Facing a severe drought this year, Thailand is pumping water from the Mekong river to irrigate farms inland. It also wants to divert larger volumes, despite warnings from environmentalists about the downstream impact.
Pumping is now taking place in north-eastern Thailand, a parched region separated from Laos by the Mekong. In Nong Khai province, where a sluice gate between the Mekong and its tributary located within Thailand is now closed, temporary pumps are extracting water from the river at a rate of 15 cu m per second to water crops.
The Royal Irrigation Department expects to extract up to 47 million cu m of water over the next three months - about as much water as in 18,800 Olympic-size swimming pools. The authority says other river users should not be concerned.
"We believe it does not lower the Mekong level in the process," the department's director of project management, Dr Somkiat Prajamwong, tells The Straits Times.
But there are bigger plans in store. In the longer term, the temporary pumps are expected to be replaced by permanent ones that could operate at up to 10 times the initial capacity. If feasibility studies work out, this scaled-up operation could also be based in neighbouring Loei province, where another Thai tributary feeds into the Mekong.
The plans are unsettling the kingdom's neighbours downstream. The Mekong, which originates in the Tibetan plateau, travels for more than 4,000km through China, Myanmar, Laos, Thailand, Cambodia and Vietnam before draining into the South China Sea. It supports the world's largest inland fishery, and is a vital source of water for agricultural communities in that area.
Yet it is also a contested resource. China's hydroelectric dams to the north, as well as those being built in Laos, have been fingered for hampering the migration of fish and blocking the movement of nutrient-rich silt downstream.
Riverside communities suffering sudden, drastic fluctuations in water level they attribute to dam operations upstream fear Thailand's plans will only make their lives more difficult.
Environmentalists say Thailand needs to consult the Mekong River Commission (MRC) before diverting water. Thailand and the three other countries in this inter-governmental organisation - Cambodia, Laos and Vietnam - are bound by an agreement that requires them to inform or consult one another, depending on the type of water diversion planned.
But Dr Somkiat argues that water can be considered "diverted" only if it is extracted from one river basin for use in another. Since north-east Thailand is considered part of the Mekong river basin, the water extraction should not be considered a diversion, he says.
The MRC rules say otherwise. "During the dry season, intra- basin diversion requires prior consultation while inter-basin diversion requires a specific agreement," the MRC secretariat wrote in response to queries from The Straits Times. It added that it had "not received any official notification that the Thai government plans to divert water from the Mekong river".
Thailand's plans have made headlines in Vietnam and Cambodia, where local officials and environmental activists are fretting about the potential damage to agriculture downstream.
Online news website VietnamNet on Tuesday ran an article with the headline "Thailand diverts Mekong, Vietnam put in danger".
Within Thailand, the diversion has similarly attracted criticism, with environmentalists alleging the government is slowly trying to revive a mega scheme called the "Kong Chi Mun" project.
Ms Pianporn Deetes, Thailand campaign coordinator for California-based advocacy group International Rivers, says the project did not factor in the salinity of soil in the north-east, which would threaten crops by making dammed water too salty.
Dr Kanokwan Manorom, a rural development specialist from Ubon Ratchathani University, says: "The Royal Irrigation Department wanted to make this scheme possible during this difficult time. But the scheme is hotly debated and I am sure other Mekong riparian countries (will) disagree."