Hydropower, or hydroelectricity, is electricity generated by the force of moving water in the penstock of a hydropower unit. Turbines are used to capture the kinetic energy of water by converting it to electricity as the falling water spins the turbine. Hydropower plants may be located below reservoirs or built in rivers (called “runoftheriver” units) with no water storage capacity. Hydropower is considered a renewable source of energy, as it relies on water which is continuously renewed through the natural water cycle.

Hydroelectricity’s low cost, nearzero emissions, and ability to be dispatched quickly to meet peak electricity demand have made it one of the most valuable renewable energy sources worldwide. Hydropower accounts for about 17 percent of the world’s total electricity generation.