Hydropower

electricity. Water stored in a reservoir can be accessed quickly for use during times when the demand for electricity is high.

Dammed hydropower projects can also be built as power storage facilities. During periods of peak electricity demand, these facilities operate much like a traditional hydropower plant — water released from the upper reservoir passes through turbines, which spins generators to produce electricity. However, during periods of low electricity use, electricity from the grid is used to spin the turbines backward, which causes the turbines to pump water from a river or lower reservoir to an upper reservoir, where the water can be stored until the demand for electricity is high again.

A third type of hydropower project, called "run of the river", does not require large impoundment dams (although it may require a small, less obtrusive dam). Instead, a portion of a river's water is diverted into a canal or pipe to spin turbines.

How Hydropower is Used
Hydropower is currently the largest and least expensive source of renewable electricity produced in the United States.

Large and small-scale hydropower projects are most commonly used by clean power generators to produce electricity. The Buying Clean Electricity section provides information on buying electricity generated from hydro and other renewable resources in your state.

Many large-scale dam projects have been criticized for altering wildlife habitats, impeding fish migration, and affecting water quality and flow patterns. As a result of increased environmental regulation, the National Hydropower Association forecasts a decline in large-scale hydropower use through 2020. Research and development efforts have succeeded in reducing many of these environmental impacts through the use of fish ladders (to aid fish migration), fish screens, new turbine designs, and reservoir aeration. Although funding has been limited, current research focuses on the development of a "next generation turbine, which is expected to further increase fish survival rates and improve environmental conditions.

A very small hydropower (called microhydro) project can also be installed to meet the electricity needs of a single home or small business, and is especially useful for those in remote areas. Our Making Your Own Clean Electricity section provides more information on issues involved with producing your own electricity.

Where Hydropower is Used
Hydropower is used throughout the United States, although it is more common in West Coast (especially Northwest) states.

To find out about the hydropower resources (both developed and undeveloped) in your state, visit the Hydropower Resource Assessment page of the Idaho National Engineering & Environmental Laboratory.