Environmentalists won a reprieve last month against construction of the Xayaburi dam on the lower Mekong River in Laos (Nature doi:10.1038/news.2011.220). But it is the Laos government that will have the final say.

China is leading this hydropower boom in southeast Asia, and aims to increase its hydropower from 200 to 380 gigawatts by 2020. Dams are planned or completed at sites along other international rivers, including 13 on the Salween or Nujiang, which is protected by UNESCO (United Nations Educational, Scientific and Cultural Organization), and 20 along the Brahmaputra — all in rare and fragile environments.

In 2004, Chinese Premier Wen Jiabao halted the development of dams along the Salween. But the order was lifted after the National Development and Reform Commission called last year for dam building to proceed, prompted by soaring power demands and the energy and water conservation targets of China's latest five-year plan.

This wave of development in hydropower and its effect on water resources is likely to intensify water-related disputes among neighbouring riparian countries. To assess properly the impact of building hydropower dams, transparent policies and multinational cooperation are crucial.