Subansiri river
Topic: Drainage System of India: Rivers, Basins and Patterns · NCERT: Class 11, Ch 3 "Drainage System"
Meaning
The Subansiri river is a right-bank tributary of the Brahmaputra. It rises in Tibet, crosses the Himalayas in Arunachal Pradesh and joins the Brahmaputra in the Assam valley. It is an antecedent river, which means it is older than the mountains it crosses. As the Himalayas slowly rose, the river kept cutting down, so today it flows through a deep gorge across the ranges. Its steep fall and large volume of water make it a big source of hydropower.
Example
The 2,000 MW Subansiri Lower hydroelectric project stands where the river leaves the hills, on the Arunachal Pradesh–Assam border. It is one of India's largest hydro projects and was being commissioned in 2025–26 (check its current status).
Don't confuse with
- Dibang and Lohit: these join the Brahmaputra on its left bank near Sadiya. The Subansiri joins on the right bank, along with the Kameng, Manas and Sankosh.
- Consequent river: this kind of river follows a slope that already exists. An antecedent river like the Subansiri is older than the slope and cut through the mountains as they rose.