Even without dams or advanced technology, the use of water power to do work has been around for thousands of years. More than 2,000 years ago, the Greeks used waterwheels to grind wheat into flour. In contrast, the history of using moving water for hydropower is relatively shorter, having only been around for about 100 years. It wasn't until 1882 that the Appleton Power Plant in Wisconsin opened, becoming the world's first hydroelectric plant. (“Energy.gov”)Figure 1: Three Gorges Dam in ChinaHydropower uses the energy of flowing water to produce electricity. (“National Geographic”) This is a form of renewable energy because the system uses only renewable resources and does not directly produce hazardous waste. It is an alternative to generating electricity from fossil fuels. Although it doesn't produce as much electricity as fossil fuels, it produces enough electricity to "prevent the burning of 22 billion gallons of oil or 120 million tons of coal each year." Since 2012, hydropower has produced approximately ⅕ of the world's electricity. (“Alternative Energy”) The main concept of hydroelectric power plants is when water flows through a dam built into a river. Many basic elements of a hydroelectric plant include a dam, which holds back water and creates a reservoir. When the dam gates open, water flows into a connected pipe that leads to the turbine. The pressure increases as it flows through the pipe and turns the large blades of the turbine, which is connected to a generator. As the turbine blades turn, the generator magnets rotate in front of the copper coils and produce alternating current by moving the electrons. The transformer inside a power plant takes alternating current and converts...... middle of paper ...... also affected due to the barrier of dams and the changing flow of water . Dams limit the number of young salmon able to survive, as many are killed while swimming downstream by the blades of hydroelectric turbines. The reproduction of adult salmon moving up the river is also affected because it is difficult to cross the dams. (“EPA”) In addition, they are also often devoured and picked by birds in flight at the foot of dams. Data shows that the population of Atlantic salmon in the United States has declined significantly, from 50,000 to just a few thousand due to the effect of dams. With a looming energy crisis and a rapid and unstoppable decline in fossil fuels, the need for renewable energy is greater than ever. Yet it is inevitable that each new solution will have consequences. People can only hope that the energy crisis will be resolved with each new advanced generation of scientists..