Construction of the Don Sahong hydropower project in southern Laos is likely to decimate an already dwindling population of critically endangered Mekong dolphins, according to a World Wildlife Fund science brief published today.

About 85 dolphins inhabit a deep-water pool restricted to a stretch of the Mekong River mainstream that runs through northeastern Cambodia – an area that will witness intense industrial activity if the dam moves forward, WWF-Cambodia country director Chhith Sam Ath said.

“Plans to construct the Don Sahong dam in a channel immediately upstream from these dolphins will likely hasten their disappearance from the Mekong,” Sam Ath said.

“The dam’s impacts on the dolphins probably cannot be mitigated, and certainly not through the limited and vague plans outlined in the project’s environmental impact assessment,” he added.

The company’s environmental impact assessment published last year offers ways to mitigate risks to dolphins, including deepening a neighbouring channel to provide an alternative dry-season fish passage.

However, the excavation necessary to deepen the channel would require explosives that create strong percussive forces that could potentially kill the dolphins, Gerry Ryan, a technical adviser to WWF-Cambodia, wrote in the brief.

“If nearby explosions do not kill dolphins outright, injury could severely compromise the animals’ ability to find food, navigate or communicate, indirectly causing their death,” the brief states.

According to the Mekong River Commission’s assessment, the excavation process would require explosives to clear 1.9 million cubic metres of sediment from the riverbed, an amount capable of devastating the river’s ecosystem.

Construction is also likely to indirectly affect the dolphin population by disrupting sediment and water flow and interrupting fish migration, said Ame Trandem, Southeast Asia program director for International Rivers.

Dam builder Mega First Corporation Berhad did not respond to questions before press time.