Description:
Thompson Falls Dam is a seven-unit hydroelectric plant on the Clark Fork River in Thompson Falls. The units have a total generating capacity of 94 megawatts. he Thompson Falls plant, which began operation in 1915, consists of a main dam and a dry-channel dam with an island in between. Both dams are used to regulate the reservoir, which has a storage capacity of 8,300 acre-feet, and control flow during high spring runoff. The main dam is 913 feet long and 32 feet high. The dry-channel dam is a concrete gravity structure with an overflow spillway and an overall length of 289 feet. The structure has an average height of 17 feet above the riverbed. It is raised by flashboards and 8-foot drop panels. Thompson Falls is classified as a “run-of-river” project because it can generate electricity using the water that flows down the river, without the need to store additional water supplies. The Clark Fork River at Thompson Falls was originally a natural waterfall. After the dam was built, westslope cutthroat trout (a species of special concern), the threatened bull trout and other fish species instinctively jumped on the rocks to get upstream. PPL Montana has installed a mechanism to help fish reach the river on the upstream side of the dam.