PHNOM PENH – With horror images showing fields of plastic rubbish bobbing on turquoise seas around the world, one could be forgiven for welcoming the sight of one of the world’s great rivers turning a fresh blue.
However the azure hue seen in recent weeks along stretches of the Mekong is stirring concerns that dozens of hydroelectric dams, the biggest of which are in China, are interrupting the river’s natural flow and blocking sediment that should be carried to farmland downriver that helps feed 60 million people.
Earlier this month the Mekong River Commission, a regional intergovernmental body, put the colour change down to “extremely low flow, slow drop in the river sediments,” after warning last month that the Mekong region could face serious drought over the turn of the year.
Over the past month two new hydropower projects opened on the Laotian part of the river, with the 1.3 gigawatt Xayaburi dam built to export electricity to Thailand and the smaller Don Sahong project helping to power the grid in Cambodia, where outages are common even in capital Phnom Penh.
On Tuesday Utrecht University published scientific research saying that “increased salt intrusion and tides in the Mekong Delta relate to sediment starvation from upstream dams and sand mining in the delta.”
The Mekong runs for nearly 3,100 miles through or along China, Laos, Myanmar, Thailand, Cambodia, filling a vast rice-bowl delta in Vietnam that then empties into the South China Sea around Ho Chi Minh City, once known as Saigon. Vietnam’s National Center for Hydrometeorological Forecasting said on Tuesday that the delta could face a 35-40% decrease in water flow between now and February.
The Mekong, a popular cruise route for tourists, irrigates or fertilises a catchment area three times the size of the U.K., taking in Cambodia’s Tonle Sap, the biggest lake in Southeast Asia. Annual monsoon rains deluge the river and lake, causing the flow to reverse and carry huge quantities of fish into the the nets of eager fishermen waiting on the lake’s still waters. As the monsoon ends, the waters revert and fish and sediment are washed upstream and downstream.
This year, however, the phenomenon barely made a ripple. “Typically the Tonle Sap heartbeat – the duration from the beginning of its expansion to the beginning of its contraction is four to five months – but this year it only lasted for five weeks due to the combined factors of the El Nino drought and upstream dams,” said Brian Eyler, author of Last Days of the Mighty Mekong.
“Most signals point to a new normal for the Mekong system – one where efforts will likely shift from avoiding the worst impacts from dams and climate change to struggling through and adapting to those impacts as they continue to affect the region,” Eyler warned.
Concerns have also been flagged about the river’s wildlife. The 300kg Mekong catfish, one of the world’s biggest freshwater fish, is listed as endangered, while Irrawaddy dolphin population was a mere 92 at last count a year ago, a slight increase on the 80 recorded in 2015 after fishing restrictions were imposed on Cambodian stretches of the river.Show