Montana's Hydroelectric Portfolio

Thompson Falls Dam is a seven-unit, run-of-the-river, 94-Megawatt facility on the lower Clark Fork River. Completed in 1915. 


Hebgen Dam backs up a storage reservoir on the upper Madison River. The dam was completed in 1915 and is named for a general manager of the Montana Power Company. A history of the dam is available on the NorthWestern Energy website. 

Hebgen Dam

The Madison Dam is a four-unit, run-of-the-river, 9-Megawatt facility on the Madison River at the head of Bear Trap Canyon. Originally built in 1901 with replacement in 1905-06. NorthWestern Energy portfolio.


Hauser Dam is a six-unit, 19-Megawatt, run-of-the-river facility on the upper Missouri River. Completed in 1911 following failure of initial dam in 1908. Hauser is part of the NorthWestern Energy portfolio.


Holter Dam is a four-unit, 48-Megawatt, run-of-the-river facility on the Missouri River. Completed in 1918. NorthWestern Energy portfolio.


Black Eagle is a three-unit, 21-Megawatt, run-of-the-river facility on the Missouri River. Completed in 1891 with new dam and powerhouse rebuild in 1926-27. NorthWestern Energy portfolio.

Black Eagle

Rainbow is a single-unit, 60-Megawatt, run-of-the-river, Missouri River. Completed in 1910 with eight-unit, 35-Megawatt capacity; new single-unit powerhouse completed in 2013. NorthWestern Energy portfolio.


Cochrane is a two-unit, 64-Megawatt, run-of-the-river facility on the Missouri River. Completed in 1958. NorthWestern Energy portfolio.


Morony is a two-unit, 48-Megawatt, run-of-the-river on the Missouri River. Completed in 1930. NorthWestern Energy portfolio.


Ryan Dam is a six-unit, run-of-the-river, 60-Megawatt facility on the Missouri River. Completed in 1915 as Volta Dam. NorthWestern Energy portfolio.


Formerly known as Kerr Dam, Seli's Ksanka Qlispe' is a three-unit, storage facility generating 194 Megawatts on the Flathead River at the outlet of Flathead Lake. Completed in 1938. Confederated Salish and Kootenai Tribes exercised an option to purchase in 2015 as the PPL hydroelectric portfolio was being transferred to NorthWestern Energy.    

Mystic Lake is a two-unit, 12-Megawatt, storage facility on Rosebud Creek in the Beartooth Mountains. Completed in 1925. NorthWestern Energy portfolio.


Fort Peck is the largest earth-fill hydroelectric facility in the U.S. Construction was started in 1933 on the Missouri River with full-pool attained about 1940. Generators were installed in the 1940s and today the facility has three generating units completed in 1951 at 105 Megawatts, and two completed in 1961 at 80 Megawatts. Generation is divided between the Western Interconnect and the Eastern Interconnect with one generator capable of switching between the two. The facility is named for an old trading post in the area and is operated and managed by the U.S. Army Corps of Engineers.          

Fort Peck

Milltown Dam was built as Clark Dam in 1908 at the confluence of the Blackfoot and Clark Fork Rivers. It was a run-of-the-river facility with a capacity of about 3 Megawatts. The dam backed up a great deal of metal-laden sediment dating to the flood year of 1908. The dam was decommissioned and removed between 2007 and 2010. 

A run-of-the-river facility does not rely on stored water to turn generators; rather, while each backs up water in a reservoir, the flow of the river is adequate to generate electricity at, or near, nameplate capacity. Storage facilities are sometimes called impoundment facilities and use stored water releases to generate electricity, oftentimes to address demand calls. In Montana, these types of facilities were usually built as multi-purpose projects to provide irrigation, flood control, as well as electricity generation.

The images of the Madison, Hauser, Black Eagle, Cochrane, and Ryan Dam are provided from NorthWesern Energy's Hydroelectric Facilities page .

Canyon Ferry Dam Image provided by Helena