For many years the warning signs flashed the same message: the Mekong River, Southeast Asia’s main waterway, was headed toward environmental disaster. The 2,700-mile-long ribbon of water, scientists cautioned, could not withstand the onslaught of dam construction, overfishing, and pollution. Yet somehow the river that might be called the most important in the world continued to provide a livelihood for the tens of millions of people in the Lower Mekong Basin.
Then, in 2019, the bounty seemed finally, and literally, to dry up. The monsoon rains that fill the river each year and turn the basin into a wonderland of biological riches didn’t come until the mighty Mekong had been reduced, in parts, to a virtual trickle. In Cambodia’s interconnected Tonle Sap Lake, the heart of the world’s largest inland fishery, some fishers reported catch declines of more than 80 percent.
What caused this? An El Niño-induced drought, exacerbated by climate change, no doubt played a part. But so did the cascade of hydroelectric dams that China operates in the upper reaches of the Mekong basin, which starts in the Tibetan highlands and runs through six countries. As the drought intensified, China held back an even greater share of the river severely disrupting the water flow downstream.