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Indus Valley Civilization lived without an active, flowing river system

The Indus Valley Civilization was a bronze-age civilization, extending from what today is North-East Afghanistan to Pakistan and North-West India more than 5,000 years ago. Along with Ancient Egypt and Mesopotamia, it was one of three early civilizations of the ancient world and most widespread of the three. The people of the Indus civilization farmed everything from cotton to dates and eventually established at least five major cities with basic indoor plumbing and public sewage systems. (Facts about Indus Valley Civilization)

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Most major ancient urban civilizations, such as Egypt and Mesopotamia, formed around big rivers like the Nile as the flowing waters brought an abundance of fertile land and allowed groups to easily transport and trade goods long distances. Research into early civilizations has focused on the role of rivers drying up leading to an abandonment of urban centers by ancient communities. During the late 1800s, archaeologists and geologists noted a dry paleochannel, like an old riverbed that ran through many of these settlements. Following, a major Himalayan river dried up, either due to climate change or tectonic plate shift. It is believed that the colony who settled here expanded along the river but also got thinner with decreasing water-flow of the river.

However, a new research discovers that this old story is totally incorrect because until now, scientists had not been able to pinpoint the time that the river had dried up. The research concludes that ancient urban centers didn’t necessarily need an active, flowing river system in order to thrive. The new study has now shown that a major Himalayan river did not flow at the same time as the development of Indus settlements. Furthermore, it says that the river which filled the dry channel dried up more than 3,000 years before the epitome of the Indus civilization. In fact, the ancient people of the Indus valley civilization may have been depended on seasonal monsoon flooding and the rich, water-trapping clays of the old river valley for their systems of ancient agricultural.

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This map of northwestern India and Pakistan shows the locations of ancient Indus settlements. Though some larger cities are on modern Himalayan rivers, most of the villages sit in areas not fed by major rivers (source)

Head researcher Sanjeev Gupta, a sedimentologist at Imperial College London says, “They were able to survive in a very diverse landscape and it makes it a richer story.” This region occupied by the Indus people was a semi-arid landscape. Yet, it is surprising that they were able to support themselves and develop an urban culture by utilizing the landscape. The mystery of the paleo-channel of the Ghaggar in India and the Hakra in Pakistan is yet unknown. Hence, Gupta and his colleagues have been working to unravel this for many years. The team drilled cores through the dried Ghaggar-Hakra river bed and discovered more about the history of the region’s rivers. The researchers sliced the cores in half lengthwise so that they could use one semicircular half to analyze the types of sediment and the other to undergo a barrage of sophisticated analyses to reveal ages.

Analyzing thousands of grains the team found that the ages of the sediments matched 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 it was yet to know when the Sutlej river avulsed.

A Landsat 5 composite satellite image shows the Ghaggar-Hakra paleochannel in dark blue. The former river channel left behind a low-lying area rich with groundwater and muddy soil. (source)

To find out, the researchers using another technique, the researchers dated their five Kalibangan cores, along with six other cores from other locations along the former Sutlej path. The results showed that in the period from 4,800 to 3,900 years ago, the sediments were dominated by fine sands and muds when the Indus villages were at their peak. To add up, the Sutlej once ran through the old channel, washing down glacial sediments and probably bringing raging seasonal floods to the region. Plus, the dating showed that between 15,000 and 8,000 years ago, the Sutlej changed course. The course change left behind a low-lying river valley, rich in groundwater and likely fed by small, seasonal monsoon rivers that would inundate the valley in the fertile mud. In addition to being a safer place to live than to live next to a raging glacial river.

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The new information about water resources could change the way researchers think about Indus settlement patterns. With no rivers in the Ghaggar-Hakra channel area, ancient people may have moved around in pursuit of water rather than staying in villages for generations. Also, although the groundwater has been depleted in the region today, groundwater still feeds agriculture in that area. Hence, scientists are now working on a project to understand how the groundwater flows and how it can best be managed in the future. In conclusion, either then or today, water resources are always important.