Canadian large-scale hydro projects have an ongoing carbon footprint that is approximately 40% that of electricity generated by burning natural gas. These emissions do not include the carbon footprint of dam construction.
Solar and wind, on the other hand, have a carbon footprint of 4% to 8% of natural gas, even when including the carbon footprint of construction. In other words, solar and wind power are at least five times cleaner than large-scale Canadian hydro. (Ben Gordesky in VT Digger Op Ed)