Smith Mountain Lake and Leesville Lake, with Smith Mountain in-between
Source: US Geological Survey, Seamless Data Viewer
As described by American Electric Power, which constructed and operates Smith Mountain Lake:1
Smith Mountain is a pumped storage project that utilizes an upper reservoir (Smith Mountain Lake) and a lower reservoir (Leesville Lake.) 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) license.
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 elavation at Smith Mountain can fall below 793 feet.
1. American Electric Power, Smith Mountain Dam Project Description, www.smithmtn.com/Project%20Description/Smith%20Mountain/smithmountdam.htm (last Checked May 8, 2004)
