Rights advocates have called for construction of the Lower Sesan II hydropower dam in Cambodia’s Stung Treng province to be halted until new environmental and social impact assessments can be carried following changes allegedly made to the project’s plans.

Hydrolancang International, which is building the dam with Cambodia’s Royal Group, has redesigned it with the aim of improving sediment management, NGO International Rivers has learned.

The planned changes include lowering the height of the dam and installing sluice gates, which will affect the size of the reservoir and the dam’s downstream impacts.

Hydrolancang has yet to publicly confirm the redesign and company representatives did not return calls or respond to emailed requests for comment yesterday.

Royal Group representatives could also not be reached.

Ame Trandem, Southeast Asia program director at International Rivers, said the construction, which began over a year ago, should stop until new studies could be carried out.

“Numerous scientific studies have come out over the past few years highlighting how serious the impacts of this dam will be to fisheries, food security, hydrology and the Tonle Sap lake. It’s clear that this is a project that should not be built,” she said.

Sao Sopheap, Ministry of Environment spokesman, was not aware of the reported redesign plans, but said if the firms had changed the design, the dam “must be looked at carefully to see if there’s a real need for conducting a new environmental and social impact assessment”.

The government has also commissioned a feasibility study for a “fish passage” to determine whether it could mitigate some of the impacts on fish species caused by the project, Trandem said.

But Ouk Vibol, deputy director of the Department of Fisheries Conservation, said that even with such a feature, only a small proportion of the fish stocks could be saved.

“They are thinking of a fish passage or gate, but I am not quite sure if they will build one or not. But even if we have [one] only about 30 to 40 per cent [of fish] will survive.”

A 2012 International Union for Conservation of Nature study found that fish catches on the Tatai River had declined by up to 90 per cent since the construction of the Stung Tatai hydropower dam.

Meach Mean, coordinator of the 3S Rivers Protection Network, said a number of villagers to be affected by the Sesan had recently accepted compensation offers, but others continued to resist relocation.

Members of the National Assembly’s Environment Commission will leave Phnom Penh today for a four-day fact-finding mission to the dam site.

Fort Kheun, a representative of the communities that will be affected by the dam, said he would tell the commission that many people were unwilling to be resettled for the project.

“It is very important for us to let them know that we are not agreeing to go; we want to live in our homes.”

ADDITIONAL REPORTING BY MAY TITTHARA