Hydroelectricity is a form of renewable energy. That means its source — water — is naturally renewing and doesn’t get used up in the process of generating power.

Other renewable energy sources include solar power, wind power, biomass, and increasingly, geothermal energy.

Hydropower is the single largest source of renewable energy in the U.S. Combined, renewable sources produce 17 percent of the United States’ energy, with 7 percent coming from hydropower.

Read more: earth911.com