Late in the 2nd millennium BCE the Ghaggar-Hakra fluvial system dried up, becoming the small seasonal river it is today, which affected the Harappan civilisation. Paleobotanical information documents the aridity that developed after the drying up of the river. The diminishing of the monsoons particular effected the Ghaggar-Hakra system, which became ephemeral and was largely abandoned, with the IVC reorganizing in local settlements some 4000 years ago. In the late Harappan period the number of late Harappan sites in the middle Ghaggar-Hakra channel and in the Indus valley diminished, while it expanded in the upper Ghaggar-Sutlej channels and in Saurashtra. The IVC-people migrated east toward the more humid regions of the Indo-Gangetic Plain, where the decentralised late Harappan phase took place.