How Hydropower Missed the Boat on the American Climate

by Colin Mequet

America’s dams are crumbling. Across the nation, aging embankments––sometimes centuries old––that once evoked human ingenuity and subjugation of nature are suffering from neglect and abandonment. Now, many dams are being removed to prevent collapse and flooding. In many cases, renewable energy infrastructure is implicated. Hydroelectric facilities are being decommissioned at increasing rates, a surprising phenomenon amid the world’s race to decarbonize.

Meanwhile, global hydropower development is experiencing unprecedented growth. Researchers have found that global hydroelectric dam development is expected to massively proliferate this decade in the name of sustainable development. The International Energy Agency estimates that hydropower must double its current five-year growth rate through 2030 if the world is to reach net-zero carbon emissions by 2050.

The United States, however, is still happy to watch from the sidelines. Even as climate change tasks the world with an existential imperative to decarbonize, largescale hydropower expansion is looking increasingly unlikely. America’s second-largest renewable energy source still suffers from the same sustainability issues that have plagued the country for decades, and environmental advocates want to explore other solutions to the climate crisis.

The strong opposition to dams in the United States draws its roots from hydroelectricity’s initial rise to prominence. The American dam boom lasted from the late 19th through the mid-20th centuries, in a period of rapid, virtually unchecked construction.

dams in the United States that was really part of Manifest Destiny,” said Meg Mills-Novoa, assistant professor within the Division of Society and Environment and the Energy and Resources Group at UC Berkeley. “These dams were about energy production, but they were also about claiming territory and generating electricity for things like mining, for urban expansion.”

“What we saw as a result of that was incredible ecological and environmental consequences,” she said. “And we also saw social backlash where communities were dispossessed and relocated, where control over water was held by external forces. There was both a social and environmental movement, and consciousness grew.”

Heavily criticized by environmentalists and a hard sell to local communities, hydropower development slowly halted as the 20th century wore on. Its share of the United States’ energy mix peaked at 5.02% in 1983 before plateauing between 2.4-3.4% until present. During its decades of stagnation, natural gas, wind, and nuclear energy all rapidly expanded, joined more recently by solar energy. Hydroelectricity earned the nickname “the forgotten giant of renewable energy” as its decline wore on.

However, as this dam boom infrastructure ages and deteriorates, it is beginning to re-enter the national consciousness. By 2025, 70% of U.S. dams will be over 50 years old, and many are already falling into decrepitude. The National Inventory of Dams classifies 17% of dams nationwide as “high hazard,” meaning that failure or misoperation would “probably cause loss of human life.”

“In the late 19th century, we saw an explosion of

With communities and property at risk, there is an imperative to act now. But in light of increasing knowledge of large hydroelectric facilities’ impacts on local environments, it is clear that centuries-old concerns surrounding large hydropower projects and their environmental impacts were never quelled. America’s robust dam opposition has been reignited, and it is being channeled into ensuring that the world’s dam boom does not infiltrate the United States.

Colleen McNally-Murphy, associate director of the Hydropower Reform Coalition, points to an increasing knowledge of large hydroelectric facilities’ reservoir emissions as a key reason for hydropower’s inability to renew itself today. “It’s important to recognize that hydropower is not emissions free,” she said. “In fact, at some reservoirs, the emissions coming out of these projects are significant. Some colleagues in Alabama just published their results from studying a couple of their dams, and one of these projects has emissions that are on par with natural gas facilities.”

McNally-Murphy references an Alabama Rivers Alliance study, part of the Hydropower Reform Coalition. It examined emissions from two Alabama reservoirs, finding that they released “substantial amounts of methane,” with total emissions that equated one and a half to four times the “clean energy” threshold proposed by Congress.

These studies have created major cleavages within environmental and energy communities on the ideal role of hydropower in the future energy grid. The resulting disharmony between allies of the climate transition, coupled with opposition from local communities that are broadly against mega-dam construction in their backyards, has created a unique, powerful alliance of dam obstructionists.

“Indigenous communities, indigenous coalitions, environmental activists, environmental institutions, even just local community groups are concerned,” Mills-Novoa said. “And most of those actors are relying on the permitting process to impede [large dams]. And in many cases, they have been really effective.”

The result: As dams reach the end of their life cycles, many will not be reconstructed. 21st-century dam opponents are building on the work of the 20th century to ensure that dams are aged into decommissioning. This was formalized by the United States Federal Government in the allotment of dam funding in the Infrastructure Investment and Jobs Act. The $1.2 trillion infrastructure bill, which passed in November 2021, contained $2.4 billion dollars to be spent on dam infrastructure, of which two-thirds were earmarked for dam removal and dam safety upgrades –– no money went to the creation of new hydroelectric facilities.

“We’re really done with the dam building era,” said McNally-Murphy. “Now, we’re realizing that the hydropower fleet that we have in this country is not necessarily the hydropower fleet that we need for a clean energy future.”

Even as the U.S. opens its checkbook to finance the climate transition, dam opponents have been successful in ensuring that large hydropower remains a forgotten energy source.