China’s Hydropower May be Global Warming Time Bomb

China is scrambling to build massive hydropower dams to curb pollution and slake its thirst for energy, but scientists warn that reservoirs can also worsen global warming by emitting a powerful greenhouse gas.

Methane, which traps heat much more efficiently than carbon dioxide, is produced by plants and animals rotting underwater and released when that water rushes through hydropower turbines.
In a country that is already the world’s top hydropower generator and aims to more than double capacity, dams could raise methane emissions by around 8 percent, recent research shows.

The flammable gas could also be trapped and used for power generation if dam designs were adapted, providing Beijing with cheap and clean energy instead of a global warming burden.

But the data is so new that even United Nations rules on calculating national emissions do not require dams to be included, dimming the chances of fast action.

China is set to overtake the United States as top producer of carbon dioxide this year and is the leading emitter of acid-rain causing sulphur dioxide. As part of a bid to constrain emissions growth, it is promoting renewable energy.

A string of hydropower reservoirs are the centrepiece of this plan, and their methane emissions may offset many benefits.

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