Discover

The 'American Falls Dam' is a concrete gravity-type dam located near the town of American Falls, Idaho, on the Snake River. The dam and reservoir are a part of the Minidoka Irrigation Project on the Snake River Plain and are used primarily for flood control, irrigation, and recreation. When the original dam was built by the Bureau of Reclamation, the residents of American Falls were forced to relocate three-quarters of their town to make room for the reservoir.^[2] A second dam was completed in 1978 and the original structure was demolished.

Contents

Geology

Geography

1880-1925

1925-1960

1960-1978

External links

References

Geology

A lava dam created a broad shallow lake in the area of the Raft River during late Pliocene time, over one million years ago. Much of the basin filled with fine sand, silt, and gravel; then the dam was breached and the lake drained. These sediments (called the Raft Formation) lie beneath most of the present-day American Falls Reservoir. At other times the Snake River was dammed completely by basalt flows extruded from vents. One lava dam a few miles downstream from the present American Falls Dam formed a reservoir in which more than 80 feet of sediments (clay, silt, and sand) were deposited. This series of basalt flows and original sediments were covered by the new lake bed sediments and are named the Snake River Group and the American Falls Lake Beds. These events occurred up until the late Pleistocene, less than one million years ago. The Snake River has continued to erode its channel in the basalt and modify the lake bed sediments until the present time. Water resources of the Aberdeen – Springfield area, Bingham & Power Counties, Idaho, , Paul M., Castelin, Idaho Department of Water Administration, 1974,

Geography

The dam at American Falls is on the Snake River Plain at an elevation of 4357/1328 (ft/m). The topography in the immediate vicinity of the river is gently rolling, with differences in elevation of less than 200 ft (60 m). The original falls occur where the river channel narrows to about 600 ft (180 m) and cascades about 50 ft (15 m) in several 6-10 ft. drops over highly jointed basalt. ^[3] The final drop is about a 15 ft. plunge.

1880-1925

Plans for Power House on American Falls (1902)

The city of American Falls was first platted in the early 1880s. It was named for the waterfall on the Snake River near the settlement. During the last part of the 19th century, privately financed irrigation canals were created to sustain the emerging agriculture industry in southern Idaho and other parts of the west. The Carey act (1894) paved the way for private investment in irrigation projects. By 1895, the American Falls irrigation project came before the Idaho State Land Board. In 1902 the National Reclamation Act was signed into law and federal funds from the sale of public lands became available to create and maintain irrigation projects in the Western United States. The first power plant was built in 1902 on the falls.
Damming the rivers became the preferred method for harnassing the abundant water of the western rivers. Irrigated Agriculture Idaho's Economic Lifeblood Sherl L. Chapman The reservoirs could then provide year-round downstream irrigation via canals, even during traditional low water times.
The use of eminent domain by the government to appropriate the original townsite in 1923 resulted in several lawsuits. One in particular, ''BROWN v. U S, 263 U.S. 78 (1923) '' allowed that the property valuation should include the value of the streets and improvements which would need to be replaced in the substitute site. BROWN v. U S, 263 U.S. 78 (1923)

1925-1960

American Falls Dam (1947)

Power House on American Falls (1947)

The first dam at American Falls was begun in 1925 by the Bureau of Reclamation and was completed in 1927. The river was temporarily impounded while the new concrete structure was put in place. The Oregon Short Line Railroad bridge over the river had to be raised to allow for crossing the new reservoir. Construction of the American Falls Dam

1960-1978

The existing dam is the second structure to be called the American Falls Dam. Core samples taken in of the concrete of the original structure Minidoka project' , had deteriorated so a second dam was built just downstream in 1978. Replacement of the original dam was authorized by a congressional act of December 28, 1973 (87 Stat. 904, Public Law 93-206) A act to authorize the Secretary of the Interior to convey certain facilities of the Minidoka project to the Burley Irrigation District, and for other purposes
When the second dam was planned, members of the Shoshone and Bannock communities opposed expansion as it would further flood the lands of the Fort Hall Bottoms. Native Americans have inhabited this region for at least 10,000 years and the area is an important resource for them. Many scientists were opposed as well because of the loss of natural habitat and access to fossil records of the Bottoms.^[4]

External links

American Falls Dam

★ American Falls Dam at US Bureau of Reclamation

★ American Falls Dam at Idaho Public TV

★ Data from American Falls Dam (downstream) from the Teton Dam Failure

References

1. United States Bureau of Reclamation
2. American Falls Dam
3. Idaho for the Curious, , Cort, Conley, Backeddy Books, ,
4. Expansion of Idaho reservoir: Indians, scientist on the warpath, , Bryce, Nelson, Science (New Series),