Lower Granite Dam

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Lower Granite Dam
View from the northwest
Country United States
Location Garfield / Whitman counties,
Coordinates 46°39′38″N 117°25′41″W / 46.66056°N 117.42806°W / 46.66056; -117.42806Coordinates: 46°39′38″N 117°25′41″W / 46.66056°N 117.42806°W / 46.66056; -117.42806
Construction began July 1965
Opening date June 1975 [1]
Construction cost $624,098,663[2]
Operator(s) U.S. Army Corps of Engineers
Dam and spillways
Type of dam Gravity dam
Impounds Snake River
Height 100 ft (30 m)
Length 3,200 ft (980 m)
Spillway type Service, gate-controlled
Spillway capacity 850,000 cu ft/s (24,000 m3/s)
Creates Lower Granite Lake
Total capacity 440,200 acre·ft (0.5430 km3)[3]
Surface area 8,900 acres (36 km2)
Normal elevation 741 ft (226 m)
Power station
Type Run-of-the-river
Turbines 6 × 135-155 MW units[4]
Installed capacity 810 MW
Columbia River Basin

Lower Granite Lock and Dam is a concrete gravity run-of-the-river dam on the Snake River, and bridges Whitman County and Garfield County, in the U.S. state of Washington.[5] The dam is located 22 miles (35 km) south of the town of Colfax, and 35 miles (56 km) north of Pomeroy.

Lower Granite Dam is part of the Columbia River Basin system of dams. It was built and is operated by the United States Army Corps of Engineers. Power generated is distributed by the Bonneville Power Administration.

Lower Granite Lake, which extends 39 miles (63 km) east to Lewiston, Idaho, is formed behind the dam. Lake Bryan, formed from Little Goose Dam, runs 37 miles (60 km) downstream from the base of the dam.


Construction began in July 1965, but was halted less than two years later.[6] Work restarted in 1970 and the main structure and three generators were completed in 1975.[1] An additional three generators were finished in May 1978,[7][8] bringing the generating capacity to 810 megawatts, with an overload capacity of 932 MW. The spillway has eight gates and is 512 feet (156 m) long. An 86-by-74-foot (26 m × 23 m) navigation lock was also included in construction.[2]


Lower Granite Dam is the most upstream dam in the Snake River system that has a fish ladder to allow adult salmon and steelhead to migrate upstream. The Columbia River treaty tribes along with some environmental groups have recommended that this dam along with the other three lower Snake River dams be decommissioned and/or removed because of their impact on threatened and endangered chinook (threatened) and sockeye salmon (endangered) and steelhead (threatened) populations.,[9][10] A significant increase in the Sockeye Salmon return to the Columbia River in 2008 proved a pleasant surprise and raised hopes for increased salmon runs across the Lower Granite. Wildlife officials were not certain of the reason for the increased salmon return (Idaho Statesman, June 28, 2008) The Army Corps of Engineers has installed new devices such as removable spillway weirs in an attempt to make the dam less harmful to juvenile salmon.

There is also a juvenile bypass/collection facility that collects juvenile migrating salmon and steelhead so they can be transported downstream by barge.

Navigation lock
  • Single-lift
  • 86 feet (26 m) wide
  • 674 feet (205 m) long
Lower Granite Dam with the lock in the center, the power generation on the south side of the river, and spillway in the middle of the dam, between the powerhouse and the lock.

See also[edit]


  1. ^ a b Harrell, Sylvia (June 20, 1975). "Dedication: Andrus brings a warning". Lewiston Morning Tribune. p. 1. 
  2. ^ a b "LOWER GRANITE LOCK AND DAM--LOWER GRANITE LAKE". U.S. Army Corps of Engineers. Retrieved 17 July 2010. 
  3. ^ "The Four Lower Snake River Dams". Bluefish.org. Retrieved 17 July 2010. 
  4. ^ "Lower Granite Dam". Washington.edu. Retrieved 17 July 2010. 
  5. ^ "The Columbia River System Inside Story". BPA.gov. pp. 14–15. Retrieved 17 July 2010. 
  6. ^ "Engineers award contract for Lower Granite Dam". Lewiston Morning Tribune. May 14, 1970. p. 16. 
  7. ^ "Lower Granite power complex complete". Lewiston Morning Tribune. May 13, 1978. p. 6A. 
  8. ^ "Lower Granite Dam powerhouse finished". Spokane Daily Chronicle. May 16, 1978. p. 15. 
  9. ^ http://www.pcffa.org/fn-aug99.htm
  10. ^ "5-Year Review: Summary & Evaluation of Snake River Sockeye, Snake River Spring-Summer Chinook, Snake River Fall-Run Chinook, Snake River Basin Steelhead". National Oceanic and Atmospheric Administration. 2011. Retrieved 2013-12-03. 

External links[edit]