Electricity is produced at Smith Mountain using pumped storage. Smith Mountain Lake
serves as the upper reservoir and Leesville Lake
as the lower reservoir.
The water that is stored in Smith Mountain Lake first passes through turbine-generators
in the powerhouse to produce electricity and is then discharged into Leesville Lake.
Most of this water is retained in the Leesville Lake and is pumped back into the
Smith Mountain Lake for re-use. A portion of the water goes through the turbine-generators
at the Leesville powerhouse to generate additional electricity and to meet the minimum
discharge requirements of the project's Federal Energy Regulatory Commission (FERC)
The Smith Mountain development utilizes a two-foot power pool. This means that when
Smith Mountain generates power by passing water through the turbines, the Smith
Mountain lake level can fluctuate up to two feet before the Leesville lake becomes
full. In other words, a two-foot decrease in Smith Mountain results in Leesville
Lake increasing thirteen (13) feet or from a minimum elevation of 600 feet to maximum
elevation of 613 feet. Once Leesville is full, power cannot be produced at Smith
Mountain until some portion of the water is pumped back to Smith Mountain Lake.
There is no set schedule for operating the project. Generation generally takes place
when the demand for electricity is high and water from the lower reservoir is pumped
back into the upper reservoir when the demand for power is low. The operation of
the project can change on an hourly basis depending on system demand.
The normal full pond elevation at Smith Mountain is 795 feet but the normal operating
range under full pond conditions is considered to be between 793 feet and 795 feet
because of the two-foot power pool. Normal operating range for Leesville is between
600 feet and 613 feet. Under low in-flow conditions, the pond elevation at Smith
Mountain can fall below 793 feet.
See annual maximum and minimum reservoir elevations and dates here.
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