In the generation of power, water from the reservoir enters gate-controlled intakes into the powerhouse, rotates the turbines, and discharges through draft tubes into the river below the dam. Generators, mounted on the same shafts with the turbines, produce the electric current. It is increased in voltage by transformers and carried from the power plant by transmission lines leading from the switchyard.
The power plant is operated so as to use as much of the water flow as possible for power production: during periods of high stream flow, the spillway gates are opened to pass the water in excess of the capacity of the turbines and as necessary for retention and regulation of floodwaters through surcharge operation. The upper portion of the reservoir, corresponding to a five-foot depth above the normal headwater level, is provided for surcharge storage. This storage space is utilized by raising all of the spillway gates in small equal increments, thus permitting passage of some water under them but retaining or forcing into storage all inflow to the reservoir in excess of the spillway discharge and power releases.