Mekong River’s new colour may be a sign of trouble

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In this Wednesday, Dec. 4, 2019, photo, fishing boats are moored in Mekong River, which has turned blue instead of its usual muddy color, in Nakhon Phanom province, northeastern Thailand. Experts say the aquamarine color the Mekong River has recently acquired may beguile tourists but it also indicates a problem caused by upstream dams. The water usually is a yellowish-brown shade due to the sediment it normally carries downstream. But lately it has been running clear, taking on a blue-green hue that is a reflection of the sky. The water levels have also become unusually low, exposing sandbanks in the middle of the river. (AP Photo/Chessadaporn Buasai)

BANGKOK: The Mekong River has recently acquired an aquamarine colour that may beguile tourists but also indicates a problem caused by upstream dams, experts in Thailand say.

The river usually has a yellowish-brown shade due to the sediment it normally carries downstream. But lately it has been running clear, taking on a blue-green hue that is a reflection of the sky.

The water levels have also become unusually low, exposing the sandbanks.

Low water levels pose an obvious problem for fishermen and farmers, but experts say the decline in sediment exposes a different danger that can result in greater erosion of the river’s banks and bed.

The experts and people living along the river blame a large hydroelectric dam upstream in Laos that began operating in October for contributing to both problems, though rainfall has also been sparse.

Around 70 million people depend on the Mekong River for water, food, commerce, irrigation and transportation.

Critics charge that large-scale development projects such as the Xayaburi dam dangerously disrupt the region’s ecology.

The dam blocks much sediment from moving further downstream, which accounts for the water becoming clear, said Pravit Kanthaduang, chief of the fishery office at Bueng Khong Long, Bueng Kan province.

Less sediment means less nutrition for plants and fish in the river, threatening the ecological balance, he said.

With less sediment, the water also has more stream power, a phenomenon known as “hungry water”, said Chainarong Setthachau of the Faculty of Humanities and Social Science at Mahasarakham University in Thailand’s northeast who has studied changes in the Mekong’s ecology for the past two decades.“The current has less sediment, which unleashes energy onto the river banks downstream, ” Chainarong added.

“This so-called ‘hungry water’ will cause much more erosion to the banks, uprooting trees and damaging engineering structures in the river.” — AP