Tennessee Valley Authority. Section of one of the switchyards from which high-tension lines carry generated at the TVA's hydroelectric plant at Wilson Dam. Located near Sheffield, Alabama, 260 miles above the mouth of the Tennessee River, the dam has an authorized power installation of 288,000 kilowatts, which can be increased to a possible ultimate of 444,000 kilowatts. The reservoir at the dam adds 377,000 acre-feet of water to controlled storage on the Tennessee River system