Water is another very important energy resource. People, plants and animals all depend on water. Hydropower is energy that comes from the force of moving water. The word "hydro" means water.
Hydropower is the most widely-used renewable source of energy. The sun heats the oceans turning it into water vapor. This is called evaporation. When the water vapor rises it turns into clouds. The cold air above the earth mixes with the clouds and releases rain or snow called precipitation. This water cycle goes on repeating forever making this a renewable energy source.
Hydropower is also a clean source of energy and the cheapest form of energy. There is no fuel to burn, so there are no harmful emissions released into the air. These reservoirs can also offer recreational areas for swimming, boating and fishing.
History of Hydropower
Since ancient times people have found ways to harness the energy produced by moving water. Rain or melted snow from hills and moutain areas create moving streams and rivers of water.
For example the water wheel was first used around 200 B.C. for tasks like grinding grain and irrigation. Over 2,000 years ago the Greeks used water as an energy source to turn water wheels for grinding wheat into flour. The running water would flow over the wheel into buckets attached to the wheel and force the wheel to turn. In the early 1800s, Americans and Europeans used water wheels in factories to power machines like saws in lumber mills.