Five civil society organisations (CSOs) in Cambodia working on the Luang Prabang hydropower project in Laos said in a press statement on Tuesday that it should be delayed because Lao authorities have insufficient details concerning the transboundary impact assessment and don’t have concrete measures to mitigate its impact on lower Mekong countries.

The CSOs have been involved in the consultation process of the project since late last year, and they have requested that further studies be carried out with relevant stakeholders before operations commence.

The press statement further said the issues are related to fish migration, hydrology and sediment flow which could impact the Tonle Sap lake. Without concrete mitigation measures, the CSOs said, negative impacts would result.

Mak Bunthoeurn, the coordinator of the Rivers Coalition of Cambodia (RCC), which is led by the NGO Forum on Cambodia, said on Wednesday that the change of natural water flow would impact Tonle Sap lake, fish farming and Cambodian food security.

He said the assessment of the project’s impact on Tonle Sap Lake being used was published in 2014, even though more recent studies have been conducted.

He further said that cascade dams on the Mekong would capture much of the sediment flowing from upstream.

The water flow will severely fluctuate and diminish sediment flows downstream leading to concerns of bank erosion and related alterations of the river.

He said aquatic and terrestrial biota could also be affected. None of these concerns is mentioned in the assessment currently being used in the project.

“Given the potential risks caused by mainstream hydropower dams to Cambodian communities who rely on the Mekong for their livelihood, CSOs working on water governance in Cambodia are requesting a delay on the proposed project,” he said.

The representative of the Lao Embassy in Cambodia did not respond to request for comment on Wednesday.

Deputy secretary-general of the Cambodia National Mekong Committee (CNMC) Kol Vathana said the Luang Prabang hydropower project is located more than 1,000km from the Cambodia-Lao border.

Vathana said according to the laws concerning the Mekong, member states have no right to oppose the project. The Lao side has no right to develop it without consideration of impacts on other countries either, he added.

He said before studying the project, the CNMC had considered the impacts and taken recommendations by CSOs.

“We allowed them [CSOs] to identify all the problems. We will continue to listen to their ideas. Normally, CSOs do this work because they get aid from foreigners. But concerning development or conservation, we understand it already. It is nothing problematic,” he said.

He said the Luang Prabang hydropower project is located in northern Laos upstream from the Xayaburi hydropower dam and downstream from the Pak Beng Dam.

It is a development project between Laos and a company connected to the Vietnamese government, Petro Vietnamese Corporate.

The project is scheduled to begin construction later this year and is expected to be completed in 2027. The hydropower dam is designed to generate 1,460MW of power, which will be sold to Thailand and Vietnam.