Ryan Dam is a

hydroelectric dam Hydroelectricity, or hydroelectric power, is Electricity generation, electricity generated from hydropower (water power). Hydropower supplies 15% of the world's electricity, almost 4,210 TWh in 2023, which is more than all other Renewable energ ...

on the

Missouri River The Missouri River is a river in the Central United States, Central and Mountain states, Mountain West regions of the United States. The nation's longest, it rises in the eastern Centennial Mountains of the Bitterroot Range of the Rocky Moun ...

, 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 so ...

Montana Montana ( ) is a landlocked U.S. state, state in the Mountain states, Mountain West subregion of the Western United States. It is bordered by Idaho to the west, North Dakota to the east, South Dakota to the southeast, Wyoming to the south, an ...

. The dam is long and high; its

reservoir A reservoir (; ) is an enlarged lake behind a dam, usually built to water storage, store fresh water, often doubling for hydroelectric power generation. Reservoirs are created by controlling a watercourse that drains an existing body of wa ...

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 amou ...

dam. The dam is built on the largest of the five Great Falls of the Missouri, 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 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 ni ...

, 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 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 as and is part of the S&P 500. As of 2022, the compa ...

purchased it in 1997 and sold it to NorthWestern Corporation 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, and Black Eagle Dam. The next dam downstream is Morony Dam.

References

External links

Ryan Dam at pplmontana.com
*

Historic American Engineering Record Heritage Documentation Programs (HDP) is a division of the U.S. National Park Service (NPS). It administers three programs established to document historic places in the United States: Historic American Buildings Survey (HABS), Historic American E ...

(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