One of China’s two major rivers is “pirating” water from the other, according to new research. Over the past 1.7 million years, the Yangtze River has been stealing water from the Yellow River, and the theft could worsen dangerously low water levels in the latter.
The Yangtze and Yellow Rivers are among the longest in the world. They stretch thousands of miles across China and supply hundreds of millions of people with water. And now, researchers estimate, the Yellow River has lost some five billion square meters of water to the Yangtze every year on average over the long term. The findings, which were published last week in the Journal of Geophysical Research: Earth Surface, add critical insight to China’s plans to combat water shortages caused by climate change and human overuse of the Yellow River. In other words, to reshape a river, you need to understand the ancient forces that are already acting on it.
If you were to float down the Yangtze, you’d look up to steep gorges. But if you took a ride down the Yellow River, the Yangtze’s sister river to the north, you’d see a more gradually inclining topography. Those geographic differences are evidence of a long-standing tug-of-war for water between the two rivers over millions of years—and the Yangtze appears to be the clear winner.
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Using a combination of field observations and modeling, researchers tracked several climate-fueled “capture events”—when one river hijacks water from another, essentially—between the Yangtze and the Yellow River from 1.7 million to 0.8 million years ago. The water captured by the Yangtze is so significant that it’s forcing a 3,000-kilometer-long divide between the two rivers’ headwaters to migrate, the researchers write in the study.
The geological war over water may have deep implications for the people who rely on the Yellow River for water. China plans to initially divert some four billion cubic meters of water from the Yangtze to the Yellow River annually in the first phase of part of the South-to-North Water Diversion Project—but that’s less water than what’s being captured by the Yangtze, the study authors warn.
“This highlights a profound disconnect between the timescales of landscape evolution and water resource engineering,” the researchers write.