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Glendo Unit
Photo of Glendo Dam and Reservoir
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Pick Sloan Missouri Basin Program
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Glendo Unit History (56 KB) (pdf)
General Description | Plan | Development | Benefits
General Description

The Glendo Unit is a multiple-purpose natural resource development. It consists of Glendo Dam, Reservoir and Powerplant, Fremont Canyon Powerplant, and Gray Reef Dam and its reregulating reservoir. The unit features, which are located on the North Platte River in eastern and central Wyoming, are adjacent to and work in conjunction with other units of the Pick-Sloan Missouri Basin Program, as well as the Kendrick and North Platte Projects.

The unit furnishes a maximum of 40,000 acre-feet of water annually from Glendo Reservoir for irrigation in Wyoming and Nebraska, and electrical power is supplied to Wyoming, Colorado, and Nebraska by Glendo and Fremont Canyon Powerplants, which have installed capacities of 38,000 and 66,800 kilowatts, respectively.

The Glendo Unit is operated in conformity with the North Platte River Decree of 1945. It provides irrigation, power generation, flood control, fish and wildlife enhancement, recreation, sediment retention, pollution abatement, and improvement of the quality of municipal and industrial water supply in the North Platte River Valley between Gray Reef Dam and Glendo Reservoir.

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The irrigation water from Glendo Reservoir is delivered to water users in the North Platte River Valley at and below Whalen Diversion Dam, a feature of the North Platte Project. These water users have early natural flow water rights but no storage rights and, therefore, need the dependable storage provided by Glendo Reservoir.

An amendment to the North Platte River Decree was approved in 1953 by the States of Colorado, Wyoming, and Nebraska, and by the U.S. Supreme Court. It provides for retaining the existing regimen of the natural flow of the North Platte River below Pathfinder Dam, except that not more than 40,000 acre-feet of water plus space obtained by evaporation losses may be stored in Glendo Reservoir for irrigation during any water year, and the amount held in storage at any time for irrigation may not exceed 100,000 acre-feet. The amended decree permits the release from storage of 15,000 acre-feet of water annually to Wyoming and 25,000 acre-feet annually to Nebraska for irrigation.

Within the limits of the amended decree, storage facilities of the North Platte River system provide considerable flexibility. Maximum capacity for regulation and storage is afforded through exchange of water between Glendo Reservoir and upstream reservoirs. Exchange water stored in Glendo is released by the close of the irrigation season. The proprietary and contractual interests in storage water are identifiable at all times regardless of location of the water in the system. Floodwater stored in Glendo Reservoir is released under regulations prescribed by the Secretary of the Army under authority of the Flood Control Act of 1944.

Facility Descriptions
Glendo Dam, Reservoir, and Powerplant

Glendo Dam is a zoned earthfill structure on the North Platte River about 4.5 miles southeast of Glendo. The embankment has a structural height of 190 feet and a length of 2,096 feet along the crest. About 2,800 feet of dikes are required across a low area on the south side of the reservoir 1.5 miles west of the dam. The dam forms a reservoir 14 miles in length, having a total capacity of 795,196 acre-feet at water surface elevation 4653, the top of the flood control capacity. Space is provided in the reservoir for storing 115,000 acre-feet of sediment, an estimated 100-year accumulation. There are 454,337 acre-feet allotted for irrigation and power and 271,917 acre-feet for flood control. In addition, a surcharge capacity of 329,251 acre-feet is available. These capacities differ slightly from the original storage allocations because of sediment accumulation.

An uncontrolled concrete spillway 45 feet wide is located about 450 feet north of the right abutment of the dam. The Glendo Powerplant is joined to the Glendo Reservoir by a diversion tunnel 21 feet in diameter and 2,100 feet long. The plant contains two units having a maximum rated head of 130 feet. Each unit has an installed capacity of 19,000 kilowatts.

Fremont Canyon Powerplant

The Fremont Canyon Powerplant, on the left bank of the North Platte River at the head of Alcova Reservoir, consists of two 33,400-kilowatt generators, driven by two 33,500-horsepower Francis-type hydraulic turbines. The turbines operate at a maximum head of 350 feet and an effective head of 300 feet. The powerplant generates power during releases of stored floodwater, irrigation water, and water to satisfy prior water rights from Pathfinder Reservoir of the North Platte Project. Water for power generation is conveyed to the powerplant by a 3-mile-long 18-foot-diameter, concrete-lined pressure tunnel. The tunnel branches to two 10.75-foot-diameter penstocks upstream of the powerplant. This conduit is controlled by a 14- by 18-foot fixed-wheel gate located 243 feet downstream from the inlet. Access to the powerplant is provided by a 1,692-foot-long unlined tunnel 16.5 feet high and containing a 16-foot-wide roadway.

Gray Reef Dam and Reservoir

Gray Reef Dam is on the North Platte River about 27 miles southwest of Casper, and 2 miles downstream from Alcova Dam. The earthfill structure has a structural height of 36 feet, a crest length of 650 feet, and contains a volume of 40,000 cubic yards of material.

The spillway consists of a concrete chute near the center of the dam controlled by two 35- by 20-foot radial gates. Capacity of the spillway is 20,000 cubic feet per second. There are no outlet works in the dam.

The reservoir has a total capacity of 1,800 acre-feet, with a surface area of 182 acres. Gray Reef Reservoir is operated to reregulate widely fluctuating water releases from the Alcova Powerplant of the Kendrick Project.

Operating Agencies

The Bureau of Reclamation operates and maintains all of the unit`s works.

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From the beginning of the early settlement, livestock ranching has been the principal economic activity in the area. The North Platte River Valley served as a passage for early explorers and later as a route for settlers from the eastern States through the higher plains to the Rocky Mountains and the western States. Sites of stations which served the Pony Express, the Overland Stage, and the first transcontinental telegraph are still to be found.

The first irrigation systems in the valley were built shortly after 1880 without large storage reservoirs. The North Platte Project, authorized by the Congress in 1903, was completed in 1927. Pathfinder Dam and Reservoir were built during 1905-1909. The Guernsey Dam and Reservoir were completed in 1927. The Kendrick Project was first investigated in 1904, and construction started in 1936. Seminoe and Alcova Dams were completed in 1939.


Preliminary investigations for the Kortes Unit started in 1933 and for the Glendo Unit in 1944. Both were included in Senate Document 191 as a part of the Missouri River Basin Project and were authorized for construction under the Flood Control Act of 1944.

The original authorization provided for a storage capacity of approximately 150,000 acre-feet in the Glendo Reservoir for additional sediment storage and replacement of capacity lost to sediment in Guernsey Reservoir; reregulation of return flows from upstream irrigation; and flood control and the development of power. Subsequent investigations disclosed the necessity for increasing the capacity of Glendo Reservoir to provide for adequate control in the highly developed reach of the North Platte River Valley in Wyoming and Nebraska below the Glendo Reservoir site and the reregulation of upstream power releases so river water could be utilized more effectively for hydroelectric power production. As a result of these investigations, the total storage capacity was increased to 798,000 acre-feet, exclusive of a flood surcharge capacity of an additional 330,000 acre-feet.


The Glendo Unit was authorized for construction under the Flood Control Act of December 22, 1944, Public Law 534, which approved the general plan set forth in Senate Documents 191 and 475, as revised and coordinated by Senate document 247, 78th Congress, 2d session. The project was reauthorized by Public Law 503, 83d Congress, on July 16, 1954.

Construction of Gray Reef Dam and Reservoir was authorized separately by Public Law 85-695 (72 Stat. 687), approved August 20, 1958.


Construction began December 1954 on the Glendo Dam, Reservoir, and Powerplant and was completed in 1958. Construction of the Fremont Canyon Powerplant and power conduit was begun in 1956 and completed in 1961. Construction of Gray Reef Dam and Reservoir was started in 1959 and completed in 1961.

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Water is released from Glendo Reservoir to supplement the irrigation water supplies of contracting users in Wyoming and Nebraska. The water users need dependable storage in addition to their natural flow water rights. This makes possible the improvement of crop production and an increased crop yield. Principal crops are beans, potatoes, alfalfa, corn, and small grains.

Recreation, Fish & Wildlife

The Unit provides opportunities for recreation, fishing, and hunting. Camping, picnicking, boating, and water sports opportunities are available at Glendo Reservoir. A boat ramp, accessible restroom, accessible fishing pier, picnic tables, and campground are located immediately below Gray Reef Dam. Glendo Reservoir is stocked with fish by the Wyoming Game and Fish Commission and, to a lesser extent, fishing is afforded at Gray Reef Reservoir. Hunting for waterfowl is available at both reservoirs.

Hydoelectric Power

Addition of Glendo Unit power generation facilities increases available power in the North Platte River Basin by about 500 million kilowatt-hours annually. This increase comes principally from the Glendo and Fremont Canyon Powerplants; however, some of the gain is due to the conversion of the Alcova Powerplant from seasonal to year-round operation made possible by the regulation afforded by Glendo Reservoir.

Flood Control

Glendo Reservoir has an exclusive flood control capacity of 271,917 acre-feet and a surcharge capacity of 329,251 acre-feet for a total flood capacity of 601,168 acre feet and controls floods that menaced the local area and the valley downstream prior to construction of the dam. As of 1998, Glendo Reservoir has prevented $49.6 million in flood damages.

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Last updated: Jul 23, 2012