Ghaggar-Hakra River

The Ghaggar-Hakra River is an intermittent river in India and Pakistan that flows only during the monsoon season. The river is known as Ghaggar before the Ottu barrage at 29.4875°N 74.8925°E / 29.4875; 74.8925, and as Hakra downstream of the barrage in the Thar Desert. In pre-Harappan times the Ghaggar was a tributary of the Sutlej. It is still connected to this paleochannel of the Sutlej, and possibly the Yamuna, which ended in the Nara River, presently a delta channel of the Indus River joining the sea via Sir Creek.

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 years ago, the Indus Valley Civilisation declined when the monsoons further diminished, and the Ghaggar-Hakra dried up, becoming a small seasonal river.

Nineteenth and early 20th century scholars, but also some more recent authors, have suggested that the Ghaggar-Hakra might be the defunct remains of the Sarasvati River mentioned in the Rig Veda, fed by Himalayan-fed rivers, despite the fact that the Ghaggar-Hakra had dried up by that time.