Decline of the Indus Valley Civilization

Nearly two-thirds of the 1,500 archaeological sites related to the Indus Valley Civilization, occur on the dried up banks of the present-day Ghaggar river.

Around 1900 B.C.E., one of the major rivers of the Indus Valley, the Ghaggar-Hakra (also called the Saraswati), began to shift its course and eventually dried up, leaving many sites without a viable subsistence base. These communities would have migrated to other farming regions or to cities such as Mohenjo Daro and Harappa, resulting in overcrowding and civic disorder.

1500-2000 years before Christ, the Indus Valley civilization witnessed large scale deurbanization, population decrease, abandonment of many established settlements, lack of basic amenities, interpersonal violence and disappearance of the Indus Valley script.

Previously scholars argued that the Indus cities were suddenly abandoned around 1750 B.C.E., but recent work at Harappa has clearly demonstrated that during its late phase, from 1900 to 1300 B.C.E., Harappa was indeed inhabited. 

In fact, signs that drains and city walls were not maintained provide proof of crowding and a breakdown of civic order. The remains suggest that the ruling elites were no longer able to control the day-to-day functioning of the urban center. This loss of authority must have eventually led to a reorganization of society, not just in Harappa but throughout the entire region that the upper classes had dominated for 700 years. Similar changes were occurring at the other big cities, such as Mohenjo Daro to the south and Dholavira in western India.

The crisis led to a cessation of the hallmarks of Indus elite culture. The distinctive pottery with ritual motifs and Indus script and traditional square seals with unicorn and other animal motifs disappeared. Cubical weights for taxation and trade fell into disuse, and the international trade networks began to deteriorate. Shells from the coastal regions no longer made their way to the northern sites, and lapis lazuli from the north failed to reach the sites in the plains. In Mesopotamia the texts that had recorded ongoing trade with a region called Meluhha, which is probably the Indus Valley, no longer mentioned it.