EcoSpark works with communities and with schools, providing them
with the knowledge and tools to monitor their environment and
take action for positive environmental change.
Hyrdoelectric Power
Student Area Menu
Hydroelectric power is water power. Hydroelectricity is derived from the energy created by running or falling water. The pressure of flowing water turns underwater turbines, which are connected to a generator that produces electricity. Sometimes water flow and pressure are natural, but often they are created by dams constructed for that purpose.
Dams produce water flow by elevating the water upstream from an electricity generation station. They create water reservoirs, the contents of which can be released depending on varying electricity demands. For more information on how hydroelectric power and dams work, have a look at this video.
There are two basic set-ups for hydro: the dam system and the run-of-river system. Dams are used for large capacity hydroelectric plants, while run-of-river systems have small plants with a very minor dam or none at all. The run-of-river system diverts some of the water in a river into a canal that sends the water through turbines at a small generation station. After that, it is channeled back to the river. The run-of-river system does not significantly alter the flow or water level of the river, unlike dams and reservoirs.
Hydroelectric power is a major electricity source in Ontario and the largest source in Canada overall. Most electricity in Canada is derived from large-capacity hydroelectric plants with dams, which have a more serious environmental and social impact than do small-capacity plants.
What are the benefits of hydroelectric power that make it so popular in Canada? And what environmental impacts should we consider when using electricity generated in this way?
Hydroelectric power creates no air pollution or greenhouse gas emissions- With hydroelectric power (unlike power derived from fossil fuels), no combustion occurs during electricity generation. Therefore, no GHGs or air pollutants are released at that point.
Water is a renewable electricity source
- Rivers, streams, reservoirs, and other bodies of water are naturally replenished by the hydrological cycle.
- Hydroelectric generation stations have a long lifespan, because water is naturally replenished.
- Canada has a lot of water available for hydroelectricity.
- It costs nothing to use flowing water (though there are costs related to the technology that harnesses it).
- Because it is readily available in most areas of Canada, it can provide a source of electricity for remote communities.
- Water can be kept in reservoirs and released when needed to meet electricity demands. This makes it a non-intermittent and flexible source of electricity.
- If water is stored in reservoirs, the potential for creating electricity is always there. Small-capacity systems, even with small dams, are less reliable because they do not have reservoirs.
Hydroelectricity is relatively cheap
- Hydroelectricity generated at large-scale plants is relatively inexpensive, which keeps the cost of electricity to consumers low. (The cost of generating electricity from a small-scale plant is slightly higher, due to economies of scale.)
Reservoirs have other benefits
- Reservoirs offer other benefits, such as holding water for irrigation, and for recreational activities.
Hydroelectricity can complement intermittent sources
- Renewable but intermittent electricity sources, such as wind and solar power, can use hydroelectric power as a back-up.
- Large-capacity generating systems require dams and reservoirs, which means massive flooding. Flooding:
- destroys terrestrial ecosystems;
- displaces local communities; (see CBC clips on the Cree's opposition to the James Bay Project, or the BBC article on the China's Three Gorges) and
- releases harmful substances into the water; until flooding, these substance, including mercury, had been stored in the ground;
- Dams alter waterways and fish habitats, change the migration routes of fish and other animals, and disrupt the natural flow of nutrients and sediment. This is less of a problem with small-capacity run-of-river hydroelectric systems, since they have no either a very small dam or none at all.
- The construction of hydro plants and dams is fossil fuel-intensive and releases GHGs.
- Areas flooded to create reservoirs, especially in shallow tropical areas, give off GHG from decaying plants killed by flooding.
Large-scale projects are expensive
- Large-scale projects require the construction of costly dams and reservoirs.
Hydro plants may be affected by seasonal flows or have issues with freezing water
- This is a problem for smaller-scale, run-of-river systems.
For more information:
Centre for Energy (2010). What is hydroelectricity? Available here.
National Geographic (2010). Hydropower. Available here.
With support provided by:
