AHMEDABAD: There has been a strong belief that the Harappan civilization depended on monsoons. But now there is ample evidence that a large number of Harappan settlements had mushroomed and flourished along the ancient course of the modern seasonal stream, Ghaggar, in northwestern India. And this ancient course was that of the mythical river Saraswati.

A new research — led by the Physical Research Laboratory (PRL), Ahmedabad, in collaboration with IIT-Bombay — has reported “unequivocal evidence” that there existed a perennial river on the plains of northwestern India. The river, according to the researchers, flowed roughly along the course of the modern Ghaggar. Researchers say that this river was the Saraswati mentioned in the Rig Veda.

Later epics such as the Mahabharata describe the Saraswati’s diminishing flow till it disappeared completely. The research has been published in the latest issue of the journal “Scientific Report” of Nature Publishers and is in the public domain.

The researchers provide evidence that the Saraswati was perennial and had flowed from the Higher Himalayas between 7,000 BC and 2,500 BC, and that the Harappans had built their early settlements along this powerful river between 3,800 BC and 1,900 BC. The research posits that the decline of the Saraswati had led to the collapse of the Harappan civilization. The demise of the river and the civilization approximately coincide with the beginning of the Meghalayan Stage — the current dry phase in the global climate that began about 4,200 years ago.

The scientists behind the study — Anirban Chatterjee, J S Ray and Anil Shukla of PRL, and Kanchan Pande of IIT-Bombay — say that the Saraswati had sources in the glaciated regions of the Higher Himalayas, similar to the Ganga, Yamuna and Sutlej. The modern Ghaggar has no direct connection to the Higher Himalayas and originates from the foothills of the Himalayas — the Siwaliks. Ray explains, “The only likely path for the glacier-melt water for the ancient course of present-day Ghaggar (Saraswati) could have been through the distributaries of the mighty Sutlej River.”

The scientists reached this conclusion by determining the depositional ages of the coarse-grained white sand layers that occurred 3-10 metres below the modern alluvium of the Ghaggar’s floodplain. The dating was done with radiocarbon and optically stimulated luminescence methods at the PRL.

“We found that the perennial river had uninterrupted flow starting 80,000 years ago; that flow continued till 20,000 years ago,” says Ray. “It then diminished due to the extreme aridity of the last glacial period. However, the river revived its strength about 9,000 years ago and flowed for the next 4,500 years.”

Ray says the duration coincides with the flourishing of the Pre-Harappan and Early Harappan cultures along the river’s banks. “The river later lost its perennial strength again,” he says.

“The final decline of the Ghaggar was probably due to the rapid drying up of the Sutlej-fed channels that had fed the Saraswati in the ancient times,” Ray adds.

