Dams and reservoirs are significant emitters of methane, but currently, their footprint isn’t being tracked by the federal government. That could change with the success of a new petition that calls for the EPA to include these emission sources in the federal government’s Greenhouse Gas Reporting Program. The petition, brought by more than 130 groups, including Patagonia, Sierra Club, and other businesses and environmental organizations, was filed by Earthjustice, and calls out the “lack of awareness and mistaken assumptions regarding dams and reservoirs” [Greenhouse Gas] emissions.”

Even though the government isn’t currently tracking these emissions, some scientists have. Studies show that the Hoover Dam and Lake Mead reservoir emit approximately 12.3 million metric tons of carbon dioxide equivalent annually.

Why This Matters

The first step to tackling emissions is with proper monitoring and data. Given that methane is one of the primary gases causing global warming (about 30% can be traced back to it), reducing methane emissions is key to preventing the most severe impacts of the climate crisis. A better understanding of these emissions will lead to better decision-making for developing clean energy infrastructure in this critical decade. Hydropower is often presented as a zero-emissions form of energy, but it’s not when the dams and reservoirs it depends on are taken into account.

"You can’t solve the biggest problem facing humanity without good information,” Patagonia CEO Ryan Gellert argued in a statement. "The United States is investing record amounts of money in infrastructure and energy. We need all the information we can gather about the climate impacts so communities and the government can make sound decisions to protect our planet and support communities.”

Breaking Down The Emissions

The EPA is currently tracking nearly 8,000 sites, but dams, reservoirs, and hydropower facilities aren’t included even though they emit methane as well as carbon dioxide and nitrous oxide. These emissions come from multiple points, including hydropower turbines, spillways, and downstream water discharges. Dams also trap both organic and human-made materials that decompose under reservoir waters.

Worldwide, reservoirs emit around 1.07 gigatons of carbon dioxide, the equivalent weight of 10,000 US aircraft carriers and more than annual emissions of Germany, the world’s sixth-largest emitter.

"Dams and reservoirs that send potent methane into our atmosphere have been given a free pass even from disclosure,” Gary Wockner, executive director of Save the Colorado and leader of the petition process, said in a statement. "We are tolerating a myth that hydroelectric power is clean energy. It isn’t. If you start to count the methane emissions generated from damming rivers and filling reservoirs, we can build some accountability.”