Idaho is home to some majestic landscapes, but not all of its lakes are natural. In fact, there are more than 30 dams across the state, which create man made lakes. Let’s examine the largest man-made lake in the state and what purpose it serves.
The Largest Man-Made Lake in Idaho
Located near the historic town of American Falls, American Falls Reservoir is the largest man-made lake in Idaho. At full pool, this freshwater reservoir features a surface area of 56,000 acres or 87 square miles. That makes American Falls Reservoir not only the largest reservoir but also the third-largest lake in the state. The original thought behind the American Fall Reservoir aimed to provide water storage and irrigation for agricultural production. Today, the reservoir also generates electric power (via the American Falls Dam) and provides protection against flooding.
American Falls Reservoir features over 100 miles of shoreline for visitors to explore. While it ranks as the largest reservoir in Idaho in terms of surface area, it lags other reservoirs in capacity. American Falls Reservoir holds a total capacity of 1,671,300 acre-feet. That means it holds less than half the amount of water as Dworshak Reservoir, which contains 3,469,900 acre-feet of water. This makes sense, given American Falls Reservoir’s average depth is 30 feet, much less than Dworshak’s 636-foot maximum depth.
Numerous important ecological sites border American Falls Reservoir. The Fort Hall Bottoms wetlands lie near the northern end of the reservoir, which gets fed by the Snake River. Ten miles to the southwest lies the Minidoka National Wildlife Refuge. Approximately 200 different bird species live or visit the reservoir, making it one of the most diverse bird locations in Idaho. The reservoir also supports a variety of different native and introduced game fish.
In particular, the reservoir features some of the best rainbow trout fishing in the state. Aside from fishing, other water recreation activities in the area include boating, canoeing, swimming, water skiing, and windsurfing. Alternatively, many visitors come to the area to hike, picnic, or appreciate the reservoir’s scenery and wildlife. Keep reading to learn more about the history and geography of the largest man-made lake in Idaho.
Where Is American Falls Reservoir Located on a Map?
American Falls Reservoir is located 18.1 miles to the west of the town American Falls. It can be reached from the town in 27 minutes’ drive. State Route 39 traverses the top of the reservoir’s dam for more than 0.5 miles. The reservoir is part of three counties in Idaho: Bannock, Bingham, and Power.
History of American Falls Reservoir
For 10,000 years, Native American tribes lived in the lands around the modern-day American Falls Reservoir. The Shoshone and Bannock communities kept permanent settlements around the Snake River in southern Idaho and hunted and fished along its borders. In fact, the nearby city of Pocatello to the southeast of the reservoir gets its name from Chief Pocatello, a mid-19th century Northern Shoshone chief. Several wars, including the Snake War and Bannock War, eventually drove the Shoshone and Bannock tribes off of most of their native land and onto reservations.
In the early 1880s, the town of American Falls was platted along the Snake River. The town gets its name from a waterfall on the river, which in turn got its name from a group of American trappers whose boat went over the falls. By the early 19th century, increased demand for agricultural irrigation in southern Idaho led to calls for additional irrigation projects. Around the same time, the U.S. Bureau of Reclamation started work on the Minidoka Project. The project consisted of a series of dams and canals located along the Snake River in Idaho and Wyoming to control flooding and provide irrigation. The 1902 National Reclamation Act then made it possible for the sale of public lands to expand irrigation for farmland and food production. In the same year, the first power plant was built along the American Falls.
Creating the Reservoir
The Bureau of Reclamation started building the original dam at American Falls in 1925. In order to complete the project, the entire town of American Falls had to be relocated outside the proposed reservoir zone. This marked the first time in the history of the United States that an entire town got relocated. Construction of the dam finished in 1927, but the original dam began to fail within just 40 years. A second dam was planned and constructed just downstream of the original dam, with construction taking place between 1976 and 1978. The new American Falls Dam stands 94 feet high and measures 5,277 feet long. This concrete gravity-type dam contains a power plant that consists of three generators. Together, these generators can produce 112 megawatts of hydroelectricity, enough energy to power between 48,000 and 108,000 homes each year.
American Falls Reservoir resides within the Snake River Plain in southern Idaho. Although the American Falls Dam sits within Power County, the reservoir also borders Bingham and Bannock counties. The Snake River feeds into the northern part of the reservoir. Meanwhile, the American Falls Dam rests at the southern end of the reservoir. The basin of the reservoir consists mostly of silt, sand, and gravel. Much of this sediment came from a shallow lake created by a lava dam that emerged over a million years ago. To this day, the Snake River continues to erode its surrounding channel and deposits new sediment into the reservoir.
Several small communities surround American Falls Reservoir. Most of the landscape in the area is dedicated to farming and ranching. Some of the small, unincorporated communities in the area include Sterling, Fairview, Bannock, Fingal, and Springfield. The larger town of Aberdeen is located to the west of the reservoir. Meanwhile, the largest city in the area, Pocatello, resides to the east. The town of American Falls, from which the reservoir gets its name, lies to the south of the reservoir and next to the American Falls Dam.
You can find numerous points of interest in the area around American Falls Reservoir. The Fort Hall Bottoms on the northern shores of the reservoir features diverse wetlands. In addition to fishing and bird-watching, the area also contains numerous sites of great importance to the local Shoshone and Bannock tribes. Ten miles west of the reservoir lies Massacre Rocks, an important site along the Oregon Trail. Massacre Rocks State Park features interesting rock formations created by flooding that occurred in the region around 14,500 years ago. These formations, along with local wildlife, make it a popular hiking and camping location.
Reviews of American Falls Reservoir and its surrounding parks tend to be overwhelmingly positive. The reservoir offers plenty of recreational opportunities, including water sports, boating, hiking, and sightseeing. Anglers frequently mention that the reservoir features excellent fishing opportunities. As a matter of fact, the largest catch-and-release rainbow trout on record in the state was caught in the reservoir in 2020. The reservoir also boasts excellent perch fishing, as a decent angler can haul in dozens of perch in a single day. You can access the reservoir from multiple boat ramps, and most sites feature plenty of parking. Additionally, the nearby Massacre Rocks State Park features plenty of camping and hiking opportunities, as well as an 18-hole disc golf course.
However, not everyone who visits the area around American Falls Reservoir reports having a good time. People who visit the town of American Falls state that there isn’t much to do there. It has few restaurants, only one major grocery store, a gas station, and no retail stores to speak of. If you want to go shopping, you’ll need to go to Pocatello, a 30-minute drive east. Additionally, visitors tend to avoid visiting the reservoir in the winter. Drops in the reservoir water levels leave visible rings around the edges of the reservoir, which many people consider unsightly. That said, you can still enjoy a visit to American Falls Reservoir in winter, especially if you like ice fishing.
FAQs (Frequently Asked Questions)
What is the largest man-made lake in Idaho?
Located near the historic town of American Falls, American Falls Reservoir is the largest man-made lake in Idaho. At full pool, this freshwater reservoir features a surface area of 56,000 acres or 87 square miles. That makes American Falls Reservoir not only the largest reservoir but also the third-largest lake in the state.
Is the American Falls Reservoir a good place to visit?
Reviews of American Falls Reservoir and its surrounding parks tend to be overwhelmingly positive. The reservoir offers plenty of recreational opportunities, including water sports, boating, hiking, and sightseeing. Anglers frequently mention that the reservoir features excellent fishing opportunities.
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- , Available here: https://idfg.idaho.gov/visit/hatchery/american-falls
- , Available here: https://www.niche.com/places-to-live/american-falls-power-id/reviews/
- , Available here: https://www.recreation.gov/camping/gateways/105