1991 North Platte Hydrology Study

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9 North Platte Project Nebraska: Morrill, Sioux, and Scotts Bluff Counties Wyoming: Carbon, Goshen, Natrona, and Platte Counties Lower Missouri Region Bureau of Reclamation The North Platte Project extends 111 miles along the river valley from near Otiernsoy, W"., to below Bri4ge- The city of Scottsbluff is near the center of the development. The project provides water for irriga- tion of approximatel t -, into f r° f distrfts. A sup t # is f rr*ish- ed.,v- eight° water- user associations serving a combined area.of about 109,000 acres. Electric power is supplied to the project area. Project features are the PmW&udqr Dam and Reservoir; GUftis� Dam, Reservoir, and Powerplant;- "alai Diversion Dam; L = L&e 1Vhmtare, and two other regulating reservoirs; over 2, a,als, laterals, and drains; and about 160 miles of electric power transmission lines. PLAN The North Platte River, fed by many mountain streams rising in the Rocky Mountains of Colorado and Wyo- ming, is the most important river in southeastern Wyo- ming and western Nebraska. Its waters are stored and used for irrigation and power development for the North Platte Project, the Kendrick Project, and the Kortes and Glendo Units of the Pick -Sloan Missouri Basin Program. Storage structures for these projects are interspersed along the North Platte River and require close coordina- tion of operations. Project operation is further complicated by agreements and laws governing water rights. The use and quantity of water are allocated for certain defined purposes —some on a priority basis, some on a proportionate share basis, and some on a geographical source basis. Pathfinder Dam and Reservoir Waters of the North Platte River must pass the Seminoe alld Kortes Dams before entering the reservoir atE fi , which impound9 the flow from Sweotwatft Wer. Pathfinder Reservoir has a storage capacity of Rev. 9/81 (From Project Data Book) 1 sere -f#et and holds much of the North Platte Project water. During the nonva#osion *@awn,& mall amount 424xar ed -to *atisfy other water rights, enhance fish and wildlife, and operate powerplants downstream. During the irrigation season, water is released as required, including water flowing from Sem- inoe Reservoir to be diverted at Alcova Dam for irriga- tion on the Kendrick Project. Pathfinder Dam is one of the first constructed by the Reclamation Service. The dam is in a granite canyon on the North Platte River about 3 miles below its junction with the Sweetwater River and about 47 miles southwest of Casper, Wyo. It is made of granite quarried from nearby hills and is faced with large rectangular blocks laid in horizontal courses. It is an arch dam with a gravity -type section, and has a structural height of 214 feet. Pathfinder Dike fills a depression in the natural ground surface about 0.25 mile south of the dam. It is an earth - fill structure, 38 feet high, with a concrete corewall. Guernsey Dam and Powerplant One hundred and eighty miles below Alcova Dam and m belowlen consols riWr,flow. Water released from Pathfinder Reservoir can be stored and released to fit varying irrigation demands. Water is released through the ( ogplant. Guernsey Dam is in a rocky canyon 2 miles upstream from Guernsey, Wyo. It is a diaphragm -type embank- ment of sluiced clay, sand, and gravel that forms an im- pervious core. Its slopes are protected by a thick layer of rock riprap. The structural height of the dam is 135 feet. The m^iginal capacity of the reservoir was 73,810 oote- feet, but this has been greatly reduced by silt deports. The powerplant is on the right bank below the dam and has tvro 2,400- kilowatt generator. Power is transmitted to towns and industries down the valley over project and other interconnected transmission system lines.