... new research reveals that this old story is entirely wrong. In fact, the river that once filled the dry channel dried up more than 3,000 years before the heyday of the Indus civilization. Instead, the ancient people who populated those villages may have relied on seasonal monsoon flooding and the rich, water-trapping clays of the old river valley for a flourishing system of agriculture. 

"They were able to survive in a very diverse landscape," said lead study researcher Sanjeev Gupta, a sedimentologist at Imperial College London. "It makes it a richer story."

An excavated street at the Indus site of Kalibangan, a Bronze Age settlement that sits right along the Ghaggar-Hakra paleochannel, visible in the background
An excavated street at the Indus site of Kalibangan, a Bronze Age settlement that sits right along the Ghaggar-Hakra paleochannel, visible in the background © S. Gupta/Imperial College London

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"We found these beautiful river deposits with all the hallmarks of Himalayan rivers," Gupta said, including dark-brown and gray sands washed down from the rugged mountains. To figure out which river had brought these mountainous deposits down, the researchers used dating techniques to figure out the ages of two minerals in the sands: mica and zircon. Analyzing thousands of grains (the mica alone took six straight weeks of 24-hour work), the team found that the ages of the sediments matched one river, and one river alone: the Sutlej, which now flows in a westerly direction across the Punjab region.

The discovery reveals that the Sutlej once flowed through the now-dry paleochannel but shifted course at some time during history. This process, called avulsion, happens occasionally with rivers. But when had the Sutlej avulsed?

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