The Dalles Dam
Last September, the Washington Post wrote about a study conducted by researchers at Washington State University. The study, which provides a more comprehensive look at all known greenhouse gas emission estimates from reservoirs around the world, found that reservoir methane emissions have probably been under reported due to different measurement techniques. Methane is a greenhouse gas that has a very strong short-term warming effect.
At the Council's power committee meeting, Energy Policy Analyst Mike Starrett presented his analysis of the study's finding and relevance to the Pacific Northwest's reservoir system.
A key characteristic of reservoirs that emit high levels of methane is that they have a lot of plant growth and algae. WSU News notes:
"Unlike natural water bodies, reservoirs tend to have flooded large amounts of organic matter that produce carbon dioxide, methane and nitrous oxide as they decompose. Reservoirs also receive a lot of organic matter and 'nutrients' like nitrogen and phosphorous from upstream rivers, which can further stimulate greenhouse gas production."
Starrett found that, according to the best available information, the federal Columbia River system doesn't produce that kind of nutrient-rich environment that supports excessive plant growth, and therefore it's unlikely to emit large levels of methane gas.
The Council's analysis confirms conclusions by various regional utilities and the U.S. Army Corps of Engineers. According to the Corps:
"For the relatively clean reservoirs of the Federal Columbia River Power System, which include the lower Snake River dams, conditions for low dissolved oxygen concentrations are not prevalent, thus methane gas is generally not an issue."
For more information:
Bubbling Up: Methane from Reservoirs Presents Climate Change Challenge
Methane Emissions May Swell from Behind Dams