Leesville Lake is downstream of Smith Mountain Lake, and Roanoke River water is pumped back to Smith Mountain Lake so it can flow through the turbines and generate electricity again to meet peak power demand
Source: US Fish and Wildlife Service, Wetlands Mapper
Smith Mountain Lake was created by a privately-owned hydroelectric project, built by American Electric Power on the Roanoke River at a gap in Smith Mountain.
The Roanoke River was named after shells that were used for money by tribes downstream on the Atlantic Ocean coast, while the stretch also known as the Staunton River was named after the wife of colonial governor William Gooch. The mountain was named after a pair of early settlers (brothers Daniel and Gideon Smith) who had arrived in 1740.1
The authorization for a dam at Smith Mountain gap dated back to 1924, when Roanoke-Staunton River Power Company obtained the first rights. The Niagara Dam upstream had been built in 1906, 24 years after the first US hydroelectric plant went into operation in Wisconsin.2
American Electric Power generates hydropower at the tiny Niagara Dam near Roanoke, as well as at the giant Smith Mountain Dam/Leesville Dam project downstream
Source: ESRI, ArcGIS Online
After the Roanoke-Staunton River Power Company determined the project was not going to be profitable, local boosters tried to get the Federal government to build the dam. The US Army Corps of Engineers recommended a dam there, as one of eleven projects to control flooding on the Roanoke River, but Congress declined to authorize construction at Smith Mountain Gap. Opponents included railroads and coal companies, who saw hydroelectric power as a competitor.
Under President Eisenhower, the Federal government encouraged private utilities to build hydroelectric projects on navigable rivers. In 1953, the Supreme Court cleared the way for an investor-owned utility to build on the Roanoke River. The Federal court declared that the Federal Power Commission (now the Federal Energy Regulatory Commission) could authorize privately-owned dams separately from the flood control projects proposed by the US Army Corps of Engineers.
In 1954, American Electric Power purchased the rights of the Roanoke-Staunton River Power Company to construct a privately-owned hydroelectric project on the Roanoke River at the gap in Smith Mountain. Residents who would be displaced by the new reservoir objected, but the local officials in Bedford and Franklin counties endorsed the project and formally abandoned roads to clear land titles for Appalachian Power.
Gates on the dam were closed in 1963, and Smith Mountain Lake reached "full pool" on March 7, 1966. Runoff from Roanoke's extraordinary 41" of snow in January helped fill up the reservoir.3
Smith Mountain Lake was built as a pumped storage project. The project uses more electricity than the turbines generate each year - normally not a formula for success for a power-generating plant. However, Smith Mountain Lake is valuable because of the times when the hydropower is generated.
Water is released through the turbines at Smith Mountain Lake to generate electricity when customer demand for electricity peaks in the morning at breakfast time and in the evening after workers return home for dinner. The water is trapped downstream by Leesville Dam. When customer demand is low (between 11:00pm-6:00am, perhaps), Smith Mountain Lake pumps water back uphill from Leesville Lake, so that water can go through the turbines again.
Smith Mountain Gap was plugged and Leesville Dam built downstream in 1963, to create a pair of lakes for a pumped storage hydropower project
Source: US Geological Survey (USGS), Smith Mountain Dam 7.5x7.5 topographic quadrangle (1967)
The pumping during periods of low demand uses electricity generated at baseload power plants. American Electric Power's coal-burning generators run most efficiently when they are in steady operation, ignoring the peaks and valley of customer demand. Excess electricity, produced by baseload plants during the midnight shift or in the middle of the day, is used to pump water back into Smith Mountain Lake so the utility can meet the surge of demand at breakfast and dinner time.
The reservoir is designed so water above 795 feet in elevation will flow over the spillway. Between 1966-2015, the reservoir exceeded that level and spilled water less than 20 times.4
topography reveals why Smith Mountain Dam was built at Smith Mountain Gap on the Roanoke River
Source: USGS National Elevation Dataset, NED Shaded Relief - Virginia
Pumped storage plants offer great flexibility, which can be more valuable than lowest-cost electricity. Electricity can not be stored easily after it is generated; there are no batteries for multi-megawatt power plants like there are for automobiles. To prepare for a spike in demand, utilities can stockpile fuel - including water pumped uphill.
in periods of low demand for electricity, water in Leesville Lake is pumped back into Smith Mountain Lake so it can be reused to generate electricity during peak power periods
Source: US Army Corps of Engineers, National Hydroelectric Power Resources Study (Volume X, November 1981)
As described by American Electric Power, which constructed and operates Smith Mountain Lake:5
Smith Mountain Lake is split between three counties
Source: ESRI, ArcGIS Explorer
The Roanoke River flows from the Valley and Ridge physiographic province, through a gap in the Blue Ridge, and is trapped in the lake by Smith Mountain Dam on the border of Pittsylvania and Bedford counties. Creation of the artificial lake has resulted in the incongruous sight of large yachts in the middle of the Blue Ridge.
Smith Mountain Lake serves as a water supply reservoir, in addition to a hydropower generator. When the city of Bedford reverted to "town" status in 2013, the Bedford Regional Water Authority decided that Bedford County should shift its water source from Lynchburg to Smith Mountain Lake.6
the headwaters of the Roanoke River are in the Valley and Ridge physiographic province
Source: US Geological Survey (USGS), National Atlas Streamer
Leesville Dam and Leesville Lake
Source: US Geological Survey, Leesville 7.5/7.5 topographic quadrangle (2010)
when Joshua Fry & Peter Jefferson mapped Virginia in 1751, the river running through Smith's Mountains was called the Staunton (or Smith's) rather than the Roanoke River
Source: Library of Congress, A map of the most inhabited part of Virginia containing the whole province of Maryland with part of Pensilvania, New Jersey and North Carolina. Drawn by Joshua Fry & Peter Jefferson in 1751
prior to the Civil War, the Staunton River was undammed - and the town on the Virginia and Tennessee Railroad upriver from Smith Mountain was called Big Lick
Source: Library of Congress, A map of the state of Virginia, constructed in conformity to law from the late surveys authorized by the legislature and other original and authentic documents (1859)