Water covers 71% of the Earth's surface and is vital to our daily lives. It can also be a clean, renewable, reliable source of electricity. Hydroelectric energy comes from capturing the force of moving water that's in our Earth's rivers and oceans. We do this by using the movement of the water to spin hydraulic turbines. That generates kinetic energy which is converted to electricity through a generator and then sent to the power grid. Most hydropower is generated from dams built on rivers and streams, often where there's a big drop in elevation, so gravity can help us out. Dams block the water's natural flow and force it through a large pipe with the turbine and generator, before releasing it back into the stream on the other side of the dam. Today we know that dams, most of which were built before the 1960s here in the US, can disrupt river ecosystems. There haven't been many new hydro plants built in the U.S. in a few decades, but some existing dams are beginning to be tapped for their electricity generating potential, and existing hydro facilities are being upgraded to be less harmful to plants, fish, and wildlife. This helps us get the electricity we need by protecting the natural environment around us.