Developers of the Xayaboury hydropower plant in northern Laos expect to complete the redesign of the first run-of-river dam planned for the lower Mekong within the next few months, aiming to mitigate any negative impacts on neighboring countries.

“We are redesigning the power plant and its hydraulic model is now being tested at the Asian Institute of Technology in Bangkok,” Xayaboury Power Company Deputy Managing Director, Mr Rewat Suwanakitti, said last week, adding that the new design should be completed within three months.

The developers of the 1,285MW hydropower plant took the decision to redesign the dam after Cambodia and Vietnam expressed concerns that in its present form the migration of fish would be affected. They also said the dam would prevent the natural flow of sediment to downst ream areas of the Mekong.

Fish is the main food source for Mekong riparian communities while sediment is both a fertiliser and a food source of aquatic species. Some environmentalists are concerned that when the dam is built it will have an adverse effect on the biodiversity of the river and the millions of people who live downstream.

Mr Rewat said the redesign of the dam would not have any cross border impact on Cambodia and Vietnam, which are located more than 1,500 km downstream. Based on recommendations from independent consultants Poyry and Campagnie Nationale du Rhone, the Xayaboury run-of-river dam will be equipped with a number of fish passage facilities, including a fish ladder. This will ensure that fish can migrate up and down the Mekong through the 40 metre dam as the structure won't block their natural access, Mr Rewat said.

“The length of the fish ladder will be extended from the original 800 metres to 3 kilometres so that fish can pass through the dam,” he said. The project developers hired fish experts AF Colenco and Teraplant to study fish migration at the project site and create the best system for fish to pass through the dam.

Mr Rewat said the dam will be equipped with a sediment flushing system to ensure the flow of sediment downstream. He said this system had proved effective in many dams in Europe. Laos was not the first country to build a run-of-river dam, he noted, adding that this was an opportunity to learn about the positive and negative aspects of previous projects.

The project developers had agreed to fund the redesign and construction of the power plant to create one of the world's most modern dams.

Mr Rewat stressed that the Xayaboury dam was based on the run-of-river principle and did not store water like other dams. The development concept was to build a transparent dam, meaning that everything that enters the dam can pass through it.

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