Moving water has energy that can be harnessed and used to generate electricity. This is called hydroelectric power, and is a renewable source of energy.

The most common type of hydroelectric power plant uses a river dam to store water in a reservoir. As it is released from the reservoir, the water flows through a turbine, generating electricity. But a large dam is not necessarily required: some hydroelectric power plants just use a small canal to channel river water through a turbine.

Pumped storage plants can store power. Water is pumped to an upper reservoir at night, when power usage in the area served by the generator is low. When demand is higher, it flows back down into the lower reservoir, producing electricity.

A small hydroelectric power system can produce enough electricity for a home, farm, or ranch.

Advantages of hydroelectric power

• No pollution or waste.

• The river flows continually and provides a constant source of energy.
• Once built, the supply of electricity is relatively cheap.
• There is usually very little effect on the landscape.

Disadvantages of hydroelectric power

• The building of large dams floods land and causes damage to existing habitats.
• Changing the flow of a river will affect the water supply to lands nearer the sea. This may cause problems of irrigation for crops.