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Thank You, EPA, For Reporting Greenhouse Gas Emissions From Dams and Reservoirs to the U.N.

Thank You, EPA, For Reporting Greenhouse Gas Emissions From Dams and Reservoirs to the U.N.

EPA sets March 17 Deadline for Public Comment on 2023 Report

It’s been 10 years since I first learned and wrote about how dams and reservoirs emitted greenhouse gases and made climate change worse, and so it’s great to see the U.S. Environmental Protection Agency finally taking action on the problem.

For the first time in history in 2022, the U.S. government reported the methane emissions from dams and reservoirs across the U.S. to the United Nations using the recommended protocol from the Intergovernmental Panel on Climate Change (IPCC).

For over 15 years, the IPCC has recommended that all U.N. countries report reservoir methane emissions, but it wasn’t until an update to the IPCC protocol in 2019 that made it easier for countries to report. The U.S. Environmental Protection Agency (EPA) is the agency that now calculates and reports these methane emissions to the U.N.

This is great news for the U.S. to be a leader in methane reporting, one of the most potent greenhouse gases. It’s also great news for the ongoing battle to protect rivers from dams, and can even help decommission dams. Because of the carbon and biodiversity that river ecosystems protect and sequester, free-flowing rivers are increasingly seen as important nature-based solutions in the fight against climate change.

The genesis for this U.N. reporting began over thirty years ago when a small team of scientists in Brazil started measuring the methane produced at hydropower reservoirs. The scientists found surprising results, indicating that hydropower dams and reservoirs in tropical countries like Brazil emit high levels of methane, sometimes equivalent to as much as a coal-fired power plant or more. The scientists involved with these studies started calling these tropical hydropower projects “methane factories.”

Why do dams and reservoirs produce emissions like methane? Dams, of course, block rivers and create large non-natural reservoirs on top of landscapes that were never naturally flooded. When organic material such as vegetation, sediment, algae and other runoff is trapped in, or flows into, a reservoir, that material decomposes underwater releasing methane. This is a natural process called “anaerobic decomposition,” but it is unnatural and dramatically intensified in reservoir systems that are not natural lakes.

These emissions occur at reservoirs all over the planet, not just in tropical countries. A study published in September 2016 by a team of Swiss scientists, used previous methane measurements at dams and reservoirs around the world to create a statistical model that estimated emissions from nearly 1,500 hydropower plants across the planet. The study’s conclusions further rocked the climate change world. As one example, methane emissions from Hoover Dam and Lake Mead on the Colorado River near Las Vegas were estimated to be about equal to a coal-fired power plant that produced the same amount of electricity. Hoover Dam provides electricity to parts of Southern California. Many other large U.S. reservoirs had similar results.

Also In 2016, an international team of scientists synthesized dozens of studies around the globe and found that hydropower’s methane emissions have been dramatically under-measured. This analysis, published in the journal Bioscience and funded by the Army Corps of Engineers, the EPA and U.S. National Science Foundation, made international news with its conclusion that the Intergovernmental Panel on Climate Change needed to revise its calculations and include hydropower’s significant emissions in its climate change scenarios. And in 2019, the IPCC did that.

The U.S. reporting fits in nicely under President Biden’s “new initiative to curb methane”, and will help scientists and policy makers better understand the role that reservoir-emitted methane plays in current and future climate impacts.

Further, the EPA is currently refining its methods for counting and reporting methane emitted from dams and reservoirs, a process that will likely result in even more methane being reported. In fact, the EPA’s 2023 draft greenhouse gas inventory is out for public comment right now, with a deadline of March 17, and the EPA is undergoing a rigorous study of 108 U.S. reservoir emissions that will be finalized later in 2023. I strongly support EPA’ continued research and refinement to better understand and report methane emissions from reservoirs.

Further yet, last year my organization joined Patagonia and Earthjustice and sent a formal petition to the EPA asking them to require operators of dams and reservoirs to count and report emissions for each individual large facility in the U.S. Having this publicly available information will aid public-interest groups, like ours, that engage in permitting around proposed new dams, re-licensing of dams, and even decommissioning of dams.

Finally, because the U.S. helps set climate policy across the planet and helps fund various development projects through the World Bank, International Monetary Fund, U.S. Agency for International Development, and other global financial instructions, having the U.S. lead on methane reporting will facilitate better and more informed decision-making in future dam projects everywhere.

I applaud this important step of the EPA to report the methane emissions from dams, and I encourage a vigilant effort moving forward to grapple with this large climate-pollution emitter.

Gary Wockner, PhD, is a global river-protection advocate and directs the Save The Colorado River campaign. Contact:


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