The splendid rivers of Nepal can be divided into three categories in accordance to their origins. The first category comprises the three main river systems of the country – the Koshi, Gandaki and Karnali river systems, all of them originating from glaciers and snow-fed lakes.

The Koshi River System
• The Koshi river system consists of Tamor, Arun, Dudhkoshi, Likhu, Tamakoshi, Sunkoshi and Indravati rivers.
• The Arun and Sunkoshi originate in Tibet. The confluence of these rivers is at Tribeni (near Dharan) in Sagarmatha Zone.
• Flowing for almost 10 kms through a narrow gorge before entering the plains, the ‘Sapta Kosi’ or simply the ‘Koshi’, swollen with the waters of the seven rivers, finally merges into the Ganges.
• The Kali Gandaki originates in Mustang and converges with the Trishuli at Deoghat in Chitwan. The river is then called the ‘Narayani’ and goes on to meet the Ganges.

The Gandaki River System
• The Kali Gandaki originates in Mustang and converges with the Trishuli at Devghat in Chitwan. The river is then called the ‘Narayani’ and goes on to meet the Ganges at Patna in Bihar.
• The Gandaki river system in central Nepal consists of the Kali Gandaki, Budhi Gandaki, Marsyanghi, Trishuli, Seti, Madi and Daraundi rivers.
• The Kaligandaki is the longest river and the Trishuli, the main tributary of this system.

The Karnali River System
• The Karnali river system in Western Nepal consists of the Humla Karnali, Mugu Karnali, Seti and Bheri rivers and is the longest river system in the country.
• The Humla Karnali, which rises in Tibet, is the main tributary. After entering India, this river assumes the name Gogra.