Some questions remain about whether hydro dams on the upper Mekong River in China exacerbated conditions during Cambodia’s devastating drought of 2010, environmental groups say, as China’s dam program powers ahead.

When the first power-generating unit was switched on last month at China’s giant 262-metre tall Nuozhadu hydroelectric dam, which will be largest on the river when completed in 2014, state-run newspaper the China Daily sang its praises as a dam that would significantly reduce carbon dioxide emissions.

Extensive research, the China Daily added, also showed potential impacts of the Nuozhadu and others dams on countries downstream – including Cambodia, where fishing communities along the Mekong fear Laos’s proposed Xayaburi dam – would be minimal.

Research showed “water flow in the river’s China section accounted for only 13.5 per cent of the river’s total, making the country’s hydropower development have little impact downstream”, it said.

Ame Trandem, Southeast Asia program director for International Rivers, said, however, that China’s section of the Mekong, known in that country as the Lancang River, provided as much as 50 per cent of the river’s total water flow during the dry season, when countries including Cambodia depend on it most.

An example of how important this flow is to Mekong countries, Trandem said, was the 2010 drought – one of the worst in 50 years – when China began filling the reservoir of its giant 4,200-megawatt Xiawan dam.

“[This] exacerbated the drought that the region was experiencing, because there was little rainfall in the dry season that year,” she said.

“Essentially, they were holding back water that could have come downstream.”

NGO collective Save the Mekong Coalition wrote to the Mekong River Commission at the time, inquiring about the potential effects China’s dams were having on drought conditions and had been promised a detailed report, Trandem said.

The coalition has yet to receive this analysis, she said, while China is not obliged to provide Mekong countries details of their research.

In an emailed response this week, the MRC secretariat said it had not undertaken specific analysis of the effects of China’s dams on Cambodia during the 2010 dry season.

“The MRC released various assessment reports at the time of the 2010 drought and also carried out analysis at the request of member countries,” the statement says.

“Additional data from China was also released. The MRC in 2010 provided its analysis on the drought situation in an opinion-editorial piece published in the Bangkok Post newspaper.

“The analysis revealed that the low water levels in the Mekong and its tributaries were the result of extreme natural conditions. Very low rainfall for this dry season, following a particularly early end to the wet season in 2009, led to river levels below those seen in at least 50 years.”

Srisuwan Kuankachorn, co-director of Towards Ecological Recovery and Regional Alliance, a member the Save the Mekong Coalition, said it was “not an overstatement” to draw a link between China’s dams and the drought situation in Cambodia in 2010.

China has announced plans for at least seven hydroelectric dams on its section of the Mekong, although reports outside of China suggest it plans to build more.

To contact the reporter on this story: Shane Worrell at [email protected]