A yearlong assessment of the controversial Shuangjiangkou hydropower project in southwestern China has been given approval on Monday, prompting concern among green campaigners and local residents.

Despite critics claiming the dam - on the upper reaches of Dadu River in Sichuan province - would affect water quality, kill fish and result in several nature reserves being submerged, the Ministry of Environmental Protection gave the assessment the green light.

China Guodian Corp has invested 24.68 billion yuan ($4 billion) in the hydropower project, which started construction in 2008. The project is expected to generate an installed capacity of 2,000 megawatts.