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U.S. Department of the Interior
The principal features of the project are Palisades Dam Reservoir, and Powerplant. Palisades Dam is on the South Fork of the Snake River at Calamity Point in eastern Idaho about 11 miles west of the Idaho-Wyoming boundary. The project provides a supplemental water supply to about 650,000 acres of irrigated land in the Minidoka and Michaud Flats Projects. The 176,600 kilowatt hydroelectric powerplant furnishes energy needed in the upper valley to serve irrigation pumping units, municipalities, rural cooperatives, and other power users. The principal features of the project are Palisades Dam, Reservoir, and Powerplant.
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The project, in addition to providing needed holdover storage, helps control floods, develops a substantial block of power, and permits the annual storage of about 135,000 acre-feet of water saved by shutting off canals in the upper valley during the winter. This water is stored to the credit of and delivered to the water users who make the savings possible.
Releases from Palisades Reservoir are diverted and carried to the land by previously constructed facilities.
Located on the Snake River about 55 miles southeast of Idaho Falls, Idaho, Palisades Dam is a large zoned earthfill structure 270 feet high, has a crest length of 2,100 feet, and contains 13,571,000 cubic yards of material. At the time of construction, this was the largest volume of material placed in a dam by the Bureau of Reclamation. The spillway is a 28-foot-diameter tunnel through the left abutment, with a capacity of 48,500 cubic feet per second. The outlet works and power inlet structures are controlled by a fixed-wheel gate at the entrances of the inclined shafts leading to 26-foot-diameter tunnels. The outlet tunnel conveys the water to the steel manifold transition section, where it is released to the stilling basin by regulating gates. At the lower end of the power tunnel, the water may be released to the stilling basin or to four penstocks and conveyed to the turbines for power generation. The capacity of the outlet works is 33,000 cubic feet per second. The dam creates a reservoir of 1,401,000 acre-feet capacity (active 1,200,000 acre-feet).
The powerplant is on the downstream toe of the dam on the west side of the river and initially had a total capacity of 118,750 kilowatts. The powerplant was uprated in 1994 and all four units were rewound increasing the nameplate capacity to a total of 176,600 kilowatts; 44,150 kilowatts each. As part of the mitigation for the powerplant uprate, a fish screen was constructed on Palisades Creek, a small tributary which joins the Snake River approximately 3 miles downstream from the dam.
Operating Agencies
The Bureau of Reclamation operates and maintains the project.
Following the drought period of the early 1930`s, a need was recognized for additional storage for lands already under irrigation in the Minidoka Project and in private developments, and investigations of various reservoir sites were made upstream from American Falls Dam. The Palisades site was selected for the construction of the dam and reservoir to provide holdover storage to supplement the water supply for existing irrigated lands, to develop a limited acreage of new lands, to provide flood control, and to generate electrical power. Intensive investigations at the location as now developed were started by the Bureau of Reclamation in 1934.
Authorization
The project was initially authorized by the Secretary of the Interior on December 9, 1941, under the provisions of Section 9 of the Reclamation Project Act of August 4,1939 (53 Stat. 1187, Public Law 76-260). Reauthorization of the project by the Congress occurred on September 30, 1950 (64 Stat. 1083, Public Law 81- 864), substantially in accordance with a supplemental report approved by the Secretary of the Interior on July 1, 1949.
The authorized purposes of the Palisades Project are irrigation, power, flood control, and fish and wildlife.
Construction
The preconstruction phase of the project was started early in 1945. Construction was delayed until the close of World War II and until local interests gave satisfactory assurance to the Bureau of Reclamation that they would agree to important practices in the efficient water use of the entire Upper Snake River Basin through the workings of winter water savings and exchange agreements that were entered into by some 57 water entities as a part of the Palisades Project. Actual construction of the project was initiated in 1951 and completed in 1957. All generating units of the powerplant were in operation by May 1958.
Palisades Dam provides holdover storage during years of average or above average precipitation for release in ensuing dry years to lands of the Upper Snake River Valley, the area served by diversions from the river above Milner Dam. This holdover storage assures an adequate supply of supplemental water for about 650,000 acres of irrigated lands in the valley. Principal crops are grain, alfalfa, pasture, dry beans, potatoes, sugar beets, other vegetables, and seeds.
In 1994, the United States entered into a contract with Mitigation, Inc., which provided that entity with non-contracted irrigation storage space in Palisades (18,980 acre-feet) and Ririe (80,500 acre-feet) Reservoirs in order to protect existing non-Indian water users from adverse effects that might result from implementation of the 1990 Fort Hall Indian Water Rights Agreement and Fort Hall Indian Water Rights Act of 1990. (104 Stat. 3061, Public Law 101-602).
Recreation, Fish & Wildlife
Palisades Reservoir is in a scenic river valley with forested hillsides rising from the water to the towering snowcapped mountains which form the background. Since the reservoir is paralleled by U.S. Highway 26, much of the recreational use is by tourists. The reservoir has about 70 miles of shoreline and six access roads have been built. Recreation at Palisades Reservoir is administered by the Targhee National Forest headquartered in St. Anthony, Idaho. Public use facilities include six campgrounds, five picnic areas, and six boat ramps. Two boat clubs have facilities on the reservoir and private cabins have been constructed under lease from the Forest Service. The Bureau of Reclamation has developed a day-use area and campground below the dam to provide fishing and boat launching on the Snake River.
In 1991, the State of Wyoming entered into a contract with the Bureau of Reclamation for the purchase of 33,000 acre-feet of `joint use` space in Palisades Reservoir. All Palisades Reservoir spaceholder contracts provide for use of a proportionate share of the water accruing to the Palisades Reservoir water rights, the ability to keep unused stored water for use in subsequent years, and the option of participating in the Water District 1 Rental Pool. Additionally, Wyoming has the option of making exchanges to allow the use of their Palisades Reservoir space to retain water in Jackson Lake or to increase winter flows in the Snake River to benefit cutthroat trout. The Palisades Reservoir space also insures Wyoming's ability to fulfill Snake River Compact obligations.
Hydroelectric Power
The Palisades Powerplant serves large irrigation pumping power requirements on and near the Minidoka Project in southern Idaho. Power not needed for Bureau of Reclamation project purposes is marketed in the Federal Southern Idaho Power System administered by the Bonneville Power Administration.
Flood Control
The project also provides substantial flood control benefits. A flood control operating plan has been established with the Corps of Engineers and several local interests. The plan provides for the joint use of storage capacity during flood seasons for irrigation and flood control on the basis of periodic runoff forecasts. Flood control space is held in Jackson Lake and Palisades Reservoir on a forecast basis to control the Snake River near Heise, about 48 miles below Palisades Dam, to no more than 20,000 cubic feet per second.
Endangered Species Act
In March 2005 the Fish and Wildlife Service (FWS) and National Marine Fisheries Service (NMFS) provided Biological Opinions on Reclamation's Operations and Maintenance of 12 projects and associated facilities in the Snake River Basin above Lower Brownlee Reservoir. If conditions don't change these Opinions should be valid for 30 years.
The FWS determined that Reclamation's proposed actions were not likely to jeopardize the continued existence of ESA listed species in the Snake River basin. The Opinion includes an Incidental Take Statement with Reasonable and Prudent Measures and associated Terms and Conditions to minimize incidental take for bull trout and Utah valvata. The FWS's Opinion contains its conclusions for each species in Chapters 4 through 9, respectively. Reclamation provided a Decision Document in Novemeber of 2005 as well as a Monitoring and Implementation Plan in March of 2006.
NMFS concluded that Reclamation's proposed actions were not likely to jeopardize the continued existence of the 13 salmon and steelhead evolutionarily significant units (ESUs) or adversely modify or destroy critical habitat that is designated for 3 fo the ESUs. A summary of its conclusions is contained in Section 8 of the Biological Opinion. The Opinion includes an Incidental Take Statement with Reasonable and Prudent Measures and associated Terms and Conditions to minimize incidental take.
