Thomson Dam (Minnesota)

Last updated

Thomson Dam
Thomson Dam, Minnesota.jpg
Downstream face of the main Thomson Dam on the St. Louis River in 2017
USA Minnesota relief location map.svg
Red pog.svg
Location of Thomson Dam in Minnesota
Location Carlton County, Minnesota, U.S.
Coordinates 46°39′59.10″N92°24′25.80″W / 46.6664167°N 92.4071667°W / 46.6664167; -92.4071667 Coordinates: 46°39′59.10″N92°24′25.80″W / 46.6664167°N 92.4071667°W / 46.6664167; -92.4071667
Purpose Power
Construction began1905
Opening date1907
1914-48 expanded [1]
2012 damaged
2014 reconstructed
Built by Great Northern Railway
Owner(s) Minnesota Power
Dam and spillways
Type of dam Earth Embankment, Concrete Gravity, Arch
Impounds Saint Louis River
HeightMain: 15 ft (4.6 m) [2]
Canal: 45 ft (14 m)
LengthMain: 1,600 ft (490 m) [2]
Canal: 3,500 ft (1,100 m)
Spillways 2
Spillway typegated
Spillway capacity60,000 cu ft/s (1,700 m3/s) [3]
CreatesThomson Reservoir
Total capacity4,352 acre⋅ft (5,368,000 m3) [2]
Catchment area 9,154 sq mi (23,710 km2) [2]
Surface area649 acres (263 ha) [4]
Thomson Hydro
Coordinates 46°39′17.91″N92°20′1.032″W / 46.6549750°N 92.33362000°W / 46.6549750; -92.33362000
Hydraulic head 375 ft (114 m)
Turbines 6 [1]
Installed capacity 72 MW [1]
Annual generation 280 GWh [5]

Thomson Dam, also known as the Thomson Hydro Station [1] or Thomson Water Project, [6] is an embankment and concrete gravity dam on the Saint Louis River near the town of Thomson in northeastern Minnesota, United States. It consists of a 1600-foot (488 m) long primary structure and multiple supplementary dams which, together with precambrian rock outcrops known as the Thomson formation, impound the river to create Thomson Reservoir.


The tallest dam in the complex is 51.6 feet (16 m) and the longest is 3500 feet (1067 m). A series of gate houses, a canal, forebay, and underground penstocks supply a hydropower plant located 3 miles away in Jay Cooke State Park. With an installed capacity of 72 MW and an annual generation of approximately 280 GWh, the Thomson project is the largest hydroelectric facility in the state. [7]


Thomson Dam was completed in 1907 by Great Northern Power, an operating division of the Great Northern Railway. The generating station was expanded in 1914 with the addition of Unit 4. [1] Unit 5 was added in 1918 and Unit 6 in 1948. Railroad tracks built into the generator floor allowed for installation and maintenance of the equipment. The complex was later transferred to the Saint Louis Power Company. Today it is owned by Minnesota Power, a division of Allete, Inc. [8]

Heavy rains in June 2012 created an historic flood in the region which overtopped the dam, breached the forebay canal and severely damaged the hydroelectric station. Following $90 million in reconstruction and upgrades, including the addition of a new emergency spillway, the facility came back online in November, 2014. Additional upgrades will continue through 2018, including removal of the original 46kV transmission line equipment in favor of other, higher voltage equipment that was added later. [3] [9]


The most visible part of Thomson Dam is the primary structure straddling the Saint Louis River channel near Minnesota State Highway 210. However, the Thomson Project is actually composed of multiple dams and control structures, several of which have been rebuilt and merged over the years. Today the United States Army Corps of Engineers National Inventory of Dams (NID) counts 18 structures as part of the complex, with 14 formally listed as separate. [2]

Thomson Dam - NID Registered Structures
Dam IDOther IDNameHeightWidthType
MN00604Thomson Dam15 ft (4.6 m)1,600 ft (490 m) Embankment and concrete gravity
MN00604S010Thomson Canal Dam45 ft (14 m)3,500 ft (1,100 m) Embankment
MN83020S011Thomson Dam #1-1/210 ft (3.0 m)90 ft (27 m) Embankment
MN83021S001Thomson Dam #2A, 2B23 ft (7.0 m)530 ft (160 m)na
MN83022S012Thomson Dam #2-1/29 ft (2.7 m)130 ft (40 m) Concrete gravity
MN83023S002Thomson Dam #3
(Nos 2-3/4, 3, 3A, 4, 4A)
38 ft (12 m)1,322 ft (403 m) Concrete gravity
MN83024S003Thomson Dam #523 ft (7.0 m)100 ft (30 m) Concrete gravity
MN83025S013Thomson Dam #5-1/223 ft (7.0 m)115 ft (35 m) Concrete gravity
MN83026S004Thomson Dam #651.6 ft (15.7 m)125 ft (38 m) Concrete arch
MN83027S005Thomson Dam #812 ft (3.7 m)100 ft (30 m)na
MN83028S006Thomson Dam #911 ft (3.4 m)100 ft (30 m) Concrete gravity
MN83029S007Thomson Dam #1011 ft (3.4 m)80 ft (24 m) Concrete gravity
MN83030S008Thomson Dam #11
(Nos. 11, 11-1/2 and Upper Gate House)
17 ft (5.2 m)365 ft (111 m) Concrete gravity
MN83031S009Thomson Dam #1212 ft (3.7 m)450 ft (140 m) Embankment

See also

Related Research Articles

<span class="mw-page-title-main">Hydropower</span> Power generation via movement of water

Hydropower, also known as water power, is the use of falling or fast-running water to produce electricity or to power machines. This is achieved by converting the gravitational potential or kinetic energy of a water source to produce power. Hydropower is a method of sustainable energy production. Hydropower is now used principally for hydroelectric power generation, and is also applied as one half of an energy storage system known as pumped-storage hydroelectricity. Hydropower is an attractive alternative to fossil fuels as it does not directly produce carbon dioxide or other atmospheric pollutants and it provides a relatively consistent source of power. Nonetheless, it has economic, sociological, and environmental downsides and requires a sufficiently energetic source of water, such as a river or elevated lake. International institutions such as the World Bank view hydropower as a low-carbon means for economic development.

<span class="mw-page-title-main">Small hydro</span> Hydroelectric project at the local level with a few MW production

Small hydro is the development of hydroelectric power on a scale suitable for local community and industry, or to contribute to distributed generation in a regional electricity grid. Exact definitions vary, but a "small hydro" project is less than 50 megawatts (MW), and can be further subdivide by scale into "mini" (<1MW), "micro" (<100 kW), "pico" (<10 kW). In contrast many hydroelectric projects are of enormous size, such as the generating plant at the Three Gorges Dam at 22,500 megawatts or the vast multiple projects of the Tennessee Valley Authority.

<span class="mw-page-title-main">Pumped-storage hydroelectricity</span> Electric energy storage system

Pumped-storage hydroelectricity (PSH), or pumped hydroelectric energy storage (PHES), is a type of hydroelectric energy storage used by electric power systems for load balancing. The method stores energy in the form of gravitational potential energy of water, pumped from a lower elevation reservoir to a higher elevation. Low-cost surplus off-peak electric power is typically used to run the pumps. During periods of high electrical demand, the stored water is released through turbines to produce electric power. Although the losses of the pumping process make the plant a net consumer of energy overall, the system increases revenue by selling more electricity during periods of peak demand, when electricity prices are highest. If the upper lake collects significant rainfall or is fed by a river then the plant may be a net energy producer in the manner of a traditional hydroelectric plant.

<span class="mw-page-title-main">Hydroelectricity</span> Electricity generated by hydropower

Hydroelectricity, or hydroelectric power, is electricity generated from hydropower. Hydropower supplies one sixth of the world's electricity, almost 4500 TWh in 2020, which is more than all other renewable sources combined and also more than nuclear power. Hydropower can provide large amounts of low-carbon electricity on demand, making it a key element for creating secure and clean electricity supply systems. A hydroelectric power station that has a dam and reservoir is a flexible source, since the amount of electricity produced can be increased or decreased in seconds or minutes in response to varying electricity demand. Once a hydroelectric complex is constructed, it produces no direct waste, and almost always emits considerably less greenhouse gas than fossil fuel-powered energy plants. However, when constructed in lowland rainforest areas, where part of the forest is inundated, substantial amounts of greenhouse gases may be emitted.

<span class="mw-page-title-main">Robert Moses Niagara Power Plant</span> Niagara River dam in New York State

The Robert Moses Niagara Hydroelectric Power Station is a hydroelectric power station in Lewiston, New York, near Niagara Falls. Owned and operated by the New York Power Authority (NYPA), the plant diverts water from the Niagara River above Niagara Falls and returns the water into the lower portion of the river near Lake Ontario. It uses 13 generators at an installed capacity of 2,525 MW (3,386,000 hp).

<span class="mw-page-title-main">Run-of-the-river hydroelectricity</span> Hydroelectric power station

Run-of-river hydroelectricity (ROR) or run-of-the-river hydroelectricity is a type of hydroelectric generation plant whereby little or no water storage is provided. Run-of-the-river power plants may have no water storage at all or a limited amount of storage, in which case the storage reservoir is referred to as pondage. A plant without pondage is subject to seasonal river flows, thus the plant will operate as an intermittent energy source. Conventional hydro uses reservoirs, which regulate water for flood control, dispatchable electrical power, and the provision of fresh water for agriculture.

According to the International Hydropower Association, Canada is the fourth largest producer of hydroelectricity in the world in 2021 after the United States, Brazil, and China. In 2014, Canada consumed the equivalent of 85.7 megatonnes worth of oil of hydroelectricity, 9.8% of worldwide hydroelectric consumption. Furthermore, hydroelectricity accounted for 25.7% of Canada's total energy consumption. It is the third-most consumed energy in Canada behind oil and natural gas.

The Mount Coffee Hydropower Project is a hydroelectric project in the West African nation of Liberia on the Saint Paul River. Built in 1966 with additional phases completed later, the project has a maximum generating capacity of 88 MW. The Walter F. Walker Hydro Dam and generating facilities were extensively damaged during the First Liberian Civil War in 1990 and functioning was not restored until 2018.

<span class="mw-page-title-main">Mingachevir Dam</span> Dam in Mingachevir

The Mingachevir Dam is an earth-fill embankment dam on the Kura River just north of Mingachevir in Azerbaijan. It serves several purposes to include hydroelectric power production and water storage for irrigation. The Mingachevir reservoir, behind the dam, supplies water to the Upper Qarabag and Upper Sirvan Channels which help irrigate about 1,000,000 ha of farmland in the country. Its six Francis turbine-generators were overhauled or replaced with 70 megawatts (94,000 hp) sets in 2000. Mingachevir reservoir has a storage capacity of 15.730 cubic kilometres (12,753,000 acre⋅ft), covering 605 km2 (234 sq mi). The length of the dam is 1,550 metres (5,090 ft), its width is 16 metres (52 ft) and height is 80 m (260 ft). It is the largest hydroelectric power station in the South Caucasus, is located over Kur river and not far from Mingachevir city.

<span class="mw-page-title-main">Farkhad Dam</span> Dam in Spitamen, Sughd Province

The Farkhad Dam is a hydroelectric and irrigation dam on the Spitamen in Sughd Province, Tajikistan. It is a part of the Naryn-Syr Darya Cascade. The dam is located on the territory of Tajikistan and controlled by Tajikistan, while the Farkhad hydropower station, operated by Uzbekenergo.

Ohio Falls Station is a hydroelectric power station owned by Louisville Gas & Electric (LG&E) and Kentucky Utilities (KU) which is located three miles west of Downtown Louisville, Kentucky. The generating station is located on Shippingport Island at the site of the McAlpine Dam and locks along the Ohio River in Kentucky. The plant was built in 1923 by Byllesby Engineering and Management Corporation and the U.S. Army Corps of Engineers. The plant featured eight 10.4 MW units operating at roughly 13,500 hp per unit. Each unit was composed of Allis Chamber turbines and General Electric generators. The plant is located inside the Ohio Natural Wildlife Conservation Area and is considered a large impoundment hydro power plant. The station was built after a canal and dam within the Ohio river in an attempt to allow boats to navigate the 8 ft vertical drop among the falls that spanned 2 miles wide. Production of the canal and dam began in 1825. It was not until a repair on the dam was needed that Louisville engineers had the idea of building a hydroelectric station to harvest the power of the falls.

<span class="mw-page-title-main">Broadlands Dam</span> Dam in Kitulgala

The Broadlands Dam is a 35 MW run-of-the-river hydroelectric complex currently under construction in Kitulgala, Sri Lanka. The project is expected to be completed in 2020, and will consist of two dams, and a power station further downstream.

<span class="mw-page-title-main">Kakhovka Hydroelectric Power Plant</span> Dam and power plant in Kherson, Ukraine

The Kakhovka Hydroelectric Station is a run-of-river power plant on the Dnieper River in Nova Kakhovka, Ukraine. Nova Kakhovka is a port city located on the reservoir's southern bank. The primary purposes of the dam are hydroelectric power generation, irrigation and navigation. It is the 6th and the last dam in the Dnieper reservoir cascade. The deep water channel allows shipping up and down river. The facility also includes a winter garden.

The Duber Khwar Hydropower Plant is located near the town of Pattan in Kohistan, Khyber Pakhtunkhwa, Pakistan on the Duber Khwar River, a right bank tributary of the Indus River. It is approximately 340 km NW from Islamabad, the federal capital of Pakistan.

The Moragolla Dam is a planned hydroelectric dam in Moragolla, Sri Lanka. The dam is to be 35 m (115 ft) high and is planned to create the 1,980,000 m3 (70,000,000 cu ft) Moragolla Reservoir with a maximum supply level at 548 m (1,798 ft) MSL. Upon completion, the Moragolla Power Station would have a gross installed capacity of 30 megawatts from two francis turbines, capable of generating approximately 85 GWh annually.


  1. 1 2 3 4 5 "Thomson Hydro Station". Minnesota Power: Our System. Retrieved July 30, 2017.
  2. 1 2 3 4 5 "CorpsMap: National Inventory of Dams". United States Army Corps of Engineers. October 2016. Retrieved July 29, 2017.
  3. 1 2 Peterson, Jana; Lund, Jamie (June 22, 2017). "Carlton County rebuilds smarter after devastating 2012 flood". Pine Journal. Retrieved July 30, 2017.
  4. "Thomson Reservoir". Minnesota Power: Reservoirs and Recreation. Retrieved July 30, 2017.
  5. "2015 Integrated Resource Plan" (PDF). Minnesota Power. September 1, 2015.
  6. "Thomson Dam, Thomson, MN". John A. Weeks III. Retrieved July 30, 2017.
  7. "Listing of Minnesota Hydropower Facility Sites" (PDF). Minnesota Department of Natural Resources. 2017. Retrieved July 30, 2017.
  8. "Hometown Hydropower: History". Minnesota Power. April 23, 1979. Retrieved July 30, 2017.
  9. "Minnesota Power invests in safety improvements to hydro system". Minnesota Power is an ALLETE Company. January 20, 2017. Retrieved July 30, 2017.