Hydroelectric power must be one of the oldest methods of producing power. No doubt, Jack the Caveman stuck some sturdy leaves on a pole and put it in a moving stream. The water would spin the pole that crushed grain to make their delicious, low-fat prehistoric bran muffins. People have used moving water to help them in their work throughout history, and modern people make great use of moving water to produce electricity.
Although most energy in the United States is produced by fossil-fuel and nuclear power plants, hydroelectricity is still important to the Nation. Nowadays, huge power generators are placed inside dams. Water flowing through the dams spin turbine blades (made out of metal instead of leaves) which are connected to generators. Power is produced and is sent to homes and businesses.
Hydropower is the most important and widely-used renewable source of energy. Hydropower represents about 17% of total electricity production. China is the largest producer of hydroelectricity, followed by Canada, Brazil, and the United States Approximately two-thirds of the economically feasible potential remains to be developed. Untapped hydro resources are still abundant in Latin America, Central Africa, India and China. Producing electricity using hydroelectric power has some advantages over other power-producing methods. Let's do a quick comparison:
Advantages to hydroelectric power:
Fuel is not burned so there is minimal pollution
Water to run the power plant is provided free by nature
Hydropower plays a major role in reducing greenhouse gas emissions
Relatively low operations and maintenance costs
The technology is reliable and proven over time
It's renewable - rainfall renews the water in the reservoir, so the fuel is almost always there
Disadvantages to power plants that use coal, oil, and gas fuel:
They use up valuable and limited natural resources
They can produce a lot of pollution
Companies have to dig up the Earth or drill wells to get the coal, oil, and gas
For nuclear power plants there are waste-disposal problems
Hydroelectric power is not perfect, though, and does have some disadvantages:
High investment costs
Hydrology dependent (precipitation)
In some cases, inundation of land and wildlife habitat
In some cases, loss or modification of fish habitat
Fish entrainment or passage restriction
In some cases, changes in reservoir and stream water quality
In some cases, displacement of local populations
Hydropower and the Environment
Hydropower is nonpolluting, but does have environmental impacts
Hydropower does not pollute the water or the air. However, hydropower facilities can have large environmental impacts by changing the environment and affecting land use, homes, and natural habitats in the dam area.
As this chart shows, in the United States, most states make some use of hydroelectric power, although, as you can expect, states with low topographical relief, such as Florida and Kansas, produce very little hydroelectric power. But some states, such as Idaho, Washington, and Oregon use hydroelectricity as their main power source. in 1995, all of Idaho's power came from hydroelectric plants.
The second chart shows hydroelectric power generation in 2012 for the leading hydroelectric-generating countries in the world. China has developed large hydroelectric facilities in the last decade and now lead the world in hydroelectricity usage. But, from north to south and from east to west, countries all over the world make use of hydroelectricity—the main ingredients are a large river and a drop in elevation (along with money, of course).
(There ya go! sorry if this doesn't help though )