Methane, the second largest contributor to climate change, is released into the atmosphere from space oil and gas industry, landfills again dairy farms. It also comes from another little-known source: dams.
As plants break down underwater, they create methane, which bubbles to the surface. California doesn’t know how much money comes from this water, but now several environmental groups are urging air regulators to find it, and some experts agree it’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 from water.
Pursuing it, he said, will help California make better decisions about hydropower as part of the energy mix and “improve the state’s status as a climate policy leader.”
A coalition of environmental groups – incl Friends of the River, Tell the Truth about Dams along with five other organizations, and clothing company Patagonia – submitted a request last month they said the California Air Resources Board should require reports on greenhouse gas emissions from dams and reservoirs. They oppose dams because they harm rivers.
The board is in charge of controlling air pollutants that cause global warming. California set a goal of reducing methane emissions by 40% below 2013 levels by 2030.
A drone view of Bidwell Bar Marina on Lake Oroville in Butte County, Calif., on Jan. 8.
(Nick Shockey / Calif. Department of Water Resources)
Methane from the water is a “blind spot” as California works to meet its climate goals, said Keiko Mertz, policy director for Friends of the River.
“You cannot have such a powerful greenhouse gas that is not known where it is,” he said.
His party opposes the government’s proposed construction plan Reservoir sites northwest of Sacramento, and wrangle project backers over conflicting emission rates.
Measuring methane in a lake is more complicated than measuring pipelines from natural gas wells or landfills, scientists say. Another reason is that methane is highly dispersed and satellite sensors have trouble picking it up over a large area.
The value also varies over time, making it difficult to predict.
Scientists have been working on that.
Although this methane is difficult to detect with satellites, more sensitive instruments aboard airplanes will be ready in the next few years, said Riley Duren, CEO of Carbon Mapper, a Pasadena-based nonprofit. “We’re definitely going to look at dams and reservoirs and see if we can do a better job of tracking it.”
The US Environmental Protection Agency said in 2024 report that “floodplains” including lakes represent a major source of methane. The EPA has estimated 2022 carbon emissions from floodplains as equal to 44.4 million metric tons of carbon dioxide – comparable to US iron and steel plants.
Scientists from the EPA and other government agencies too tested for given gases in some dams floating devices are used.
Both studies in 2021, researchers estimated that the water stored behind the world’s dams releases 10 and 22 million tons of methane per year – roughly equivalent to 3%-7% of all methane from human activities.
A July 2021 photo of barbed wire on a farm in the community of Sites, Calif. The proposed Sites Reservoir would put this area under water.
(Adam Beam/Associated Press)
A non-profit organization Weather TRACEwhich tracks greenhouse gases, has begun measuring thousands of dams around the world data on its websiteincluding 1,882 in the United States.
Scientists with the Environmental Defense Fund said in 2019 learn that hydroelectric plants and dams can emit large amounts of greenhouse gases, but their depth and composition, the amount of submerged vegetation, and the local climate have an impact.
They found that some hydroelectric plants emit small amounts of greenhouse gases, while in some extreme cases, emissions “can be greater than those from coal-fired power plants” per kilowatt of electricity produced.
For decades, dammed rivers have caused conflicts around the world, and international lenders have come under pressure not to support new projects. But there are currently 3,700 new hydropower plants planned or under construction around the world, so scientists say it’s important to carefully analyze the long-term climate of each project.
“We have to realize that hydropower is a carbon-free – in the sense that it has no greenhouse gas emissions – electricity source,” said Steven Hamburg, EDF’s chief scientist and co-author of the study. “In building any new facilities, we want to carefully consider those impacts and minimize them.”
Regarding the request to California air traffic controllers, Hamburg said, having more information is always good but unlike the oil industry or landfills, where people have clear strategies to reduce methane, it is difficult to curb emissions, so “the value of having high-quality data is not clear to me.”
But Harrison, of Washington State University, said having better data would be helpful. Another way, he said, would be to change the dam workers when and how much they lower the dam levels, which could contribute to the escape of more gases.
It’s also important when planning any new dam, Harrison said, to analyze how much greenhouse gases it will emit into the atmosphere over its lifetime.
The California Air Resources Board plans to respond to request at the end of July.
“This request raises important questions that CARB would like to consider,” spokeswoman Lindsay Buckley said in an email.
In creating the government’s information on greenhouse gases, the agency’s experts are looking at guidance from the UN Intergovernmental Panel on Climate Change, Buckley said. The IPCC has already explained it methods by measuring how much methane sources emit.
