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.