When you think about sources of planet-heating greenhouse gases, dams and reservoirs probably aren’t some of the first things that come to mind. But scientific research has shown that reservoirs emit significant amounts of methane, a potent greenhouse gas. It’s produced by decomposing plants and other organic matter collecting near the bottom of reservoirs. Methane bubbles up to the surface of reservoirs, and also passes through dams and bubbles up downstream. Scientists call these processes ebullition and degassing. … [Experts] estimated that if [Sites] reservoir is built and filled, it would annually emit approximately 362,000 metric tons of emissions, measured as carbon dioxide equivalent.