Ryan Dam is a

hydroelectric dam Hydroelectricity, or hydroelectric power, is electricity generated from hydropower (water power). Hydropower supplies one sixth of the world's electricity, almost 4500 TWh in 2020, which is more than all other renewable sources combined an ...

on the Missouri River, downstream from the city of Great Falls in the

U.S. state In the United States, a state is a constituent political entity, of which there are 50. Bound together in a political union, each state holds governmental jurisdiction over a separate and defined geographic territory where it shares its sove ...

Montana Montana () is a U.S. state, state in the Mountain states, Mountain West List of regions of the United States#Census Bureau-designated regions and divisions, division of the Western United States. It is bordered by Idaho to the west, North ...

. The dam is long and high; its

reservoir A reservoir (; from French ''réservoir'' ) is an enlarged lake behind a dam. Such a dam may be either artificial, built to store fresh water or it may be a natural formation. Reservoirs can be created in a number of ways, including control ...

is long and has a storage capacity of . It is a

run-of-river 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 amo ...

dam. The dam is built on the largest of the five

Great Falls of the Missouri The Great Falls of the Missouri River are a series of waterfalls on the upper Missouri River in north-central Montana in the United States. From upstream to downstream, the five falls along a segment of the riverCutright, Paul Russell, and J ...

, the " Big Falls", also sometimes called "Great Falls". Since 1915, the six-unit powerhouse on the left side of the dam has occupied a significant portion of the high waterfall. The dam, built in 1915 just upstream of the falls and a small island named Ryan Island, is divided into two parts. On the right side of the dam is a concrete-arch spillway structure, that when functioning, releases water over the remains of the waterfall. The center part of the dam consists of a dike that extends from the falls' base to Ryan Island (separating the

tailrace A water wheel is a machine for converting the energy of flowing or falling water into useful forms of power, often in a watermill. A water wheel consists of a wheel (usually constructed from wood or metal), with a number of blades or bucket ...

from the main river, which it meets a few hundred yards downstream). It also contains a concrete gravity structure facing towards the right bank of the river and tilted to face slightly downstream. This segment of the dam contains the

outlet works A gatehouse, gate house, outlet works or valve house for a dam is a structure housing sluice gates, valves, or pumps (in which case it is more accurately called a pumping station). Many gatehouses are strictly utilitarian, but especially in the n ...

, a water jet that bursts out and cascades over the waterfall. The left side of the dam is a large powerhouse topped by a concrete gravity structure.

Montana Power Company The Montana Power Company (MPC) was an electric utility company based in Butte, Montana, which provided electricity to Montana consumers and industry from 1912 to 1997. History The Montana Power Company was founded in 1912 by John D. Ryan, then ...

originally built the dam,

PPL Corporation PPL Corporation is an energy company headquartered in Allentown, Pennsylvania in the Lehigh Valley region of eastern Pennsylvania. The company is publicly traded on the New York Stock Exchange. History Pennsylvania Power & Light was founded in 1 ...

purchased it in 1997 and sold it to

NorthWestern Corporation NorthWestern Corporation owns NorthWestern Energy, a utility company that serves South Dakota, Nebraska, and Montana that is based in Sioux Falls. , the company serves approximately 718,000 customers. The company's corporate headquarters are loca ...

in 2014. Since the dam's construction in the Missouri River gorge, it has flooded a fair portion of the Great Falls - the cascades between Grand Fall and Crooked Falls, which lies several miles upstream - and reduced the flow over Great Falls to such an extent that much of the bedrock is visible. The dam was constructed on top of a cascade that Lewis and Clark observed to lie just upstream of Grand Fall. The next dam upstream is Cochrane Dam, then

Rainbow Dam Rainbow Dam is a hydroelectric dam on the Missouri River, high and long, located six miles northeast of Great Falls in the U.S. state of Montana. History The dam is named for the downstream Rainbow Falls, a waterfall that is the third of t ...

, and Black Eagle Dam. The next dam downstream is Morony Dam.

References

External links

Ryan Dam at pplmontana.com
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Historic American Engineering Record Heritage Documentation Programs (HDP) is a division of the U.S. National Park Service (NPS) responsible for administering the Historic American Buildings Survey (HABS), Historic American Engineering Record (HAER), and Historic American Landscapes ...

(HAER) documentation, filed under Missouri River, Northeast of Great Falls, Cascade County, MT: ** ** ** ** ** {{Authority control Arch-gravity dams Buildings and structures in Cascade County, Montana Dams completed in 1915 Dams in Montana Dams on the Missouri River Energy infrastructure completed in 1915 Historic American Engineering Record in Montana NorthWestern Corporation dams Run-of-the-river power stations 1915 establishments in Montana