Assessing the palaeohydrology of the lost Saraswati River in the Punjab-Haryana plains, Northwest India from satellite data

It has been suggested over a century ago that the Saraswati was a large river that flowed in the Sutlej-Yamuna interfluve, a region that is now devoid of any such large river system. This large river was commonly related to the Saraswati River described in the Rig-veda, and was correlated with the discovery of several Harappan sites in the region. Presently, there is only the ephemeral Ghaggar River that flows here with its limited discharge along the abandoned course of the 'lost' Saraswati. Also, it was hypothesised earlier that this region was drained by the waters from the drainage basins of both the glacier/monsoon-fed Sutlej and Yamuna rivers. It therefore stands to reason that this region should preserve evidence of the record of the past discharge variability that impacted this region prior to the major drainage reorganisation. This study is an attempt to reconstruct the palaeohydrology of the Saraswati River. We investigate the hypothesis, that the ancient Saraswati River used to carry a combined flow of the Sutlej, Ghaggar and Yamuna river catchments. To examine this important question, we use the channel belt width, catchment area and average annual discharge of different rivers presently flowing on Indus-Ganga-Brahmaputra plains in the Himalayan Foreland. We use these variables to establish the empirical scaling relationships between the channel belt width and average annual discharge to the catchment area. We observed rivers having a larger catchment usually carry a higher discharge and have a wider channel belt. Finally, we use these empirical scaling relationships to estimate the channel belt width and average annual discharge of the lost Saraswati River at the time when it possibly carried the combined flow of the Sutlej, Ghaggar, and Yamuna rivers catchments. We obtained the average annual discharge of the Saraswati River of an order of 3000 m3s- 1 and channel belt width of about 11 km at the location downstream of the postulated confluence of the Sutlej and Yamuna rivers at Suratgarh.

Automated summary

This study reconstructs the paleohydrology of the Saraswati River, suggesting that rivers with larger catchment areas generally have higher discharges and wider channel belts. By using empirical scaling relationships between channel belt width, catchment area, and average annual discharge of different rivers presently flowing on the Indus-Ganga-Brahmaputra plains, the study estimates the channel belt width and average annual discharge of the lost Saraswati River during a time when it possibly carried the combined flow of the Sutlej, Ghaggar, and Yamuna rivers catchments. The average annual discharge of the Saraswati River is estimated to be around 3000 m3/s with a channel belt width of about 11 km downstream of the postulated confluence of the Sutlej and Yamuna rivers at Suratgarh.