American Falls Dam
| Company type | Government project |
|---|---|
| Industry | Water management, Hydroelectric power |
| Founded | 1925 |
| Founder | United States Bureau of Reclamation |
| Headquarters | American Falls , United States |
Area served | Snake River Plain, Idaho |
| Products | Flood control, irrigation, hydroelectric power, recreation |
| Parent | United States Bureau of Reclamation |
The American Falls Dam is a concrete gravity structure situated on the Snake River near the city of American Falls, Idaho. As an integral component of the Minidoka Project within the Snake River Plain, its main functions include flood mitigation, irrigation support, and recreational use. Initially constructed in the 1920s by the United States Bureau of Reclamation, the project necessitated relocating approximately 75% of American Falls town to make way for the reservoir.
A new dam replaced the original in 1978, which was subsequently dismantled. Although the dam is positioned in Power County, Idaho, its reservoir stretches into neighboring Bingham County, Idaho and Bannock County, Idaho.
Geology
During the late Pliocene, over a million years ago, a lava flow created a natural dam that formed a broad, shallow lake in the Raft River region. This basin gradually filled with fine sand, silt, and gravel before the lava dam broke and drained the lake. These deposits, referred to as the Raft Formation, underlie much of today’s American Falls Reservoir. At various periods, basalt flows completely obstructed the Snake River channel. One such lava dam downstream of the current American Falls Dam led to sediment accumulation exceeding in thickness, consisting of clay, silt, and sand. This layered sequence of basalt flows and sedimentary deposits, overlain by more recent lacustrine sediments, is known as the Snake River Group and American Falls Lake Beds. These geological processes continued until the late Pleistocene, less than one million years ago. Since then, the Snake River has persistently eroded its basalt bedrock and reshaped lake bed sediments.
Geography
Positioned on the Snake River Plain, American Falls Dam sits at an elevation of above sea level.[1] The terrain around it features gently rolling hills with elevation variations under . The original waterfall occurs where the river constricts to roughly wide and drops approximately in a series of cascades over fractured basalt rock.[2] The final plunge measures about .
1880–1925
The town of American Falls was initially surveyed and laid out during the early 1880s, taking its name from a nearby waterfall on the Snake River. In the late nineteenth century, privately funded irrigation canals began supporting agricultural development across southern Idaho and adjacent areas. The Carey act of 1894 encouraged private investment in irrigation infrastructure. By 1895, plans for an irrigation project at American Falls were submitted to the Idaho State Land Board. The federal government’s 1902 Newlands Reclamation Act provided funding for irrigation projects in Western states through proceeds from public land sales. The first hydroelectric power facility on the falls was constructed in 1902 and later acquired by Idaho Power Company in 1916.[3]
Constructing dams became the favored approach for controlling Western water resources,[4]
In 1923, government acquisition of the original townsite through eminent domain triggered legal disputes, notably BROWN v. U S, 263 U.S. 78 (1923), which determined that compensation must reflect property values including streets and improvements that required reconstruction at the relocated site.[5]
1925–1960
The Bureau of Reclamation initiated construction of the first American Falls Dam in 1925, completing it by 1927. To accommodate the newly formed reservoir, the Oregon Short Line Railroad bridge was elevated. This initial dam design was attributed to Frank A. Banks.
1960–1978
The existing American Falls Dam represents the second dam bearing this name. In the early 1960s, core testing uncovered chemical reactions within the original concrete that weakened its structural integrity. Following congressional approval in 1973, a replacement dam was constructed downstream and finished in 1978.
In 1976, Idaho Power Company established a hydroelectric facility at the dam equipped with three generators capable of producing 112,420 kilowatts (112 MW). That year, after the upstream failure of the Teton Dam, American Falls Dam discharged water rapidly to mitigate flooding risks downstream. Although the reservoir's water level increased, it did not reach the spillway threshold.
The dam's enlargement met resistance from Shoshone and Bannock groups due to concerns over flooding at Fort Hall Bottoms—ancestral lands occupied for more than 10,000 years and crucial for their traditional resources. Environmental experts also opposed the project, citing potential destruction of habitats and damage to significant fossil sites.
See also
External links
- American Falls Dam at US Bureau of Reclamation
- American Falls Dam at Idaho Public TV
- Data from American Falls Dam (downstream) related to Teton Dam Failure
- Construction of the American Falls Dam
- ↑ [[[:Template:Gnis3]] USGS Place names]
- ↑ Conley, Cort (1982). Idaho for the Curious. Cambridge, Idaho: Backeddy Books. p. 261. ISBN 0-9603566-3-0.
- ↑ Idaho Power – American Falls
- ↑ ensuring consistent irrigation supply downstream throughout low-flow periods via canal systems.
- ↑ "BROWN v. U S, 263 U.S. 78 (1923)". Supreme Court of the United States. 1923-11-12. Retrieved 2007-03-31.