The second largest contributor to climate change is methane spewing into the atmosphere. oil and gas industry, pothole filling And dairy farm. This is also coming from another lesser known source: reservoirs.
As plants break down underwater, they create methane, which then bubbles up to the surface. California doesn’t monitor how much water is coming from these vents, but many environmental groups are now urging air regulators to find out, and some experts agree that’s important.
“Reservoirs are an important source of methane,” said John Harrison, a professor at Washington State University’s School of the Environment. studies Greenhouse gases emitted from water bodies.
Tracking this will help California make better decisions about hydropower as part of its energy mix and “enhance the state’s position as a climate policy leader,” he said.
Coalition of environmental groups – including friends of the river, tell the truth about the dam And five other organizations, plus the textile company Patagonia – submitted a petition Last month he said the California Air Resources Board should require reporting on greenhouse gases from dams and reservoirs. They oppose dams because they damage rivers.
The board is in charge of regulating pollutants that cause global warming. California has set a Target To reduce methane emissions by 40% from 2013 levels by 2030.
A drone view of the Bidwell Bar Marina in Lake Oroville in Butte County, California on January 8.
(Nick Shockey/California Department of Water Resources)
Keiko Mertz, policy director of Friends of the River, said methane from the reservoirs is a “blind spot” as California works toward its climate goals.
“You can’t just leave such a powerful greenhouse gas unaccounted for,” he said.
His group opposes the state’s proposed construction plan land reservoir northwest of Sacramento, and have debated with proponents of the project over conflicting emissions estimates.
Scientists say estimating methane from a reservoir is more difficult than measuring smoke from natural gas wells or landfills. One reason for this is that methane is more dispersed and satellites’ sensors have trouble capturing it over large areas.
The amount also changes over time, making estimation even more complicated.
Scientists are working on it.
Although this methane is difficult to detect with satellites, more sensitive instruments mounted on airplanes will be ready in the next few years, said Riley Duran, chief executive of the Air Force. carbon mapperA Pasadena-based nonprofit. “We’re definitely going to look at dams and reservoirs and see if we can do a better job of detecting this.”
US Environmental Protection Agency said in 2024 report “Flooded lands” including reservoirs represent a major source of methane. The EPA estimates that 2022 emissions from flooded lands will be equivalent to 44.4 million metric tons of carbon dioxide – the equivalent of 100,000 U.S. steel and iron plants.
Scientists at EPA and other federal agencies have also tested gases released Flotation devices are being used in some reservoirs.
in two studies In 2021, researchers estimated Water stored behind the world’s dams emits 10 to 22 million metric tons of methane per year – equivalent to about 3%-7% of all methane produced by human activities.
A July 2021 photo of barbed wire fencing on a farm in the community of Sites, California. The proposed SITES reservoir would put this area under water.
(Adam Beam/Associated Press)
non profitable climate traceThe greenhouse gas tracker has begun incorporating estimates from thousands of reservoirs around the world. Data on its websiteThat includes 1,882 in the United States.
Environmental Defense Fund scientists said in 2019 Study Hydropower plants and reservoirs can emit substantial greenhouse gases, but their depth and design, the amount of submerged vegetation, and the local climate affect how much.
They found that some hydropower plants release small amounts of planet-warming gases, while in some extreme cases, emissions per kilowatt of electricity generated can “exceed those of coal-fired power plants”.
For decades, building dams on rivers has sparked bitter disputes in places around the world, and international lenders have come under pressure not to support new projects. But there are currently 3,700 new hydropower facilities planned or under construction around the world, so scientists say it is important to thoroughly analyze the long-term climate footprint of each project.
“We must recognize that hydropower is not a carbon-free – in the sense that it has no greenhouse gas emissions – source of electricity,” said Steven Hamburg, EDF chief scientist and co-author of the study. “In building any new facility, we want to carefully look at and minimize those impacts.”
As for the petition to California air regulators, Hamburg said, it’s always good to have more information but unlike the oil industry or landfills, where people have clear strategies for reducing methane, it’s hard to curb emissions from reservoirs, so “the value of high-quality data is unclear to me.”
But Washington State University’s Harrison said it would be useful to have better data. One approach could be to require dam operators to change when and by how much they lower reservoir levels, he said, which could affect the amount of gases released.
When planning any new dam, it’s also important to analyze how many greenhouse gases it will release into the atmosphere over its lifetime, Harrison said.
The California Air Resources Board plans to respond petition By the end of July.
“This petition raises important questions that CARB would like to consider,” spokeswoman Lindsey Buckley said in an email.
In developing the state’s data on greenhouse gases, agency experts consider guidance from the United Nations Intergovernmental Panel on Climate Change, Buckley said. IPCC has already outlined methods To estimate how much methane the reservoirs are releasing.
