• Hydropower depends on the water cycle.
• Seasonal differences in precipitation and long-term variations in precipitation patterns have big influences on the availability of hydropower generation.

In 2020, hydroelectricity was responsible for roughly 7.3 percent of the entire U.S. utility-scale electricity production and 37 percent of the entire utility-scale renewable electricity production. Hydroelectricity’s share of U.S. electricity generation altogether has lessened over time, primarily due to growth of other sources of electricity generation.

Hydropower depends on the water cycle. Understanding the water cycle is critical to comprehending hydropower. There are three steps in the water cycle:

1. Solar energy heats water on the surface of rivers, lakes, and oceans, this makes the water evaporate.
2. Water vapor condenses into clouds and drops as rain and snow.
3. Rain and snow gather in streams and rivers, which unload into oceans and lakes, where it then evaporates and starts the cycle over.

The quantity of precipitation that goes into rivers and streams in an area decides the quantity of water available for making hydropower. Seasonal differences in precipitation and long-term variations in precipitation patterns, like droughts, can have big influences on the availability of hydropower generation.

Since the source of hydroelectric power is water, these power plants are typically found on or near a source of water. The amount of water flow and the elevation difference or fall from one point to another decides the quantity of available energy in flowing water. Overall, the higher the water flow and the greater the fall, the more electricity a hydropower plant can generate.

At hydropower plants, water moves through a pipe then pushes up against and rotates blades in a turbine to turn a generator to make electricity.