A dam-building boom across the developing world will bring electricity to growing, power-hungry cities across Asia, Africa and Latin America. But it can also put the world’s climate and people at risk, according to a new study by researchers aiming to reduce the host of environmental problems that can come with dam construction.
Researchers at Tübingen University in Germany have have compiled a database of the 3,700 different dam projects planned or underway worldwide. They predict that global hydropower capacity will double in the next 10 years — an increase set to reduce by 20 percent the number of free-flowing rivers left on Earth.
The building boom also poses a hazard to the rich biodiversity of major river watersheds, including those of the Mekong, Amazon and Congo, on which millions depend.
The database aims to be a resource for planners trying to reduce the environmental impact of such projects, according to the German study. The Berlin-based Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB) also took part in the project. The researchers released their study Friday in Copenhagen.
Population growth, energy demand and concerns over global climate change have spurred the development of hydroelectric dams as an energy source, but the researchers say it is not a cure-all for a warming world.
“Despite the renewable nature of hydroelectricity, this technology also comes along with severe social and ecological adverse effects, e.g. relocation of people and transboundary conflicts, fragmentation of free-flowing rivers, habitat changes, thus further threatening freshwater biodiversity,” the researchers said.
Despite their “renewable” label, hydroelectric dams can lead to the production of greenhouse gases, especially methane, when plant matter decays beneath lakes that form behind dams. The gasses bubble up to the surface, and leak into the atmosphere.
While the promise of more electricity is real, the growth in its availability “will only partially close the electricity gap, may not substantially reduce greenhouse gas emission (carbon dioxide and methane), and may not erase interdependencies and social conflicts,” the study report says.
Christiane Zarfl, the lead researcher on the project, said planners should take into account the effect of multiple dams on the same river system and the “cumulative effect” they have on the environment.
The researchers said they hope their database will serve as a resource for planners trying to reduce the environmental impact of the often massive, years-long projects. People who live behind dams sometimes have to leave, as water levels rise and flood their homes. Authorities evicted 1.3 million of people living along the Yangtze River when China’s Three Gorges Dam rose during the 2000s.
"Displacement of local human population, potential conflicts on the river as a water resource, river fragmentation and thus habitat degradation and extinction of species are other consequences that we should be aware of when to decide where and how to build and operate a hydropower dam," Zarfl said in an email, adding that even if all the planned dams come online, they'll only amount to 18 percent of the world's energy needs, up from 16 percent now.
Zarfl and fellow researchers hope that their work will lead to more sustainable hydropower investment, but some environmental activists believe there is no such thing as a good dam.
“Hydropower is inappropriately classified as renewable,” said Jason Rainey, executive director of International Rivers, an environmental and human rights group. “Once a river is dammed, it can’t be renewed.”
The long-term effects of a dam, especially a mega-project like the Three Gorges, can be incalculable, uprooting people and plants, and altering the landscape itself.
“Of course developing countries need access to electricity to prosper, and the true renewables, that’s wind, solar and geothermal, are no longer fringe or boutique, and they’re quite cost-competitive,” Rainey added, pointing to recent growth of the technology in sub-Saharan Africa.
He called the failure to account for dams’ climate impact a “travesty.”
Rainey pointed to the planned Gibe 3 dam on the Omo River in Ethiopia as an example of a dam that will cause harm to area residents — including the 300,000 living around the desert lake that the river feeds, Lake Turkana, and the 200,000 people along the river. It will cut off the flow of water to the lake, which people rely on for drinking water and fishing, and it will disrupt the flow of the river, a lifeline in the desert.
Rupak Thapaliya of the Hydropower Reform Coalition, a nonprofit dam-reform organization that works in the United States, said that the world can learn from U.S. blunders.
Many dams built across the U.S. during the 20th century went up before their long-term impacts were known. Now, Thapaliya said environmentalists and regulators focus on reducing the impact these dams have on the environment, disrupting fish, flooding areas that were previously dry and depriving other places of the water that they had before.
“We didn’t know much about the ecosystem, and we didn’t have the environmental laws we do,” Thapaliya said. “Now that we built those dams, we realize the mistakes we made.”