More than 2,700 miles before the Mekong River drains into the South China Sea, before it winds past the ancient Khmer temple of Vat Phou and the poppy fields of the Golden Triangle, it begins on the Tibetan Plateau in western China. Tibetan Buddhists believe the spiritual source of the river is an alpine lake called Zaxiqiwa. Scientists have argued for decades over the river’s geographical origin. Not one of them doubts that it trickles down from a glacier high in the serrated mountains. The question is which one.
As the river makes its way down the plateau, it carves through russet-colored sandstone cliffs and passes meadows of white and yellow wildflowers. Tibetan prayer flags suspended on ropes crisscross its banks, and rocky streams feed into its waters. As I set up camp near one of these streams in late July, I think about the only other time I have seen the Mekong. It was four years ago in Phnom Penh, the capital of Cambodia. There, the river was a murky brown and smelled of sewage. Here, its headwaters are crystalline and unspoiled.
The Mekong is the smallest of three vital rivers that begin in the glaciers, lakes, and wetlands spread across the Sanjiangyuan region. The other two are the Yellow and Yangtze. Combined, the three rivers supply water to more than 600 million people. If the Yellow River is the cradle of Chinese civilization, Sanjiangyuan is its wellspring.