are in operation. A third unit, Bluebottle Flat, has been authorized but construction has been deferred.

Four of the original seven units of the Greater Wenatchee Division have been authorized. Three of these units have been constructed-Brays Landing, East Wenatchee, and Howard Flat. Moses Coulee Unit has been authorized, but construction has been deferred.

The Oroville-Tonasket Unit (including the Oroville-Tonasket Unit Extension) and the Whitestone Coulee Units of the Okanogan-Similkameen Division have been constructed and are in operation.

The Chelan Division, Manson Unit, has been authorized and constructed. The unit is located in Chelan County, bordering the north shore of the lower end of Lake Chelan, about 40 miles up the Columbia River from Wenatchee.

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Facility Descriptions

Foster Creek Division

The Foster Creek Division provides a full water supply to some 2,900 acres of irrigable land.

Brewster Flat Unit - This unit required the construction of a river pumping plant, a booster pumping plant, a relift pumping plant, two steel reservoirs, and a closed-pipe distribution system to serve 2,432 acres of irrigable land. The river plant is on the right bank of the Columbia River and has four 11.7-cubic-foot-per-second, 190-foot head, vertical turbine deep well pumps. The booster plant is located in a building a short distance from the river. The building houses four 11.7 cubic-foot-per-second, 350-foot head, horizontal centrifugal pumping units.

A relift pumping plant at the 66,840-cubic-foot (0.5-Mgal) equalizing reservoir has three 13 cubic-foot-per-second, 150-foot head, horizontal centrifugal pumping units.

Two steel tanks, constructed on the discharge lines, serve as equalizing reservoirs for the distribution system. The lower tank has a capacity of 66,840 cubic feet and 40,100 cubic feet (0.3 Mgal) in the upper tank.

Bridgeport Bar Unit - This unit includes two entirely separate and independent systems and areas. The plan selected for the Townsite area (301 acres) which has been indefinitely deferred, involved construction of a gravity supply canal from the left abutment of Chief Joseph Dam to the existing facilities serving part of the area. A small pumping plant has been constructed to serve the remaining area, primarily the new land. The plan for the Bar area (475 acres) required a complete new system to serve the area, only a fraction of which was previously irrigated through individual systems. Major features include a pumping plant on the Columbia River, an equalizing reservoir, a steel discharge line, and a steel and asbestos-cement pipe distribution system. The pumping plant consists of two vertical turbine pumps, each capable of delivering 4.45 cubic feet per second at a dynamic head of 200 feet. The equalizing reservoir is a 13,368-cubic-foot (0.1-Mgal) steel tank.

Greater Wenatchee Division

Approximately 9,600 acres of irrigable lands are being served by closed-pipe distribution systems of the East, Brays Landing, and Howard Flat Units of the Great Wenatchee Division. The three units are separate land areas requiring independent irrigation systems.

East Unit - This unit provides a supply of irrigation water for more than 4,500 acres of land. Water is pumped from the Columbia River, lifted 677 feet to an equalizing reservoir, conveyed to the lands through a closed-pipe system, and delivered at sprinkler pressure.

Major features include a main pumping plant on the Columbia River, a booster (high lift) pumping plant, and two relift pumping plants. The river plant is on the left bank of the Columbia River and has a maximum capacity of 76 cubic feet per second at a dynamic head of 81 feet. The four vertical turbine pumps discharge directly into the two-stage horizontal centrifugal pumps in the booster plant, which has a capacity of 76 cubic feet per second with a dynamic head of 652 feet. Both plants have multiple pumping units of two sizes to give flexibility in meeting pumping requirements. The discharge line from the Booster Pumping Plant to the regulating reservoir is 12,575 feet long and ranges from 48 to 36 inches in diameter. Operation of the pumping facilities is controlled automatically by floats connected to the cubic-foot (2- Mgal) concrete-lined regulating reservoir.

A North Relift Pumping Plant (Lateral 9), adjacent to the main reservoir, serves about 320 acres of land above the main body of the project lands along Lateral 9. The plant has a capacity of 5.65 cubic feet per second at a dynamic head of 108 feet. A 10,026-cubic-foot (75,000 gal) concrete- lined regulating reservoir is provided for the area. Float-controlled switches regulate the operation of pumps served by of the relift plant.

The East Relift Pumping Plant (Lateral 10) irrigates about 1,460 acres above the main body of project lands at the east end of the unit. The plant has a capacity of 26 cubic feet per second at a dynamic head of 108 feet. A 20,052-cubic-foot (0.15-Mgal) concrete-lined regulating reservoir is located on high ground north of the plant.

Brays Landing Unit - Water for the Brays Landing Unit serves about 1,700 irrigable acres, comprised of a series of high terraces with irregular topography, that require sprinkler irrigation. Major facilities include a main pumping plant, discharge line, main regulating reservoir, closed- pipe lateral system, and four small pumping plants and reservoirs.

The Main Pumping Plant on the Columbia River 25 miles north of Wenatchee, Washington, consists of five well pumping units with a combined capacity of 32.25 cubic feet per second at a dynamic head of 135 feet. Water is also delivered to a reservoir at Pumping Plant No. 1 (booster plant) and then to a pressure pipeline and three pumping plants (A, B, and C), each with its own regulating reservoir. The pressure lateral system covers 16 miles.

Howard Flat Unit - There are over 900 acres of irrigable land in the Howard Flat Unit, which is in Chelan County on a large, relatively flat terrace about 5 miles northeast of Chelan, Washington.

A pumping plant complex near the Columbia River consists of a three-unit river (well pump) plant, with a total capacity of 16.7 cubic feet per second at heads of 110 and 112 feet, and a river booster plant. The booster plant consists of three units with a total capacity of 16.5 cubic feet per second at a head of 490 feet.

Water from the river complex is delivered to the Reservoir Relift Pumping Plant, a five-unit plant with a capacity of 16.8 cubic feet per second and a dynamic head of 178 feet.

Two smaller pumping plants are located on opposite ends of the lateral system. The North Booster Pumping Plant consists of three units with a total capacity of 5.52 cubic feet per second at a total dynamic head of 84 feet. The two-unit South Booster Pumping Plant has a capacity of 1.34 cubic feet per second at a total dynamic head of 54 feet.

Okanogan-Similkameen Division

Facilities have been completed for the two units of the Okanogan-Similkameen Division. The Oroville-Tonasket Unit is along the Similkameen and Okanogan Rivers in north-central Washington near the Canadian border. The Oroville-Tonasket Unit Extension covers the same area as the original unit with an addition of approximately 600 acres. The extension replaced most of the Oroville-Tonasket Unit diversion, conveyance, and distribution facilities. Whitestone Coulee Unit has been completed and is contained in a narrow strip of land running west from the Okanogan River.

Oroville-Tonasket Unit - This unit provides irrigation service to approximately 10,000 acres.

The purpose of the Bureau of Reclamation's involvement in the Oroville-Tonasket Unit was to rehabilitate portions of the irrigation system which had been constructed by the Oroville-Tonasket Irrigation District. The major source of water supply was by diversion from the Similkameen River, a tributary to the Okanogan River. The main canal headworks structure was relocated about 0.5 miles above the existing headworks requiring the construction of a 190 cubic feet per second unlined canal connecting to the main canal. In addition, interspersed sections of the 9 miles of main canal were rehabilitated, the Upper Okanogan Siphon crossing the Okanogan River just above the town of Oroville, Washington was replaced with a 33-inch-diameter pretensioned concrete-cylinder pipe, and three auxiliary pumping plants were constructed on the Okanogan River about 2, 11, and 13 miles south of Oroville.

Flooding of the Okanogan River in the spring of 1972 destroyed the Ellisford Siphon that carried water across the Okanogan River lower in the system. Using funds provided by the Office of Emergency Preparedness, the siphon was replaced by the Midway Pumping Plant, located about 8 miles south of Oroville, to pump directly from the Okanogan River.

Oroville-Tonasket Unit Extension - At the time of the rehabilitation work on some of the Oroville-Tonasket unit facilities, it was understood that the irrigation district would use its available financial resources to rehabilitate the extensive distribution system. However, because of the poor condition of the major facilities, the irrigation district encountered emergency repairs which left it without sufficient funds to rehabilitate the distribution system as planned.

The Oroville-Tonasket Unit Extension essentially replaced the entire irrigation system to provide full irrigation service through a pipe distribution system operating with project pressure for sprinkler irrigation. The gravity diversion from the Similkameen River was terminated and the diversion dam and most of the main canal and flumes were removed and tunnel portals sealed.

Six pumping plants, one on Osoyoos Lake and five on the Okanogan River, were constructed to lift water into eight adjacent closed pipe distribution systems. Fifteen relift pumping plants provide sprinkler pressure on the higher lands.

Osoyoos Lake is an international water body with its upper portion in Canada and lower portion, including the structure which controls lake outflow, in the United States. The Osoyoos Pumping Plant supplies water to lands on the east and west sides of the lake as well as some lands on the west side of the Similkameen River. The Upper Okanogan Siphon was modified as it is used to provide this service.

Wildlife measures were also included to compensate for loss in wildlife habitat that occurred with the removal of the old irrigation system. Mitigation measures included marsh enhancement, spring development, browse irrigation, irrigation of habitat at reregulating tanks, and buffer strips.

The authorization also provided for measures to enhance the anadromous fishery by providing access to potential spawning and rearing areas in the Similkameen River above Okanogan County Public Utility District's Enloe Dam and a companion fish stocking program. Enloe Dam and Powerplant were constructed in the 1920's for hydropower purposes, but generation was discontinued in the 1950's. No action has been taken with respect to these measures.

Title to project facilities constructed by the Bureau of Reclamation have been transferred to the Oroville Tonasket Irrigation District and the district released of it's contractual obligation pursuant to a settlement agreement entered into on April 15, 1996, and approved by Congress by the Act of April 14, 1997 (111 Stat. 16, Public Law 105-9).

Whitestone Coulee Unit - Facilities of the Whitestone Coulee Unit provide an irrigation water supply to some 2,700 acres of land in the Loomis to Ellinsforde area of Okanogan County. The water source is Toats Creek at a point some six miles west of Loomis. Toats Coulee Diversion Dam is a concrete structure with an ogee overflow section, and headworks for the main supply canal. This supply canal across Sinlahekin Creek is a 6- mile-long buried concrete pipe, 45- to 18-inches in diameter, and has a maximum capacity of 70 cubic feet per second. At the terminal of the main supply canal, a wye structure containing a sleeve valve diverts water to an outlet structure and then into Spectacle Lake Reservoir and/or the 2.78-mile-long North Branch Canal. The active storage capacity at Spectacle Lake was increased from 3,800 to 6,250 acre-feet by construction of a 24-foot-high homogeneous earthfill dike across the low point in the rim of Spectacle Lake. This also required a concrete gated outlet structure to divert water into the Spectacle Lake Canal. A small two-unit pumping plant on Spectacle Lake Canal delivers 3.6 cubic feet per second to a 20-foot-diameter regulating tank that serves about 160 acres of land. Two larger pumping plants are located on Spectacle Lake. The North Branch Pumping Plant, a three-unit installation with a dynamic head of 230 feet and total capacity of 13 cubic feet per second, delivers water through an 18-inch-diameter pipeline into the North Branch Canal. The Whitestone Flats Pumping Plant, three units with a dynamic head of 187 feet and total capacity of 17 cubic feet per second, conveys water through a 27-inch- diameter pipe into Whitestone Flats Canal.

Distribution is made through about 27 miles of lined laterals. Most lands are sprinkler irrigated, with each farm providing the pressure required.

Fish screens are included at Spectacle Lake Outlet Works and at the pumping plants. Lands were also acquired around the lake for recreation use.

Chelan Division

Manson Unit - This unit provides full irrigation service to about 6,300 acres of irrigable land; of the which some 4,000 acres were previously irrigated.

Constructed facilities have replaced most of the irrigation facilities built by the Lake Chelan Reclamation District. Antilon Reservoir is the only portion of the original system remaining and the reservoir spillway has been modified to provide a constant water surface elevation of 2,318.0 feet.

Major new works include the Lake Chelan Pumping Plant, 8 relift pumping plants, 4 booster pumping plants, 13 regulating tanks, and a pressure pipeline distribution system. The irrigation water is pumped from Lake Chelan and distributed through the pipeline system for sprinkler irrigation. Limited drainage facilities were constructed at scattered locations throughout the unit.

Lake Chelan Pumping Plant is an outdoor-type, constructed of reinforced concrete. There are eight pumping units, each consisting of a vertical turbine pump directly connected to a vertical solid- shaft motor. Total rated capacity is 106.7 cubic feet per second at a rated head of 267 feet. A traveling water screen is provided to protect the pumps from moss and debris and to serve as a fish screen.

The eight Relift Pumping Plants, A through H, are outdoor-type, reinforced concrete, flat-slab structures. There are 42 pumps in these plants, all of the motordriven, horizontal, centrifugal variety with hydraulic cylinder-operated discharge valves and valve operating systems.

The booster pumping plants are of the closed-system type and provide additional head to small acreages. Each plant is equipped with two pumping units which draw water from a 6-inch bypass, which in turn draws water from an adjacent lateral.

The 9 regulating tanks are provided as afterbays for the primary and relift pumping plants. The tanks are used to control pump operation and supply water from the related pumping plant discharge lines to downstream laterals according to demand.

Water pumped from Lake Chelan is delivered to the farm units through a system of pressure pipelines. The system consists of about 71 miles of buried noncorrosive pipe ranging in diameter from 6 to 48 inches. The Lake Chelan discharge line is steel, mortar-lined and coated pipe, about 4,000 feet long. The A and B pumping plant discharge lines and 12,000 feet of laterals total about 2.8 miles, and are reinforced plastic mortar (RPM) pipe. The remainder of the pipe is asbestos-cement. The pipe distribution system provides a peak farm delivery of 0.015 cubic feet per second (6.9 gal/min) for each acre at a minimum pressure of 35 pounds per square inch to the sprinkler nozzle at the high point of each tract.

A buried pipe drain system consists of 8.8 miles of pipe and two small pumps to lift water out of the low areas.

Fish screens were installed at the Antilon Reservoir outlet works and minimum basic recreation facilities were constructed.

Due to the failure of some of the reinforced plastic mortar pipe, about 2.8 miles have been replaced. This work was done by the Chelan Reclamation District under agreements with the Bureau of Reclamation whereby each party paid half of the cost of materials and labor.

Operating Agencies

Operation and maintenance of the facilities is the responsibility of the following entities:

DivisionUnitOperating Entity
Foster CreekBrewster FlatBrewster Flat Irrigation District
 Bridgeport BarBridgeport Bar Irrigation District
Greater WenatcheeEastGreater Wenatchee Irrigation District
 Brays LandingGreater Wenatchee Irrigation District
 Howard FlatGreater Wenatchee Irrigation District
Okanogan-SimilkameenOroville-TonasketOroville-Tonasket Irrigation District
 Whitestone- CouleeWhitestone Reclamation District
ChelanMansonLake Chelan Reclamation District

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Settlement of the north-central Washington region began soon after 1811 when agents of John Jacob Astor established a fur trading post and fort at the junction of the Columbia and Okanogan Rivers. The fort was abandoned after the treaty of 1846 established the United States-Canadian boundary at the 49th parallel.

Cattle ranching was the first agricultural enterprise, beginning as early as 1826 in the Okanogan Valley and reaching a peak during the 1870`s after being extended to the Big Bend area, now occupied in part by the Columbia Basin Project. However, settlement was slow until after 1900, when large-scale irrigation developments were started. Settlers came to Wenatchee Valley and planted orchards after the Highline Canal provided water for 20,000 acres. Settlement and development of the Foster Creek area have been related to the resources and growth of the vast north-central Washington region.

Irrigation development in the Whitestone Coulee area began in 1918 to serve 10,000 acres but because of adversities, including a critical water shortage, facilities were not completed until 10 years later and served only about 2,000 acres.

In the Manson area, the original district was formed in 1908 to irrigate some lowlands with water from Wapato Lake; however, real progress did not begin until 1911.


The investigations of the Foster Creek Division were initiated with a general Bureau of Reclamation reconnaissance of irrigation possibilities in the Okanogan River Basin, and were completed in 1950. Included in the study were some lands along the Columbia River, both upstream and downstream from the mouth of the Okanogan. These lands are not geographically part of the Okanogan Basin but were included in the study because of the interrelated water supply problems associated with diversions from Rufus Woods Lake. On the basis of information developed in the reconnaissance study, detailed investigation of the Foster Creek area was given first priority. A feasibility-type investigation of Foster Creek development was started early in 1951 and culminated in a report by the Bureau of Reclamation in October 1952. Meanwhile, the act of July 17, 1952 (Public Law 577), was enacted, providing a basis for authorization of irrigation works in connection with Chief Joseph Dam and for financial assistance to such developments from power revenues. In a final report dated December 21, 1953, the Commissioner of Reclamation modified the plan. This report was the basis for authorization of the project.

The Bureau of Reclamation made a reconnaissance study of the Greater Wenatchee area in 1945. A development investigation was begun in 1946, and a project planning report was published in 1950. Engineering investigations were made in 1952 and 1953, and economic and feasibility studies of the area were made in 1955. The final plan was prepared in 1959 and revised in 1962.

In 1950, a reconnaissance investigation was undertaken to establish a basic plan for irrigation of lands in the Okanogan Basin and lands along the Columbia River in the vicinity of Chief Joseph Dam and the mouth of the Okanogan River. This report was published in 1951. Feasibility investigations of the Okanogan-Similkameen Division were started in the fall of 1955, and a detailed land classification study was started in early 1956. The final plan was reported in September 1964.

Further investigations of the Oroville-Tonasket Unit resulted in a feasibility report completed in 1975 recommending replacement of most of the existing facilities of that unit.

Original development of the Manson Unit of the Chelan Division was a private venture. However, by passage of Public Law 577 in 1952, and at the request of local water users through their congressional representatives, feasibility investigations were begun in 1956 and completed in early 1960.


Foster Creek Division, comprising three units, was authorized by the Act of July 27, 1954, (68 Stat. 568, Public Law 83-540). This was the first authorization under the provisions of the act of July 17, 1952, which provides the basis for favorable pumping and power rates and financial assistance to irrigation development from Chief Joseph Dam Project power revenues. The purpose of these units is irrigation.

Construction of four units of the Greater Wenatchee Division was authorized by the Act of May 5, 1958 (72 Stat. 104, Public Law 85-393). The purpose of these units is irrigation.

The Oroville-Tonasket Unit of the Okanogan-Similkameen Division was authorized by the Act of October 9, 1962 (76 Stat. 761, Public Law 87-762). The authorized purposes were irrigation and the conservation and development of fish and wildlife resources. The fish and wildlife purpose was related to protective facilities and mitigation measures.

The Oroville-Tonasket Unit Extension of the Okanogan-Similkameen Division was authorized by Title II of the Act of September 28, 1976 (90 Stat. 1325, Public Law 94-423). The authorized purposes were irrigation and the enhancement of fish resources.

The Act of April 14, 1997 (111 Stat. 16, Public Law 105-9) approved a settlement agreement between the parties whereby the Oroville-Tonasket Irrigation District was released from its contractual obligation to the United States. Title to project facilities were transferred to the irrigation district except for 880 acres which had been purchased for mitigation purposes. These lands have been retained by the Bureau of Reclamation for recreation, hunting and fishing in season, and game reserves. These lands are currently managed by the Oroville-Tonasket Irrigation with oversight by the Bureau of Reclamation.

Construction of the Whitestone Coulee Unit of the Okanogan-Similkameen Division was authorized by the Act of September 18, 1964 (78 Stat. 955, Public Law 88-599). The purposes of this unit are irrigation, the conservation and development of fish and wildlife resources, and improvement of public recreation facilities. The fish and wildlife purpose is associated with the construction of the wye (or drop) structure from the main canal which delivers water to Spectacle Lake and screens at the outlet works and two pumping plants. The recreation purpose is related to the acquisition of lands.

The Manson Unit of the Chelan Division was authorized by the Act of September 7, 1966 (80 Stat. 704, Public Law 89-557). The purposes are irrigation, conservation and development of fish and wildlife resources, and enhancement of recreation opportunities. Fish and wildlife is associated with the installation of screens at the outlet works of Antilon Reservoir. Recreation is related to the construction of minimum basic recreation facilities as well as the recreational opportunities provided by the enlarged Antilon Reservoir.


Construction of the Bridgeport Bar and the Brewster Flat Units of the Foster Creek Division began in 1956 and was completed in 1958. Construction of the Bluebottle Flat Unit has been deferred.

Brays Landing, East Wenatchee, and Howard Flat Units of the Greater Wenatchee Division were placed under construction in 1960 and completed in 1964.

The Oroville-Tonasket Unit of the Okanogan-Similkameen Division was placed under construction in 1965 and completed in 1969. Construction of the Oroville-Tonasket Unit Extension began in 1980, and was completed in 1990.

Construction of the Whitestone Coulee Unit of the Okanogan-Similkameen Division began in 1968 and was completed in 1975. The Manson Unit of the Chelan Division was placed under construction in 1971 and completed in 1976.

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Apples, pears, cherries, and alfalfa hay are the chief crops produced in the project area. The apples are world famous for their high quality.

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Last updated: Apr 30, 2009