The Pak Mun Dam (Thai: เขื่อนปากมูล) is a gravity dam located 5.5 km west of the confluence of the Mun and Mekong rivers in Ubon Ratchathani province, Thailand. It was constructed by the Electricity Generating Authority of Thailand (EGAT) with support from the World Bank at a total cost of US$240 million, and completed in 1994.
The project has been criticized for adverse effects on the fisheries of the Mun River, insufficient compensation payments to affected villagers, and failure to produce the projected power output. The immediate impact of the dam was to flood 117 square kilometres of land and displace around 3,000 families. In all around 25,000 villagers claim to have been affected by the dam. Protests have been staged at the dam site and outside Government House in Bangkok. EGAT has paid out US$44.24 million in relocation compensation, plus US$15.8 million for loss of fisheries.Fisheries
In response to concerns about the dam's likely impact on fisheries on the Mun River, a fish ladder was incorporated into the scheme to allow fish into the Mun River to spawn. However, the ladder appears to have been unsuccessful: a report from the World Commission on Dams found that of 265 fish species previously found in the Mun river, at least 50 had disappeared and numbers of others had declined significantly. The fish catch decreased by 60-80%. However, it is uncertain what proportion of this decrease is attributable to the dam, and what proportion to other factor. There have since been reports that some of these species have started to reestablish themselves.
In response to protests, the government opened the dam gates temporarily in June 2001. Subsequently, a study by Ubon Ratchathani University recommended keeping the gates open for a further five years, and a study by Living River Siam recommended decommissioning the dam. Instead, the Cabinet decided to close the gates for eight months each year from November 2002.Electricity generation
The World Commission on Dams report also raised doubts about the amount of power which the dam can produce. It argued that the dam could not reliably produce the anticipated amount of electricity, making it economically nonviable. EGAT responded that such consistent electricity production was unnecessary, and that the dam was a useful source of electricity (although it is not clear how it is useful, since Thailand produces 130% of its daily electrical needs).