The flow of water produces hydroelectricity.

Falling water produces hydroelectric power.

The theory is to build a dam on a large river that has a large drop in elevation (there are not many hydroelectric plants in Kansas or Florida). The dam stores lots of water behind it in the reservoir. Near the bottom of the dam wall there is the water intake. Gravity causes it to fall through the penstock inside the dam. At the end of the penstock there is a turbine propeller, which is turned by the moving water. The shaft from the turbine goes up into the generator, which produces the power. Power lines are connected to the generator that carry electricity to your home and mine. The water continues past the propeller through the tailrace into the river past the dam. 

► Find out more:

• Hydroelectric Power Water Use
• Hydroelectric Power: Advantages of Production and Usage
• Hydroelectric Power: How it Works

► More photos about hydroelectricity:

• Hydroelectric power production by country in 2012
• Water can be reused to produce hydroelectric power
• Three Gorges Dam, China is the world's largest hydro facility
• Turbines in Hydroelectric Power Plants
• Hydroelectric Power: Advantages of Hydroelectric Power