Hydroelectric energy is a renewable source of energy that is not dependent on fossil fuels like oil, natural gas, and coal. It has the advantages of a longer functional life than fossil fuel generators, low carbon emissions, global accessibility, and low operation and maintenance costs. However, hydroelectric dams can disturb natural river flows, impact fish and wildlife mobility, and require high initial investment costs. The document predicts that both the United States and world will increase their reliance on hydroelectric energy in the future as alternatives to fossil fuels and to reduce emissions.