General

The Columbia Basin Project (CBP) is located in east central Washington and currently serves about 671,000 acres, or approximately 65 percent of the 1,029,000 acres originally authorized by Congress, in portions of Grant, Lincoln, Adams, and Franklin Counties, with some northern facilities located in Douglas County.  These first half of project lands were developed primarily in the 1950’s and 1960’s, with some acreages being added sporadically until 1985.  The 1945 feasibility report anticipated a 70-year period of incremental development to complete the CBP.  It was anticipated that further incremental development of the CBP would depend on future needs and any irrigation of additional lands would utilize water from the Columbia River already reserved for the CBP.

Principal project features include Grand Coulee Dam, Franklin D. Roosevelt Lake, Grand Coulee Powerplant Complex, switchyards, and a pump-generating plant. Primary irrigation facilities are the Feeder Canal, Banks Lake, the Main, West, East High, and East Low Canals, O`Sullivan Dam, Potholes Reservoir, and Potholes Canal. There is over 300 miles of main canals, about 2,000 miles of laterals, and 3,500 miles of drains and wasteways on the project.

All of the principal features have been constructed, except the East High Canal and the extension of the East Low Canal, on which construction has been indefinitely deferred.

The Odessa Subarea is a region of deep ground water as designated by the Washington Department of Ecology (Ecology), and underlies the eastern most portion of the authorized CBP, east of and uphill from the existing East Low Canal of the CBP.  Ecology permitted irrigation wells in the Odessa Subarea in the mid-1970s, anticipating that the CBP would eventually provide project water to these lands via the construction of a second canal, the East High Canal.  However, this canal has not yet been built; and as a result, ground water pumping has continued.  The aquifer is declining to such an extent that the ability of farmers to irrigate their crops is at risk and domestic, commercial, municipal, and industrial uses and water quality are affected.  The urgency of this matter will continue to grow. 

History

The earliest settlement of the project area centered upon extensive use of the natural grasses for dryland grazing on unfenced rangeland. In the first decade of the 20th century, large numbers of homesteaders moved into the project area, acquired land under homesteading laws, and undertook conventional dry farming. Since the average annual rainfall over the entire area is less than 10 inches, dry farming could not result in permanent agricultural development. A few years of above-normal rainfall lent an appearance of success to farming operations after the grasslands were first plowed, but dry farming was doomed to failure on all but those lands with deep soils and high water-holding capacities. Even so, dry farming of cereal grains on a permanent basis was possible only through the consolidation of land holdings and the farming of very large tracts of land.

Investigations
With the establishment of the Reclamation Service in 1902 (now Bureau of Reclamation) and the already apparent difficulties of dry farming in the area, interest developed in the possibility of irrigating with water from the Columbia River. The Reclamation Service undertook certain general investigations in 1904, but the basic problem of lifting Columbia River water from its deep canyon onto the plateau surface was more than the young agency could hope to contend with at that time.

In 1918, local interests initiated a proposal for irrigation of the project area; they worked resolutely in the following years to achieve that goal. It was proposed that a high dam be built on the Columbia River at the head of the upper Grand Coulee, a unique geological feature in the ancient riverbed of the Columbia, formed when the original channel was blocked by glaciers during one of the Ice Ages. By building such a dam, irrigation water could be made available to the irrigable lands lying 50 miles to the south.

An alternative proposal, which had strong backing in the State of Washington, called for construction of a canal to convey water from the Pend Oreille River in northern Idaho generally westward across the plateau surface and into the middle portion of the project area.

Many engineering and economic studies were made by various organizations and governmental agencies. The conclusive and culminating study was prepared by the Corps of Engineers and published as House Document No. 103, 73d Congress, 1st session. The report recommended constructing the high Grand Coulee Dam at its present site and pumping irrigation water up into the Grand Coulee. In connection with this report, the Bureau of Reclamation submitted a report on the proposed irrigation plan for the Columbia Basin Project. The Reclamation report, dated January 7, 1932, recommended construction of the project essentially as it is now being built.

The landowners in the project area worked throughout the latter part of the 1930`s to organize irrigation districts as a prerequisite to the construction of irrigation works. The three irrigation districts formed by February 1940 were the Quincy-Columbia Basin Irrigation District, the East Columbia Basin Irrigation District, and the South Columbia Basin Irrigation District.

In 1939, the Bureau of Reclamation, with the cooperation and assistance of about 45 different Federal, State, local, and private organizations, undertook a program of nonengineering studies important to settlement and development of this large project. This program of 28 problem studies was known as the Columbia Basin Joint Investigations. They were carried to completion, and the reports were published during World War II. The conclusions and recommendations made regarding the 28 problems were heavily drawn upon in drafting the Columbia Basin Project Act of 1943.

A rapidly expanding power market in the Pacific Northwest experienced power shortages in 1951-1952. Investigative studies were undertaken as a result of these shortages and in February 1954, the Bureau of Reclamation prepared a report on a proposed Third Powerplant at Grand Coulee Dam. It was concluded that the Third Powerplant was feasible from an engineering point of view; however, it was recommended that the development be held in abeyance until such time as prospective requirements for capacity, and energy resulting therefrom, provided definite prospects for financial feasibility. In January 1965, a feasibility report was issued recommending authorization to construct the Third Powerplant with a rated capacity of not less than 3.6 million kilowatts. Authorizing legislation followed in June 1966.

Authorization
The Columbia Basin Project was begun with the allocation of funds for Grand Coulee Dam pursuant to the National Industrial Recovery Act of June 16, 1933. The project was specifically authorized for construction by the Rivers and Harbors Act approved August 30, 1935 (49 Stat. 1028, 1039-1040, Public Law 74-409), The Columbia Basin Project Act of March 10, 1943 (57 Stat. 14, Public Law 78-8), reauthorized the project, bringing it under the provisions of the Reclamation Project Act of 1939.

Units 7, 8, and 9 of the Right Powerhouse were authorized by a finding of feasibility approved by the Secretary of the Interior on January 5, 1949.

Construction of the Third Powerplant was authorized June 14, 1966 (80 Stat. 200, Public Law 89-448), as amended by the Act of September 7, 1966 (80 Stat. 714, Public Law 89-561).

The authorized purposes are the control of floods, improvement of navigation, regulation of stream flow, storage and delivery of stored water for reclamation of lands, and other beneficial uses, and the generation of electric energy. Storage and delivery of water for municipal and industrial purposes is a beneficial use and a project purpose.

In 1980, the U.S. District Court confirmed that fish and wildlife was also a project purpose pursuant to the Fish and Wildlife Coordination Act of August 12, 1958 (72 Stat. 563, Public Law 85-624).

Plan

The Columbia River is characterized by heavy, sustained flows during the late spring and early summer months, the peak flow usually occurring in mid-June. Most of the water comes from the forested slopes of the Rocky Mountains in British Columbia, western Montana, and northern Idaho, where snow and heavy rains result in prolonged summer riverflow. There is usually ample water for irrigation and power generation (both irrigation pumping and commercial) and for reversible pump-generation. Releases are made in July and August to ensure adequate water in the lower Columbia River to enhance fish migration.

Irrigation water is pumped from Franklin D. Roosevelt Lake by the Grand Coulee Pump-Generating Plant, adjacent to the reservoir at the left abutment of the dam. The Pump-Generating Plant has a total of 12 units, which include 6 pumping units and 6 pump-generating units.

The widely distributed irrigation works that extend southward from the Grand Coulee Pump- Generating Plant begin with the 16 mile feeder canal which carries water to Banks Lake, the equalizing reservoir. This 27-mile-long reservoir occupies the floor of the upper Grand Coulee between North Dam near the town of Coulee Dam, Washington, and Dry Falls Dam near Coulee City. The Main Canal flows southward from the outlet works at Dry Falls Dam into the northern end of the irrigable area. The West, East High, and East Low Canals are fed by the Main Canal and carry water over a large portion of the project area. O`Sullivan Dam, in the central part of the project area, created the Potholes Reservoir where return flows from the northern part of the project are recaptured. The Potholes Canal extends into and serves the southern part of the project area.

Facility Descriptions

Grand Coulee Dam and Franklin D. Roosevelt Lake
Grand Coulee Dam is one of the largest concrete structures ever built. This barricade, which raises the water surface 380 feet above the old riverbed, was originally 4,300 feet long, 550 feet high, and contains about 12 million cubic yards of concrete. The original dam was modified for the Third Powerplant by construction of a 1,170-foot-long, 201-foot-high forebay dam along the right abutment approximately parallel to the river and at an angle of 64 degrees to the axis of Grand Coulee Dam. The total length of the main dam, forebay dam, and wing dam is 5,223 feet. The spillway of the dam is controlled by 11 drum gates, each 135 feet long, and is capable of spilling 1 million cubic feet of water per second with Lake Roosevelt at fullpool (1290.0 feet above sea level). The dam also contains forty 102- inch-diameter outlet tubes. Within the dam are 8.5 miles of inspection galleries and 2.5 miles of shafts.

Franklin D. Roosevelt Lake, the reservoir behind the dam, extends 151 miles northeast almost to the Canadian border and up the Spokane River, a tributary of the Columbia, to within 37 miles of Spokane. The total storage capacity of the reservoir is about 9.4 million acre-feet, and the active capacity is about 5.2 million acre-feet.

The average discharge at Grand Coulee over a period of years is approximately 109,000 cubic feet per second. On June 12, 1948, during an historic Columbia River flood period, the maximum discharge (turbine and spill) recorded was 637,800 cubic feet per second. The annual volume inflow has varied from a minimum of 48.5 million acre-feet to a maximum of 111.8 million acre-feet. The average annual inflow to Lake Roosevelt is 99.3 million acre-feet. The April through July inflow accounts for 65 to 70 percent of the total annual inflow volume.

Grand Coulee Powerplant Complex
Power facilities at Grand Coulee Dam consist of a powerplant on both the left and right sides of the spillway on the downstream face of the dam, the Third Powerplant on the downstream face of the forebay dam, an 11.95/115-kilovolt switchyard, a 230-kilovolt consolidated switchyard, and the 525-kilovolt Third Powerplant cable spreading yard and switchyard located high on the hills west of Grand Coulee Dam.

As constructed, the Left and Right powerplants contained a total of eighteen 108,000-kilowatt units, nine in each powerplant. Rewinding these units has increased the capacity to 125,000 kilowatts each, for a total of 2.25 million kilowatts. Three small station service units of 10,000 kilowatts each in the left powerplant increase the total to 2.28 million kilowatts for the left and right powerplants.

The Third Powerplant has six units. The first three units have a nameplate rating of 600,000 kilowatts each and the last three are rated at 805,000 kilowatts each, for a total of 4.215 million kilowatts in the Third Powerplant. Total generating capacity for Grand Coulee (including the Grand Coulee Pump-Generating Plant) is 6.809 million kilowatts.

Before construction could start on the Third Powerplant, it was necessary to modify transmission of power from the existing Right and Left Powerhouse and route all generation to a new 230-kilovolt low-profile consolidated switchyard. Originally there was a switchyard on each side of the river, one for each of the existing powerplants. The right switchyard was in the area now occupied by portions of the forebay dam and the Third Powerplant. A new oil-filled pipe-type 230-kilovolt cable system running the Left and Right Powerhouses through galleries in Grand Coulee Dam and through an underground tunnel was installed to convey power up to the new consolidated switchyard. Due to many problems with this cable system it was replaced with overhead lines in 1987-1989.

Power generated at the Third Powerplant is transmitted by 525-kilovolt cables, almost 5 inches thick, that run from the powerplant transformers through a gallery in the dam and through a tunnel to the 525-kilovolt cable spreading yard and then overhead to the switchyard on the hills west of the dam. About 4 miles of the 525-kilovolt cable is required for each of the six units in the Third Powerplant. The oil impregnated insulation around the cable is efficient to the point where a hand can safely be placed on the cables only 1.5 inches from the copper core which carries the electrical energy.

At the switchyards, power generated at Grand Coulee Dam is delivered to the transmission lines of the Bonneville Power Administration, a Federal marketing agency for federally produced power in the Pacific Northwest.

John W. Keys, III Pump-Generating Plant
Six pumping units, each rated at 65,000 horsepower and with a capacity to pump 1,350 cubic feet per second at a 292- to 310-foot head, initially were installed in the plant to lift water from Franklin D. Roosevelt Lake to the 1.6-mile-long feeder canal for delivery into Banks Lake.

The plant was designed to accommodate 12 such units. In the early 1960`s, with the Northwest facing power shortages, investigations showed the potential the site offered for pump-back storage. It was determined feasible that the last six units be reversible; that is, that water be returned from Banks Lake back through these units to generate power during peak power demand periods. Units 7 and 8 are each rated at 67,500 horsepower and lift 1,605 cubic feet per second in the pumping mode (with both Franklin D. Roosevelt Lake and Banks Lake full). They are each rated at 50,000 kilowatts in the generating mode. The last four units are each rated at 67,500 horsepower and can lift 1,700 cubic feet per second in the pump mode and 53,500 kilowatts in the generating mode. The total generating capacity of the John W. Keys, III Pump-Generating Plant is 314,000 kilowatts.

Banks Lake, North Dam, Dry Falls Dam
Banks Lake, the equalizing reservoir, was created by building two rock-faced, earthfill dams at the north and south ends of the Ice-Age channel of the Columbia River, now known as the Grand Coulee. This 27-mile-long reservoir, with an active storage capacity of 715,000 acre-feet, feeds Columbia River water into the Main Canal. In addition, it provides water on a return flow basis to produce power when the pump generating units are operating in the generating mode.

Major features forming and serving Banks Lake are the feeder canal with a capacity of 26,000 cubic feet per second, North Dam, 2 miles southwest of Grand Coulee Dam, and Dry Falls Dam and Main Canal headworks near Coulee City, 29 miles south of Grand Coulee Dam.

In conjunction with the addition of the six pump/generating units the canal size was increased. The south side of the canal was removed, the base widened from 50 feet to 80 feet, an entire new south wall constructed, 8 feet added to the top of the north wall, and a new flume section was added to bypass a duplex tunnel cut-and-cover section. This increased the operating capacity to 26,000 cubic feet per second. Reconstruction was completed in 1981.

Main Canal, Pinto Dam
The Main Canal begins at the headworks at Dry Falls Dam and consists of unlined and concrete- lined sections. Total length of the canal, including siphons, tunnels, and Billy Clapp Lake, is 18.4 miles. The first 1.8 miles from Dry Falls Dam to the Bacon Siphon and Tunnel structures has been increased in capacity from 13,200 to 19,300 cubic feet per second. Bacon Siphon and Tunnel structures consist of two siphons, each about 1,000 feet long, and two tunnels, each about 2 miles long, that carry the water to Billy Clapp Lake. This lake, some 6 miles long and formed by the construction of the earthfill Pinto Dam, is a segment of the canal system. Construction of an equal length of very difficult and expensive canal was thus avoided.

West Canal
The West Canal has an initial capacity of 5,100 cubic feet per second and a length of 82.2 miles. It is one of two canals formed by the bifurcation of the Main Canal. The West Canal skirts the northwest periphery of the project and en route is carried across the lower Grand Coulee through the world`s largest inverted siphon at the north end of Soap Lake. The canal continues around the upper margin of Quincy Basin to the northern base of Frenchman Hills, which it penetrates by a 9,000-foot tunnel, ending in an easterly branch across the Royal Slope. The capacity of the canal is reduced progressively as water is diverted into lateral distribution systems built to serve the entire northwestern portion of the project.

East Low Canal
The East Low Canal, having an initial capacity of 4,500 cubic feet per second, also begins at the bifurcation of the Main Canal. The East Low Canal extends southerly in a contour course through the rolling eastern uplands, passes through or near the towns of Moses Lake and Warden, and terminates just east of the Scooteney Reservoir. An extension of the canal which would carry water southward and to the east of the towns of Connell, Mesa, and Eltopia, has been deferred.

O`Sullivan Dam
O`Sullivan Dam, one of the larger zoned earthfill dams in the United States, is on Crab Creek about 15 miles south of Moses Lake. The 27,800-acre Potholes Reservoir formed by this dam collects return flows from all irrigation in the upper portion of the project for reuse in the southern portion. Active storage capacity of the reservoir is 332,200 acre-feet. A system of wasteways has been built on both the West and East Low Canals to provide operational safety for the canals and a means of delivering water into Potholes Reservoir to supplement the natural and return flows.

Potholes Canal
The Potholes Canal has a capacity of 3,900 cubic feet per second, begins at the headworks of O`Sullivan Dam, and extends 62.4 miles in a southerly direction to irrigate lands in the southwestern and south-central portions of the project. Irrigation Blocks 2 and 3, located in the southernmost tip of the South District, receive irrigation water pumped directly from the rivers: Block 2 from the Snake River and Block 3 from the Columbia River.

East High Canal
This proposed 88-mile-long canal, designed for an initial capacity of about 7,500 cubic feet per second, would divert water from the Main Canal immediately above Summer Falls and Billy Clapp Lake, to serve lands east of the East Low Canal extending from the northernmost point of the project area south to Washtucna Coulee. Some 357,000 acres have been proposed for service from the East High Canal. An Environmental Impact Statement was completed in 1993 but was not filed. Construction of the East High Canal is in a deferred status.

Relift Pumping Plants
About 360,000 acres of the irrigable lands within the project are located at elevations higher than the gravity canals and laterals. Some of these high lands are being served by relift pumping plants at various points within the project.

Operating Agencies
All basic irrigation facilities applicable to the three Columbia Basin Irrigation Districts (Quincy-Columbia Basin Irrigation District, East Columbia Basin Irrigation District, and South Columbia Basin Irrigation District) are operated by the irrigation districts. Irrigation facilities operated as reserved works by the Bureau of Reclamation include Dry Falls Dam, Main Canal through the bifurcation works including Pinto Dam and Billy Clapp Lake, and O`Sullivan Dam, Potholes Reservoir, and Potholes Canal headworks. Grand Coulee Dam, Powerplant, and Pumping Plant, and Banks Lake also are operated by the Bureau of Reclamation as reserved works.

Other

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Overview

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Construction

Construction of the Columbia Basin Project, including Grand Coulee Dam and all related features, was assigned to the Bureau of Reclamation. Funds were made available by the Public Works Administration on July 27, 1933, by an allotment of $63 million under section 202 of the National Industrial Recovery Act.

A temporary project headquarters was established at Almira, Wash., 21 miles from the damsite. Excavation for the base of the dam, and construction of highway and railroad connections to the damsite and the necessary construction camp facilities was started in December 1933. In August 1934, the first of two major contracts for the construction of Grand Coulee Dam and Powerplant was awarded. Originally, the building of Grand Coulee Dam was planned in two stages. A low dam was to be built first, with a foundation designed so that a high dam could later be superimposed on it. A pumping plant and other components of the irrigation system also would be added in the second stage.

On August 30, 1935, the Congress authorized construction of the high dam and the irrigation project.

From 1933 to 1941, construction of the dam proper proceeded on a rapid schedule. By 1941, Grand Coulee Dam was essentially completed, the Left Powerhouse constructed, and the foundations placed for the Right Powerhouse and pumping plant.

During World War II, efforts centered entirely on the installation of hydroelectric power generating units in the Left Powerhouse. During this period, six 108,000-kilowatt Grand Coulee generators, two 75,000-kilowatt generators scheduled for Shasta Dam, and two 10,000-kilowatt station service generators were installed. After World War II, the two Shasta generating units were removed and three 108,000-kilowatt generators were installed in the Left Powerhouse to complete the nine planned units. A third station service generator was installed, and the Right Powerhouse completed with nine 108,000-kilowatt units installed. The last of the eighteen 108,000-kilowatt generating units was placed in commercial operation in September 1951. Thus, about 18 years after the beginning of construction on Grand Coulee Dam, the powerplant was completed as originally planned, and maximum power production was available to meet power needs in the Pacific Northwest and to pump irrigation water for the Columbia Basin Project lands.

The eighteen 108,000-kilowatt generating units were rewound to increase the rating of each unit to 125,000 kilowatts. The first unit was rewound in 1964, and the last unit was completed in August 1980.

Construction of the Third Powerplant formally began July 12, 1967, when the contract was awarded to modify the then existing switchyards, especially the right powerhouse switchyard where the forebay and forebay dam would be located. Excavation of the forebay began with a contract award on December 5, 1967. The first unit in the powerplant, rated at 690,000 kilowatts, went into operation in August 1975, and the fourth unit, rated at 805,000 kilowatts, went on the line in April 1978. The sixth and last unit was completed in May 1980, which basically completed the Third Powerplant as authorized. The stator windings in the last three units were replaced starting in October 1996 and completed in December 1998.

Due to downstream river fluctuations resulting from power peaking operations following construction of the Third Powerplant, extensive downstream riverbank protection work was done in the 7 miles just downstream of the dam. Major stabilization features included installation of automatic drainage wells, water level monitoring, monitoring wells including earth movement, three vertical drainage shafts with horizontal drainage pipes, reshaping and placing armor rock for the entire 6 miles both underwater and above water, and a real-time computer monitoring system. Currently there is a 22-foot tailbay drawdown restriction over a 24-hour period. The stabilization program exceeded $75 million in contract costs.

Construction of Irrigation Facilities
Construction of Grand Coulee Pumping Plant began in 1946. By 1951, six 65,000-horsepower pumps had been installed to serve the initial irrigation development on the project. Immediately following World War II, construction started on the primary irrigation facilities. In the spring of 1952, the first irrigation water was delivered to the irrigation system, then serving about 66,000 irrigable acres.

However, the delivery of irrigation water to this large acreage in 1952 did not mark the first irrigation of project lands. In 1948, a pumping plant on the Columbia River near Pasco was completed that served about 5,400 acres on Irrigation Block 1 (Pasco Pumping Unit). In 1950, the Burbank Pumping Plant on the Snake River south of Pasco brought water to about 1,200 acres in Irrigation Block 2 (Burbank Pumping Unit). Block 1 now receives water from the Potholes Canal.

In 1973, two of the pump-generator units were installed, each unit rated at 67,500 horsepower when pumping and 50,000 kilowatts when generating. In 1983 and early 1994, the remaining four pump/generating units, each rated at 67,500 horsepower when pumping and 53,500 kilowatts when generating, were placed in service.

Since 1952, extending the major canals and constructing relift pumping plants and lateral systems has progressed on a regular schedule. As a result, irrigation of land on the Columbia Basin Project has proceeded in an orderly and efficient manner, which has brought about a well rounded development. Roads, schools, towns to serve the newly irrigated lands, and many other aspects of the settlement and growth of a newly irrigated area have kept pace with the Bureau of Reclamation`s schedule of construction.

Benefits

Irrigation
Construction of the Columbia Basin Project has brought some 671,000 acres under irrigation.

The soil and climatic conditions are favorable to the growth of grain, alfalfa hay, ensilage crops, dry beans, fruit, sugar beets, potatoes, sweet corn, and seed and other specialty crops. Dairy farming and beef production are significant in the area.

Recreation
Stretching from as far north as the Canadian border and south to Pasco, Washington, the Columbia Basin Project offers a vast recreation resource base characterized by long summers, mild winters, and an abundance of year-round sunshine. There are 350,000 acres of land and water available for recreation. Prior to development of the project, there were 35 lakes; there are now over 140 lakes, ponds, and reservoirs.

Franklin D. Roosevelt Lake is the largest reservoir on the project; it stretches for 151 miles with about 600 miles of shoreline. A portion of the lake area has been designated a National Recreation Area and is administered by the National Park Service. Portions of the lake area within the Colville Confederated Tribes Reservation and the Spokane Tribe Reservation are managed by the respective tribes through a management agreement with Reclamation, NPS, and BIA.

Reclamation's visitor center at Grand Coulee Dam is also the starting point for guided tours of the dam and powerplant complex. Recreation facilities have been constructed at many of the project reservoirs. There are State parks at Banks Lake, Billy Clapp Lake, and Potholes Reservoir, and a county park at Scooteney Reservoir.

The Columbia Basin is on the Pacific Flyway, a major waterfowl migration route, and the many acres of wetlands within the project area are used by numerous species. There is excellent hunting, and pheasant, a favorite upland game bird, has been stocked throughout the project. A portion of the Potholes Reservoir area has been included in the Columbia National Wildlife Refuge which is administered by the Fish and Wildlife Service.

The Bureau of Reclamation and the Washington State Department of Fish and Wildlife have cooperated in stocking most bodies of water in the project area with a variety of fish which provide year-round fishing.

Power
The average annual net generation for the Grand Coulee Powerplant from 1994 through 2005 was about 21.2 billion kilowatt-hours; this compares to an average of 11 to 15 billion kilowatt-hours prior to the Third Powerplant. Hydroelectric power generated at Grand Coulee Dam furnishes a large share of the power requirements in the Pacific Northwest. Energy produced by the Third Powerplant alone is sufficient to furnish the power needs for the cities of Seattle and Portland. As required by law, the revenue derived from this power not only will repay the power investment but also will repay a large portion of the irrigation investment on the Columbia Basin Project.

The power operation at Grand Coulee is for both base load and peaking power.

Flood Control
Sufficient space is maintained in Franklin D. Roosevelt Lake to control the Columbia River at The Dalles to no more than 450,000 cubic feet per second. Flood control parameter curves specify the amount of space required based on the forecasted runoff at The Dalles adjusted for available upstream storage capacity other than at Grand Coulee Dam. The forecast of runoff at The Dalles is made by the US Army Corps of Engineers Reservoir Control Center at Portland, Oregon. The flood control operation for the entire Columbia River is dictated by the Corps of Engineers during the flood control season.

The Grand Coulee Reservoir has 5,232,000 acre feet of capacity assigned to flood control. The Grand Coulee Project has provided an accumulated $173,976,000 in flood control benefits from 1950 to 1998.