The charade over whether to proceed with the Don Sahong Dam, the second Mekong mainstream hydropower project near the Lao-Cambodian border, will soon reach a defining moment. On Wednesday, the governments of Cambodia, Laos, Thailand and Vietnam are expected to bring to a close the Mekong River Commission’s six-month prior consultation process over the dam. The future of the river balances on what happens next.

The Don Sahong Dam’s prior consultation process requires the four countries to carry out a “due diligence” assessment of the dam’s effects on the Mekong and cooperate in “good faith” to reach agreement over whether to build the project. Despite the opportunities this presents, the consultation process has been widely viewed as little more than a diplomatic manoeuvre.

Laos made it clear from the start that the Don Sahong Dam would be built and that the process will at best serve to help improve its design. This political manoeuvring to exclude neighbouring countries from the decision to build the project on a river shared by more than 60 million people makes it clear that Laos is not acting in “good faith” and is intent on following the same failed process of the Xayaburi Dam, in which Laos proceeded on a unilateral basis, ignoring the significant concerns raised by its neighbours and their requests for more study. Laos has taken its unilateral decision before necessary baseline and transboundary impact assessments have been carried out.

Meanwhile, the Mekong River Commission, the body assigned to ensure regional cooperation over the Mekong, is going through an existential crisis. The Xayaburi Dam served as the first real test for the commission, and it’s widely acknowledged that the body lacked the political will to address the unilateral actions taken by the Lao government. The Don Sahong has now repeated this flawed process, ensuring that confidence in the commission to work for the interests of the Mekong region has reached an all-time low.

The implications of the business-as-usual approach towards the future of the Mekong are chilling. Scientific studies have overwhelmingly demonstrated that a healthy Mekong is irreplaceable, for the region’s rich inland fisheries and the food security it provides. Should the cascade of 11 mainstream dams be built, vital fish migration routes of the world’s largest inland fisheries would be blocked, along with sediment flows necessary for replenishing nutrients to the region’s agriculture, forcing the region perilously close to a food security calamity. Furthermore, research by Cambodia’s Fisheries Administration, WWF and the Australian National University have demonstrated that the protein, micronutrients and calories associated with the river’s fisheries cannot easily be replaced.

The Don Sahong would be built across the Mekong’s Hou Sahong Channel, the main channel supporting year-round fish migrations. While the Malaysian developer Mega-First Corporation has proposed to re-engineer nearby channels for alternative fish passage, the actual designs and fish-monitoring methods have not been made public, nor has exhaustive testing been carried out, rendering the mitigation proposal risky. With more than 100,000 truckloads of bedrock to be excavated to increase flows into the Hou Sahong Channel, one of the last remaining pools of the critically endangered Irrawaddy dolphins will also likely be wiped out. With the Mekong fisheries and the region’s food security at stake, Laos has failed to consider what will happen if the proposed mitigation measures fail.

With such high risks for the Mekong and its people, its clear proceeding with the Don Sahong at this point in time is reckless and irresponsible. The absence of a strong foundation with which to evaluate the transboundary impacts of the project and reach agreement on whether or not to proceed with it, demonstrate that the prior consultation process must be reformed. The four governments should seek to extend the process as they bring forward their respective positions on the dam. With the future of the river lying in the hands of Mekong governments, it’s time the four governments act responsibly, end their diplomatic charade and back their rhetoric with action. Construction towards the Don Sahong Dam must be immediately halted and sufficient studies on the project’s impacts must be carried out. The burden of proof that the project’s impacts will be limited and mitigation measures will succeed must be on the developer. Agreement must then be reached between all four countries and their people before proceeding.

The free reign of Mekong mainstream dam building must end now.

Ame Trandem is the Southeast Asia program director for International Rivers, an NGO working to protect rivers and the rights of communities who depend upon them.