Canada has been using water to make electricity for over a century. In fact, some of Canada’s hydroelectric stations are over 100 years old and are still generating electricity for us today.

Sir Adam Beck Generating
The Sir Adam Beck Generating Stations near Niagara Falls can provide enough electricity to meet the needs of 10% of the entire province.

Hydroelectric power stations convert the kinetic energy of falling water into electrical energy. To convert the kinetic energy of falling water to electricity, most hydroelectric stations use either the natural drop of a river, such as a waterfall, or build a dam across a river to raise the water level and provide the drop needed to create a driving force.

Water is collected at the top of the dam in what is called the forebay. From there, the water flows into a pipe called a penstock which carries it down to a turbine water wheel. The water pressure increases as it flows down the penstock. The pressure and flow of the falling water drives a turbine which in turn spins a generator. This creates electricity that can be sent across transmission lines to wherever the power is needed.

Hydroelectricity is one of the most economical and environmentally friendly ways of generating electricity. It produces virtually no smog or greenhouse gas emissions and is a renewable energy source — the water can be used again and again.

Ontario currently has over 70 hydroelectric generating stations but there are only a few rivers left in the province where new stations can be built. After that, other sources of energy will be required to meet our need for electricity.

Hydroelectric generating station
Diagram of a hydroelectric generating station.

Hydroelectricity in Canada

Canada is the largest producer of hydroelectricity in the world, generating over 60% of its electricity using hydroelectric dams. The source of energy for a hydroelectric dam is water. The mechanical energy of the moving water is converted into electricity by spinning large turbines connected to electric generators. Some rivers have either a steep enough grade or sufficient water flow to generate electricity as the water passes directly through the dam. Hydroelectric dams of this type are called “run of the river” dams. Other hydroelectric dams require the creation of an artificial headpond or reservoir which raises the water level on one side of the dam by holding back large volumes of water.

Hydroelectric dams not only produce low cost electricity but often the reservoirs created are used for flood control, to irrigate farm land, supply towns and cities with drinking water and create recreation and camping areas.

Originally it was believed that hydroelectric dams do not produce any greenhouse gases, but it was later discovered that decaying trees and other organic matter submerged under water during the creation of reservoirs, does in fact release carbon and methane into the atmosphere, although the process is much slower than if they were burned.

Hydroelectric dams provide clean affordable electricity but great care must be taken when they are constructed. Hydroelectric dams are artificial barriers to fish which then must be given artificial means to navigate upstream to spawn either by the use of fish ladders built into the dam, or by catch and release programs operated by the electric utility. They must also be able to withstand unexpected natural events such as floods and earthquakes.

Canada’s electric utilities have done a good job in engineering, constructing and maintaining their hydroelectric dams. In some countries, this has not been the case. In 1975, the Banqiao hydroelectric dam in China collapsed during Typhoon Nina. This collapse caused several other dams downstream to also collapse killing 26,000 people. Another 145,000 deaths were caused indirectly due to disease and famine created by the disaster, making the Banqiao dam collapse one of the greatest man-made disasters in human history.

Today, the decision to build more hydroelectric dams is a controversial topic in many parts of the world as people re-examine the environmental impact of flooding large areas of land on wildlife, fish habitat and communities surrounding sites where new hydroelectric dams are being considered.


Canadian Energy Research Institute, World Energy: The Past and Possible Futures 2007, 2008 p. 75, www.cna.ca/english/pdf/Studies/CERI/CNA_CERI07_EN.pdf.
Renewables Global Status Report (2006), www.ren21.net/globalstatusreport/download/RE_GSR_2006_Update.pdf.
Ontario Power Generation, http://www.opg.com/communities-and-partners/teachers-and-students/Documents/grade9student.pdf.