Nepalese rivers can be grouped into three categories on the basis of their origin.

1. Antecedent to himalaya
2. After The Mahabharat
3. 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 alongwith the development of mosoon climate. After the formation of Mahabharat hills, the antecedent rivers changed their courses as Mahabharat stood as a barrier. As a result, most of the these rivers were responsible to deposit the sediments in the Churis basin.

The major river system namely the Koshi, the Karnali and the Gandaki belong to the antecedent group. Rivers originating from the Mahabharat range and cutting through Churia hills come under the second group, these include Kankai, Bagamati, Kamala etc. the third group of riverd orginate from the southern face of the Churia hills. For the purpose of commercial rafting, the following rivers are in use.

1.SaptaKoshi River System (East Nepal)
2. Narayani or Saptagandaki River System (Central Nepal)
3. Karnali River System (West Nepal)

Sixteen rivers in the three river system are open for tourists for Rafting. The rivers are;

The Trishuli River (Trishuli-Narayanghat Section) The Kali Gandaki River (Kusma-tiger Tops Section) The Bheri River (Birendranagar-Chisapani Section) The Seti River (Damouli-Tiger tops Section) The Sunkoshi River (Baseri-Chatara section)

The Tama Koshi River (Busti-chatara Section) The Arun River (Tumlingtar-Chatara Section) The Budhi Gandaki River (Arughat- Trishuli Section) The Bhote Koshi River (Kodari- lartza Bridge Section) The Marshyangdi River (nadi-Bimalnagar Section)