Water Power
Power from water can be made in many different ways. The most common way is through a hydroelectric dam. This is where a river is blocked until the water builds up into a large lake, or reservoir, behind a tall dam wall. The water is released through an opening over the dam and as it falls, it flows through a machine called a turbine and turns the propellers attached to an electric generator. This creates the electricity. The greater height from which the water falls, the more power it makes.
A Fish with a Ladder
To protect salmon and other spawning fish that are blocked by dams, fish ladders were created. A fish ladder (also called a fish way or fish pass) is a man-made structure built around a dam to allow fish to still make their way upstream to spawn. They are often a chain of low steps up, which the fish can leap. The flow of water has to be just right to attract the fish to the ladder but not tire it out.
Organic Taste Test
Do foods grown organically taste better than foods grown with chemicals? You can do a test to find out. You will need to go to your local food co-op and buy a few things. Try a few organic foods like an apple, cheddar cheese, and carrots. Now buy the same foods from your grocery store. Make sure they are not organic (most stores have special displays for their organic foods). You will need some taste-testing volunteers and a grownup to help you cut up the food. Have a paper and pencil to write down the comments from each taste tester about the foods they tried.
Have them each taste a slice of apple. Do not tell them if it is organic or not!
Give them each a sip of water. Then have them each taste a slice of the other kind of apple.
Ask them which tasted better and why. Write down their responses.
Try this with all the foods you bought.
Afterward, see how the comments rated the organic food compared to the chemically treated food. What did you find out?
Natural waterfalls like Niagara Falls work in much the same way. The power in the falling water makes the generator work, which makes the electricity. It is gravity working on the water that gives us this power. Power lines connected to the generator carry the electricity where it needs to go.
Hydroelectric power is a clean and renewable power source. There is no pollution given off while using hydroelectric power. The reservoir behind the dam can be a place for people to swim, boat, and fish. Farmers can use some of the water for irrigation of their fields. A dam, once built, can last for 100 years.
The Dark Side of DamsThere are a few bad things about dams that are important to know. To build a hydroelectric dam, a large area must be flooded behind the dam to make the reservoir. Whole communities sometimes have to be moved to another place. Entire forests can be drowned. Rotting vegetation under the water can give off methane. The water released from the dam can be colder than usual and this can affect the ecosystems in the rivers downstream. It can also cause erosion downstream, washing away riverbanks and scraping away life on the river bottom. The worst effect of dams has been seen on salmon that have to travel upstream to spawn, or lay their eggs. If blocked by a dam, the salmon life cycle (and that of many other fish) cannot be completed. To try and solve this, fish experts designed fish ladders to get fish over the dam.
Tidal PowerOther forms of water power include capturing the energy of the rising and falling tides. In some ways, tide power is more dependable than wind and solar power because the tides go in and out all day and night at a rate we know. Though tides never change, they do grow during storms and, because they are controlled by the gravitational pull of the moon, the tides do differ according to what phase the moon is in. People have been using the tides to power little coastal mills to grind grain for generations.
River PowerAnother form of water power is a simple water wheel placed in a river. The water flowing down-stream turns the wheel and generates power. The water wheel has been used to mill grains, mine ore, pump water, and power iron forges for more than a thousand years.
