The governments of four south-east Asian nations have agreed to delay the construction of a series of major hydropower plants pending a review of the impacts that the projects would have in the region.

Cambodia, Laos, Vietnam and Thailand say that development of the Xayaburi Dam on the Mekong River will not go ahead until further studies have been carried out.

Environmental groups have welcomed the decision and have called for a clear timetable and further consultation.

The Xayaburi project is the first of 11 dams proposed for the Mekong that have come under intense scrutiny because of their potential impacts on fisheries, farmers and local communities. Laos has already started construction at the Xayaburi site while Thailand has held talks over agreements to sell the output of the plant.

The decision builds on the outcomes of a meeting of the four governments last April, when Cambodia, Thailand, and Vietnam called for further studies of the project’s transboundary impacts and public consultations before deciding on the dam. At that time, Vietnam also called for a ten-year moratorium on all mainstream dams in line with the recommendations of a 2010 Strategic Environmental Assessment prepared for the Mekong River Commission.

A study released in December indicated that power from Xayaburi and other mainstream dams was not needed to meet Thailand’s energy demand, and that cheaper and cleaner options exist that would lower electricity bills and reduce greenhouse gas emissions.