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How do hydroelectric plants affect the environment?
Nikki Jones, Midland, Ontario, Canada

Hydroelectric power is a clean, renewable form of energy that accounts for about 2/3 of the power produced in Canada. Canada produces a surplus of power that is exported and helps to keep the cost of electricity low. The use of hydropower reduces air emissions by reducing the amount of coal and oil that is burned to produce power. Hydropower is also a more flexible source of power than coal because turbines can be started or stopped in minutes. This flexibility makes hydropower especially useful for meeting peak power demand or serving as a back up in case of outages.

Many hydroelectric plants require the construction of a dam and reservoir, and most of the environmental impacts are associated with construction and operation. Placing a hydroelectric plant into an existing dam or a run-of-the-river plant would not create many of these impacts. The hydro plants on the St. Lawrence and St. Mary's Rivers, for example, are part of multi-use structures and are operated in a much different manner than they would be if they were only operated for hydroelectric power generation.

Hydroelectric plants can have a wide range of effects on the environment, as well as some socio-economic impacts. Opinions vary on the extent to which these impacts may or may not be mitigated.

Some of the potential impacts of hydroelectric plants on the environment are:

• loss of land in the flooded areas due to the presence of the hydro dam, which includes loss of animal habitat, green spaces, agricultural lands, forests, pasture lands and wetlands;
• soil erosion, sedimentation and a decrease in water quality;
• air pollution due to construction;
• destruction of vegetation or alternately, the proliferation of vegetation due to increased nutrients in the water which may impede the flow of water from the dam and lead to difficulties in irrigation and navigation;
• dams can become obstacles to the migration of fish, may cause the disturbance and possible endangering of fish populations;
• increases in air humidity, the frequency of fog, and the creation of conditions that are favourable to the proliferation of various insects and carriers of disease.
• the plant may be considered unattractive or an infringement on a natural area and some plants reduce the flow over falls which reduces the natural spectacle.

Socio-economic issues related to hydroelectric plants are closely related to these environmental impacts. These may include:

• social disruption and decrease in the quality of life for displaced communities once living in the flooded areas;
• disruption of aboriginal communities;
• health and hygiene problems for local residents;
• an increase in water-borne diseases;
• disappearance of historical and culturally significant sites;
• human conflicts with regards to demands on water resources.

What can be done to reduce the negative effects of hydroelectric plants?

• Sites for new water dams should be chosen carefully with due respect for socio- economic and environmental concerns. In Canada, major projects are subject to an environmental impact assessment.
• People who have to relocate because of the project or have other economic losses caused by the project should be treated fairly.
• Water Management Plans should balance the use of water resources.
• Fish passage / diversion / by-pass structures, such as fish ladders, louvres, downstream fishways, have been used to facilitate the migration of fish around barriers. Structures or other deterrent measures can be used to prevent fish from entering turbines, spillways and canals. Trucks and barges have also been used to move fish around barriers.
• Discharge facilities can be designed for mitigation if there is a concern about the release water.
• Opportunities for recreational and other uses in similar areas have been improved to compensate for losses due to projects.

For more information on hydroelectric power plants and their impacts, please visit the following Web sites:

Hydroelectric Power Generation

Canadian Environmental Assessment Agency

Canadian Dam Association

World Commission on Dams

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