With the Red River turning a surprisingly clear blue-green shade in its upstream sections, the absence of its usual muddy, pinkish color is being blamed on dams and polluting factories. 

The Red River flowing through Lao Cai has been surprisingly clear for about a week,
February 2021. Photo by VnExpress/Pham Ngoc Trien.

For a week now, the Red River section that flows through Lao Cai Province has become so clear that there are some shallow areas towards the banks where the river bed can be seen at a depth of one meter. While this looks like a welcome development, experts say this is happening because of "withheld" alluvium and pollution caused by factories on the river banks.

The Red River, over 1,100 km long, originates in China and flows through Lao Cai, Yen Bai, Phu Tho, Vinh Phuc and Hanoi. The river section that flows through Vietnam is about 510 km long.

Nguyen Thi Lan, a resident of Lao Cai, said the water of the Red River in her neighborhood is normally a thick brown color, and if seen from afar, it looks like a pinkish strip.

"It is really strange now that the river has such a clear green shade," she said.

Locals people swim in the Red River in 2017. Photo by VnExpress/Ngoc Thanh.

Vu Dinh Thuy, deputy director of Lao Cai's Natural Resources and Environment Department, said this is not the first time the Red River has changed character and color. This phenomenon has been happening around this time of year for the past five years, Thuy said.

"Maybe the reason is that the natural alluvium that has always flowed down naturally from further upstream has been absent, and also northern Vietnam has had no rainfall this season (to muddy the waters)."

Dao Trong Tu, chairman of the Vietnam Rivers Network, also set out two possible reasons for the changes seen in the Red River.

He said a series of hydropower plants and reservoirs operated by China further upstream could have held back alluvium.

The other reason, he said, could be the pollution caused by factories operating in upstream areas and along the banks of the river.

Tu added that theory of pollution would require specific monitoring and study of the water samples to arrive at a final conclusion.