<P> The Ghaggar - Hakra system was rain - fed, and water - supply depended on the monsoons . The Indus Valley climate grew significantly cooler and drier from about 1800 BCE, linked to a general weakening of the monsoon at that time . The Indian monsoon declined and aridity increased, with the Ghaggar - Hakra retracting its reach towards the foothills of the Himalaya, leading to erratic and less extensive floods that made inundation agriculture less sustainable . </P> <P> Aridification reduced the water supply enough to cause the civilisation's demise, and to scatter its population eastward . According to Giosan et al. (2012), the IVC residents did not develop irrigation capabilities, relying mainly on the seasonal monsoons leading to summer floods . As the monsoons kept shifting south, the floods grew too erratic for sustainable agricultural activities . The residents then migrated towards the Ganges basin in the east, where they established smaller villages and isolated farms . The small surplus produced in these small communities did not allow development of trade, and the cities died out . </P> <P> There are archaeological evidences of major earthquakes at Dholavira in 2200 BCE as well as at Kalibangan in 2700 and 2900 BCE . Such succession of earthquakes, along with drought, may have contributed to decline of Ghaggar - Harka system . Sea level changes are also found at two possible seaport sites along the Makran coast which are now inland . Earthquakes may have contributed to decline of several sites by direct shaking damage, by sea level change or by change in water supply . </P> <P> Archaeological excavations indicate that the decline of Harappa drove people eastward . According to Possehl, after 1900 BCE the number of sites in today's India increased from 218 to 853 . According to Andrew Lawler, "excavations along the Gangetic plain show that cities began to arise there starting about 1200 BCE, just a few centuries after Harappa was deserted and much earlier than once suspected ." According to Jim Shaffer there was a continuous series of cultural developments, just as in most areas of the world . These link "the so - called two major phases of urbanisation in South Asia". </P>

Which of the following is associated with indus valley civilisation