The Sutlej changed its course about 8,000-10,000 years ago, leaving the Ghaggar-Hakra as a system of monsoon-fed rivers terminating in the Thar-desert. The Indus Valley Civilisation prospered when the monsoons that fed the rivers diminished around 5,000 years ago, and a large number of sites from the Mature Indus Valley Civilisation (2600-1900 BCE) are found along the middle course of the (dried-up) Hakra in Pakistan. Around 4,000 the Indus Valley Civilisation declined when the monsoons further diminished, and the Ghaggar-Hakra dried-up, becoming a small seasonal river.