Question: When hydroelectric dams are constructed, the land upstream is flooded, often burying organic material underwater. How would you expect this to affect greenhouse gas emissions?
Burying biomass underwater provides an anaerobic environment for methane-producing microorganisms. Coupled with the CO2 release from decomposition of organic material, reservoirs for hydroelectric dams can potentially release large amounts of greenhouse gases into the atmosphere.
The net effect of greenhouse gas emissions from hydroelectric dam construction varies depending on factors such as depth, temperature, age and size. Nonetheless, this form of electricity production is not usually carbon neutral or emission free. In fact, under some conditions, the greenhouse gas emissions from hydroelectric reservoirs can exceed those of a coal powered plant generating the same amount of electricity.