Hiwassee Dam
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| Hiwassee Dam | |
|---|---|
 | |
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| Official name | Hiwassee Dam |
| Location | Cherokee County, North Carolina, U.S. |
| Coordinates | 35°9′5″N 84°10′39″W / 35.15139°N 84.17750°W |
| Construction began | July 15, 1936 |
| Opening date | February 8, 1940 |
| Operator | Tennessee Valley Authority |
| Dam and spillways | |
| Impounds | Hiwassee River |
| Height | 307 ft (94 m) |
| Length | 1,376 ft (419 m) |
| Reservoir | |
| Creates | Hiwassee Lake |
| Total capacity | 434,000 acre⋅ft (535,000 dam3) |
| Catchment area | 968 sq mi (2,510 km2) |
| Power Station | |
| Installed capacity | 185 MW |
Hiwassee Dam is a hydroelectric dam on the Hiwassee River in Cherokee County, in the U.S. state of North Carolina. It is one of three dams on the river owned and operated by the Tennessee Valley Authority, which built the dam in the late 1930s to bring flood control and electricity to the region.[1] The dam impounds the Hiwassee Lake of 6,000 acres (2,400 ha), and its tailwaters are part of Apalachia Reservoir. At 307 feet (94 m), Hiwassee Dam is the highest overspill dam east of the Mississippi River and is second only to Grand Coulee dam in the nation.[2] At the time it was completed, it was the highest overspill dam in the world.[3][4]
Hiwassee Dam is the third highest dam in the TVA system, behind only Fontana and Watauga.[5] The dam and associated infrastructure was listed on the National Register of Historic Places in 2017.[6] Hiwassee Dam is classified by the U.S. Army Corps of Engineers as a high-hazard dam, meaning a dam failure may pose a deadly threat to nearby residents. The dam's condition is not made available to the public due to security concerns.[7][8]
Hiwassee Dam is named after the Hiwassee River.[1] The river's name is derived from the Cherokee word for savanna, or large meadow. Two of the tribe's towns along the river in the 18th century were also called Hiwassee.[9]
The Hiwassee River flows northwestward from its source in Towns County, Georgia through Western North Carolina, where it proceeds to slice a scenic valley through the southern Appalachian Mountains en route to its mouth along Chickamauga Lake in Tennessee.
Hiwassee Dam was constructed nearly 76 miles (122 km) above the river's mouth, at the downstream end of a large bend in the river known as Fowler Bend. The dam is 10 miles (16 km) upstream from Apalachia Dam (which is near the Tennessee-North Carolina state line) and 45 miles (72 km) downstream from Chatuge Dam. Hiwassee Dam and its reservoir are surrounded by the Nantahala National Forest.
Hiwassee Village, a small community that developed alongside the dam and reservoir, is located immediately south of Hiwassee Dam. North Carolina Secondary Road 1314 (Hiwassee Dam Access Road) crosses the top of the dam.
Capacity
Hiwassee Dam is a concrete, gravity-overflow dam 307 feet (94 m) high and 1,376 feet (419 m) long, and has a generating capacity of 185,000 kilowatts.[10] The dam's spillway is controlled by seven radial gates, which, along with four regulating conduits at the bottom of the dam, give the dam a total maximum discharge of 112,000 cubic feet per second (3,200 m3/s).[1][5]
Hiwassee Lake stretches along the river for approximately 22 miles (35 km) to the town of Murphy, North Carolina. It has 180 miles (290 km) of shoreline, a storage capacity of 434,000 acre⋅ft (535,000 dam3), and 205,590 acre⋅ft (253,590 dam3) of flood storage.[1][10] The reservoir's operating level varies by roughly 38 feet (12 m) in a typical year.[10]
Pumped storage
In the 1950s, TVA began experiments with pumped storage at Hiwassee Dam. It used an energy-generating turbine that was run in reverse during low-demand hours to pump water from below the dam into the upper reservoir. This integration of pump and turbine was the first of its kind in the United States; further, at the time it was the largest and most powerful pump in the world, capable of pumping 1,750,000 gallons of water per minute.[4] The "pump-turbine" at Hiwassee is designated as a "National Historic Mechanical Engineering Landmark" by the American Society of Mechanical Engineers (ASME).[11][12]
