On a daily basis electricity generated from nuclear energy and fossil fuels are of minimal importance in the St. Lawrence area . However, during periods of low water or peak energy demands fossil fuel and nuclear power is needed to support human activities in the area. Thermal plants are located adjacent to the St. Lawrence mainly because they use hydrocarbons such as coal and oil that are ponderous goods to carry and waterways are privileged means to ship them. In Ontario, some oil and nuclear power facilities exist along the Great Lakes. Northern and Western regions of the province are dependent on nuclear power.
Nuclear power is economical in Ontario because the province has significant uranium resources.
Nuclear power plants are built near large lakes and rivers because water is needed to generate steam and to cool the nuclear reaction in case of emergencies. In summer 1997, the nuclear power generation system in Ontario was in a state of crisis as seven nuclear stations were shut down because of poor repairs and management. To compensate, several conventional thermal plants will have to be put online. The nuclear power system used in Canada is called Candu. For detailed information on the Candu system and non-hydro energy systems in Canada refer to the web links provided below.