Experts say a recent change in the color of the Mekong River – from yellowish-brown to sky-blue – could be a worrying sign. They say the change suggests a possible problem caused by dams that have been built along the Mekong.
The river covers a distance of 4,300 kilometers. It begins high in the mountains of Tibet, flowing through China and five other countries: Myanmar, Thailand, Laos, Cambodia and Vietnam. The river eventually joins with the South China Sea.
The Mekong usually has a yellowish-brown color that results from the sediment it normally carries. But recent reports say it has been running clear, taking on a bluish-green color like that of the sky. The water levels have also become unusually low, creating sandbanks that enable people to stand in the middle of the river.
The low water levels clearly cause problems for fishermen and farmers. But experts in Thailand say the decrease in sediment represents a different threat, one that can result in a greater erosion of the sides and bottom of the river.
Experts and people living along the river blame the changes on a large hydroelectric dam upriver in Laos. The Xayaburi dam began operating in October. Critics say it is blocking much sediment from flowing down the river.
About 70 million people depend on the Mekong River for water, food, jobs, agriculture and transportation. Critics say several large dam projects along the Mekong are harming the river and its environment.
Pravit Kanthaduang is chief of the fishery office at Bueng Khong Long District in northeast Thailand. He told The Associated Press the Xayaburi dam is responsible for the water becoming clear. Less sediment means less nutrition for plants and fish, possibly threatening the river's ecological balance, he added.
With less sediment, the force of the water also strengthens, Chainarong Setthachau told The AP. Chainarong teaches at Mahasarakham University and has studied changes in the Mekong's environment for more than 20 years.
Pravit Kanthaduang是泰国东北部Bueng Khong Long区渔业办公室的负责人。他告诉美联社Xayaburi大坝负责使水变得清澈。他补充说，更少的沉积物意味着更少的植物和鱼类营养，可能威胁河流的生态平衡。
Chainarong Setthachau告诉美联社，由于沉积物减少，水的力量也增强了。 Chainarong在Mahasarakham大学任教，研究湄公河环境的变化已有20多年了。
"The current has less sediment, which unleashes energy onto the river banks downstream. This so-called ‘hungry water' will cause much more erosion to the banks, uprooting trees and damaging engineering structures in the river," Chainarong said.
The dam's developers have denied responsibility for low water levels that critics have said were caused by equipment tests that began in March.
In October, the Xayaburi Power Co. Ltd.said the project had spent more than $640 million to lessen harmful effects on the environment. The company said this included the building of outlets for sediment to pass through and systems to permit the passage of fish. The total cost of the dam project was $4.47 billion.
十月，Xayaburi Power Co. Ltd.表示，该项目已花费超过6.4亿美元，以减轻对环境的有害影响。该公司表示，这包括建造沉积物通过的出口和允许鱼类通过的系统。该水坝项目的总成本为44.7亿美元。
Daeng Pongpim lives about 800 kilometers downstream from the Xayaburi dam. She is from a farming family that used to fish in Ubon Ratchathani province. She told The AP she believes the dam is responsible for the river's recent unusual condition.
Daeng Pongpim居住在Xayaburi大坝下游约800公里处。她来自一个曾经在乌汶府（Ubon Ratchathani）钓鱼的农业家庭。她告诉美联社，她认为大坝是造成河流最近异常状况的原因。
"I am 67 years old and have never seen anything like it before. What makes me concerned the most is the low level of the water," she said. "Now, we are in early winter, the water level should not be this low. I can't imagine how hard it could be for us at the height of the dry season, in March and April."
Words in This Story：
sediment – n.materials that collect at the bottom of a liquid
erosion – n.when parts of something or damaged or removed by the sea, rain or wind
unleash – v.to suddenly cause a strong reaction
Co.– abbreviationshort for the word company
Ltd.– abbreviation short for the word limited