Hydroelectric power has been in use for a long time now. The UK alone has benefited from this type of energy for more than 100 years and with the quest to find more renewable sources of energy for the future, it is likely we will see this in use more and more.
This type of energy produces electricity by harnessing the energy within flowing water. The water will move a turbine, which then moves a shaft that is directly connected to a generator. At some hydroelectric plants there are dams in place that will direct the water through the turbine so that energy production can be controlled.
However, not all sources of flowing water are suitable for hydroelectric plants. This is because 
large volumes of water are needed, along with a large drop to create the energy within the water that can be harnessed. The higher the volume of water and the higher the elevation, the more energy can be created.
There are several different types of hydropower. The first is dams, as already mentioned. The second is pumped storage, where water is moved between different reservoirs which are located at different elevations. This can be used to create a source of ‘on-demand’ power. Where a smaller amount of power is required, some rivers are used. However, should the flow of water be interrupted this could be a problem. The last type is tidal power. Tides are predictable so they can actually be used to create a large amount of energy or electricity twice each day.