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Fossil Fuels

   • History
   • How it Works
   • Benefits
   • Limitations
   • Geography
   • Sources


Hydropower uses the power of water to produce energy. Water sitting in a dam has potential energy – the massive volume of water sits behind a dam until it is allowed to run through turbines. At this point the water becomes kinetic energy . It is moving. The running water spins turbines that run generators, which produce electricity.

What comes to mind when you think of water? A long cool drink on a sweltering hot day? Running through the sprinkler, diving into the deep end? How about a big burst of electricity? Water’s raw power provides the energy to produce enough electricity for 28 million Americans every year. Worldwide, hydropower generates more than 2.3 trillion kW hours of electricity, the energy equivalent of 3.6 billion barrels of oil. Dive in, explore more about the power of water.

hydroelectric damHistory
For thousands of years, the pure power of water has been utilized around the world. Wherever rivers ran, people took advantage of the water’s force to do the work of grinding grain and operating machinery like mills. During the 20th century, water’s power was put to work generating electricity, and continues to be an important fuel for our huge energy appetite.

How it Works
hydroelectric damCapturing water’s energy and transforming it into electricity is a simple process that often relies on a dam. Hydropower dams are designed to create a significant drop in the downhill flow of water, which increases the water’s speed. The falling water is directed to a turbine through a long tunnel called a penstock. The kinetic energy of the falling water does the work of turning a turbine. The turbine is connected to a generator which spins, producing electricity. The amount of power generated by this process depends on several variables: the volume of water, the speed of the water’s flow , and the height of the water’s fall. As more water is pushed through towards the turbine, the faster it flows. And the farther it falls, the higher the power output. A hydropower plant design takes all of these variables into consideration.

Water is a very clean way to produce power. No emissions, no waste. Hydropower plants are efficient, reliable and flexible. Their simple design means maintenance levels are low. The plants don’t have to ship fuels in, which lowers operating costs. Hydropower plants have the ability to adapt quickly to satisfy the needs of shifting electrical demand. Plants contribute to both base load and peak load demand for electricity. Day to day, plants produce steady reliable amounts of electricity. During periods of peak demand, the plants can bring additional generators online very quickly, providing more power.

hydroelectric damWhile hydropower is a clean renewable resource, there are limitations. Hydropower plants can have dramatic affects on the environment.

  • Building dams can flood land and affect fish and wildlife habitats.
  • Dams also limit the way people can use waterways for transportation.
  • Dam construction can cause significant changes in a river’s flow, affecting entire ecological systems.
  • Dams can pose a major obstacle to fish, preventing them from moving upstream to spawn.

Because of the potential ecological effects, the federal government imposes strict licensing procedures on hydropower projects, increasing startup costs. Those startup costs are one of the reasons there hasn’t been major growth in this energy area. Another reason is the simple lack of sites. Many of the best sites have already been built on, limiting growth.

Geographical Considerations
The best sites for dams are mountainous regions with heavy rainfall. These areas have an abundance of the natural resource needed — water. They also tend to provide naturally steep drop-offs, one of the variables important to maximizing water power. Iowa in particular and the Midwest in general do not provide good opportunities for hydropower because the region is generally flat. Iowa does have the Mississippi River as a resource, which provides a large volume of water, another variable important to producing hydropower.

What do you think?
As the world’s appetite for energy grows larger and larger, hydropower will continue to be an important resource to satisfy our needs. Should hydropower’s piece of the energy pie be larger? Is hydropower a practical solution to meet your community’s energy needs?

Check it Out!
Explore More about the inner workings of a hydroelectric plant. Check out this site from the USGS.


  1. Brown, Phil. "Tidal Energy." (Online) http://www.geology.wisc.edu/~pbrown/g410/tidal/tidal.html. September 2001.
  2. Grand Coulee Dam Basin Project. "History of the Columbia Basin Project." (Online) http://users.owt.com/chubbard/gcdam/html/history.html. September 2001.
  3. International Council for Local Environmental Initiatives. "Energy Fact Sheet." (Online) (Originally published by the Energy Educators of Ontario, 1993.) http://www.iclei.org/efacts/tidal.htm. September 2001.
  4. Iowa Department of Natural Resources. "Hydropower." (Online) http://www.state.ia.us/dnr/energy/pubs/irerg/hydropower.htm. June 2001.
  5. National Renewable Energy Laboratory. "Hydroelectric Power." (Online) http://www.nrel.gov/lab/pao/hydroelectric.html. September 2001.
  6. U.S. Army Corps of Engineers, Portland District. "The Dalles/John Day/Willow Creek Project." (Online) http://www.nwp.usace.army.mil/op/D/standard/td/fish/td_fish.htm. September 2001.
  7. World Nuclear Association. "Renewable Energy and Electricity." (Online) http://www.world-nuclear.org/info/inf10.htm. September 2001.

Can a Fish Climb a Ladder?
fish ladder diagramNo, it’s not a bad riddle and the answer is yes – if it’s a fish ladder. More

The Grand Coulee Dam, located on the Columbia River in Central Washington, is the largest hydropower producer in the United States and the third largest in the world. More