BY S VENKAT NARAYAN Our Special Correspondent Courtesy The Island

April 17, 2018, 12:00 pm

NEW DELHI, April 16: The Indus Valley Civilisation (IVC) was wiped out 4,350 years ago by a 900-year-long drought, scientists at the Indian Institute of Technology in Kharagpur (IIT-Kgp) have found.

Evidence gathered during their study also put to rest the widely accepted theory that the said drought lasted for only about 200 years. The stud will be published in the prestigious Quaternary International Journal by Elsevier this month.Researchers from the geology and geophysics department have been studying the monsoon’s variability for the past 5,000 years and have found that the rains played truant in the northwest Himalayas for 900 long years, drying up the source of water that fed the rivers along which the civilisation thrived. This eventually drove the otherwise hardy inhabitants towards the east and south, where rain conditions were better.

The IIT-Kgp team mapped a 5,000-year monsoon variability in the Tso Moriri Lake in Leh-Ladakh — which too was fed by the same glacial source — and identified periods that had continuous spells of good monsoon as well as phases when it was weak or nil.

“The study revealed that from 2,350 BC (4,350 years ago) till 1,450 BC, the monsoon had a major weakening effect over the zone where the civilisation flourished. A drought-like situation developed, forcing residents to abandon their settlements in search of greener pastures,” said Anil Kumar Gupta, the lead researcher and a senior faculty of geology at the institute.

These displaced people gradually migrated towards the Ganga-Yamuna valley towards eastern and central UP; Bihar and Bengal in the east; Madhya Pradesh, south of Vindhyachal and south Gujarat in the south, Gupta added.

The IVC encompassed much of today’s Pakistan, western India, and northeastern Afghanistan; extending from Pakistani Balochistan in the west to Uttar Pradesh in the east, northeastern Afghanistan in the north and Maharashtra in the south. Shortugai to the north is on the Oxus River, the Afghan border with Tajikistan, and in the west Sutkagan Dor is close to the Iranian border. The Kulli culture of Balochistan, of which morethan 100 settlement sites are known, can be regarded as a local variant of the IVC, or a related culture.

The geography of the Indus Valley put the civilisations that arose there in a highly similar situation to those in Egypt and Peru, with rich agricultural lands being surrounded by highlands, desert, and ocean.

Recently, Indus sites have been discovered in Pakistan’s Khyber Pakhtunkhwa as well. Other IVC colonies can be found in Afghanistan while smaller isolated colonies can be found as far away as Turkmenistan and in Maharashtra. The largest number of colonies are in the Punjab, Sindh, Rajasthan, Haryana, and Gujarat belt Coastal settlements extended from Sutkagan Dor in Western Baluchistan to Lothal in Gujarat.

An Indus Valley site has been found on the Oxus River at Shortughai in northern Afghanistan, in the Gomal River valley in northwestern Pakistan, at Manda, Jammu on the Beas River near Jammu, India, and at Alamgirpur on the Hindon River, only 28 km from Delhi. Indus Valley sites have been found most often on rivers, but also on the ancient seacoast, for example, Balakot, and on islands, for example, Dholavira.

It flourished along a system of monsoon-fed perennial rivers in the basins of the Ghaggar-Hakra River in northwest India, and the Indus River flowing through the length of Pakistan. There is evidence of dry river beds overlapping with the Ghaggar River in India and Hakra channel in Pakistan.

A total of 616 sites have been discovered along the dried up river beds of the Ghaggar-Hakra River and its tributaries, while 406 sites have been found along the Indus and its tributaries. According to Shereen Ratnagar, the Ghaggar-Hakra desert area has more remaining sites than the alluvium of the Indus Valley, since the Ghaggar-Hakra desert area has been left untouched by settlements and agriculture since the end of the Indus Valley Civilisation.