new wind and solar facilities are generating more electricity nationwide, but generation at hydropower plants is not increasing because no new dams are being constructed
Source: US Department of Energy, 2015 Renewable Energy Data Book (U.S. Renewable Electricity Generation by Technology)
Moving water has been used to supply energy for food production and transportation; to power iron furnaces, mills, and other industrial facilities, and to generate electricity.
Native Americans used streams to leach the tannins out of acorns. The harsh bitterness of the tannins is a natural deterrent created by oak trees, so more acorns would survive intact and produce new trees rather than feed wildlife. The first residents in Virginia cracked open the acorns and placed them in a small riffle or below where water flowed over a rock, converting the acorns into an edible source of protein.
The Native Americans and early European colonists took advantage of river currents to move boats downstream, and used the twice-daily tides to move upstream with less effort.
A dozen years after arriving at Jamestown, the English colonists stated building an ironworks at Falling Creek. The mechanical energy of the water dropping over the Fall Line was sufficient to power a bellows at the first iron blast furnace in North America.1
Other colonists on the Coastal Plain used falling water to power mills that ground grain and sawed lumber. When settlement extended upstream across the Fall Line, the greater topographical relief offered far more opportunities to generate energy. Water-powered mills were common, including private mills that met the needs of just one landowner/family and large merchant mills that serviced the local community.
Many of the ponds remain, though few mills have survived on the Coastal Plain. For example, colonial settlers dammed Cat Point Creek to create Chandler's Millpond in 1670. The dam was maintained until September 1993, when a heavy rainstorm caused the dam to break. When it was rebuilt, a fish ladder was included to allow anadromous fish to get past the barrier and spawn.2
Chandler's Mill Pond, near Montross in Westmoreland County, was first built in 1670
Source: ESRI, ArcGIS Online
Canals built for transportation also provided hydropower. The flour mills in Richmond depended upon the energy in falling water to spin the grinding wheels and move the grain within the mills. The Tredegar Iron Works in Richmond used water from the James River and Kanawha Canal to turn turbines, and the energy was transmitted by leather belts throughout the factory to shape metal.
mill races carried water from the James River and Kanawha Canal to power equipment at the Tredegar Iron Works
Source: Library of Congress, Illustrated atlas of the city of Richmond, VA (1877)
Electricity is generated at dams where the mechanical energy in falling water is used to spin magnets inside a turbine lined with copper cables. Unlike electricity generated at facilities fueled by coal or natural gas, hydropower is "renewable." Rain falling in the watershed upstream will provide a new supply of water to spin the magnets.
A "run of the river" turbine can be used to generate hydropower without a dam. A rural home might get enough electricity from a Pelton wheel in a stream, but during droughts and winter freezes the supply would be interrupted. Utilities have built dams across rivers to create reservoirs that stockpile water, just as millers built dams to wnsure they could operate flour mills when desired. Reservoirs store mechanical energy the way batteries store chemical energy.
most hydropower facilities generate a surplus of electricity, but pumped storage projects consume more electricity than they generate by recycling water to provide "peak" power
Source: Federal Energy Regulatory Commission, Diagram of a Pumped Storage Project
City of Radford operates a 1MW hydroelectric plant on the Little River
Little River reservoir
the tiny Little River reservoir limits hydropower production
discharge after spinning the turbine