A solitary Thai Customs officer shuffles papers in an empty office. One of the world’s great rivers flows, sluggish and slow, past a silent port.
“The big boats cannot move because the water is so low,” said the owner of the Chiang Saen dockside restaurant.
Crewman Zheng Liang, 24, from south China’s Yunnan province, said he was one of a handful left to watch the rusty ships. “The others have all gone back home.”
The Mekong was always shallow in the cool, dry season. But now it is extreme and unpredictable. It rises and falls suddenly. Silt and sediment change the riverbed.
Crops along the banks face odd floods or drought. Fishermen say catches are down. The likely reason: six giant dams built hundreds of kilometres upstream in China.
“About 90 per cent to 95 per cent of the water at Chiang Saen flows from China and after the dams were built we saw unnatural water fluctuations,” said Pianporn Deetes, of environmental group International Rivers. “Sometimes it happens without any explanation. We don’t even know how much water is coming each day.”
Market trader Sanchai Somkien pointed to baskets of dried small fish, a staple protein of the fiery local diet. “Not many,” he said, “and more expensive.”
The mighty Mekong rises high in the Tibetan plateau, fed by snowfields. It flows though China and Myanmar until it forms the border dividing Thailand and Laos, then on through Cambodia until its delta spreads across Vietnam and into the South China Sea.
Along its 4350km, more than 40 million people depend on the river for their food security and livelihood. Its unique monsoon flows create the world’s biggest inland fishery, with more than 850 species, and irrigate ricefields.
That is now under threat. In a quest for hydropower, China plans to build 14 more dams in the next decade. Hidden in remote regions behind formidable security, the dams are not open to scrutiny and, until recently, were regarded as state secrets.
“All these factors could spell disaster for countries that depend on the river’s water and sediment flow for agriculture, navigation, fish migration and other critical ecosystem services,” said an International Rivers report.
But China is not alone in taking far-reaching environmental decisions without consulting its neighbours or its own people. Laos and Cambodia have big plans for up to 11 dams on the lower Mekong.
Across the river from Chiang Saen, in Laos, construction is accelerating on the $US4.5 billion ($5.7bn) Xayaburi dam. Downstream, Thai fishermen complain that tides and catches have already changed. In one three-day period the water level rose and fell by more than 1m.
A court is to hear a case brought by residents in eight Thai provinces alleging that a contract between the Xayaburi dam operator and the Thai electricity utility is illegal because there has been no assessment of health and environmental impact.
But the Marxist-Leninist regime in Laos, ruling one of the poorest countries in Asia, is desperate for hydropower and revenues. It wants to become “the battery of Asia” and plans a second dam, known as Don Sahong, close to the point where the Mekong flows into Cambodia. One of its critics, environmental campaigner Sombath Somphone, 63, was detained in the capital, Vientiane, in December 2012 and has not been seen since. The Lao government has ignored appeals from Amnesty International, the UN and the EU for his safe release.
Cambodia has reached a deal with a Chinese state-owned firm to build a $US1bn dam on a tributary of the Mekong. It will affect the Tonle Sap, a giant freshwater lake vital to Cambodian agriculture and fisheries. Four more dams are planned. A rare spat between Southeast Asian nations over plans to exploit the Mekong for energy emerged last month. At a meeting of the Mekong River Commission, which groups Laos, Thailand, Vietnam and Cambodia, the Lao delegation agreed to hold more talks on the Don Sahong project.
It was a respite from the dam-building bonanza, which critics allege is prone to corruption and abuse. A scientific survey for the commission in 2010 warned that if all the proposed dams were built, 55 per cent of the lower Mekong would become a series of stagnant lakes and floods would increase.
The survey predicted that fishery stocks might fall by between 26 and 42 per cent, and up to 100 species, including the giant catfish and the Irrawaddy dolphin, could become extinct. The flow of nutrient-rich sediment would be cut by more than half, the study said.
It recommended that decisions on mainstream dams should be postponed until 2020 to examine the risks and work out ways of making hydropower sustainable.
Judging from the cracked mudflats and the hush along the riverside at Chiang Saen, however, time may already be running out.