Loss of Hydropower on Colorado River Likely Won’t Increase GHG Emissions

Glen Canyon and Hoover Dams: As hydropower falters at Glen Canyon and Hoover Dam due to falling reservoir levels caused by the extreme drought and climate change, various media outlets and stakeholders are claiming that replacing Colorado River hydropower with coal and natural gas generated electricity will result in an increase in Greenhouse Gas (GHG) emissions. However, the best available science indicates that this claim is likely not true.

A 2016 study by Swiss scientists, using state-of-the-art methodology (at the time) for estimating GHGs caused by hydropower, indicated that emissions from Glen Canyon dam were roughly 1/2 of that of natural gas powerplants while emissions from Hoover Dam were roughly equal to a coal-fired powerplant producing the same amount of electricity.

The U.S. Bureau of Reclamation has stated in public documents that “Reservoirs such as Lake Powell would be expected to produce some amount of GHG emissions consistent with levels reported for reservoirs in the semiarid Western U.S.”

Further yet, advances in the science (since 2016) of methane measurement produced by dams and reservoirs suggests that emissions are likely higher than those estimated by the 2016 study. In March of 2022, a research and advocacy team led by Patagonia, Save The Colorado, and Earthjustice submitted a petition to the U.S. EPA calling for dam/reservoir emissions to be counted in the EPA’s GHG reporting program. In that petition, a white paper discusses additional emissions sources and pathways that, if counted, could dramatically increase the estimates from Colorado River hydropower. The petition to the EPA was co-signed by over 140 environmental groups and is currently under consideration by the EPA.

Stating that hydropower generated by Glen Canyon and Hoover Dam is ‘clean energy’ or ‘carbon free’ is not true. The U.S. government, first and foremost, must stop making this claim and must correct the public record, agency communications, and media reports.

It’s likely that replacing Glen Canyon and Hoover Dam hydropower with natural gas-fired powerplants would not increase GHG emissions. Further, replacing Hoover Dam electricity with natural gas would likely decrease GHG emissions, while replacing both hydropower facilities with wind or solar would almost certainly reduce GHG emissions.

For a discussion of how hydropower produces GHG emissions, especially methane, see this 2022 article in The Revelator that interviews EPA scientists and petition leaders.