Understanding The River System
The rivers of Nepal can be grouped into three categories on the basis of their origin:
Antecedent to Himalaya
After the Mahabharat
After the Churia range
Antecedent rivers belong to the period prior to the rise of the Himalaya. These rivers added their tributaries during or after the Himalayan origin along with the development of monsoon climate. The major river systems namely the Koshi, the Karnali and the Gandaki belong to the antecedent group.
After the formation of Mahabharat hills, the antecedent rivers changed their courses as Mahabharat stood as a barrier. As a result, most of the rivers changed their courses either to the east or west. Rivers originating from the Mahabharat range and cutting through Churia hills come under the second group; these include Kankai, Bagmati, Kamala etc.
The third group of rivers originates from the southern face of the Churia hills. For the purpose of commercial rafting, the following river systems are in use.
• Saptakoshi River System (East Nepal)
• Narayani or Saptagandaki River System (Central Nepal)
• Karnali River System (West Nepal)