Throughout Canada, there are 933 large dams according to the Canadian Department of the Environment. Large dams are defined as hydropower facilities with a capacity of more than 30 megawatts. These megadams have a detrimental effect on the environment and the ecosystems that they impede.

Grandes Chutes today, after Hydro-Quebec’s Romaine River project that includes four megadams.

As the Canadian Department of the Environment states on their website, “When a dam is constructed it can have an effect on the water quality of a river system. The land behind it is flooded which may mean the loss of valuable wildlife habitat, farmland, forests, or town sites. Accumulation of sediments in the reservoir can have a detrimental effect on water quality by creating increased concentrations of harmful metal and organic compounds in the reservoir. If vegetation is not removed behind the dam before flooding, other problems can occur. ” These “problems” include the poisoning of food webs by the neurotoxin methylmercury as well as the destruction of boreal forests and peatlands.

Newly released maps showing damaging transmission corridors and megadam projects in Canada and the U.S.

Map of New Dams and Proposed Corridors (NAMRA)