6th Grade Science / Lesson 9 -Falling Water
What will we be learning today?
How Can Falling Water Give Us Energy?
What can falling water be used for? The kinetic energy of falling water can be captured and used to turn a wheel. This principle can be used to generate electricity. The dam shown here has large turbines at its base. Water from the lake behind the dam can be made to flow through the turbines, causing them to spin and drive electric generators. When electricity is produced by flowing water in this fashion, it is called hydroelectricity.
Hoover Dam creates Lake Mead. Lake water rushing through the turbines below the dam structure makes electricity. Like wind power hydroelectricity is really a form of solar energy. The Sun warms water in oceans and lakes, causing it to evaporate. The water vapor rises high in the atmosphere and can fall as precipitation at high elevations. As the water from the precipitation runs downhill due to gravity, it gains kinetic energy. This is the energy that can be tapped for hydroelectricity.
Flowing water causes this wheel to turn. Presently the U.S. gets about 15 percent of its electricity from hydroelectricity. The good things about hydroelectricity are that it causes little pollution and it will always be available as long as it rains or snows. But hydroelectricity does present problems. The number of sites where more large dams can be built are not great in number. Building such dams can be damaging to the environment. It takes very careful planning to make sure animal and plant species are not harmed in some way by dams.
Dams in the Pacific Northwest could stop salmon from migrating upstream. Fish ladders, shown below, allow fish to get past dams.