Hydropower Energy

A Guide to Hydroelectricity: Water Power

You probably know that beavers build dams. Beavers don't live in their dams, though. They build their dams as barriers, and then they live in the ponds that the dams create, where predators can't get to them as easily. Humans build dams, too, but for other reasons. One of the reasons people build dams is for energy. The energy produced using dams is called hydroelectric power. "Hydro" means "water," and the water that flows through dams in the United States satisfies nearly 10% of all of the country's power needs.

What Is Hydroelectricity?

Hydroelectricity is the electricity that can be created using the power of moving water. Building a dam on a big river traps the water, and then water can then be directed through special pipes to make turbine blades turn. The blades are connected to a generator, which converts the energy of the turning blades into electricity. As long as the water keeps moving, the turbine blades will keep turning and the power will continue to flow.

Most dams create a big lake or reservoir of water. A hydroelectric dam has special valves that can be used to control how quickly or slowly the water can move through the pipes to turn the turbine blades. Another type of hydropower energy plant doesn't use a dam. This type of plant has canals that move water toward the turbine blades. There's also a third way that water can be used to make electricity. In this method, other types of power, like solar or wind power, are used to pump water uphill into a reservoir. When more power is needed, the water can be released to generate electricity.

History of Hydroelectricity

People have been using water to produce power for hundreds of years. Even in ancient civilizations, people understood the power of water, and they used it to help them do hard jobs like grinding grain. In colonial America, people used hydropower to help them saw wood. The first hydroelectric power plant was built in Appleton, Wisconsin, in 1882. The Hoover Dam, one of the most famous hydroelectric dams, was built in 1936. Currently, there are more than 90,000 hydroelectric dams operating in the United States.

Pros and Cons of Using Hydroelectric Power

There are advantages and disadvantages to using hydroelectricity. Although hydropower is considered to be a renewable energy source, there are a few environmental challenges that go along with this method of producing power.


  1. Hydropower plants can be built and be ready to operate quickly. Construction costs are relatively low.
  2. Hydropower is a clean fuel source because it doesn't pollute the environment.
  3. The United States is able to produce this type of power independently.
  4. The natural water cycle is the power behind hydropower, so it should never run out.
  5. It's possible to control how and when water flows, so the hydropower plants can produce energy as people need it.
  6. The reservoirs created for hydropower plants can also be used for fun activities like swimming, boating, and fishing.


  1. Fish living in the reservoirs can't migrate past the dams. Some hydropower plants are set up to help the fish by using special traps to catch them and move them upstream or downstream past the dam.
  2. Producing hydropower may reduce oxygen levels in the water, which can harm plants and animals. Special equipment may need to be used to add oxygen to the water.
  3. Droughts can cause problems at hydropower plants. If water levels are low, they can't produce as much electricity.
  4. Building large new hydropower plants takes up a lot of land, which may impact the environment. Animals and plants may lose their habitats to make way for these hydropower plants.

Additional Resources