Dams Are Methane Machines—It’s Time for California to Acknowledge It
San Luis Reservoir during a significant toxic algae bloom. San Luis is estimated to emit more methane from turbine degassing than any other dam in the state. Credit: DWR
A dirty and inconvenient truth is hiding in plain sight: dams and reservoirs emit significant amounts of methane, one of the most potent greenhouse gases. Although California prides itself on climate leadership, the State does not include these emissions in its climate accounting. That’s why Friends of the River and other organizations have petitioned the California Air Resources Board, our state’s key emissions regulator, to require dam and reservoir operators to measure and report their greenhouse gas emissions(1).
You can help. Sign this letter of support.
The science behind the petition is well established. When rivers are dammed, organic material builds up in the reservoir and breaks down in low-oxygen conditions. The warming effect of the methane that is produced as a result is 20-80 times stronger than the warming effect of carbon dioxide, and it’s faster too. In other words, methane heats the atmosphere up more quickly and intensely than carbon dioxide. Because of the outsized impacts of methane, California has committed to cutting methane emissions by 40% by 2030. Yet reservoirs continuously generate and release these emissions from their surfaces and through hydropower turbines. This is one of the reasons that hydropower cannot be considered “green,” or “climate-friendly” energy.
The scale is not trivial. Estimated greenhouse gas emissions from California’s largest reservoirs are roughly equivalent to 1.2 million gas-powered cars on the road each year(2). The proposed Sites Reservoir alone is anticipated to add the emissions equivalent to another 80,000 cars(3). The threshold for reporting emissions is 10,000 metric tons of CO2 equivalent per year. Many dams in California greatly exceed that limit. For example, San Luis Dam is estimated to produce 28 times that amount.
California already requires major emitters like the oil industry, power generation, and landfills to measure and report their emissions. Those measurements are then included in the State’s Cap and Trade program, which is one of its main tools to fight climate change. Not measuring reservoir emissions creates a gap in the effectiveness of this program, and undermines our credibility as climate leaders. For over 15 years, the Intergovernmental Panel on Climate Change (IPCC), the international authority on climate change policy, has recommended that all United Nations member countries report their reservoir greenhouse gas emissions. We must catch up.
Dams and reservoirs should be treated like other major polluters
Dams and reservoirs should be added to California’s Mandatory Greenhouse Gas Reporting Program as soon as possible. The best available science, including the methods recommended by the IPCC, should be used to measure those emissions to ensure the best accounting possible.
For decades, we have understood the many harms caused by dams, including blocking fish passage, disrupting sediment transport and river connectivity, trapping and concentrating contaminants in reservoirs, and degrading important economic and cultural uses. The growing body of science on greenhouse gas emissions is simply the latest evidence that highly engineered river systems come with real and lasting costs. As California confronts a changing climate, we must take a harder look at the tradeoffs of our water infrastructure. Our values are shifting, and our decisions must shift with them. A sustainable future means working with rivers and with nature, not against them.
Resources
(1) Petition to CARB, and bibliography
(2) Full report on the estimated methane emissions for major California dams and reservoirs
(3) Estimate of Greenhouse Gas Emissions for the Proposed Sites Reservoir Project
(4) LA Times—Would a new reservoir give off lots of greenhouse gases?
