Madison Dam

Madison Dam
Madison Dam, January 2015
Location	Madison County, Montana
Coordinates	45°28′12″N 111°38′18″W / 45.47012°N 111.63831°W / 45.47012; -111.63831Coordinates: 45°28′12″N 111°38′18″W / 45.47012°N 111.63831°W / 45.47012; -111.63831
Purpose	Hydroelectric, Flood Control, Water Supply, Recreation
Owner(s)	PPL MONTANA, LLC
Operator(s)	NorthWestern Corporation
Dam and spillways
Type of dam	Timber Crib
Spillway capacity	7700 cfs
Reservoir
Total capacity	42053 ac.ft.

Madison Dam is a hydroelectric dam on the Madison River in Madison County, Montana, in the southwestern part of the state.

The timber-crib dam was constructed in 1906 as a replacement for a similar 1901 dam and powerhouse on the same site. The dam is 39 feet high and 257 feet long at its crest,^[1] placed into the narrows of Bear Trap Canyon. As one of eight PPL Montana hydro projects, it has a generating capacity of nine megawatts in a run-of-the-river configuration.^[2] Montana Power Company acquired the dam in 1912 as part of a merger, PPL Corporation purchased it in 1997 and sold it to NorthWestern Corporation in 2014.

The reservoir it creates, Ennis Lake, is 2.6 miles long and has a maximum storage capacity of 42,053 acre-feet.^[3] The lake is relatively shallow and warms significantly during the summer, which tends to decrease fish populations.^[4] The lake supports recreational fishing for brown trout and rainbow trout, camping, boating, and white-water rafting in Bear Trap Canyon downstream (north) of the dam.^[5]

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