The Sutlej rises at Rakshastal near Mansarovar in Tibet, cuts through the Himalaya at Shipki La, and runs about 1,450 kilometres to join the Chenab. It is the longest of the five rivers and the only one that rises outside the subcontinent.
It was the boundary of the Sikh state after 1809 and the boundary between British and Sikh Punjab for thirty-six years. Ludhiana and Phillaur faced each other across it. Everything about Cis-Sutlej and Trans-Sutlej Punjab begins with that line.
Bhakra dam holds it at the Shivalik gorge. Below that the Ropar and Harike headworks take most of what is left into canals, and by Ferozepur the bed is often dry or carrying effluent rather than water.
The Buddha Nullah at Ludhiana carries industrial and municipal discharge into it. Water quality below Ludhiana has been the subject of repeated pollution board findings and of the Kali Bein style clean-up campaigns that have not yet worked at this scale.
The Sutlej is the river of the Malwa and it is the most heavily worked river in Punjab. There are stretches where the river as a river does not exist for most of the year.
It rises near Rakas Tal in Tibet, cuts through the Himalaya, and enters the plain at Bhakra, which is the deepest gorge crossing of any of the five rivers.
It is the river of the eighteenth and nineteenth centuries: the 1809 line, the Anglo-Sikh war crossings, the Sirhind Canal, Bhakra, Harike and the Indira Gandhi canal all sit on it.
Below Harike it carries very little water and a great deal of effluent for much of the year. What crosses into Pakistan at Ferozepur in the dry season is largely Ludhiana's drainage.