In anticipation of a regional summit this weekend, government officials and civil society have their sights locked on a controversial hydropower development just across the Cambodian border in Laos.

NGO Forum submitted an open letter yesterday urging Prime Minister Hun Sen to confront Laos about its Don Sahong hydropower project, which environmentalists have described as a potential disaster for the Mekong’s biodiversity and the food security the river provides to millions.

The letter contains more than 400 thumbprints collected during a march against the dam last weekend. “We hope these thumbprints motivate the leader, as they are the evidence of direct victims from this dam,” Tek Vannara, executive director of NGO Forum, said.

The last-minute plea for action comes just days before the 2nd Summit of the Mekong River Commission in Ho Chi Minh City, where prime ministers from Cambodia, Thailand, Vietnam and Laos are expected to discuss transboundary cooperation and sustainable development in the Lower Mekong Basin.

Since the first summit in 2010, conservationists have expressed concern that it – and the regional cooperation it purportedly assists – is on the verge of collapse, with Laos unilaterally going ahead with work on the first two mainstream hydropower dams, Don Sahong and Xayaburi.

“Rather than taking steps forward in the sustainable management of the Mekong River, we have taken a leap backwards, leaving the region at even greater risk,” Pianporn Deetes, Thailand campaigns coordinator for International Rivers, said in a statement released yesterday.

Preceding Saturday’s summit, the commission is hosting a conference during which the Cambodian delegation is expected to stage an intervention and demand the Don Sahong project be redesigned with downstream impact in mind, according to Conservation International.

Such a move by the delegation is urged by international groups that hope government leaders will agree to postpone mainstream projects during the summit.

“It is critical that Mekong leaders . . . issue a declaration condemning dams on the Mekong mainstream,” International Rivers’ Southeast Asia coordinator Ame Trandem said. “If the summit becomes nothing more than a public relations exercise at the expense of the millions of people in the Mekong region who depend on the river, the international community must work with leaders to find a new platform for regional cooperation and improved decision-making on the mainstream dams.”