NASHVILLE DISTRICT

Old Hickory Dam

The reservoir is essentially a run-or-river type without regulating storage other than for incidental flood control through surcharge operation, and for pondage for power generation and lockages; hence, low water flow of the river will be increased only indirectly through the use and passage of discharges from upstream plants.  Such releases, however, result in a more sufficient and higher quality of water for domestic and industrial consumption and use are effective in pollution abatement downstream.  Due to the fairly constant level maintained under normal operating conditions, the reservoir is well suited for conservation and recreational purposes.

Powerplant

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.