History

Hydropower is, very simply put, energy derived from the flow of water. Utilizing water flow is not new: more than 2000 years ago, the ancient Greeks used water wheels to grind grain. Additionally, the power of the water has been used to saw wood and power textile mills and manufacturing plants. The following are significant dates in the development of modern-day hydropower:

Why Hydropower?

• Providing a renewable source of energy:
• Hydropower is a clean, reusable source of electricity. It produces no emissions and its fuel (water) can be used at each downstream dam.
• Hydropower is domestic. Our supply of water is continually replenished through rain and snowmelt. We are not dependent upon foreign fuel supplies and their possible interruption.

• Providing an affordable and efficient source of energy:
• In the Northwest, electricity from hydropower typically costs $10 per megawatt hour to produce. This compares to $60, $45 and $25 per megawatt hour to produce electricity, respectively, at nuclear, coal and natural gas plants. To determine these price comparisons, planners calculate what it costs to build, maintain and operate these differing generation facilities.
• Hydropower also is more efficient than any other form of electrical generation.  It is capable of converting 90 percent of available energy into electricity. The best fossil fuel plant is only about 50 percent efficient.

Hydropower can easily respond to power needs by its ability to be turned on and off quickly. Other forms of electrical production, such as a coal power plant, require a great deal of time to start or stop producing electricity.

How Hydropower Works

Generating hydroelectricity starts with the annual hydrologic, or water cycle, providing seasonal rain and runoff from snow pack. The runoff from rain and snow collects in lakes, streams and rivers and flows to dams downstream. Hydropower facilities intercept the water on its downward path, converting its mechanical energy into electricity. Because the cycle of water evaporating from the heat of the sun and falling back to earth is continuously renewed by the sun's energy, hydropower is truly a renewable energy resource. Water entering a powerhouse powers a turbine, which turns a shaft that rotates a series of magnets past copper coils in a generator to create electricity. The water then returns to the river. From the powerhouse, transmission lines carry electricity to communities.

There are several types of hydropower facilities:

• "Storage" projects impound water behind a dam, forming a reservoir. Water is released through turbine-generators to produce electricity. The water storage and release cycles can be relatively short, for instance, storing water at night for daytime power generation. Or, the cycles can be long, storing spring runoff for generation in the summer when air conditioner use increases power demand. Some projects operate on multi-year cycles carrying over water in a wet year to offset the effects of dry years. 
• "Run-of-river" projects typically use relatively low dams where the amount of water running through the powerhouse is determined by the water flowing in the river. Because these plants generally do not hold back water behind storage dams, they tend to affect upstream water levels and downstream stream flow less than storage projects. Electricity generation from these plants will vary with changes in the amount of water flowing in the river.

Hydropower in the Northwest

There are a total of 40 major dams on the Columbia and Snake rivers providing clean and renewable energy to residents and businesses throughout the Northwest. Of these, 23 are Federal projects.

• Ten of the 40 major dams are owned and operated by the Bureau of Reclamation.
• Thirteen of the dams are owned by the Corps of Engineers.

The remaining 17 major dams are owned and operated by local utilities, PUDs, municipalities and private companies.