Explanation:

 The Zanskar River is a north-flowing tributary of the Indus and although the Indus is 500km away from its source near the Kailash-Mansarovar in Tibet, Zanskar is its first main tributary. In its upper reaches, the Zanskar has two main branches-the Doda, which has its source near the Pensi-la and flows south-eastwards along the main Zanskar valley leading towards Padum and the second branch, which is formed by two main tributaries known as Kargyag river and Tsarap river.