Small Isn’t Beautiful

It’s time to rethink the world’s growing interest in using small dams to generate clean electricity, two Indian researchers argue. On closer look, small hydropower could bring many of the same environmental problems that now haunt big dams around the planet.

Concerns about climate change and fuel prices have helped create “a great resurgence of interest all over the world in the development of ‘small’ hydropower systems (SHSs),” which typically generate less than 25 megawatts of power, Tasneem Abbasi and S.A. Abbasi of Pondicherry University in India write in Renewable and Sustainable Energy Reviews. “The surge is essentially propelled by the belief that SHSs… are a source of clean energy with little or no adverse impacts on the environment.” A 1998 International Energy Agency review, for instance, concluded that SHSs “tend to have a relatively modest and localized impact on the environment.”

That view has helped drive a surge in small dam construction. Worldwide, small hydro now produces 47,000 megawatts of power, according to the European Renewable Energy Council, with production doubling in some areas over the last decade. Asia and Europe are small hydro leaders, with China alone already boasting some 100,000 small dams. And “other countries, including two the world’s fastest growing economies – India and Brazil – are putting in place increasingly ambitious plans to tap” small hydro, the authors note.

The rush, however, reminds the authors of the “very optimistic, almost reverential, attitude towards hydropower projects which…prevailed during the early 1950s.” Then, they note, nations built hundreds of large dams that later turned out to have extensive environmental consequences, ranging from destroyed fisheries to declining water quality. Now, the authors worry we’re ready to repeat history.

“By all reasoned assessments, the environmental problems caused by small hydro look small in comparison to large hydro,” they concede. But after walking through a series of scenarios, they argue those advantages fade when large and small projects are compared by “the scale of impact per kilowatt of power generated. Once this is done, it emerges that the problems that would be caused due to widespread use of SHS would be no less numerous, and no less serious, per kilowatt generated, than those from centralized hydropower.” Problems such as siltation and eutrophication, for example, are likely to be common at “mini” and “micro” projects because they tend to create small, shallow pools. And the emissions of methane and other greenhouse gases from such muddy lagoons could rival emissions from rice paddies, they add.

“It is a moot point,” they conclude, “whether the adverse impacts of a large number of small hydro would be only as severe as, or worse than, the impact of the ‘known devils’ – large hydropower projects of equivalent capacity.” It’s time, they say, to put in place rules and remedial measures that “may save the world from considerable disillusionment and environmental damage.” David Malakoff | March 10, 2011

Source: Abbasi, T., & Abbasi, S. (2011). Small hydro and the environmental implications of its extensive utilization. Renewable and Sustainable Energy Reviews, 15 (4), 2134-2143 DOI: 10.1016/j.rser.2010.11.050

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